There are a few questions which transcend science and capture the imagination and thoughts of the greater population. One such question sits at the nexus of the fields of anthropology, sociobiology, ethology, psychology, evolutionary/population genetics, primatology, and archaeology there sits a question which is the Holy Grail of biological inquiries. Progressive hypotheses have been posed for hundreds of years, hopefully been getting closer and closer to the truth. But we're still not there. It is a topic which has influenced religion, literature, philosophy; thousands of books and stories have hinged on this question, some of the most notable recent examples include Philip Pullman's His Dark Materials, the Chrono series, and even the modern reinterpretation of Battlestar Galactica.
Simply put, the question is, "Why are we here?" However, with our existing knowledge of physics and the biology of natural selection, we can focus the question into "How did we get here?" Well, where exactly is here? We know how we got to this planet - astrophysics and primordial soup. So where have we gone that other life hasn't? Well, we appear to defy many "rules" of nature, and we've created complex cultures and vast civilizations, spanning the entire globe. No other creature has come close to extending as far as our species has. "How did we get to where we are today?"
My actions at this very moment rely on a collection of unique human accomplishments: writing this blog post about human understanding of natural science on the internet for a global community. Your pet snake and my monkey friends will never see one of their species capable of understanding even one of these concepts. So, the question has now reached the form, "How were humans able to become civilized and advanced beyond any other animal?"
The question is not, "How are humans different form other animals?" This question has been addressed for years, and our understanding of the answer is quite concrete. To be certain, this information is important to understanding my question, but alone it is not a solution. If you're interested in the answer to this other question, I recommend Human, by neuroscientist Michael Gazzaniga, a modern overview of the known difference between man and the other apes.
The real question, the true Grail, concerns events which happened tens of thousands of years ago. Humans weren't always able to do these neat things we take for granted in the modern age. So when and did these developments start? For hundreds of thousands of years, we lived as hunter-gatherers (H-G), and for millions of years past our emergence, our authrolopithecine ancestors lived this way as well. The prehistoric hunter-gatherer lifestyle is actually quite similar to how modern chimpanzees live. Even my friends, the baboons, gather their food in much the same way our cro-magnon ancestors did.
Then something happened. It transpired tens of thousands of years ago, and may have been a transition which itself took thousands of years.
Agriculture used to be a big deal in terms of fundamental human achievements. Don't take this the wrong way, the invention of agriculture was huge, but it wasn't what set us apart. Something happened before agriculture, something which allowed us to develop massive living groups.
A hundred thousand years ago and earlier, our ancestors lived as simple hunter-gatherers. Between simple hunter-gatherers and agricultural based towns is an intermediate step: complex hunter-gatherers. Complex hunter-gatherers lived in a larger groups, used more complex tools, and practiced the gathering tactic of radiating mobility.
Simple hunter-gatherers are characterized by their circular mobility and lack of permanent settlements. They would travel from place to place, using some of the local resources and then moving on before completely draining the area. They would follow game to satisfy their need for protein, and gather as they would go, altering their movements seasonally to accommodate migration and ripening of fruit. The baboons do almost exactly what I'm describing, except without the hunting.
Complex tools and sophisticated hunting and gathering techniques are no big deal. We're part of the branch of primates (chimpanzees) which excels at technology. It makes decent sense for us to be able to do the seemingly insane things we do with technology, both modern and ancient.
It is the large group size which is the confusing part of this situation. Chimps can maintain group sizes of 70 at the most. Complex hunter-gatherers managed to push this number up into the hundreds and beyond. Simple hunter-gatherering humans didn't live this way. They still don't. Contemporary African bushmen camps contain about a dozen tiny stick huts populated by approximately 40 people.
So how'd we do it? We lived as simple hunter gatherers for hundreds of thousands of years. Why the sudden change to larger groups? Animal behavior is adaptive, which means we wouldn't have done it unless it helped us out somehow. In hindsight, the advantages of agriculture over complex H-G over simple H-G are obvious, and our vast population expansion which occurred over the last ten thousand years is further proof of our unique accomplishments. But why should we have managed to succeed when in the millions of years of hominid history, no one else figured it out?
Scientists have ideas. Lots of them. Yet, whatever happened, it happened so long ago that little evidence remains. This is the biggest impediment we face in our attempts to tackle the question. We must work with extremely limited remains of tools, shelters, and bodies. Human remains provide limited genetic data, which may be the most useful data at our disposal.
My main purpose in writing this is so I have the neccessary background info readily at hand for discussions of the various theories which seek to answer the question. There are a slew of papers, some old, most new, which seek to give answer(s). They're interesting to read and this is "kind of a big deal" so I think they are worth the attention. Although, I'll also say right here and now that I don't believe any of these papers have it right, which makes the debate all the more fun.
Why am I personally interested? Well, we're basically talking about figuring out the most important development in human history! That sounds pretty exciting to me. Its also controversial, and I can't help myself, I'm drawn towards a good struggle. Plus, I have the advantage of having already read many of these papers, and I believe there are some conclusions being misrepresented, and something I can add from there...
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Next week: "Dishonor"
ReplyDeleteMore seriously, I don't think the argument you are making here is very compelling. You seem to feel that the change from small to large hunter-gatherer groups was a profound development (more important than agriculture, you seem to imply). I agree that agriculture is not what sets us apart, but there is no reason to think large social groups are either.
Consider this scenario. Competition drives early humans to larger and larger brain sizes with correspondingly greater intelligences. This leads to improved efficiency in terms of food gathering, even at the small group level. (Humans are capable of advanced planning, knowing when certain foods will be available, keeping track of supplies, and--perhaps most importantly--efficiently allocating resources among group members in ways that baboons or even chimps are completely incapable of.) The improved intelligence thus leads to better food collection, which makes large groups more useful. No longer is the entire population engaged in food finding. Some members may engage in additional pursuits, which enrich the whole group; and there are obvious economies of scale that favor large assemblages once semi-specialists enter the economy. (A large group can simply support more of them.) Eventually, it is the same analytical skills that allowed for improved food gathering that lead people to develop agriculture; once one has the capacity and a modicum of free time to observe plant life cycles, crop planning is a natural step. The key development, which was an improvement in intelligence and abstract thinking ability, occurs at the small group level; the subsequent societal developments are not fundamental but outgrowths of enhanced intellect and food-management efficiency.
I have a further suggestion, based on my understanding of (relatively) large paleolithic cultures that have persisted into modern history and been observed. For example, the American Indians of eastern North America. At most times, their group size was small, typically dozens (or less) people living together. However, these small functional bands had larger tribal affinities. The tribes could number in the hundreds or even thousands, but interactions involving the whole tribe were infrequent or in some cases nonexistent. What seems to be unique to humans is the ability for an individual to develop an affinity with a group that is too large for them to have any personal interactions with most of the members. This is a consequence of a greater degree of abstract thinking than is seen in other animals. It also relies on our extremely detailed theory of mind. We alone among animals are able to make reasoned judgments about the fitness of others based solely on second-hand observations and opinions of those we trust. (Other primates cannot do this. Immigration in primate groups entails an incoming member developing at least a superficial degree of relationship with every other member of the entered group.) In this light, the existence of large hunter-gatherer groups is not so much a change in day-to-day existence (which is still based around a small group) but is based on the understanding among the small groups that regular interactions (including trade, and outbreeding) are beneficial to them all.
There are several problems with your counter-proposal.
ReplyDeleteFirstly, fossil evidence shows that our brain size is the same as a cro-mangnon. A neanderthal's is about the same, too (yes a bit smaller, though this might not be significant). Nevertheless, I think you may be meaning that intelligence increases in a population over time. This is harder to refute because it cannot be directly measured in fossil evidence. However, the literature seems to indicate that species do not increase their intelligence significantly over time. Plus, Heidelbergensis had language and survived for hundreds of thousands of years, so what was stopping them?
Secondly, there is a time between 70000 and 50000 years ago when archaeologists noted that tool technology in H-Gs "picked up." Our species had been stagnant for 200,000 years, and then suddenly we started to see complex core designs and such. Point is - it was not gradual as you suggest, but actually quite sudden.
Thirdly, your example is interesting, but you're making a lot of assumptions. Contemporary groups do not have the same genetic distributions as they did 20000 years ago. This might matter, it might not (I happen to believe it does), but it makes the example of the American Indians extremely dubious. From my experience, while people are capable of empathizing and understanding others' fitness needs to an extent, I do not believe it is as strong as you argue. What people can do and what they do are very different.
Ultimately, you're basically arguing for a form of Group Selection which, well, just doesn't work. There are a lot of problems with big groups being stable, which experienced theorists have never managed to get around satisfactorily. I plan to review much of the literature on this at a later time.
Your fundamental flaw is that you're comparing to chimps, not hominids. As I mentioned, our recent ancestors should have been capable of all these insights, and had the time to figure it out. But they didn't. So one needs to find where the difference lies. As I indicated in the post, its easy to suffer from hindsight bias in these discussions, which is what I think is happening here.
This reply may be a bit abrasive because I'm composing it when I should be asleep, but I felt the need to reply as soon as I could.
Please tell me you'll be in Chicago next Thanksgiving -- I want to see you guys talk in person :)
ReplyDeleteI don't think you sound abrasive, but I don't believe we are understanding each other. You say you think that I am arguing for signficantly increasing intelligence within our species over the last hundred thousand years. I am not; in fact, I thought that was the theory you were advocating. (That still seems to be what you're saying with your disputation of my comparison to American Indians.) This is a sufficiently complicated discussion that I don't think we are going to figure out our misunderstandings in this venue. Pfeng is right; it will be much better handled in a bar at Thanksgiving.
ReplyDeleteI am glad that we all agree that there's no way in Hades this is going to be figured out here.
ReplyDeleteThough, "The key development, which was an improvement in intelligence..." would never be uttered by this mouth.
And I realized later I think that I meant "rough around the edges" which in my sleep deprived state I failed remember this was one of those contexts where it doesn't quite mean the same thing as abrasive...