According to work by Aaron Miller bipedalism in primates began with our lineage some 20 million years ago, producing the apes as we know them today – gibbons, siamangs, orang utans, gorillas, chimps, bonobos and us – plus dozens of extinct species. So while bipedalism is important to our lineage, it isn’t a key to what makes humans human. Then sometime between 6 and 4 million years ago we became genetically distinct from our closest relatives, the chimp/bonobos (who split 2 million years ago), but at that time we were probably identical in morphology and remained so for millions of years. The two probably parted company thanks to the African Rift Valley’s geographic barriers and eventually the chimp/bonobos moved into the rainforests of West Africa, while we adapted to the more open forest around the lakes of East Africa.
Some 2.6 million years ago the first evidence of intentional modifications to stones can be found – our ancestors began breaking up stones to make crude sharp-edges for tools. No chimp/bonobo has ever done so, even though they do use stones to hammer at hard nuts. While this seems like a uniquely human thing to do the Oldowan stone technology (as it’s called) lasted a million years more or less unchanged – a very non-human approach to tool-making. Humans are too restless to let things remain unmodified, but the Oldowan people were happy with their stone flakes for millennia.
Around 2 million years ago humans under went a lot of changes producing Homo erectus and Homo habilis – the former being like us in body proportions, the latter being an odd hybrid of old ape and new human body forms. Homo habilis spread into Eurasia and seemingly became Homo erectus there – the hominids at Dmanisi, Georgia seem to be intermediate between the two. In a very short span the proto-humans filled Eurasia, though they avoided going too far northwards perhaps because their use of fire was haphazard and unable to provide sufficient protection against the seasonal cold. A new stone tool technology arose, the Acheulean, centred on the making of “hand axes” which are more like a multipurpose blade used for all sorts of things, from display (some were artistic) to wood-work.
Sometime around half a million years ago the Acheulean people became more like us, now known as Homo heidelbergensis or Homo antecessor. Their brains were bigger than Homo erectus and they seemed to have built shelters, used fire-hardened wooden tools, and eventually they birthed our own species, in Africa, and Homo neanderthalensis, in Europe. Homo erectus, in its later forms, survived until about 40,000 years ago in the Far East. An even earlier form, maybe Homo habilis, was survived by its diminutive off-shoot Homo floresiensis, the Hobbit, up until their (possible) extinction some 12,000 years ago.
In the last 300-200 thousand years the pace of technological change increased, producing a new tool set amongst the Africans and the Europeans, known as the Mousterian. Big things were happening in South Africa after 200,000 years ago – cave sites near the old sea-shore are revealing traces of modern behaviour, dating back to 164,000 years ago, perhaps further back. Further to the north in Herto, Ethiopia, anatomically modern humans appear 195,000 years ago. Even further north true Neanderthals appear in Europe along with Mousterian technology. Many of the diagnostic features of modern humans appeared piece-meal – use of ochre, symbolic engravings, micro-blades, bone tools, and so forth – over about 150,000 years between the Herto hominids and the explosion out of Africa.
And that explosion seemingly signaled a qualitative change in human beings. In all respects, bar that change, the humans between 200,000 and about 60,000 years ago were identical to us. Between 150,000 to 70,000 years ago Africa went through a series of massive droughts due to a glacial advance during the Ice Age, which might have driven humanity very close to extinction. There is evidence for some kind of genetic bottleneck that cut down our species to just a few thousand people. That we survived needs some kind of explanation, and would perhaps simultaneously explain what propelled those survivors out of Africa.
Between 60-40 thousand years ago the species burst forth into Eurasia and Austronesia, Australia itself by 50,000 years ago, and eventually into the Americas by 15,000 years ago. An unstoppable tidal wave of technological and culture change meant that humans developed projectile weapons (eg.boomerangs, bow-and-arrow, spear-throwers), sailing vessels, sewn clothing, thread and fabric, and a multitude of other advances that we take for granted. By developing all these things humans were able to adapt to an ever wider environment with wider extremes of weather – thus eventually allowing the long trek to America past the glaciers, either via the near-shore sea-route or via inland corridors.
After such a slow pace of change what came together some 60,000 years ago to propel our species forward? Did that mark our arrival as modern humans? Certainly genetically we’re all related by the groups that left Africa and I would argue that we all share the same basic cognitive tools, the same propensity that allows adaptive change via technology, perhaps producing the same belief in unseen “spirits” and “gods”. Even the most ancient human groups believe in invisible people like ‘gods’ – the !Kung Bushmen, for example, believe in a Father Creator, whose two wives produced the Sun and the Moon. Just how such beliefs arose and, more importantly, why they arose will give us untold insights into the human mind.
But will that knowledge tell us anything about those invisible people?