Palaeontology

10 March 2022: ‘Us’ Part 6 – Kith and kin

Hobbits and their ancestors

One of the great palaeoanthropological bombshells of the last generation was the discovery of Homo floresiensis on the Indonesian island of Flores. For years scientists debated what ancestor this new and somewhat diminutive hominin – dubbed the ‘Hobbit’ by the media – had come from, or indeed if it should even be included in our genus.

Homo floresiensis reconstruction. Courtesy of Creative Commons. This image created by ATOR.

While now generally accepted as a member of our broader tribe, its origins are still fiercely argued, many insisting it’s nothing more than H. erectus that’s undergone insular dwarfism. But I think a 2017 paper written by Colin Groves, Debbie Argue, Michael Lee and William Jungers, convincingly demonstrates that H. floresiensis is not derived from H. erectus (or is a diseased example of H. sapiens), but rather from a much earlier hominim such as H. habilis or a sister species.[i]

A second paper, published in 2020[ii], backs up this hypothesis, and concludes with this statement:

‘ … something which on account of our inadequate current taxonomic framework we have to call “early Homo” differentiated in Africa, possibly as early as 2.8 (mya) … Subsequently, one or more members of this group reached the Mediterranean fringe and spread Out of Africa at 2.5 Ma. After successfully expanding over Asia, at least one of those hominins … gave rise to new species that reached the Caucasus by around 1.8 (mya), and thence Europe by ca. 0.9 (mya) … (the) eastward expansion (or occupation) in Asia of small-bodied and archaically-proportioned hominins continued, possibly in multiple waves; and, by ca. 0.8 (mya), representatives of this group had penetrated as far as insular southeast Asia, where H. floresiensis ultimately emerged … ’

Indeed, some scientists considered this possibility as early as 2005. A report about the brain of H. floresiensis published in Science in that year[iii] concludes with these lines: ‘Although it is possible that H. floresiensis represented an endemic island dwarf that, over time, became subject to unusual allometric constraints, an alternative hypothesis is that H. erectus and H. floresiensis may have shared a common ancestor that was an unknown small-bodied and small-brained hominin.’

Homo habilis. Courtesy of Creative Commons. Photographer unknown.

I think an increasing weight of evidence strongly suggests that the first major exodus of our genus from Africa was carried out by H. habilis or one or more of her sisters. Furthermore, I think it’s possible that these closely related species then gave rise to H. erectus, H. pekinensis, H. luzonensis[iv] and H. floresiensis in Eurasia, while those remaining in Africa gave rise to H. ergaster. This does not preclude the possibility, or perhaps probability, of any or all of these species crossbreeding if they ran across each other.

But what of H. sapiens, our own species? As with H. ergaster and H. erectus, the evidence here is convoluted, confusing and often contradictory.

Mongrel

For those, like Colin Groves, who think H. ergaster is a species in its own right, the line of descent works something like the following.

Homo heidelbergensis. Courtesy of Creative Commons. This image created by ATOR.

About 600,000 years ago, H. ergaster, either directly or through an intermediary species called H. rhodesiensis, gave rise to H. heidelbergensis. This species was our size physically, and his brain capacity was well inside the standards of Anatomically Modern Humans (AMH). Following the great tradition of hominin migration, something that seems as ingrained in our genus as bipedalism, some members of this new species moved to Europe[v]. About 400,000 years ago, they gave rise to H. neanderthalensis. In a case of ‘well, we’ll show you’, those who stayed behind in Africa gave rise to H. sapiens at least 300,000 years ago, and possibly as long as 350,000 years ago.[vi]

I can’t stress this enough. Homo sapiens are Africans. It is where our archaic ancestors and AMH first appear[vii]. (Let me also stress that this story, as complicated as it gets from now on, does not resurrect the Multiregional Model for our evolution, where H. erectus gave rise to H. sapiens across its whole range at the same time, from Africa to Asia. This is an old theory, now largely discredited by the extensive fossil and DNA evidence that our species first evolved in Africa.[viii])

What happened next has been slowly and painstakingly uncovered by palaeoanthropologists doing field work throughout Africa and Eurasia, and by the outstanding work performed at the Max Planck Institute’s Department of Evolutionary Genetics, headed up by Svante Pääbo, into hominin DNA.[ix]

What the DNA evidence strongly suggests is that H. sapiens successfully left Africa between 70,000 and 100,000 years ago. (Although this wasn’t the first migration into Eurasia by our species. It is usually held that previous attempts left no trace in the DNA of AMH outside of Africa, but see these earlier posts, here and here.)

Female Homo neanderthalensis. Courtesy of PLOS ONE.

Members of the most recent migration interbred with H. neanderthalensis, probably in what is now the Middle East, and later with the Denisovans, another possible descendant of H. heidelbergensis, deeper in Eurasia[x]. To this day, the average ex-African H. sapiens carries between 1%-2% of the Neanderthal genome; but it is not the same one or two percent: we overlap. Overall, we carry up to 40% of the Neanderthal genome in our own genes. But the story gets more complex still: the genome of people from Oceania, such as Papuan New Guineans and Australian Aborigines, can have between 5-6% Denisovan DNA[xi]; indeed, recent research suggests that Ayta Magbukon Negritos in the Philippines have Denisovan ancestry 30-40% higher than either of these two groups.

The Natural History Museum of London’s Professor Chris Stringer says, ‘It is now clear there was a lot more interbreeding between ancient species, including early Homo sapiens and others, and that there was a lot more movement of populations both in the distant past – and relatively recently.’[xii]

Homo sapiens (Oase 2) reconstructed from bones 37,000-42,000 years old discovered in the cave of Peştera cu Oase in Romania. Around 7.3% of his DNA is from H. neanderthalensis, from an ancestor 4-6 generations back. Courtesy of Creative Commons. Photo: Daniela Hitzemann.

Talking about recent research, in June last year Chinese scientists announced that a cranium first discovered in China almost a century ago, is a new species of Homo with a brain easily the equal of any AMH in size and carried inside a skull more massive than ours. Those making the announcement have named the new species H. longi (‘Dragon man’, and just as Denisovans are sometimes described as a sister species to Neanderthal, so H. longi is being claimed as a sister species to H. sapiens[xiii]).

As Lee Berger, from the University of Witwatersrand and the discoverer of Australopithecus sediba and H. naledi, has suggested, perhaps the different paths of human evolution are not best thought of as branches spreading from a single tree trunk, or even a messy, many-twigged bush, but rather a braided stream[xiv] with tributaries constantly running across each other before separating, rejoining and separating once more.

The Waimakariri River in New Zealand is braided along almost its entire length. A good metaphor for hominin interbreeding? Courtesy of Creative Commons. Photo: Greg O’Beirne.

We, Anatomically Modern Humans, are the result of all this evolution. We are nothing more than a mongrel species.

What a splendid, exhilarating thought.

Other posts in this series can be found here:

‘Us’ Part 1 – Out of Africa

‘Us’ Part 2 – Burdalone

‘Us’ Part 3 – The devil in the detail

‘Us’ Part 4 – Using your noggin

‘Us’ Part 5 – Feet and socks


[i] https://www.sciencedirect.com/science/article/abs/pii/S0047248417300866

And this from the Australian Museum: ‘Most scientists that accept H. floresiensis as a legitimate species now think its ancestor may have come from an early African dispersal by a primitive Homo species similar in appearance to H. habilis or the Dmanisi hominins. This means that it shared a common ancestor with Asian H. erectus but was not descended from it. Cladistic analysis supports the lack of a close relationship with H. erectus.

[ii] https://onlinelibrary.wiley.com/doi/abs/10.1002/evan.21863

[iii] Falk, Dean, et al. ‘The Brain of LB1, Homo floresiensis’. Science, 308, 242 (2005).

[iv] https://www.nature.com/articles/s41586-019-1067-9

[v] The first H. heidelbergensis fossils were found near Heidelberg in 1907.

[vi] Although this paper suggests the split between our two species might be found much further back … up to 800,000 kya or more!

[vii] Recent research from scientists at Australia’s Garvan Institute of Medical Research reveals that southern Africa is home to the oldest evidence for AMH: ‘… to contemporary populations that represent the earliest branch of human genetic phylogeny.’ The date they arrive at is 200,000 years ago.

As well, a report in the February issue of Science describes how thousands of genome sequences were collected from modern and ancient humans to create a family tree. In the words of the report’s first author, Anthony Wilder Wohns, ‘ … we definitely see overwhelming evidence of the Out-of-Africa event … ‘

[viii] See Stringer, C. & Andrews, P. The Complete World of Human Evolution. London, 2011. P 140 ff for a discussion of the two main theories for the evolution of Home sapiens: ‘Multiregional’ and ‘Out of Africa’.

[ix] And now, besides DNA, they are using protein analysis to identify ancient hominins, most recently the first Denisovan found outside of the Denisova Cave in Siberia … on the Tibetan Plateau of all places! See https://www.nature.com/articles/s41586-019-1139-x, 16 May 2019.

[x] Very recently, H. sapiens remains were discovered in the Grotte Mandrin rock shelter in the Rhône Valley in France that date back 54,000 years ago, pushing back our species arrival in Europe by at leat 10,000 years from previous estimates.

[xi] Please watch this fascinating talk Svante Pääbo gave at the University of California in 2018 after receiving the Nierenberg Award for Science in the Public Interest. It goes into all of this in much more detail. As Pääbo points out in the talk, the DNA evidence indicates humans ‘have always mixed’.

[xii] https://www.theguardian.com/science/2017/nov/19/human-evolution-dna-revolution-mapping-genome

[xiii] See here and here.

[xiv] See Berger talk about this towards the end of this Nova documentary, the Dawn of Humanity.

04 March 2022: ‘Us’ Part 5 – Feet and socks

One foot in front of the other

Humans walk upright, gorillas and chimpanzees walk on all fours, resting their weight on their knuckles, and orangutans can do just about anything – they hang and swing by their arms from branches, sometimes with the help of their oddly-shaped feet, and on the ground they can walk either upright or on all fours.  The structure of the postcranial skeleton in all four animals is very different and reflects these locomotor patterns.  Non-human great apes have short legs and long arms, whereas we have very long legs. With the gorilla and chimpanzee it is the shortness of the legs that differs from humans, the arms being much more similar in length compared to the torso; only the orangutan has enormously lengthened arms.  When other great apes stand upright, their legs are straight from hip to ground, whereas humans are ‘knock-kneed’, as the thighs slope inward from the hip to the knee.  The pelvis is very different in appearance: in humans the hip bone (ilium) is low and very broad, but in great apes it is high and fairly narrow. In humans the great toe is long and stout and aligned with the other toes, but in great apes it is divergent from the other toes (less in the gorilla), and in the orangutan it is very short.

Courtesy of Creative Commons. Artist unknown.

In most great apes, the spinal column is more or less straight, but in humans the spine is curved into a double-S: the cervical (neck) vertebrae curve forward, the thoracic (chest) vertebrae curve backward, the lumbar vertebrae (those in the small of the back) curve forward again, the sacral vertebrae (which are fused together, and form the back wall of the pelvis) curve back again, and the coccyx (the partially fused vertebrae which are the tiny remnant of the tail) curves forward once more.  The ribs (which are very variable in number, but average 12 in humans and orangutans, and 13 in chimpanzees and gorillas) together form the thorax; in humans the thorax is barrel-shaped (narrow at the top, broad in the middle, narrower again at the bottom), whereas in great apes it is funnel-shaped (narrow at the top, and broadening towards the bottom).

All of these differences between humans and the other great apes are developments stemming from bipedalism. So why did humans adopt bipedalism? Well, walk with me and we’ll take a brief look at the major theories.

Doing a runner

There seems to be a growing consensus among many scientists that our ancestors evolved bipedalism for several reasons rather than one overriding factor. What many of the competing theories do agree on, however, is that rainforest giving way to savannah because of climate change around 7.0 – 5.0 mya was a strong influence. Grassland with only scattered trees and no closed canopy meant tree-climbing primates had much more open territory to cover. Walking on two legs freed hands to carry infants, food or tools, including weapons. Walking on two legs made us taller, meaning we could locate food, potential predators and safe havens from further away; it also made it easier to pick low-hanging ripe fruit from trees. Walking reduced the amount of body surface area we exposed to the sun while in the open.

Early morning on the savannah. The change in the landscape from rainforest to savannah between 7 mya to 5 mya probably helped kickstart bipedalism in hominins. Photo: Simon Brown.

Of course, in some circumstances some of these ‘advantages’ could become disadvantages. For example, although bipedalism meant we could locate a predator from further away, it also meant if it was looking in the right direction, a predator could see us from further away as well (and our chief predators – leopards, hyenas and lions – all have good eyesight, not to mention excellent hearing and sense of smell). On the other hand, when our ancestors became active hunters, our extra height gave us an advantage over prey animals, many of whom rely on their sense of smell rather than their eyesight.

Our genus has evolved to become a natural endurance runner, and through that a natural persistence hunter. Courtesy of Creative Commons. Photographer unknown.

More recently, one of the major arguments for the successful adaptation of bipedalism was that it is a much more energy efficient method of locomotion[i]. Whatever the arguments for or against all these hypotheses regarding the origins of walking, when it came to running there is no denying our bodies evolved to make us one of nature’s supreme endurance runners[ii]. This seems to have happened about two million years ago and was a real game-changer when it came to predating: our ancestors evolved into persistence hunters, able to wear down much larger animals such as kudu and oryx[iii]. Basically, humans ran their prey into the ground, and much of our body shape is particularly adapted to long-distance running.

In other words, the characteristics that make us superb walkers and runners are the characteristics that most set us apart from other great apes. As Chris Stringer and Peter Andrews write in The Complete World of Human Evolution, ‘at present … (bipedalism) is taken as the earliest adaptation by which we can recognise human ancestors in the fossil record.’[iv]

The odd-sock drawer

Now it’s time to deal with one of the most controversial species in the human lineage – Homo ergaster. This species was described by Colin Groves and Vratislav Mazák in 1975[v]. Since then, palaeoanthropologists are divided on whether H. ergaster is a distinct species, or a subspecies belonging to H. erectus, palaeoanthropology’s pin-up boy and all-purpose species.

Once they learned to walk, our ancestors just kept on walking. In fact, they walked right out of Africa, into the Middle East, then east into Asia and Sahul, north to Europe, and eventually across the Bering Strait and into the Americas. On the way they continued evolving into new species that seemed to interbreed with each other at every opportunity, creating yet more new species, and eventually discovering agriculture, television and the internet. And interestingly, it’s the use of technology that provides us one piece of evidence that H. ergaster and H. erectus were two different species.

But first, let’s talk more about bones, specifically those belonging to the original H. erectus, parts of which were first discovered 1891 by Eugène Dubois, a Dutch doctor working for the army in Java. In fact, he went to Java with the objective of discovering evidence supporting the theory that H. sapiens evolved in Asia, an idea most determinedly supported by German naturalist Ernst Haeckel. Haeckel had hypothesised that our species’ progenitor, which he names Pithecanthropus alalus, had evolved on Lemuria, a mythical continent that subsequently sunk beneath the Indian Ocean (thereby conveniently leaving no fossils behind to prove – or for that matter, disprove – his theory).

Eugène Dubois, discover of Homo erectus. Courtesy of Creative Commons. Photographer unknown.

Although Dubois had discovered ancient hominin fossils, he found little or no support among scientists in Europe that they amounted to anything significant. It wasn’t until Sinanthropus pekinensis was discovered in China over a quarter-century later that enthusiasm for Dubois’s discovery really picked up. In the early 1950s, Ernst Mayer reclassified both P. alalus and S. pekinensis as H. erectus[vi]. Since then, hominin fossils with roughly the same estimated brain size as H. erectus and aged between 2 million years old to just over 100,000 years old have been thrown in with H. erectus like differently coloured socks thrown into an odd-sock draw. It has become the species to have when you want to cover all of Africa and Eurasia and two million years of history.

In the early 1970s, for example, Richard Leakey and Alan Walker described two partial skulls found in Kenya as belonging to an African offshoot of H. erectus based on the fact that their calculated brain capacities (848 cc and 803 cc) were not dramatically smaller than that of some H. erectus skulls (around 950 cc), which is like arguing that since the Volvo S60 and the Volkswagen Passat have similar interior space, they’re both examples of a Toyota Camry.

However, in 1975, Colin Groves and Czech colleague Vratislav Mazák, after a comprehensive metric analysis of fossils from Koobi Fora, discovered they had uncovered a new species they names H. ergaster. Their argument was that there was no African version of H. erectus; further, Colin Groves believed that H. ergaster evolved in Africa and then migrated into Eurasia, eventually giving rise to H. erectus.[vii] The earliest dates for the new species goes back 1.9 million years[viii], as opposed to 1.6 million years (or 1.8 according to some estimates) for H. erectus, making H. ergaster the first truly human-looking hominin to stride the planet – tall, thin, decidedly bipedal, with a flatter face than its ancestors and an active hunter, fire-user and tool-maker.

KNMER 3733, possible cranium of a female Homo ergaster. Photo: Simon Brown.

Now, nearly fifty years after the initial paper by Groves and Mazák, a fierce debate still continues between those who think the two hominins are separate if linked species, or just subspecies. In common parlance, it’s a debate between splitters and lumpers.[ix]

But besides the obvious difference in the skull shapes of H. ergaster and H. erectus, another line of evidence convinces me that Colin was right in his opinion that we are talking about two species. This evidence involves tool making.

Out with the old, in with the new

Until the appearance of H. sapiens and H. neanderthalensis, stone age technology is divided into two broad and overlapping stages: Oldowan and Acheulean (sometimes called Modes 1 and 2). Oldowan technology was first discovered in the 1930s by Louis Leakey at the Olduvai Gorge in Tanzania. The oldest examples have been found at Gona in Ethiopia, and date back about 2.5 million years[x]. The technology seems to have spread very quickly, and recent discoveries have found stone tools in Jordan dated at 2.5 mya and China at 2.1 mya[xi]. This technology, the use of very simple flakes and rocks, had been developed before the appearance of H. habilis, possibly by Australopithecus garhi. Acheulean technology which started about 1.76 mya, is closely associated with the appearance of H. ergaster and involves more refined knapping and the development of specialised tools such as hand axes.

This doesn’t imply that Oldowan technology suddenly evaporated, and every hominin adopted the new style of knapping chert. In some places, Oldowan and Acheulean stone tools are found at the same site from the same period, suggesting that while H. ergaster or one of its descendants employed the improved technology, one of our cousins continued using the older method.  But it’s clear Acheulean technology obviously conferred a significant advantage over the old style. It didn’t take long for it to spread beyond Africa, either because H. ergaster itself started spreading beyond Africa, or because it spread by ‘word-of-mouth’: neighbouring hominis picked up on the new fashion of making tools and copied it. Acheulean tools appear in what is now India, for example, by 1.5 mya, and in Europe by about 900 kya.

Acheulean hand axes. Compare the careful knapping done here to the more primitive Oldowan tools illustrated in the previous post. Courtesy of Creative Commons. Photographer unknown.

However, Acheulean technology did not seem to reach Java, where our friend H. erectus resided.

Which presents lumpers with a problem. If H. ergaster is indeed nothing more than a subspecies of H. erectus, then fossil evidence suggests this single species arose in Africa before spreading throughout Eurasia. Yet if this is also the species that developed Acheulean technology soon after evolving, why didn’t the technology travel with them to the far east?

On the other hand, if we are talking about two species, then it’s quite possible for Acheulean technology to be developed by H. ergaster in Africa, spread slowly throughout Eurasia, but never quite reach the home of H. erectus in Java.

If this was in fact the case, it raises a more important question: even if we accept H. ergaster is a separate and earlier species than H. erectus. Does it necessarily follow that H. ergaster gave rise to H. erectus? What if the two species are cousins rather than mother and daughter?

This is something we’ll discuss in the next, and final, post of ‘Us’.

Other posts in this series can be found here:

‘Us’ Part 1 – Out of Africa

‘Us’ Part 2 – Burdalone

‘Us’ Part 3 – The devil in the detail

‘Us’ Part 4 – Using your noggin

‘Us’ Part 6 – Kith and kin


[i] https://www.newscientist.com/article/dn12269-walking-on-two-feet-was-an-energy-saving-step/

But then again, see https://www.sciencedirect.com/science/article/abs/pii/S0047248412001443

[ii] https://www.nature.com/articles/nature03052

[iii] https://en.wikipedia.org/wiki/Persistence_hunting

[iv] Stringer, C. & Andrews, P. The Complete World of Human Evolution. London, 2011. P 19.

[v] https://www.irmng.org/aphia.php?p=taxdetails&id=10031853

[vi] According to Britannica, Mayr did this in 1944. But see Bernard Wood who writes it was Franz Weidenreich who first came up with the idea in 1940:

‘(He) was the first to suggest that the genus Pithecanthropus should be subsumed into Homo, and in the same paper he proposed that fossils recovered from what was then called Choukoutien (now called Zhoukoudian), which were initially assigned to Sinanthropus pekinensis,26 should also be transferred to Herectus.’

[vii] From the Australian Museum:

‘A growing number of scientists have redefined the species Homo erectus so that it now contains only east Asian fossils. Many of the older African fossils formerly known as Homo erectus have now been placed into a separate species, Homo ergaster and this species is considered to be ancestral to Homo erectus. The redefined Homo erectus is now generally believed to be a side branch on our family tree whereas Homo ergaster is now viewed as one of our direct ancestors. ‘

[viii] Oldest fossil dates according to the Australian Museum for H. ergaster here and for H. erectus here. Recent work reported in the journal Science may push the dates even further back, between 1.95-2.04 mya (although in this paper the discussed specimen is describe as preserving ‘characters that align it morphologically with H. erectus sensu lato (including Homo ergaster)’. Go figure.

[ix] For a fuller description of the often heated debate about what makes a species, see here.

[x] Stringer, C. & Andrews, P. The Complete World of Human Evolution. London, 2011. P 208.

A new kind of stone age technology – Lomekwian – has been suggested after the recent discovery of stone tools at Lomekwi that predates Oldowan by more than 700,000 years. See the previous post for more details.

[xi] https://onlinelibrary.wiley.com/doi/abs/10.1002/evan.21863

28 February 2022: ‘Us’ Part 4 – Using your noggin

It’s not how big it is, but what you do with it

Forgive the pun, but for decades it seemed a no-brainer that the chief qualification to be considered human was the size of your brain. Obviously, it had to be a of a certain respectable capacity, never quite defined, but a degree or two larger than a chimpanzee’s organ was a good start. There was some embarrassment when it was determined that the average brain capacity of Homo neanderthalensis was larger than our own[i], but that misgiving aside it was assumed that if not a directly comparative intelligence was a prerequisite, then certainly something within shooting distance.

One mistaken assumption here is between brain size and intelligence, something made very clear in recent years by the discovery of the stone tool-making H. floresiensis (with a brain the size of a chimpanzee). Recent work done on corvids, for example, suggests that ravens and crows possess a Theory of Mind[ii] – the capacity to imagine that another crow might have its own thoughts – which in turn suggested a reasonably developed sense of self-awareness, an emergent property traditionally associated with intelligence[iii].

Homo heidelbergensis had a brain around 1200 cc, well within the range of H. sapiens. Photo: Simon Brown.

Another mistaken assumption is that our larger brain size is extraordinary among our cousins, but average brain size has not increased dramatically in total capacity since H. heidelbergensis, a species that first saw light of day 600,000 years ago.[iv]

Indeed, Homo species sit comfortably on the line that matches a generic primate’s brain size to its body size. In other words, if you’re a primate, the bigger you are the bigger your brain gets. (This isn’t peculiar to primates, of course, and applies to many mammalian groups, eg rodents, elephants and aardvarks, but primates do have larger brains than mammals of similar body mass).[v]

Interestingly, there are three exceptions to this general rule, all three of which are closer to us genetically than any other primates: the orangutan, the chimpanzee and the gorilla. The orangutan falls just below the curve, the chimpanzee falls a little further, and the gorilla furthest of all. Extensive studies with chimpanzees and gorillas, however, show that both species are intelligent and self-aware enough to have developed a Theory of Mind.

Demonstrably, brain size is not irretrievably married to a set physical size, just as brain size is not irretrievably married to a set level of intelligence.

I know that you know that I know …

It does seem self-awareness, or sentience, is an emergent property of intelligence.[vi] In other words, as an animal increases in intelligence, at some point it will become aware of its own existence. This is more than simply being able to experience pleasure or pain, but the ability to experience life subjectively.

Objects found with the remains of H. floresiensis strongly suggests they made stone-age level weapons and tools.[vii] Obviously, such complex toolmaking suggests an active intelligence capable of learning new skills and – as importantly – passing those skills on to the next generation. This in turn suggests H. floresiensis possessed a language; if not a spoken language such as ours, with a huge vocabulary and complex rules of grammar, then at least some way to transmit a limited amount of information effectively and efficiently.

Evidence also exists that H. floresiensis hunted and scavenged animals such as the dwarf stegodon, a kind of elephant. To be clear, a dwarf elephant could still grow to more than two metres in height. For something the size of H. floresiensis to hunt stegodon strongly suggests they hunted in groups, which in turn strongly suggests their language was something more than a series of grunts.

With H. naledi, we are on somewhat less firm ground. Although they were larger-brained hominins than H. floresiensis, the remains of at least 15 individuals from the Rising Star Cave in South Africa were discovered without any tools or evidence of tool making. However, the species possessed a hand not dissimilar to our own, and would probably have been capable of tool-making. It is hard to imagine a hominin species living in Africa in this period, between 236,000 and 335,000 years ago, and not picking up the skill from one of the other hominin species occupying southern Africa at the same time (including, quite possibly, our own).

The Rising Star Cave in South Africa, where the fossils of several Homo naledi were discovered in the Dinaledi Chamber. H. naledi almost certainly would have needed fire – and a great deal of determination – to find their way to the chamber from its entrance. Courtesy of Creative Commons.

Furthermore, palaeoanthropologist Lee Berger, who led the expedition to recover the H. naledi remains from the Rising Star Cave, believes bodies were intentionally and repeatedly deposited there. This implies two things: first, ritual behaviour on the part of the species, and second, that they were capable of making fire, since the chamber the bones were discovered in is at the end of a long, dark, dangerous and narrow route.[viii]

I may not know much about art, but …

In his influential work on human development, The Ascent of Man, Jacob Bronowski wrote, ‘Man is not the most majestic of creatures. Long before the mammals even, the dinosaurs were far more splendid. But he has what no other animal possesses, a jig-saw of faculties which alone, over three thousand million years of life, make him creative. Every animal leaves traces of what it was; man alone leaves traces of what he created.’[ix]

Whether or not Bronowski used the term man to mean, specifically, H. sapiens, or more broadly to mean humans in general, we know that our cousins left behind more than traces of what they created. We have hundreds of stone tools, the tailings and debris of stone-tool manufacturing, and even examples of art.

I would suggest this equates to culture.

But what if there are no physical signs of culture, does it mean culture does not exist? It is often fallacious to argue that absence of evidence is not evidence of absence, but in cultural endeavours such as language or dance, there can be no evidence before the invention of writing and art.

Vervet on the lookout for predators. Photo: Simon Brown.

Simple language can be identified in many primates. Vervet monkeys, for example, have distinct calls for each of their four main predators: pythons, baboons, leopards and eagles. But we will probably never know which human species was the first to communicate with what we would describe as a complex language, one capable of conveying abstract thought. Vervet monkeys may be able to tell their fellows that a leopard is approaching, but they cannot say the leopard is hiding behind that bush or over that hill, let alone discuss the rights and wrongs of predation.

We see culture operating among our more social hominid cousins, the chimps and gorillas. Long-term field studies suggest, for example, that cultural variation exists among different chimpanzee groups, including differences in grooming, courtship and tool usage.[x] It is the ‘combined repertoire’ of chimp behaviours that is significant, demonstrating a range of cultural behaviours, a diversity that once was attributed only to our own species.

It is with the application and development of tool usage that the first signs of a distinct ‘human’ culture are found in palaeoanthropology. Whereas chimps and some bird species, like humans, use tools made from plants to gather food or built shelter, humans are the first animals to make stone tools, improving on the original material through knapping. Later, humans combined stone with other material, such as wooden handles, to improve their effectiveness; in other words using tools to make better tools. Indeed, the making of stone tools was once considered the boundary marker between members of Homo and earlier genera. Since then, the boundary for stone-tool making has been pushed well beyond those species traditionally grouped under our own genus.

Oldowan stone age tools. Courtesy of Wikimedia Commons. Photographer: Didier Descouens.

The oldest crafted stone tools found so far are from Lomekwi in Kenya, dating back 3.3 mya[xi]. First discovered in 2011, they were probably made by a species belonging to either the Australopithecus or the Kenyanthropus genera. The tools were found in an area where Kenyanthropus platyops fossils had been found earlier.

But we have to wait more than 700,000 years before there is clear evidence of stone-tool making on a large scale, something we’ll cover in detail in a later post.

Eventually some hominins were not simply making stone tools: ‘The people who made the hand axes clearly had a specific shape in mind, and often went far beyond a purely utilitarian form in the care with which they produced them.’[xii] This is an example of humans crafting tools for aesthetic appeal, not just knapping to produce a sharp edge or a convenient grip.

Earliest example of art was created by Homo erectus 500,000 years ago. Courtesy of Creative Commons. Photographer unknown.

It is with H. erectus we find the first real example of an attempt at making what we would now call ‘art’. In 2014, scientists from Netherland’s Leiden University announced the discovery of a sea shell that had been engraved with a zigzag pattern 500,000 years ago, something identified by ANU scientist Dr Stephen Munro (who did his PhD under Colin Groves!). The shell was originally collected with others at the end of the 19th century by Eugène Dubois – the discoverer of H. erectus in Java – but had not been closely examined since the 1930s. The scientists demonstrated that not only was the engraving not the result of natural forces, but that the pattern was made by ‘a strong and skillful tool-maker’[xiii]. The new date pushed back the first evidence for art by 400,000 years.

With language we’re on much shakier ground. Research suggests the physiological requirements for language exist in at least some monkeys. The stumbling block seems to arise in the way the brain is wired[xiv].

Nonetheless, as noted above with vervet monkeys, a language with a basic vocabulary exists among many primate species. It has even been shown that different species of monkey may understand some of each other’s vocabulary[xv]. Some species have even developed a basic grammar[xvi].

Extensive work has been done on language among the great apes, both in the wild and under controlled conditions. For example, the remarkable success scientists have had teaching American Sign Language to Washoe, a chimpanzee, and Koko, a lowland gorilla, demonstrate their capacity to learn quite complex vocabulary, often using it to express emotions such as sadness.

Koko, a western lowland gorilla, with her pet cat All Ball. Courtesy of Creative Commons. Photographer unknown.

But even the most optimistic view of these experiments shows that non-human great apes never demonstrate a level of intelligence found in a three-year old human child. No chimpanzee or gorilla, for example, has ever used their acquired vocabulary to ask a question.[xvii]

There is genetic evidence to suggest that the development of the capacity for language accelerated in humans after we split from the chimpanzees some seven to eight million years ago[xviii], but precisely when humans started speaking in a way that we would describe as ‘human’ is unknown; it may never be known. As with so many things in evolution, the development of a complex language capable of expressing abstract thoughts almost certainly occurred along a spectrum.

Between them, language and craft handed humans a huge advantage in the evolutionary stakes. Making stone tools, for example, minimised our weaknesses, knives and hammers allowing us to make up for a lack of sharp claws and fangs. Later, bows and throwing spears made up for our lack of speed in the chase.

Language allowed us to magnify our strengths, especially the ability to learn new things and pass that learning on to succeeding generations.

Language, and culture generally, seems to be something we share with other members of our genus, and indeed, as they are presently classified, earlier genera.

In the next post we’ll talk about bipedalism and one of the most controversial of hominin species – H. ergaster.

Other posts in this series can be found here:

‘Us’ Part 1 – Out of Africa

‘Us’ Part 2 – Burdalone

‘Us’ Part 3 – The devil in the detail

‘Us’ Part 5 – Feet and socks

‘Us’ Part 6 – Kith and kin


[i] Specifically, larger on average than the modern human brain, although the brains of archaic H. sapiens were in fact comparable to H. neanderthalensis. The following excerpt is from here.

‘To measure fossil brain volume, anthropologists have traditionally filled skulls with beads or seeds, and dumped the contents into a graduated cylinder (a precise measuring cup). They’ve also submerged molds of skulls into water, measuring the volume displaced. Today CT (computed tomography) scanning methods offer more accurate (and less-messy) measurements, but much of the data in textbooks and other references was collected the old fashioned way.

‘Based on these values, we can confidently say fossil Neanderthals and modern humans from the same time period had similar brain sizes. Twenty-three Neanderthal skulls, dating between 40,000 and 130,000 years ago, had endocranial volumes between 1172 to 1740 cm3. A sample of 60 Stone Age Homo sapiens ranged from 1090 to 1775 cm3.’

[ii] https://www.nature.com/articles/ncomms10506

[iii] And there is now evidence that some birds, eg the Australian magpie, can demonstrate altruism. See here.

[iv] Modern H. sapiens have brains ranging between 1030cc-1620cc; judging from what fossil skulls we have, the H. heidelbergensis brain averaged around 1250cc. See https://australian.museum/learn/science/human-evolution/homo-heidelbergensis/

[v] For a great explanation of how all this works, check out The Human Advantage by Suzana Herculano-Houzel. It’s a great read! See https://mitpress.mit.edu/books/human-advantage

[vi] For example, see https://www.frontiersin.org/articles/10.3389/fnins.2020.548071/full and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7304239/

[vii] http://www.nature.com/nature/journal/v532/n7599/full/nature17179.html

[viii] https://elifesciences.org/articles/24234

[ix] Bronowski, J. The Ascent of Man, London, 1976 (BBC Edition), p 42

[x] https://www.nature.com/articles/21415

[xi] https://www.nature.com/articles/nature14464

[xii] Stringer, C. & Andrews, P. The Complete World of Human Evolution. London, 2011. P 209.

[xiii] http://www.news.leiden.edu/news-2014/the-story-behind-the-discovery-that-turned-archaeology-on-its-head.html

[xiv] http://www.sciencemag.org/news/2016/12/why-monkeys-can-t-talk-and-what-they-would-sound-if-they-could

[xv] http://rspb.royalsocietypublishing.org/content/282/1807/20150265

[xvi] http://www.pbs.org/wnet/nature/clever-monkeys-monkeys-and-language/3948/

[xvii] Some scientists argue that Koko’s language skills were a result of ‘operant conditioning’, whereas others state she was indeed capable of simple questions. See Wikipedia entry here for more information and references.

[xviii] https://www.nature.com/articles/nature01025

24 February 2022: ‘Us’ Part 3 – The devil in the detail

Species are what, exactly?

Most of us did some biology at school, and most of us came out with the idea that species are groups of populations that cannot interbreed. When we’re reminded of mules, which are the offspring of horses and donkeys, we think ‘Ah, but they are sterile, aren’t they?’ Almost invariably, although there have been a few cases of fertile mules, but when cattle and bison interbreed, while the male offspring are sterile, the female offspring are fertile. All the big cats can also mate with each other, producing hybrids (where the female is fertile), and in the case of the leopon, the hybrid between a leopard and a lion, even the male might be fertile.

A tigon: hybrid from tiger father and lion mother. Because it’s a male, it would be infertile. Courtesy of Creative Commons. Photographer unknown.

Now that we can trace the ancestries not only of individual people, but whole populations and whole species, through DNA, it turns out that there has been a whole lot of successful – that is, fertile – interspecies breeding in the past. And it sometimes turns out that different species even today may interbreed with their neighbours on the quiet. For example, the primatologist Kate Detwiler discovered that two species of small monkeys in Tanzania’s Gombe National Park, the red-tailed monkey (Cercopithecus ascanius) and the blue monkey (Cercopithecus mitis), are found living in separate troops in some of the forested valleys, but in other valleys interbreed – in fact, in one or two valleys the monkey population consists entirely of hybrids.[i]

The idea that different species don’t interbreed is simply not true. They may not do so usually – but that is another thing entirely. We cannot use non-interbreeding as a criterion for species.

How then, can we define species?

George Gaylord Simpson. Courtesy of Creative Commons. Photographer unknown.

For over 150 years now, the basic guiding principle of biology has been evolution – so the question we should be asking is what is the evolutionary status of species? The palaeontologist George Gaylord Simpson (1902-1984) suggested in 1961 that the essence of species is that they are evolutionary lineages. He got little reaction at the time because his colleagues largely were hung up on the non-interbreeding criterion, but from the late 1990s his insight has been more and more appreciated. The best way to recognise an evolutionary lineage is, quite simply, that it differs from other evolutionary lineages. Horses and donkeys differ consistently and therefore represent two separate evolutionary lineages, and are therefore two different species. Similarly, blue monkeys and red-tailed monkeys differ consistently and therefore constitute separate evolutionary lineages, and again represent two different species.

Stumptailed macaque. Courtesy of Creative Commons. Photographer unknown.

            If there are whole populations which consist of hybrids between two species, then what? Sometimes hybrid populations remain isolated for a good length of time and become homogeneous – and a new species is born. At least one species of monkey, the stumptailed macaque (Macaca arctoides) of mainland Southeast Asia, is thought to have arisen about 1 million years ago from a hybrid population between two other species.[ii]

For a more detailed discussion about the arguments about how to define species, especially the contest between the Biological Species Concept and the Phylogenetic Species Concept, go here.

So … generally speaking, what are genera?

So what about genera, families and other taxa?

While the taxa at both ends of the ranking are pretty straight forward – ‘species’ is eminently useful, and ‘domain’ and ‘kingdom’ are irresistibly sensible – all the ranks in between can get awfully confusing. And they are actually rather arbitrary. When, for example, do we know that a group of organisms constitute a genus rather than a family?[iii]

One simple solution would be to organise those in-between ranks chronologically. In other words, the order Primates would include all those monkey, ape and human-like species which existed from the Palaeocene epoch, and the family Bovidae would include all those antelope, buffalo and cattle, and sheep and goat species which existed from the early Miocene epoch.

This is an idea first forcefully proposed by German biologist Willi Hennig (1913-1976), considered the founder of cladistics – or ‘phylogenetic systematics’ if your thesaurus is turned on.

Willi Hennig. Courtesy of Creative Commons. Photographer unknown.

In 1966, Hennig proposed linking the taxonomic rank of a clade to its time of origin. He argued that if taxa are to mean anything they must represent monophyla – that everything in that group must be descended from a common ancestor. He also argued that taxa had to be characterised chronologically.

Hennig was an entomologist and realised while many genera of insects separated from one another tens of millions of years ago, the genera of mammals and the genera of birds separated more recently.

The idea was taken up by American scientist Morris Goodman (1925-2010), one of the founders of molecular genetics. He set about constructing a consistent scheme for the group of mammals about which he was most familiar – the primates. In 1997, he suggested that a reasonable time depth for a primate genus would be seven million years, partly because this would do the least violence to the presently accepted system of determining genera.

This is where Colin Groves enters the story.[iv]

Colin surveyed many of the mammalian genera that taxonomists had recognised and found that most had separated from each other less than seven million years ago. Subsequently, he proposed that five million years was a more appropriate time depth for mammalian genera: the Miocene-Pliocene boundary.

Furthermore, Colin suggested that the taxonomic rank of ‘family’ had a time depth of 24 million years, separate families splitting around the time of the Oligocene-Miocene boundary. Going up one more ranking, the different ‘orders’ separated around the time of the Cretaceous-Tertiary boundary (the famous K-T boundary that marks the arrival of the asteroid that wiped out non-avian dinosaurs[v]).

Colin Groves. Photo: Simon Brown.

One of the consequences of Goodman’s proposals for palaeoanthropology is that most if not all members of the human lineage would belong to a single genus. Indeed, using his original suggested time depth of seven million years, Goodman even included chimpanzees into Homo. Overall, the later modifications devised by Colin play less havoc with the established order, but they would still require that most human fossils be placed in the same genus as ourselves.

Arguments about when hominins evolved into a genus that can be described as wholly human traditionally revolved around the relative importance of different physical characteristics: brain size, dentition, general morphology (body size, especially the extent of sexual dimorphism), and primary form of locomotion.

Other more controversial factors sometimes taken into consideration include tool-making, art and other signs of culture, and evidence of community living.

For example, some experts such as Ian Tattersall, curator emeritus with New York’s American Museum of Natural History, argue that the cranium of Homo floresiensis (the Hobbit, see here, here and here) is too archaic for it to be included in our genus.

This leads us to our second, and more controversial opinion: following Colin’s plan our genus would include not only H. floresiensis but even older and more archaically featured species traditionally belonging to other genera, such as the Australopithecines, for example, which include the Taung Child and Mrs Ples.

Colin argued that the Miocene-Pliocene boundary more or less corresponds to the onset of the only characteristic definitely belonging solely to our genus and to no other genera among the great apes – bipedalism. By bipedalism we mean that the main form of locomotion is walking or running on two legs, with the big toe aligned with the other toes in the foot.[vi]

Accepting this argument has two major implications and several minor ones for palaeoanthropology. First, and least controversially, brain size is not by itself a qualification for membership of the human genus. Specifically, a small brain does not exclude membership.

Homo naledi. Courtesy of Creative Commons. Photographer unknown.

The discovery of H. floresiensis and H. naledi in the 21st century, with an average brain size of around 420 cm3 (about the size of a modern chimpanzee) and 500 cm3 respectively, clearly demonstrates that many humans were small brained compared to H. sapiens but possibly still capable of sophisticated tool-making and ritual behaviour.

Secondly, accepting a time criterion in determining what species do and do not belong to the genus Homo means that strictly morphological traits are no longer intrinsic in determining human status.

In the next post, we’ll look in more detail at brain size, culture and bipedalism as criteria for determining whether or not a species is human.

Other posts in this series can be found here:

‘Us’ Part 1 – Out of Africa

‘Us’ Part 2 – Burdalone

‘Us’ Part 4 – Using your noggin

‘Us’ Part 5 – Feet and socks

‘Us’ Part 6 – Kith and kin


[i] https://phys.org/news/2018-04-genetic-evidence-ongoing-distinct-species.html

[ii] https://pubmed.ncbi.nlm.nih.gov/29614345/

[iii] Sigwart, J., Sutton, M. D., & Bennett, K. (2017). ‘How big is a genus? Towards a nomothetic systematics’. Zoological Journal of the Linnean Societyhttps://doi.org/10.1093/zoolinnean/zlx059

[iv] Groves, Colin. ‘Time and taxonomy’. Ludus Vitalis. Vol IX. No 15. 2001.

& Groves, Colin. ‘Speciation in hominin evolution’. African Genesis: Perspectives on Hominin Evolution. Ed Reynolds, Sally & Gallagher, Andrew. Cambridge University Press. 2012.

& Groves, Colin. ‘Current taxonomy and diversity of crown ruminants above the species level’. Zitteliana B32, International Conference on Ruminant Phylogenetics, ed. Prof. Dr G Worheide, Bavarian State Collection for Paleontology and Geology, Munich.

[v] Now also sometimes referred to as the Cretaceous-Palaeogene (K-Pg) boundary.

[vi] For a more detailed explanation, see here.

18 February 2022: ‘Us’ Part 1 – Out of Africa

It’s us and us, not us and them

This and the following five posts will be about Us. Not Uncle Sam or Ultra Sound or Ultimate Spas. Not you and me. But all of Us. Every single human alive today and every single human who has existed in the past. And by every human I mean every member of the genus Homo, and every member of the genera Australopithecus, Kenyanthropus and Paranthropus, a lineage that stretches back nearly five million years in the past and is still going strong today.

I considered another title for this series of posts – ‘Mongrel’ – because Homo sapiens are mongrels. I don’t mean in the way an Australian might call you a ‘mongrel’ if you rear-end his ute or support a different footie team, but in the sense that we are animals of mixed breeding.

Colin Grove. Photo: Simon Brown

I want to write about the revelation made by palaeoanthropology over the last 25 or so years that Anatomically Modern Humans (AMH) have no single direct ancestor. The different species that gave rise to us bred with each other again and again, cross-pollinating over millions of years. We are, each and every one of us a mulatto, a crossbreed, a cafuzo, a zambo … in short, a mongrel. This is something for us to crow about. We are the beneficiaries of millions of years of striving, surviving and thriving by many other members of our hominin tribe. Having said that, recognising that we owe our existence to a plethora of species and not to one single predestined or divinely sanctioned line of descent, may also help us shed our belief in the exceptionalism of H. sapiens.

These posts are also a way for me to record a project I long dreamt of doing and eventually started some six years ago but can no longer complete, a book about hominin evolution I was writing with my friend, the late Colin Groves[i]. I cannot write that book without Colin –  his knowledge and experience were unique even in the rather rarefied circle of palaeoanthropology – but what I can do is finally record as faithfully as possible some of his ideas about hominin evolution.

To start with, I’d like you to meet a small child. A child named Taung.

Darwin was right

The child first came to attention in 1924 when it’s tiny skull was discovered by Raymond Dart in one of two boxes of tufa and sandstone debris he received as he was dressing to attend a wedding as best man.

Dart, an Australian doctor and anatomist, had only recently taken up the post of professor at the University of Witwatersrand in Johannesburg, and had spread the word he was interested in any fossils his students or acquaintances might uncover to help stock his fledgling laboratory. In this case, the debris was from a limestone quarry in Taung, a small mining town in South Africa’s Northwest Province.

When the boxes arrived he hurriedly inspected them. In the second box he saw something that changed his life and the history of palaeoanthropology.

In his own words, a thrill of excitement shot through him.

‘On the very top of the rock heap was what was undoubtedly an endocranial cast or mold of the interior of the skull. Had it been only the fossilised brain cast of any species of ape it would have ranked as a great discovery, for such a thing had never before been reported … a brain three times as large as that of a baboon and considerably bigger than that of an adult chimpanzee …

Cast of Taung child. Photo: Simon Brown

‘But was there anywhere among this pile of rocks, a face to fit the brain? I ransacked feverishly through the boxes. My search was rewarded, for I found a large stone with a depression into which the cast fitted perfectly … Here I was certain was one of the most significant finds ever made in the history of anthropology.

‘Darwin’s largely discredited theory that man’s early progenitors probably lived in Africa came back to me.’[ii]

Indeed, Dart’s discovery eventually switched the focus of palaeoanthropology’s search for the origin of our species from Eurasia to Africa, an origin Charles Darwin had predicted in The Descent of Man in 1871.

Using his wife’s knitting needles, it took Dart weeks to separate the Taung Child (Taung 1) from its breccia matrix. The paper[iii] he wrote about the discovery appeared in Nature in early 1925, and in that paper he named the specimen Australopithecus africanus, Africa’s southern ape.

Raymond Dart with the skull of the Taung child. Courtesy of Creative Commons. Photographer unknown.

At first, the scientific establishment reacted negatively to Dart’s hypothesis that the Taung Child represented an ancestor of modern humans. Heretofore it had been believed humans must have evolved in Europe or Asia, a belief reinforced with the discovery of H. neanderthalensis in 1829 (but not recognised as a different species from us until 1856) and H. erectus in Java in 1891 (a story we’ll come back to later in this series of posts).

Over the following decades, however, the number and diversity of fossils uncovered in southern and eastern Africa have overwhelmingly supported the ‘Out of Africa’ hypothesis for human origins.[iv]

The Taung Child itself was thought to be about three years old when it died. Not only was its life short, it ended violently. In 2006, the University of Witwatersrand’s Lee Berger wrote that marks in the Taung Child’s eye sockets and on its skull suggested it was probably killed by a large bird of prey.[v]

Even though it was the first described member of the genus, it turned out A. africanus was not its oldest member, and may not even have been one of our direct ancestors.

Meet the great-great-great-grandparents

At the risk of making a bad rhyme, exactly what does it mean to be an Australopithecine?

This is a matter of debate. Some scientists merge a chronologically older primate genus, Ardipithecus, with Australopithecus, to make the subtribe Australopithecina. Others leave out Ardipithecus, and include Paranthropus and Kenyanthropus with the Australopithecines. While they’re at it, some scientists consider Australopithecines to be a member of the human family, while others think the family starts much later – with the first species in the genus Homo.

It gets very confusing very fast, especially since every new discovery – and over the last 25 years there have been many of those – seems to generate a new species and subsequently a new debate of what it means to be human, hominin, or hominini (generally accepted to be humans plus chimpanzees). Or for that matter, what should be included in the genera Australopithecus, Homo, Paranthropus and so on and so forth.

For the sake of these posts, I’m assuming at this point that Australopithecines are fine and upstanding members of our human family. Great-great-great-grandparents (or cousins to the nth degree), in a manner of speaking. At a later point  I’ll be examining more deeply what makes a genus … but we’ll paddle that delta when we get to it.

Australopithecus anamensis: the first human? Courtesy of Creative Commons. Photographer unknown.

The oldest species belonging to this genus is A. anamensis[vi], kicking off just over four million years ago (mya). Other Australopithecines include A. garhi, A. afarensis (Lucy is probably the most famous example of this species, if not the most famous human fossil of all), A. bahrelghazali, A. deyiremeda, A. prometheus and A. sediba. A. sediba is the last known of the genus as well as the most recently discovered[vii], existing as recently as 1.8 mya, making it a contemporary of one of our ancestors, H. ergaster.

Over the two million plus years the genus existed, cranial capacity jumped from around the 360cc mark (slightly smaller than the average for a chimpanzee) to nearly 440cc, an increase of over 20%.

The Australopithecines are generally thought to have given rise to our genus around 2.4 mya. Occasionally one Australopithecine or another is nominated as materfamilias, but the truth is no one really knows which species – if any of those so far discovered – gave rise to our side of the family. As well, there is constant toing and froing about how many species there actually are (and as we’ll see the same toing and froing goes on in discussions about the members of our own genus).

In the next post I’ll discuss what lays at the heart of all of these debates: the big question, a question that may never be satisfactorily answered.

What makes a human … well, human?

Other posts in this series can be found here:

‘Us’ Part 2 – Burdalone

‘Us’ Part 3 – The devil in the detail

‘Us’ Part 4 – Using your noggin

‘Us’ Part 5 – Feet and socks

‘Us’ Part 6 – Kith and kin


[i] For a full obituary, refer to the ANU’s Life Celebrations.

[ii] Dart, Raymond A. with Dennis Craig, Adventures with the Missing Link, London 1959.

[iii] https://www.nature.com/articles/115195a0

[iv] Including the discovery of Mrs Ples (STS 5) in 1947 by Robert Broom and John T. Robinson, an almost complete skull of A. africanus. (For more on Mrs Ples, see my earlier blog here.)

[v] https://www.semanticscholar.org/paper/Brief-communication%3A-predatory-bird-damage-to-the-Berger/15a0f813e5c4c978810bfee965fea1dcfdcb67f0

[vi] https://www.abc.net.au/news/science/2019-08-29/ancient-fossil-skull-found-in-ethiopia-fills-human-evolution-gap/11444130

[vii] In 2008, by Matthew Berger, the 9 year old son of University of Witwatersrand palaeoanthropologist Lee Rogers Berger.

14 January 2021: An introduction to Mrs Ples

Mrs Ples is the oldest thing in my house. Although, to be honest she’s just a representation of the original Mrs Ples. And, to be even more honest, my Mrs Ples is only one-third the size of the original.

Mrs Ples has more than one name, and her history is, to say the least, turbulent.

But first, the big reveal. Mrs Ples is the oldest complete skull we have of Australopithecus africanus, a member of the great apes that includes us – the hominims. I bought the replica that now rests proudly on my bookshelf at the Cradle of Humankind in August 2018.

I think she’s beautiful.

And yes, it’s reasonably likely that Mrs Ples is not Mr Ples, although the issue is not yet settled. When the original fleshy envelope holding her passed away, she was middle-aged, not bad going for someone from her time. Standing in her socks she was about the same height as a chimpanzee, and her brain was about the same size as a chimp’s as well.

But, unlike a chimp, she was bipedal. She proudly walked on two legs, occasionally retreating to a tree if something bigger than a hedgehog threatened her.

In her modern incarnation, she entered the world with a bang. Literally. The rock matrix enclosing her skull was blown apart by dynamite. It took a lot of work to get all the pieces together again.

At first, she was Plesianthropus transvaalensis; later, scientists discovered she was actually related to the Taung child, the first early hominin ever found in Africa, and already given the binomen Australopithecus africanus. So she lost her first official title and took up another; in honour of that first name, however, she has since been called Mrs Ples.

Her other name is her catalogue number, in this case STS 5, which indicates the fossil was found at Sterkfontein.

Despite being blown up, misnamed and constantly man-handled by grubby palaeoanthropologists, she is regarded with wonder by those in the know. In fact, when South Africa’s free-to-air broadcasting company aired a show in 2004 called Great South Africans, Mrs Ples made the list.

Not bad for someone who’s been dead for at least 2.1 million years.

Sadly, Mrs Ples was among the last of her kind. Soon after she was extinguished, so was her species. A sister species, A. sediba, lived in southeast Africa for a while longer, but it too eventually disappeared, probably the last of the australopithecines.

And for those who want to know what she looks like … here she is …

06 April 2020: Possible new date for arrival of Homo sapiens in Australia

In an earlier blog I mentioned a letter to Nature that suggests up to 2% of the Papuan genome originated ‘ … from an early and largely extinct expansion of anatomically modern humans (AMHs) out of Africa.’

If correct, this is important because it pushes back the earliest currently accepted dates for the human occupation of Australia (well, Sahul back then) beyond 50,000 – 60,000 years.

New evidence for a possible earlier date has now come from a site near Warrnambool, a town on the southwest coast of Victoria, where scientists have been investigating a site at the mouth of the Hopkins River. In a paper from CSIRO, it is described as an ‘erosional disconformity of last Interglacial Age’ where the shells of edible molluscs and transported stones were discovered.

Hopkins River mouth

The mouth of the Hopkins River. (Photo from Warrnambool local government website.)

It is not known for sure whether humans or animals such as seabirds made the formation, but the site has been confirmed as a midden, and evidence for fire damage to the stones suggests they may have been used to make a hearth.

Thermoluminescence analysis of the stones, together with independent stratigraphic evidence, suggests the hearth could date back between 100,000 – 130,000 years.

If true, not only does this double the possible dates for the earliest occupation of the Australian landmass, it also considerably pushes back the earliest currently accepted dates for the first successful emigration – an emigration resulting in living descendants – of AMHs out of Africa by as much as 20,000 – 50,000 years.

(The research was presented to the Royal Society of Victoria by, among other academics, Jim Bowler, who discovered Mungo Man in 1974. The Guardian’s Paul Daley wrote about the paper and interviewed Bowler in March last year. Also, see this from the Royal Society of Victoria’s own website.)

24 August 2018: When did humans first leave Africa?

This blog post is titled ‘When did humans first leave Africa?’ I confess, it’s a trick question, but we’ll come back to that later.

So to start with, let’s attempt to answer not a trick question but a trickier question: when did Homo sapiens first reach Australia?

This has been a contested debate for several decades, with proposed dates stretching from 75,000 years ago to 40,000 years ago. The bottom mark was established by the dating of the remains of Mungo Man, the oldest remains  of anatomically modern humans (AMH) yet found outside Africa.

Mungo Man

Mungo Man

Towards the upper end, luminescence dating of sediments around artefacts recently found at Madjedbebe in the Northern Territory give a date of around 65,000 years, although this is contested.

In a recent article in The Conversation, ‘When did Aboriginal people first arrive in Australia?’, authors Alan Cooper, Alan N. Williams and Nigel Spooner state the ancestors of Aboriginal Australian first reached Australia sometime between 50,000 and 55,000 years ago, just after AMH left Africa.

This date comes from geneticists working on Neanderthal ancestry in the modern human genome. In ‘Tracing the peopling of the world through genomics’, authors Nielsen et al. write that:

‘All non-African individuals studied so far contain around 2% Neanderthal ancestry, suggesting that admixture mostly occurred shortly after the dispersal of anatomically modern humans from Africa … the date of hybridization has been estimated to be approximately 50–65 kyr ago …’

33.1 H. neanderthalensis Amud 1 0.4-0.04 mya

Cast of H. neanderthalensis (Amud 1) from the Australian National University. Photo: Simon Brown

This date is now generally accepted by palaeoanthropologists.

But that presents us with a quandary. As I wrote in an earlier blog, fossils from the cave of Jebel Irhoud in Morocco, together with genetic data from a 2,000 year old Khoe-San skeleton, suggests our species arose in Africa at least 300,000 years ago. So why did it take our species a quarter of a million years to find the exit?

Well, as it turns out it, it didn’t.

In a January 2018 report in Science, authors Chris Stringer and Julia Galway-Witham note that recent fossil evidence from Israel suggests our species had left Africa by 180,000 years ago. The report also recounts genetic analyses of Neanderthal fossils from two caves, Denisova in Russia and Hohlenstein-Stadel in Germany, that ‘indicate at least one earlier phase of introgression, from H. sapiens into Neandertals … estimated at 219,000 to 460,000 years ago’.

At this stage, it seems that AMH could have left Africa over 200,000 years ago, and yet DNA evidence strongly suggests the ancestors of all non-African members of our species left Africa no earlier than 60,000 years ago.

So what’s going on?

Nielsen et al. write that the latter date indicates when the ‘ultimately successful’ dispersal of H. sapiens from Africa occurred. In other words, those members of our species who left earlier are now extinct and left no trace in our genetic record.

Stringer and Galway-Witham write that there is evidence there were several humid phases between 244,000 and 190,000 years ago. But these phases were bracketed by severe periods of aridity, which meant ‘the region was probably more often a “boulevard of broken dreams” than a stable haven for early humans.’

Chris Stringer

Chris Stringer, Research Leader in Human Origins, Natural History Museum

On the other hand, a letter published in Nature in 2016 suggests that earlier migrations of H. sapiens from Africa may have left their mark on some of us after all; specifically, Papuans.

After analysing ‘a dataset of 483 high-coverage human genomes from 148 populations wordwide … ‘ Pagani et al. found ‘ … a genetic signature in present-day Papuans that suggests that at least 2% of their genome originates from an early and largely extinct expansion of anatomically modern humans … out of Africa.’

This brings us back to the article in The Conversation. Cooper et al. discuss how Aboriginal Australians moved to and occupied Australia around 50,000 years ago. Of course, 50,000 years ago it wasn’t Australia, it was Sahul, a single landmass comprising Australia, Tasmania and Papua New Guinea.

Sahul

Sahul

Yet the letter in Nature suggests that Sahul might in fact have been occupied by H. sapiens before that date. Its authors hypothesise either that these people came from an unsampled archaic human population that split from modern humans ‘either before or at the same time as did … Neanderthal’, or that they were a modern human population that left Africa ‘after the split between modern humans and Neanderthals but before the main expansion of modern humans in Eurasia’.

The data from all this research is sometimes confusing and contradictory. Over the last quarter century palaeoanthropology has undergone a great revolution driven partly by discoveries of new hominin fossils (eg H. floresiensis and H. naledi), and partly by new and refined techniques in analysing DNA. There is a lot of data to sort through, doublecheck and assess. Nevertheless, as measurements are refined and new discoveries are made, we learn more about our past and so more about ourselves.

#

So, why is the header a trick question?

H. habilis

Homo habilis

All the above information deals with the history of just one species, our own. But H. sapiens were not the first humans to leave Africa. For example, some members of H. heidelbergensis left Africa around half a million years ago, evolving into H. neanderthalensis in Europe. Those that remained in Africa almost certainly gave rise to H. sapiens.

And if the conclusions of a recent paper by Argue et al. studying the phylogeny of H. floresiensisis are correct, then another and possibly earlier human migration out of Africa occurred. This species’ forebears are closely related to H. habilis, the oldest species in our genus, Homo.

It’s almost as if the need to migrate is as defining a feature of our genus as bipedalism, a large brain and an opposable thumb.

14 December 2017: Colin Groves (24 June 1942 – 30 November 2017)

1

My friend Colin Groves died two weeks ago this day. It came a surprise, although I knew he was in palliative care. He seemed invincible as those with a great intellect always seems invincible, as if death could be put off indefinitely. Although aged he was never an old, and although physically ill his mind was as sharp as an Acheulean hand-axe.

In a real sense his work makes him immortal, at least as far as any human can be immortal. I knew him chiefly as a friend and fellow skeptic, and more recently as a co-writer. Although I had some knowledge of his standing among taxonomists, anatomists, biological anthropologists, primatologists and palaeontologists, he was overwhelmingly modest. Just the preceding list of fields should give you some idea of the breadth of his knowledge.

When Jane Goodall was asked what it felt like to be the world’s foremost primatologist, she replied ‘You’re mistaken. The world’s foremost primatologist is Colin Groves.‘[i]

At his funeral, colleague Professor Kristofer Helgen noted that Colin had named more than 50 new kinds of mammals, and that the first, the Bornean Rhino, remains the largest living mammal described in recent generations.[ii]

‘Colin was the most influential large-mammal taxonomist of the last half-century. His discoveries and impacts are astonishing … The last species he named, in a paper which appeared … in the last month of his life, was the Tapanuli orangutan, one of only eight living great apes on our planet … ‘

As Professor Helgen points out, Colin is probably best known for describing Homo ergaster in 1975, together with Vratislav Mazák. Homo ergaster, which lived in Africa between 1.4 and 1.9 mya, was probably one of our direct ancestors.

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Homo ergaster. ANU cast of cranium KNM ER 3733, discovered at Koobi Fora, Kenya, in 1975 by Bernard Ngeneo.

Professor Helgen said Colin Groves was an original.

‘He was a gentle soul, but could be an immovable opponent. And he was genuinely brilliant, yet every bit as genuinely modest … When I think of Colin, I see him in my mind’s eye in his office at the ANU, decked from floor to ceiling with books and journals and reprints, all of his key resources, usually reckoned obscure to all others, within arm’s reach.’

This rings a cathedral of bells. Whenever something came up in our conversation about – well, almost anything – Colin would have a book, journal or anecdote to clarify, correct or corroborate any fact, no matter how obscure.

But my overriding memory of Colin isn’t his intellect or reputation, but his enormous kindness and placidness. He was never overtaken by anger, only bewilderment at the occasional fecklessness or waywardness of his fellow Homo sapiens.

He was one of my dearest friends, and his passing leaves a gaping hole in the lives of everyone who knew him.

Below is the eulogy I delivered at his funeral last Thursday.

Colin Peter Groves

As I look up at the Canberra’s first blue sky in five days, I’m tempted to think that while Colin did not believe in god, god almost certainly believed in Colin.

Although I knew him for 30 years it wasn’t nearly long enough, but perhaps long enough to discern the three great loves of his life.

Most importantly of all, his partner, best friend, constant companion and carer, Phyll.

Second, his love of science, particularly biology of course, and how it revealed to him the universe he shared with his fellow-primates, ungulates, big cats, avian dinosaurs, tardigrades, dogs, bats and cetaceans.

Third, his love of chinwagging. All the creatures I just mentioned could happily be included in a single lunchtime conversation with Colin. You might start discussing sexual dimorphism among species of African antelope and end by discussing the size of Donald Trump’s genitalia. (Amazingly, and somewhat distressingly, size does matter in nature.)

Let me deal briefly with each of these three great loves, from last to first.

It seemed to me that Colin was in his element when he shared conversation with friends and colleagues. If food and drink were included, so much the merrier, which added a cruel twist to the illness that eventually took him from us.

Although most discussions started with and usually revolved around science, his interests were catholic: skepticism, history, music, art, literature, film and television, and a hundred other subjects. He didn’t possess a ‘comfort zone’ as such; he was happy drifting on a sea of titbits, anecdotes, quotes, and bad puns (because, as Colin would patiently explain, a good pun isn’t a pun but a joke, and the quality of a pun is directly proportional to the volume of the groan it elicits).

He also had a deep and abiding love for startling and unexpected facts.

I remember how much he enjoyed discovering that the Great Pyramid of Khufu, built around 2560 BC, was the tallest building in the world until succeeded by – of all things – Lincoln Cathedral in 1311. A 3,800-year old record. He was just as delighted to learn that when Lincoln Cathedral’s centre spire collapsed in 1549, the Great Pyramid couldn’t resume its title as the world’s tallest building because erosion had reduced its height to below that of a church in Germany.

While an hour’s conversation with Colin could be filled with minor revelations such as these, they were never random thoughts. They were either staging posts that guided you safely to the end of a conversation, or points that illustrated a greater truth Colin was pursuing with the gentle doggedness of a modern-day Socrates.

In a conversation about intelligence and self-awareness, he might include the latest research about the Theory of Mind among corvids, Mozart’s Marriage of Figaro, gorillas studying their reflection in mirrors while trying on different hats, and the British television series Peaky Blinders. But every diversion would have a point, and every point would add weight in support of an argument for or against a main proposition.

I briefly mentioned Donald Trump. It seemed to me that while Colin never avoided discussing politics, what he cared about were the issues important to all of us in a free and democratic society, issues shaped and sometimes decided by politicians, pundits and lobbyists. It was people that Colin cared about, not cant. It was ideas Colin cared about, not ideology. What Colin wanted for our society was equality, opportunity, fairness and boundless curiosity.

Colin’s second great love was science, particularly anthropology and taxonomy. To say he was a biological anthropologist, while absolutely accurate, is entirely insufficient. Robert [Attenborough] has already talked about Colin’s amazing academic career, but I first met Colin because of his opposition to those forces that set themselves against science, particularly religious inerrancy, with a special focus on the shallow, silted stream of creationism.

From the first time I attended a meeting of the Canberra Skeptics, Colin immediately stood out as the most determined, the most knowledgeable and the most resilient opponent of creationism I have ever encountered. I never imagined someone as steeped in science as Colin would also be so utterly familiar with the Christian bible he could quote chapter and verse.

It wasn’t the idea of opposition that excited him, but the idea of investigating claims and when found wanting, standing up against them. I never once saw Colin angry, at least not in the sense most of us would understand the word, but when confronted by blind stupidity or blind faith, his eyes would open slightly in surprise, then narrow as he marshalled his arguments in defence of rationality.

The only other time I saw this response was when he was confronted by casual arrogance, wilful pride or careless prejudice. He understood how all these were used to stifle debate or to keep underdogs in their place, and he resented it.2

Colin was not a skeptic for the sake of it. It was just the flipside of the scientific method he applied to his everyday investigations of the natural world. It was as much a part of him as that sense of wonder that shone from him whenever he talked about the discovery of a new hominin fossil, or a new species of orangutan, or gravity waves.

Ultimately, forever and always, Colin’s greatest love was Phyll. On those few times I visited when Colin showed off just how much he knew about obscure science or history or culture, he wasn’t doing it to impress me. I think he was doing it because he just loved flirting with Phyll.

Phyll was his touchstone and keystone, his measure and the source of his strength. When she spoke, he listened. Even when he disagreed, he listened, and he listened closely.

And one never visited Colin, one always visited Colin and Phyll. They were as close to being a single unit as any two people I’ve ever met. Two minds, two voices, often two very different opinions, but a single soul, a word even Colin would agree with in this context.

They generously shared their life with family, friends, colleagues and students.

For that I will always be grateful.

[i] Mittermeier, Russell A. & Richardson, Matthew. Foreword to Extended Family: Long Lost Cousins, by Colin Groves. Conservation International, Arlington, 2008.

[ii] Helgen, Kristofer M. 2017. ‘Eulogy for Colin Peter Groves’, Canberra, 7 December.

09 November 2017: the eighth great ape and the problem with ‘species’

Until recently, only seven species made up the group of primates known as the great apes, or Hominidae. Two orangutan species (Sumatran and Bornean), two gorilla species (eastern and western), two chimpanzee species (chimpanzees and bonobos), and us.

But in a report recently published in Current Biology, an international team of scientists announced a new hominid with fewer than 800 members, Pongo tapanuliensis, found just south of Lake Toba in Sumatra. To save your tongue twisting around that particular binomen, we can call it the Tapanuli orangutan.

The scientists compared skull, jaw and dental characteristics of a Tapanuli specimen with those of the Sumatran and Bornean species, and analysed 37 orangutan genomes as a second line of evidence.

Orangutan

Three species of orangutan: from left, Bornean, Sumatran, Tapanuli. Photo credits: Eric Kilby, Aiwok, Tim Laman

The report gained a great deal of media attention: not only because we humans had a new cousin, but because the Tapanuli is an endangered species.

However, there were dissenting voices. In an interview with the ABC, for example, Lee Christidis from Southern Cross University pointed out that the analysis had been carried out on only one specimen and that the DNA evidence was at best ambiguous.

It’s only fair to point out that it’s often the case that a species will be described by a single representative organism, or, as happens frequently in palaeontology, those fragments of a single organism that have been fossilised or otherwise survived over many millions of years.

The report also generated discussion about what we mean by the word ‘species’. Jerry Coyne, professor emeritus at the University of Chicago and author of the excellent Why Evolution is True, wrote in his blog:

‘Not only do I see this new “species” as merely an isolated and genetically differentiated population (as are many human populations regarded as H. sapiens), but I’d also contend that there is only one species of orangutan overall, with these three groups all being subspecies. Sadly, a lot of systematists don’t see it that way, as they seem to think that any isolated population, if it can be told apart morphologically or genetically from others, warrants being named as a new species. Yet to evolutionists, a “species” is not an arbitrary segment of nature’s continuum, but real entities that maintain their “realness” because they don’t exchange any (or many) genes with other such entities where they cohabit in nature.’

But is this indeed the definition of species with the greatest currency among most biologists?

To start with, there has to a definition that works across all fields. A primatologist cannot have a different concept of species from, say, an entomologist, or the whole point of taxonomy – the orderly classification of living things that demonstrates their evolutionary relationships – starts to fall apart.

This doesn’t mean that definitions in biology – or any scientific endeavour, for that matter – are written in stone. As our knowledge of the world around us grows, the language we use to explore, explicate and explain that knowledge must also grow.

The definition I was taught at school is not dissimilar to Coyne’s quoted above, and is based on what is called the Biological Species Concept (BSC), developed by Ernst Mayr and Theodosius Dobzhansky in the early 1960s (Coyne did some graduate work under Dobzhansky at Rockefeller University). As Colin Groves, professor emeritus at the Australian National University, wrote, ‘This concept states that under natural conditions a species ‘should not exchange genes with other species’[i]. Groves goes on to point out that ‘ … the popular idea that two species are “unable” to interbreed is  a misunderstanding: it is not that they cannot interbreed, it is that they do not.‘

The BSC was further refined by Mayr and Jared Diamond in a paper on Melanesian birds in 2001, and then in 2004 by the aforementioned Jerry Coyne with H. Allen Orr in a book about speciation called, appropriately enough, Speciation.

Groves argues that the modified definition of BSC risks different standards of comparison in different taxonomic groups: it’s a definition that won’t work across different fields, in other words.

Groves again: ‘If a genus contains a pair of sympatric[ii] sibling species (species that differ only slightly, inconspicuously), the standard for species recognition will be set much “lower” than in a genus in which sympatric species pairs are grossly different. It is the search for objective standards – for an operational means of distinguishing species – that has been responsible for the controversies that marked taxonomic discussions over the past 15 or 20 years.’[iii]Taxonomy

Many biologists now use what is called the Phylogenetic Species Concept (PSC), developed by American biologist Joel Cracraft from the early 1980s. Put very simply, in this concept a species is the smallest population of organisms that is measurably different from other populations sharing the same ancestry. Note that this concept says nothing whatsoever about species sharing genes, such as happened between Homo sapiens and H. neanderthalensis around 100,000 years ago.

It’s important to note that both the BSC and the PSC are attempts to operationalise the evolutionary concept of species; that is, that a species is an evolutionary lineage.

While the report in Current Biology describing the Tapanuli orangutan as a new species of great ape has, for the most part, been received positively, the fact that many distinguished scientists question the findings shows that the debate about what constitutes a species is ongoing.

[i] Groves, Colin. ‘Speciation in hominin evolution’; African Genesis: Perspectives on Hominin Evolution; ed Reynolds, Sally C. & Gallagher, Andrew; Cambridge University Press; Cambridge; 2012, p 46.

[ii] Sympatry occurs when two or more species live in the same geographic area.

[iii] Ibid.