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.


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