FEATURE
Does human palaeontology perplex? Don’t know your hobbit from your habilis, or Neanderthal from naledi? DYANI LEWIS explains what we know about the human origin story.
— Where humans came from
MODERN HUMANS, Homo sapiens, are a single twig on a branch of the evolutionary tree that reaches back some seven million years, to when we split from our closest living relatives, the chimpanzees and bonobos.
Human evolution, however, “is not a line of cartoons from a bent-over chimpanzee to a modern human,” says Fred Spoor, a palaeoanthropologist from University College, London. “It’s a complex business.” So what do we know? We know that Homo sapiens evolved in Africa perhaps as far back as 300,000 years ago, and then travelled north into Eurasia. They dispersed though Europe and Asia, reaching Australia about 55,000 years ago and the Americas about 15,000 years ago.
Most current accounts, drawn from the fossil record and studies of ancient and modern human DNA, suggest two waves of global migration. The first migration had Homo sapiens reaching the Middle East as early as 125,000 years ago, and China 80,000 years ago. By the time a second wave of Homo sapiens left Africa around 60,000 years ago, the first wave had probably either retreated or become extinct.
Genetic studies that determine how living populations have interbred and mixed throughout history suggest most non-africans living today can trace their heritage to the second exodus from Africa. A recent study suggests the founders of Sahul (the ancient continent comprising Australia and Papua New Guinea) might have been part of the first migration.
Tracing a direct line of ancestry for Homo sapiens back along our branch of the evolutionary tree is difficult, because the fossil record is a patchy mosaic of incomplete skeletons. Few early humans died at the right time and place for their remains to be preserved.
Entire species probably became extinct without leaving a single toe bone for us to dig up in the smattering of places we are looking.
The fossil record for two to three million years ago, when our oldest Homo – or “upright” – ancestors emerged, is particularly sparse, says Spoor, making it “one of the least understood parts of human evolution”.
Early human species that have been discovered are just as likely to be ancient “cousins” – offshoots of the branch leading to us – as they are ancestors.
Here’s a short guide to the most prominent members of the the extended ancient human family.