I’ve read in a number of places that the human brain reached it’s modern size 100,000 years ago. Despite this nothing much happened in the way of advancing how stone tools were made. The style remained little changed from periods ranging back a million years to Homo erectus. This despite a much larger brain. Than, 60,000 years after the brain reached its present size (40,000 years ago), our ancestors underwent a “creative explosion” where inventions like the bow and arrow and fish hooks appeared.
I have three questions –
First, what happened 40,000 years ago that lead to this “creative explosion.”
Second, why was there a 60,000 year gap between the brain reaching it’s modern size and the “creative explosion” mentioned.
Third, does anyone know whether “reaching modern size” equates with a conclusion that there was a similar amount of neocortex, which is the portion of the brain associated with higher reasoning.
Opinions / theories are also very welcome – since there may be no definitive answer.
I’m no expert, but i think the most popular current view is that social interaction and language was the main factor behind mankind’s increase in intelligence, and brain size. Tool making abilities were kind of an added bonus. Hence why the gap between development of intelligence, and this “creative explosion”.
Beyond the issues of When did it really happen? and What caused it? we need to remember that knowledge and technical advancements do not follow a straight line progression.
For example, various breakthough technologies or events have happened in very few locations, spreading over the world from only one or a few locations. Obviously, the peoples who adopted the improved methods were smart enough to recognize the their importance and smart enough to even improve upon them. Yet, no one in the receiving cultures happened to have come up with the original idea.
Agriculture, domestication of livestock, the wheel, and written language are all things that arose in very few locations. Among those, written language finally provided a way to make advances build on themselves and then increase exponentially.
There also needs to be enough population to carry on the traditions of new improvements. If the various small clans of humans acted with hostility toward other clans, on the grounds they were in competition for the same food, then a better blade or an improved tool would tend to disappear if the clan died out through disease, famine, or warfare. (And, as a programmer, I will note that a lot of good ideas are still ignored by people either because the potential recipient suffers from the Not Invented Here syndrome or because some inventors actually hide their techniques so that they can maintain a pre-imminent social postion. If the inventor then dies before passing on the knowledge of the manufacturing technique, then the new invention dies with the inventor.) It might simply be that it was only 40,000 years ago when enough humans began to come in contact with each other to consider building treaties and living in relative peace and begin looking to steal other people’s ideas instead of simply killing the others and ignoring the others’ inventions.
The real explosion of inventions began fairly soon (geologically speaking) after agriculture (giving rise to larger societies) and writing (giving a way to pass knowledge between generations). From that point, the knowledge curve has soared upward.
There’s been a lot of talk lately, too, about the genetic bottleneck our species went through ca. 70,000 years ago–there was apparently some temporary climate change (major volcanic activity of some sort?) that correlates pretty well with what genetic evidence shows for our (i.e., all human beings) last common ancestor. Some estimate that we dropped to a few hundred or thousand individuals at that point. So maybe, on top of all of the slow, gradually accumulating changes, we got kicked out of the garden, had to hit the road, and had to work harder and be more inventive to survive at that point.
Plus, remember that the majority of the things hunter-gatherers use (clothing, wooden tools, wooden bowls, gourds for carrying water, tanned and stitched animal skins, etc.) don’t last long enough for archaeologists to find (save in rare circumstances). So it’s possible they were making advances in other areas, other types of tools, etc., but the only thing that survived til now were the stone tools (which perhaps were “good enough”).
the Stone Age is really a misnomer, since, according to ethnographic data, it was much more a Wood, Bone, Antler, Skin, Shell etc. Age. There are relatively few things in a forager’s life where stone is absolutely necessary - the vast majority of hunter-gatherer trappings are biodegradable, but the few stone implements never rot and accumulate over the eons, giving a false picture.
Stone tools don’t have to be fancy to be highly useful - most cutting, slicing, crushing and killing can be done with crude flakes and cores. I’d say that a pretty big part of the ‘improvements’ in stone technology had more to do with artistic ambitions than any inherent increase in tool/weapon - efficiency
For an interesting discussion and speculation about these questions, see The Third Chimpanzee, by Jared Diamond. Yes, THAT Jared Diamond. The one that wrote Guns, Germs, and Steel, though Chimpanzee isn’t as good.
One thing you got right is that there is not a definitive answer. Also, keep in mind that Neanderthals had brains, on average, slightly larger than ours before we appeared a bit before we appeared on the scene.
The most likely answer is that it had to do with the organization of the brain, rather than raw size. More interconnections between neurons and different parts of the brain, allowing knowledge to be better integrated. This may also have caused a significant improvement in the complexity of language.
There’s a recent book out (can’t remember it right now) in which the author (an anthropologist) speculates that there are various types of intelligences and that the various human ancestors had various abilities to integrate these different intelligences. Thus, it is postulated, that when a Neanderthal was making a tool, he was not mentally able to apply other intelligences to this tool making activity. Or, more concretely, a Neanderthal could recognize a Mammoth, and could chip stone tools, but couldn’t integrate these pieces of knowledge such that he would fashion a stone likeness of a Mammoth. Those two intelligences were seperate and unlinkable.
This really goes against our current paradgim- and a whole lot of evidence. Remember, extraordinary claims require extraordinary evidence. This concept of the brain being uncessary would call into light a whole lot of it’s own questions- quesitons that don’t exist currently because everything we feel is true right now fits in with what we percieve as reality. If the brain isn’t necessary, why does it exist, why would the body maintain such an expensive piece of hardware for no reason? Why does a lobotomy apparently work if the pieces we cut out aren’t necessary for our personalities and learning? Why do we have mental disorders, how come SSRI’s work, how come Cocaine and alchohol amongst other drugs work?
I would say that we ARE certain the brain is necessary given the evidence at hand. Sorry, one wacky article that could very well be in the Weekly World News doesn’t do anything to convice me, and I am not even a Neurologist. I would put this on the rack with the Aquatic Ape theory myself- Unless that kid dies and we open him up and see how accurate those cat scans are. Then we can discuss science not being sure.
There are quite a few cases on record of large fluid filled cavities in a human brain - the usual result is mild to severe impairment of function, but sometimes the function seems normal.
I expect that the cases which present as normal have all the normal brain tissue compressed into a smaller volume, or possibly the cases that get reported are incompete or exaggerated.
There is no getting away from it, the brain is necessary for normal functioning.
It’s also my understanding that Neanderthals had children who may have been able to lift 200 lbs before they reacheed five years old and could lift 700 lbs as adults. Neanderthals were a ‘breed apart’ from Homo erectus. Just from that information I’d say this may explain the reason for the bigger brains. In the same way that other animals have bigger brains that present humans - it might come down to the ratio of brain to body size.
Well, in the interest of fairness, I’ll throw in an argument from what may seem like the “crackpot” side:
Ethnobotanist Terence McKenna theorized that Psilocybin Mushrooms (A.K.A. “Magic Mushrooms”) were a major catalyst in the emergence of human consciousness.
In a nutshell he contends that “mutation-causing, psychoactive chemical compounds in the early human diet directly influenced the rapid reorganization of the brain’s information-processing capacitities. Alkaloids in plants, specifically the hallucinogenic compounds such as psilocybin, dimethyltryptamine (DMT), and harmaline, could be the chemical factors in the protohuman diet that catalyzed the emergence of human self-reflection. The action of hallucinogens present in many common plants enhanced our information-processing activity, or environmental sensitivity, and thus contributed to the sudden expansion of the human brain size. At a later stage in this same process, hallucinogens acted as catalysts in the development of imagination, fueling the creation of internal stratagems and hopes that may well have synergized the emergence of language and religion.”
–Food of the Gods by Terence McKenna* (page 24)*
This is the main gist of his argument, but he does a great job in carefully laying out his theory & even manages to rebutt many objections to it (i.e. he argues that this is not a version of Lamarckism).
Anyways, since the OP asked for all theories & opinions, I thought it would only be fair to throw in a view from the fringe…