Evolution

22 May 2016: Crows got smarts

Corvus_corax_tibetanus

Corvus corax, the common raven. Photo: Pkspks [CC BY-SA 4.0]

It’s no secret that corvids – crows and ravens – are exceptionally smart for birds, especially at problem solving. Now an experiment carried out with ravens provides evidence they may have a basic Theory of Mind as well; this means they have an ability to attribute mental states they experience to another raven.

In a paper published in Nature in February, researchers Thomas Bugnyar, Stephan Reber and Cameron Buckner from the universities of Vienna and Houston, carried out an ingenious experiment that tested how ravens caching food behaved when they thought they were being seen by another raven.

There is increasing evidence that the Theory of Mind exists in chimpanzees, bonobos, scrub jays and ravens. How equivalent the experience of a ToM is between species is, so far, untestable, but the strong possibility that some form of ToM exists in different animals provides yet more evidence of the complexity of the mental life of species apart from humans.

Not only does this add weight to calls that humans should reconsider the way they relate to other animals, especially the often appalling way we treat farmed and domesticated animals, but firmly places Homo sapiens as the product of the same evolutionary process that produced ravens, dogs and garden slugs.

16 May 2016: New dates for the ‘Hobbit’

Homo floresiensis

Photo: Ryan Somma

Updating my blog celebrating the 10th anniversary of the discovery of Homo floresiensis, better known as the ‘Hobbit’, a letter in Nature has revised the most recent dates for the remains from 12,000 years back to 60,000 years. The sediment layers in the cave of Liang Bua on the Indonesian island of Flores, where the remains were discovered, had not been laid evenly, leading to an initial miscalculation.

Stone artefacts attributed to H. floresiensis are dated more recently, to 50,000 years ago.

The biggest implication of the new dates is that it is now less likely that the ‘Hobbit’ coexisted at the same time as H. sapiens on Flores. Although it cannot be ruled out, the earliest dates for human occupation at Flores is 50,000 years, leaving a very narrow window of opportunity.

11 February 2016: Digging for relatives

DSC02344

Elen Feuerriegel with thermoplastic copy of H. naledi lower jaw.

“Sometimes I can’t believe it happened,” said Elen Feuerriegel as the 3D printer by her side chugs out a thermoplastic copy of the cranium of an ancient human.

“I’m doing something ordinary, something I do every day, and then remember that two years ago I was working 30 metres underground recovering the remains of Homo naledi, a previously unknown human species.”

Feuerriegel, a PhD student in palaeoanthropology at the Australian National University, was one of six excavators – dubbed underground astronauts by an excited media – who retrieved the bones of up to 15 individuals from a small and almost inaccessible cave.

Part of an expedition organised by Professor Lee Berger from the University of Witwatersrand to investigate the Rising Star Cave in South Africa, it was the task of the Feuerriegel and the other five excavators to reach a small and unmapped annex to the cave system called the Dinaledi Chamber.

“To get to the chamber meant worming our way through a fissure that in one place narrowed to just 18 centimetres,” Feuerriegel said. “The fissure itself was a 12-metre drop that ended in a tiny landing, followed by another four metre drop to the floor of the chamber.”

What Feuerriegel first saw there will stay with her for the rest of her life.

“It was a wonderful, exhilarating experience. It was incredible amount of fossil material in one place. It was almost impossible to move without stepping on a jaw or leg bone.

“As our eyes got used to the dimness and we became more experienced at discerning fossils in the floor sediment, new finds seemed to appear out of nowhere.”

Despite her interest in science starting as a young teenager, her appearance at the Rising Star Cave System was never a given. She reached palaeoanthropology through a route almost as torturous as the entrance to the Dinaledi Chamber.

“My first love was marine biology, particularly sharks. That somehow morphed into a fascination with volcanoes. Then my mum, an information architect, helped me put together a web page for a school project I did on human evolution.”

Feuerriegel speaks about evolution through natural selection with a focused passion.

“For me, evolution is the great leveler. We humans are as subject to evolutionary forces as other species.”

The American crime procedural CSI: Crime Scene Investigation also stirred in her an interest in anatomy.

She did her first degree in sociocultural anthropology at the University of Queensland. “I’d given up on the idea of palaeoanthropology until I did an intensive summer course on human evolution.”

With an honours degree in her pocket, Feuerriegel came to the ANU to do her masters, and in 2013 began her PhD in palaeoanthropology.

Later that year, Lee Berger put the call out for people with a special and unusual skill set.

“He wanted skinny palaeoanthropologists who were also experienced climbers or cavers.”

Feuerriegel, who enjoyed wall-climbing and hiking, and had previously worked in a mine shaft in Sima de las Palomas in Spain looking for the remains of Neanderthals, applied for one of the openings.

Underground astronauts

The Underground Astronauts: Becca Peixotto, Alia Gurtov, Elen Feuerriegel, Marina Elliott, K. Lindsay Hunter, Hannah Morris. Photo: John Hawks

“Despite the specialist skill set, there were 60 applicants. I was one of six chosen.”

Within three weeks of an online interview, Feuerriegel found herself in South Africa retrieving the remains of a new human species, Homo naledi.

“We worked in two shifts, each with three excavators and two support cavers. Each shift lasted anywhere between three and six hours, depending on the task. The expedition tried to get at least two shifts down in the chamber every day, and sometimes three.

“For the first few days it could take up to an hour to get down from the surface to the chamber, but by the end of our stay there we’d reduced that to 20 minutes, giving us much more time for the real work.”

Towards the end of the work, seasonal rains raised the water table.

“There was no danger to us – the site was well above the water table – but conditions gradually got worse and surfaces more and more slippery.”

In the end, the excavators recovered the remains of 15 individuals, male and female, ranging in age from neonatal to an older female with very worn teeth.

Feuerriegel said she’s sure what the team discovered is a new species of ancient human.

“Morphologically, Homo naledi sits somewhere in the bridge between the latter Australopithecines and the early Homo, having features of both as well as some unique features all of its own. Exactly where it fits is something we don’t know yet.

“The other thing we don’t know at this point is how old the remains are. The bones we found had not yet been replaced with minerals like silica, but were still made up of hydroxylapatite, a form of calcium.”

She said if the remains proved to be between two and three million years old, H. naledi is the earliest definite example of Homo with skeletal material representing the whole body.

“If the remains are between one and two million years old, the date’s about right for a hominin of H.  naledi’s morphology.

“And if the date is less than one million years old, it means we have multiple species of hominins existing at the same time in South Africa. In that case, H. naledi’s small braincase and primitive morphology must make us seriously reconsider what it means to be a member of our own genus.”

Early reaction among some palaeoanthropologists hasn’t been all positive.

“Claims that the remains represent an early form of Homo erectus are fanciful,” Feuerriegel said. “A lot of critics have also focused on Lee’s description of the appearance of the bodies in one place as ‘ritual’.

“In this case, we aren’t suggesting anything spiritual, only that it represents repeated and deliberate behaviour.”

One of the career highlight for any palaeoanthropologist is to be one of the official ‘describers’ of a new species; thanks to her time in South Africa, Feuerriegel, at the age of 26 and still at least six months from finishing her PhD, is one of the names on the scientific paper officially naming the new species.

“I’ll also be lead author on a paper describing H. naledi’s upper limb, an area of morphology I’m particularly interested in.”

Feuerriegel said humans hold themselves on a pedestal as a species, above and apart from our ancestors.

“If there’s one thing H. naledi illustrates, it’s that the characteristics and behaviours we believe make us unique are not so unique after all.”

04 September 2015: Neither one thing nor the other

P. myojinensis

P. myojinensis. The blue structure is the nucleus, the red structures the endosymbionts.

A remarkable creature discovered in the ocean southeast of Japan – that doesn’t quite seem to belong to any of the three known domains – may provide evidence of how complex multicellular life evolved on Earth.

In 2010, a scientific expedition to the Myojin Knoll, about 35 kilometres southeast of the Japanese island of Aogashima, collected biological samples from a hydrothermal vent more than 1,200 metres below the surface.

The samples were frozen and then embedded in epoxy resin; the resin was then prepared for study by being sliced into ultrathin sections.

That’s when the researchers discovered they had collected one truly remarkable specimen, a single-celled organism that lays somewhere between prokaryotes, organisms like bacteria and archaea, and eukaryotes, the basis of complex organisms such as fungi, plants and … well … us.

The main differences between prokaryotes and eukaryotes are that the former do not have a nucleus surrounded by a membrane, or any membrane-bound organelles such as mitochondria or chloroplasts.

As described in the journal Microscopy, the cell, dubbed Parakaryon myojinensis, was discovered on one of the bristles of a type of Polychaete called a scale worm. It was 10 micrometres long and three wide, much larger than most bacteria. Inside the cell the researchers discovered a nucleus with a membrane. As well, they discovered three endosymbionts, organisms that live symbiotically inside another, also surrounded by membranes. Obviously, then, the cell was not a prokaryote.

However, the nucleus of P. myojinensis was surrounded by a single membrane and consisted of DNA fibres, whereas a nucleus in a eukaryote cell has a double membrane and consists of chromosomes.

The endosymbionts also had only a single membrane. Mitochondria in eukaryotes, like the nucleus, have a double cell wall. As well, the endosymbionts closely resembled bacteria rather than mitochondria.

This last point is what makes the discovery of P. myojinensis so important.

There are two major theories about how eukaryotes evolved. The autogenesis theory proposes that a eukaryote’s structures developed from primitive prokaryotic features. The symbiogenesis theory – first properly described by Russian Konstantin Mereschkowski in 1910 and subsequently advanced by Lynn Margulis in 1967 – proposes that eukaryotes evolved from a symbiotic relationship after a bacteria was absorbed by larger achaean, eventually becoming an integral and working part of the cell.

P. myojinensis seems to be an organism that has incorporated endosymbionts into its structure but not yet developed the full range of eukaryotic functions.

As the authors of the paper suggest, “ … it may even be a conservative descendant of the transitional lineage between prokaryotes and eukaryotes.”

For a fuller description of the possible implications of the discovery, read this article on ABC online by British scientist Nick Lane, whose latest book The Vital Question: Why is life the way it is?, is a rewarding and thought-provoking read.

12 May 2015: Dinosaurs and birds

Archaeornithura meemannae

Archaeornithura meemannae (Credit: Zongda Zhang)

Remarkable new finds announced by China’s Institute of Vertebrate Paleontology and Paleoanthropology includes the earliest date yet established for a true bird and a bird-related dinosaur with leathery wings.

In a summary report on their website, Michael Balter said a team of paleontologists led by Min Wang and Zhonghe Zhou found 130 million year old fossils of two ancient wading birds in northeast China. The two remains of Archaeornithura meemannae show many features that belong to modern birds, including fan-shaped tail feathers and “the U-shaped wishbone familiar to anyone who has carved a roast chicken.” The fossils, dating back 130 million years, pushes “back the lineage that led today’s birds by at least 5 million years.” The report suggests this means the origins of true birds is older still. In an article in Nature, scientists from the Institute described a new species of scansoriopterygidae dinosaur they called Yi qi (pron. ‘yee chee’). Not only is this the shortest binomial ever given to a dinosaur, it’s also the first dinosaur found with striking evidence of ‘bat-like’ wings. Although other species of scansoriopterygidae were first described as early as 2002, this is the first fossil found with convincing evidence of membranous wings. Sometimes defined as ‘avian dinosaurs’, the scansoriopterygidae group belongs to a clade that ultimately lead to true birds. While it is not believed the group are direct ancestors of birds, they are examples of yet another evolutionary experiment in flight. Institute palaeontologist Corwin Sullivan said the while the dinosaur probably did not fly like a bird, “our guess would be that Yi qi was gliding or maybe combining gliding with some relatively inefficient flapping.”

05 December 2014: Graffiti – a primate thing

earliest graffiti

Photo: Wim Lustenhouwer, VU University Amsterdam

What had up to now been the most ancient example of graffiti, at a respectable 100,000 years old, has just been royally trumped.

Published in science journal Nature on 3 December was the announcement by a group of scientists led by José Joordens from Leiden University in the Netherlands that a sea shell had been discovered with etchings that go back around 500,000 years.

Not only does this push the graffiti timeline back by a factor of five, it also means the rough etching wasn’t made by a member of our species.

The artist in this case almost certainly belonged to Homo erectus, which says a great deal about how deeply ingrained is the hominin need to create art.

Go here to get the story from Dr Joordens herself, who point out the contribution made by Dr Stephen Munro, a biological anthropologist from the ANU.

31 October 2014: Homo floresiensis, aka the Hobbit, now 10 years old

It wasn’t as momentous as Copernicus displacing Earth from the centre of the universe, or Darwin displacing humans from the centre of creation, but ten years ago a team of Australian and Indonesian palaeontologsits announced a discovery that changed the way scientists view not just the history of humans, but the history of the entire human clade. If Darwin’s On the Origin of Species started an earthquake, then the discovery of a recently extinct tiny-limbed and tiny-brained human on the Indonesian island of Flores started a serious tremor.

The waves from that tremor are still rippling through palaeontology. Some scientists argue that the new human, dubbed Homo floresiensis but more often referred to as the Hobbit in popular media, is nothing more than a diseased remnant of an isolated population of modern humans. It does seem, however, that proponents of this hypothesis are increasingly desperate to prove their case. The most recent argument is that the remains display classical symptoms of Downs syndrome. I’m still waiting for them to wheel out childhood smoking as the cause for the Hobbit’s miniature status.

It seems to me that the weight of evidence is overwhelmingly on the side of Homo floresiensis being a new member of the human family. It has no chin, its leg bones are unusually thick, and its wrist bones more closely resemble those of an African ape or group of ancient humans called Australopithecines.

Another piece of evidence that H. floresiensis was not a dwarf or diseased version of H. sapiens is the stone implements found with the remains. These tools are the size you’d expect them to be if made by and for humans around a metre tall. More importantly, they and the bones were found in strata laid down as long ago as 95,000 years ago. Modern humans did not arrive in Indonesia until about 45,000 years ago.

The great mystery surrounding H. floresiensis is where exactly it fits in the human clade. Most evidence suggests it is a very primitive member of the genus Homo, but perhaps, just perhaps, it belongs in the group of Australopithecines with A. afarensis and A. africanus.

The one outstanding fact about this tiny cousin of ours is that it may have survived at least until 18,000 years ago, and possibly even as recently as 12,000 years ago. The Neanderthals, our closest relative among all the species of humans that have walked the Earth, died out not later than 35,000 years ago.

Homo floresiensis was a true survivor.

[For more information about the discovery of the Hobbit, go here. For more information about the history of the debate on whether or not the Hobbit is a new species, go here.]