When and where did humans evolve?
Palaeontology, archaeology and genetics confirm Darwin was right to identify sub-Saharan Africa as humankind’s area of origin. Hominins (the group of animals to which modern humans and our immediate extinct relatives and ancestors belong) split from the lineages leading to our closest relatives (chimpanzees and bonobos) 6-7 million years ago and are known from several places in South and East Africa. Our own genus, Homo, evolved – perhaps in East Africa – about 2.5 million years ago and was the first hominin to leave Africa. But the lineages that first did so are almost certainly evolutionary dead ends. DNA analyses of people alive today show beyond doubt that all modern humans have a much more recent African origin. Along with fossil finds, they indicate that our own species, Homo sapiens, evolved south of the Sahara about 200,000 years ago.
When did we move out of Africa?
The fossil record is clear that hominins moved out of Africa more than once, the first time about 1.8 million years ago. Those movements brought several species into Europe and Asia, including the ancestors of the Neanderthals and those of the ‘hobbits’ (Homo floresiensis) found a few years ago on the Indonesian island of Flores. However, modern humans spread beyond Africa much more recently than this. A first move, indicated by 100,000-year-old fossils from Israel, is often considered a failed colonisation, though new work by Oxford’s Mike Petraglia and others suggests that it could have reached as far as India. A further expansion some 60-70,000 years ago saw people cross the Red Sea into Arabia and move around the Indian Ocean rim from there.
Who were the Neanderthals and why aren’t they here today?
DNA analyses of Neanderthal bones show their ancestors split from ours about 600,000 years ago and that genetic drift and adaptation to the severe cold of repeated Ice Age conditions produced the distinctive skeletal characteristics known from fossils across much of Europe and western Asia. In general, Neanderthals seem to have been heavily carnivorous and they were clearly efficient hunters of medium and large game. However, archaeology suggests that they probably had more limited cognitive capacities than our own ancestors. In particular, there is next to no convincing evidence that Neanderthals made and used art, jewellery or complex tools of the kind associated with Homo sapiens. It seems likely that, socially and technologically, modern humans could cope better with severe fluctuations in climate and food availability, outliving, outbreeding and outcompeting Neanderthals across their range. The last known individuals died out in Spain about 28,000 years ago.
When did we first start producing art?
The cave paintings and decorated objects left by Upper Palaeolithic people in parts of Europe (especially southwest France and northern Spain) were long thought to place the answer to this question no more than 40,000 years ago. Now, shell bead jewellery from sites in Africa and Israel demonstrates that people have been using material culture to make statements about their identity for at least 100,000 years. Equally startling, geometric designs scratched into pieces of ochre go back to around 75,000 years ago at Blombos Cave, South Africa, and can be paralleled only a little later at other sites on ochre and on ostrich eggshell.
Are there any new discoveries?
Absolutely. Just in the past few months three big ones have occurred. First, the ancestors of the Flores ‘hobbits’ turn out to have got there, across the open sea, over one million years ago. Second, mitochondrial DNA analysis of a finger bone from a cave in Russia’s Altai Mountains shows its owner to belong to an evolutionary lineage that split about this same time from those leading to the Neanderthals and us. Not only does this mean there was a third (previously unknown) hominin species in Siberia as recently as 40,000 years ago, it points to a previously unsuspected migration out of Africa about 1.0 million years ago. And third, there are the two beautifully preserved partial skeletons of Australopithecus sediba from caves near Johannesburg, a new species perhaps directly ancestral to our own, from just under 2 million years ago. Human evolution continues to surprise.