New Scientist - USA (2020-09-12)

40 | New Scientist | 12 September 2020

focus. Then palaeontologists started finding

ancient humans, like H. naledi, that are so

strange, it is as if they had walked off the

pages of a Tolkien fantasy. We can’t expect

ancient DNA to help resolve their place in

the human family tree because most of

these misfit cousins were found in places

too warm for genetic material to survive.

The trail seemed to have gone cold.

In the past few years, however, we have

learned to read the signals in other organic

molecules that tend to survive longer than

DNA and persist even in warm environments.

Researchers have already analysed samples

of proteins extracted from ancient bones

and teeth to reveal relationships between

ancient mammals. Now, some think they

could reveal how archaic humans like

H. naledi evolved and interacted. “I’m

confident that it will be possible to put

some of these very unusual hominins on

the [family] tree,” says Matthew Collins at

the University of Copenhagen in Denmark.

Human hybrids

It is no exaggeration to say ancient DNA has

transformed our understanding of human

evolution. It confirmed that our ancestors

interbred with Neanderthals between about

100,000 and 50,000 years ago. It revealed

the existence of a distinct group of Stone Age

humans we had never recognised before – the

Denisovans of east Asia – and showed that

our ancestors interbred with them too,

between about 50,000 and 15,000 years ago.

More recently, ancient DNA studies have even

begun to find evidence that Denisovans once

interbred with a far more ancient group of

humans, perhaps a species called Homo

erectus that appeared almost 2 million years

ago and vanished about 100,000 years ago.

In other words, ancient DNA has revealed

that the Stone Age world was populated by

many distinct human groups that, despite

their genetic differences, were more than

willing to interact and interbreed when

their paths crossed.

Ancient genes can’t tell us everything,

though. All of the revelations came from T-B

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Homo naledi lived in Africa

some 250,000 years ago.

The fossils we have found

don’t contain DNA, which

doesn’t survive well in warm

conditions. But if researchers

can extract proteins from the

bones, we might finally figure

out how this mysterious

ancient human is related to us