It seems we now have fossil evidence of at least 6500 individuals from ancient times; that is, older than, say, 10,000 years, and much of this evidence has appeared in the last 20 to 30 years. There is today a revolution taking place in the study of human origins. New technologies, new methods of dating, the ability to retrieve DNA from ancient bones and even from the dirt over which ancient people lived, is announced on a monthly basis, and as the new finds are reported new theories arise, are defended, some times accepted. We know today that there were several different types of ancient humans coexisting together and that these different types interbred and produced offspring. We know, for example, that many of us contain Neanderthal DNA, or Denisovian DNA. Yet, while the fossil record may reflect 6500 individuals, there are only about 200 fossil skulls that have been found, which suggests that, given all the effort and energy expended searching for human origins, the evidence is still very sparse.
There is another debate that occurs, as well, concerning when these ancient humans became “modern,” whatever that means. It seems that some versions of ancient humans were as large as humans today, with a brain case as large or larger than today, extending back at least 600,000 years. Yet evidence for modern behavior – burial of the dead, artwork, sculpture, sophisticated tool kits and technology – is generally agreed to only extend back into the past 70,000 years, although sites in Africa much older show red ochre as a possible decoration. This raises the question – what happened, then, that enabled humans to develop culture, technology, community as we understand it today; what was the incident or event that caused a being with a certain brain size and structure to suddenly begin leaving behind evidence of myth, dreams, narrative, and history?
It is agreed that hominids arose in Africa, and extended from Africa to the rest of the world, maybe in a couple of migrations, the first being Homo Erectus almost two million years ago and a latter migration much later about the same time as modern humans appeared. But the evidence is contested. Some argue the first modern humans were found in northeast Africa, others say the Middle East, there is even a find in eastern China that may be older still. There seems to be general agreement that humans crossed the sea to reach Australia 80,000 years ago, and it is also generally accepted that the western hemisphere, North and South America, was empty of hominids until the end of the most recent ice age when some humans crossed the Bering Land bridge and entered North America, either along the coast or inland once some ice had melted. There are disagreements about this, of course, with some arguing humans made it to the Americas about 14,000 years ago and others arguing humans arrived much earlier. There is a site in the Yukon, Old Crow, that may be 24,000 years old. A few argue that humans came to the Americas far earlier than that. However, there are hardly any archeological finds older than 14,000 years to support such an argument.
For decades the belief was that humans crossed the Land Bridge, then waited for a channel to melt in the two great ice sheets covering Canada, then raced south to fill the continent, killing all the great animals on the way. More recently another argument has emerged, arguing that humans first made it to the Americas by traveling the coast in boats or canoes, beach to beach or island to island, living off the marine resources and bypassing those places where the ice sheets met the sea. One big challenge with this thesis is that during the ice ages the sea level was as much as 330 feet below present day sea level, meaning any coastal communities or evidence lies buried beneath tons of water. The beach scene pictured above, Olympic National Park in northwestern Washington State, which is probably what that ancient shore looked like tens of thousands of years ago, was, back during the ice time, on a slope hundreds of feet above the beach below it.
We now know that ancient humans were capable of using boats or canoes and fishing offshore, and moving island to island. In Timor evidence of tuna fishing was found, 40,000 years old, and to catch such tuna one needs to travel beyond the sight of land.
Two factors seem to be missing from all these arguments, at least in the research I have done. The first applies to the animals among which these humans lived, and how their presence and behavior might have influenced human decisions and choices as to places to shelter. The second concerns the relationship between human behavior and movement and the frequent ice ages that swept across the top half of the world – one every 100,000 years for at least two million years.
In response to your question of what happened that enabled humans to develop culture, Madelaine Bohme in her book, “Ancient Bones, Unearthing the Astonishing New Story of How we Became Human,” discusses the relationship of the use of fire to the development of human intellect. The first traces of cooking fires were found in a cave in Botswana; the researchers dated the traces of fire at that location back at least 1 million years. By cooking food, much more starch is available to maintain a high-performance brain, i.e., intelligence through starch (and reduced tooth size). Interestingly, and controversially, she hypothesizes that humans may come from a line of Eurasian ape species that were adapted to savannah lands that once covered Greece and S. Germany. More fossil finds needed!!
This is true and surely a very good explanation although one theory holds that by cooking food the digestive system doesn’t need all that energy and oxygen to break down plants and starches – unlike apes with huge bellies to handle all those plants – leaving then more energy for the brain. The teeth became a lot smaller at the same time, too. Makes sense. But this in itself does not explain language or planning. I think you can argue that controlled use of fire might be something that can be done without language, just as team strategy and hunting is possible (packs of wolves hunt as teams for example). The record is very thin but it does seem as if widespread use of ritual and art and culture did not appear until 50,000 to 70,000 years ago. Maybe it was as long as 200,000 years ago. But humans had the same bodies and brains earlier than that, ie the ginormous brain long before so called “modern” behavior. So what happened to make that change? I think what happened was the merging of two different hominins, somehow rewqiring the brain, around the time of the Toba eruption, changing the brain “wiring” enabling this offspring to buuild memory, learning and culture with language and stories.