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...
Selection and lactase persistence