Our direct ancestors spread out from Africa long after the first hominid exodus, and they were anatomically and behaviourally much more human
The initial hominid expansion from Africa occurred about 2 million years ago, long before the Neanderthals had evolved in Europe. The direct ancestors of our species spread out from Africa much later, after they had already become . In Asia and Europe they would encounter populations of hominid species from earlier migrations that had evolved their own differences. These species became extinct, while the new hominids from Africa went on to evolve relatively superficial features that today characterise the geographically diverse populations of our species.
Out of Africa, twice
The first hominid expansion from Africa came about 2 million years ago, as revealed by stone tools and an outstanding collection of hominid fossils at the site of Dmanisi in Georgia. This expansion has sometimes been called “Out of Africa, Part 1”, but the implication that hominids ever deserted Africa is manifestly incorrect. This continent continued to be the crucible of our evolution. Even the emigrant Homo erectus and its hand-axe technology are ubiquitous in Africa, with evidence of the species’ occupation from the Cape to near Cairo.
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Darwin predicted that Africa would one day yield fossils to illuminate human evolution. Today, he would be delighted to learn we have found fossils not only from the first two phases of human evolution, but also within our own genus, Homo. The earliest is H. habilis, makers of stone flakes and cores that dominated technology for almost a million years. Next came H. erectus. What is clear is that our ancestors continued to evolve in Africa as more northerly latitudes were repeatedly buried in thick ice.
By 160,000 years ago, African hominids were nearly anatomically modern, with faces a little taller than ours, and skulls a little more robust. Their brain sizes were fully modern. In Ethiopia, at a locality called Herto by the local Afar people, the crania of two adults and a child represent some of the best evidence of the anatomy of these early people, who lived by a lake. Among their activities was the butchery of hippopotamus carcasses with their sophisticated stone tool kits.
Herto humans were also doing things that we would recognise as distinctively human: they were practicing mortuary rituals. Fine cut marks and polishing on a child’s cranium show that it was defleshed when fresh, and then repeatedly handled.
Examination of the DNA of people today shows we all carry inside us a kind of “living fossil” that opens a window on our past. Whether modern human DNA samples are taken in the Arctic or the Congo, our DNA is remarkably similar to each other’s, especially when compared with the variation seen in most other mammals. And the variation observed is greatest among African populations.
What this means is that we are a recent species, and that the ancestors of all modern people were Africans.
Advance of civilisation
It has long been dogma that it was only when people domesticated plants and animals – otherwise known as agriculture – that they were able to settle down and begin to build cities and create monumental architecture. This plausible version of technological evolution is now being strongly challenged by .
At the site of , an 11,000-year-old site has recently been uncovered. It boasts T-shaped limestone pillars of various heights, up to 6 metres, carved with images of animals. They were erected here in a monumental circular arrangement, 20 metres in diameter. This structure pre-dates the domestication of plants and animals. The people who built it still lived by hunting and gathering.
This and other sites discovered in the region challenge the notion that agriculture was the catalyst for what we loosely call “civilisation”. Could it be that symbolism, ritual and religion came first and that these were the cause, rather than the consequence, of domestication and agriculture?
Language, symbols, farming
When did humans acquire language? It is a question that anthropologists and linguists still puzzle over. Some suggest it was very late, only after we had become H. sapiens and begun to spread beyond Africa sometime after the emergence of anatomically modern humans around 60,000 years ago. The founding of basic languages may have accelerated trade and, as Matt Ridley argues in The Rational Optimist, trade is to culture as sex is to biology.
The first evidence of symbolic behaviour comes as 100,000-year-old South African shell beads and ochre incised with designs. Around 10,000 years ago, in the Fertile Crescent of Mesopotamia and the Levant, came the planned sowing and harvesting of plants.
Those of us old enough to remember the Apollo spacecraft or the dial telephone have witnessed so much technological innovation within a couple of generations that we find it difficult to appreciate that this speed of change is exceptional. For thousands of years, Babylonian farmers did the same things, with the same tools, that their great-grandfathers had done.
Neanderthal fates
Ever since their discovery in the mid-19th century, the place of Neanderthals in human evolution has been a mystery. Early evolutionists adopted them as evidence of human evolution, but as more and more fossils were recovered from around the Mediterranean, it became clear that these forms were peculiar hominids. With the excavation of further sites in Europe, the archaeological record showed a rapid technological change just as they disappeared.
Debate about whether Neanderthals were ancestors or cousins persisted for decades, but fossil discoveries and genetics have finally solved this problem. Early anatomically near-modern and modern people lived in Africa long before the Neanderthals perished about 35,000 years ago. Genomic studies suggest that there was possibly slight interbreeding between them, with leakage – of at most a few per cent – of genes from Neanderthals into human populations.They were our evolutionary close cousins, but the equivalent of a separately evolving species.
How to spot a ‘hobbit’
The discovery of the remains of diminutive humans on the Indonesian island of Flores, east of Java, captured the world’s imagination in 2003. The remains were named Homo floresiensis and, almost inevitably, nicknamed “hobbits”.
Three hypotheses have been put forward to explain these Flores Island fossil hominids, which date from between 90,000 and 18,000 years ago. One is that their heads were abnormally small as a result of a congenital condition. However, no good match has been found between this microcephaly and a modern developmental disturbance of this kind.
The second hypothesis sees a very early occupation of Flores by hominids who were small, with small brains. In other words, far-flung Australopithecus or very early Homo. This also seems unlikely, given the times, distances, geographies and anatomies.
The third, most likely, scenario is that nearby H. erectus or H. sapiens became established there, rapidly evolving into hobbits via the well-known phenomenon of island dwarfing. All researchers agree that more evidence is needed to solve the mystery of H. floresiensis.