Humans are one of the most successful species on the planet. Over the course of human evolution we developed several traits that helped us become so dominant. In particular, we're very social and very smart. But which one played the bigger role in human evolution?
Advocating for intelligence is the "cognitive niche hypothesis". Proponents of this idea argue the secret to human success was using our smarts to adapt to new environments. This allowed us to expand and take over the planet. These benefits would also drive the evolution of even more intelligence, explaining why we have such ruddy big brains.
In the other corner is the similarly-named "cultural niche hypothesis". This claims being social was our biggest advantage. That way we could learn from one another and build on each others' inventions. Over time, this would cause our technology to improve as we built on top of each others innovations. It was this ratchet effect, made possible by our social nature, that allowed us to conquer the world.
Neither hypothesis suggests the other factor was irrelevant in human evolution. They just disagree with which played the bigger role. Did sociality or smarts matter more? Computer models might hold the answer.
Culture v. Cognition
There's a lot of things that make humans unique amongst the primates. We walk upright, we have no fur, and we talk. Of all these features, two seem to have been vital during our evolution: our sociality and our intellect.
This has led to debate over which is the more significant factor. Some argue that intelligence was the most important. This allowed our ancestors to develop new tools and technology. In turn, this meant they could adapt to their environment better; allowing us to spread around the world and become the successful primates you see today. This created a feedback loop, where being smart was beneficial so evolution made us even smarter. Which made us even more successful. Which drove us to become even smarter.
Under this model being social was still very important. Learning from one another means we didn't have to independently invent the entirety of human technology every generation. Which would take a long time. And potentially include many mistakes, which could be costly. Especially if we were - literally - playing with fire. Thus being social was important as it lowered the "cost" of getting technology, but ultimately, being smart was key. This is known as the cognitive niche hypothesis.
However, some were critical of this idea. They thought that being social was more than just a way to keep technological "costs" low. It could actually contribute to technology in it's own right. An individual learns something, improves on it, then passes on the new version. These social interactions allow for this constant improvement. The resulting benefits would drive evolution to make us more and more social, creating a similar feedback loop that made our technology better and better. Thus it was argued that our social relationships were really the key as to why humans were successful.
Again, under this idea being smart was still important. We still had to innovate and build on each others tools. But the fact there were other people around we could learn from was the key factor. This was the cultural niche hypothesis.
The road we travelled
These two ideas disagree over how important society was for human evolution. Unfortunately, society during our evolution is something we don't know much about. There wasn't really a stone-age facebook we can study.
Apart from that, both produce very similar predictions about what the archaeology of our ancestors should look like. For example, they both claim there should be an increase in population size over time (although made possible by different things). Both think technology should increase in complexity over time (but for different reasons). And both think the brains of our ancestors should get bigger over time (although - you guessed it - for different reasons).
However, a series of computer models have shown that whilst the end-product looks similar for both hypotheses, the route taken differs.
These models
The result of these models shows how the evolution of a social or smart human would differ. If people are learning from one another and then building on that learning then individuals don't actually have to be that smart. Teaching technology lowers the "cost" of acquiring it. Everyone doesn't have to start from scratch. This puts less pressure on the evolution of intelligence, slowing it down.
With less intelligence the rate of innovation is lower. That is, until intelligence evolves just enough that the next innovation becomes possible. Then that new technology explodes through the population. The result is "steps" of technological improvement. A punctuated equilibrium of stasis and innovation.
On the other hand, if being smart is the key factor then that makes intelligence very beneficial. Evolution drives it to develop rapidly. The result is a more consistent climb of intellect (and with it, technology).
Another key difference between the two is the range of technology present within each population. Intellect naturally differs between people. As such, if that's the main driver of technological development then the technology they're using would also vary. On other other hand, if it's being learnt from others then - provided everyone has access to the same teacher - it shouldn't vary as much.
Being social is special
Based on these models, it should be possible to tell which approach was driving human evolution. Does stone age technology remain in stasis, or not?
Well, it does. After the first set of stone tools was invented that remained the dominant technology for half a million years. Eventually technology took a step forward with the emergence of everyones' favourite tools: handaxes. But these also stuck around for an awfully long time. In fact, they were manufactured, almost unchanged, for at least a million years. Even as recently as the Neanderthals (who co-existed with us) technology seems to have been advancing very slowly. Except for a brief period of innovation towards the end of their existence, the Neanderthal toolkit barely changed for their whole history.
Based on that, the archaeology would seem to indicate that being social is what makes humans successful. And that's what the researcher who made these models claims. We're able to learn from each other and build on our societies ideas. This allows our tools to adapt to our environment, so we flourish. But that's all contingent on this pattern in the archaeology. A pattern many dispute.
For example, it is certainly true that the tools Neanderthals made stayed the same for most of their existence. However, the techniques they used to make them varied and improved with time. This "stasis" was only skin (or rock) deep. Similarly, there were many innovations and improvements to how handaxes were made. So if you were to line up all the stone tools our ancestors made, they would seem to fit the pattern of the cultural niche. Except if you look out how they were made you'd see changes more similar to the cognitive niche.
There is still some stasis. New methods weren't being "evovled" every day. Which raises the question: just how much stasis would be expected under the cultural model? How much under the cognitive model? Perhaps any stasis is enough to disprove the latter, meaning culture really is key. But if some stasis can be tolerated we're back to square one.
Unfortunately these models - being arbitrary sets of numbers in the real world - don't shed much light on the variation we would expect to see in the real world. So for the time being at least we're stuck not knowing.
But we're so damn close to the answer.
Summary
Computer models indicate that being social and learning from one another is how humans became successful. Whether or not those models line up with reality is a different matter.
References
Boyd, R., Richerson, P.J. and Henrich, J., 2011. The cultural niche: Why social learning is essential for human adaptation. Proceedings of the National Academy of Sciences, 108(Supplement 2), pp.10918-10925.
Gowlett, J.A., 2009. The longest transition or multiple revolutions?. In Sourcebook of Paleolithic Transitions (pp. 65-78). Springer New York.
Morgan, T.J., 2016. Testing the Cognitive and Cultural Niche Theories of Human Evolution. Current Anthropology, 57(3), pp.000-000.
Charles Perreault, P. Jeffrey Brantingham, Steven L. Kuhn, Sarah Wurz, and Xing Gao. Current Anthropology , Vol. 54, No. S8, Alternative Pathways to Complexity: Evolutionary Trajectories in the Middle Paleolithic and Middle Stone Age (December 2013) , pp. S397-S406
