we range north

I'll tell you what, when I realized we humans are on one level nothing more than furless animals, and the implications of that, it broadened my appreciation of the modern state of the human condition considerably.

In the first place I realized if it weren't for our tool making capability (our human intelligence), we would be limited to living in the tropics, or near tropics. Without fire and the ability to make warm clothing, we'd be sunk in colder climates. Humans would not have been able to range north (or south) away from warmer climes.

This led me also to thinking more about what sort of bodies we have in terms of diet. We mammals can be either herbivore, carnivore, or omnivore. I grew up thinking we humans were omnivorous, but now I wonder. Or more precisely, obviously we can be omnivorous, the question should be what is the optimum human diet... which diet contributes most to good health? Clearly, the world is not universally ready to agree there is an optimum human diet, or if there is one, what it is. We see experts of every stripe disagree on this. But curiously, there is little debate about the idea all other species on the planet have optimum "species specific" diets.

But again, similar to the "lack of fur" question, if it weren't for our intelligence and tool making capability, it seems we would clearly be more of the herbivore persuasion, with potential for opportunistic omnivorism. We clearly do not have the physical makeup of a carnivore - no claws, fangs, or digestive system of the carnivore. Without tools we would find hunting difficult. That probably goes some way to explaining why our tool less anthropoid ape cousins are nearly exclusively herbivore. There is some opportunistic omnivorism in some of the species, but when we consider total intake by calories, the insect and animal consumption are arguably negligible. The vast majority of calories of all anthropoid apes come from plant sources, except certain human populations (most humans are predominantly plant eaters however).

Unquestionably our brains expanded our capacity for adaptation tremendously, allowing us to range beyond the tropics, where it is thought first humans originated. We ate from the tree of knowledge and were cast from the garden of eden. Never looked at it that way before.

So we can adapt to some degree to any condition almost anywhere on terrestrial earth. Modern technology helps a lot too. No one would want to live at the research station in Antarctica wrapped only in fur pelts huddled by fire!

None of this, however, addresses the question of optimal conditions or diet: what diet would produce the best health, disease resistance, athletic performance, and longevity, other things equal (activity, sleep, etc.)? Too complex to be examined in total at once, studies break the question into component parts and extrapolations are made to the whole, not a true scientific "answer" to the question. As a result science isn't really asking this specific question. But we have a lot of anecdotal experience and opinion... and more debate and disagreement.

As an aside, Campbell, the topic of a previous post here, and his "China Study", is the only scientific study that I'm aware of attempting to answer the larger "optimum diet" question. But of course, there is much debate about his conclusions. I'm going to repost the link to an overview lecture of his life's work, titled "Resolving The Health Care Crisis", it's well worth 20 minutes of your time IMO, if you haven't yet, food for thought, if nothing else:
http://www.youtube.com/watch?v=1CN7PF10RKo

One thing is pretty clear, the official extrapolations we have been living by since the advent of industrialized food production have needed recent modification, and that (slow) process may still be underway. There has been a definite shift toward a greater quantity and variety of plants in our diets. It may not be coincidence given our biology, if we take adaptability out of the equation. Indeed, by that measure, it might be argued we are strongest and best with a predominantly plant sourced diet.

Oh, and that smaller population of humans I mentioned previously that does not source most of their calories from plants? That would be us, the inhabitants of the industrialized world. The ones with soaring rates of obesity, diabetes, cancer and heart disease.