We can’t extract DNA from some of the most perplexing ancient human fossils. But ancient proteins sometimes survive better, and they are finally starting to give up their secrets
9 September 2020
IT WAS an astonishing discovery: a chamber deep underground, packed full of ancient human remains. The excavators who uncovered the fossils at South Africa’s Rising Star cave in 2013 described the experience as “breathtaking” and “emotional”. Then they took a proper look at the bones, and exhilaration gave way to bewilderment. This new species of ancient human, which the researchers called Homo naledi, had such an odd combination of primitive and modern features that it was impossible to know how it was related to other ancient humans and, ultimately, to us.
About 20 years ago, it looked like the human evolutionary tree was coming into 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.