While I think the idea of adult Paleolithic hunter-gatherers regularly dying at age 30 can be laid to rest (sadly, I reckon that particular misconception has an impressive life expectancy), last week’s post on the Gurven-Kaplan paper brings up another question: if the human potential lifespan of 68-78 years, or roughly seven decades, is an evolved, inherent, even genetic trait, what is the evolutionary justification for its selection? Where is the advantage?
The classic Darwinian view is that selection of traits revolves almost entirely around fertility. Once an animal can no longer produce offspring, it has no “reason” to go on living. Since a genes’ survivability ultimately comes down to reproduction, whether an individual can have kids is the primary determinant of viability.
Speculation on ancestral lifespan is fun and potentially illuminating, but I think examining living, albeit imperfect, examples of modern hunter-gatherers offers greater insight. Sure, the environment has changed, wild food sources have shrunk in diversity and availability, and modern civilization has encroached and meddled and disrupted, but the few remaining hunter-gatherer populations exhibiting relatively untouched traditional lifestyles represent the most promising window into what life actually looked like and how long it lasted for our ancestors. Luckily, a couple of researchers – Gurven and Kaplan – had the bright idea to look at ethnographic studies on actual, living HG populations and analyze the available data on actual lifespan and mortality therein. They found some interesting stuff.
It has become an article of faith among, well, basically everyone, that our ancestors lived short, brutal lives. What are they touting as the average lifespan these days – 35 years old or so? I’ve heard anything between 25 and 40 years. The common counter is that infant mortality rates were higher than they are today, thus skewing the average. It’s also often pointed out that a relatively benign accident or illness by today’s standards – a broken arm, a rolled ankle, or a minor infection – could have prematurely ended Grok’s life. And that these cases say nothing about Grok’s potential to live 70+ years. The “short and brutal” meme has wedged itself in the public psyche, and it’s going to take a lot to extract it from its seemingly intractable position.
I’m going to riff a bit on something I’ve been thinking about regarding ancient human bones. This isn’t an official stance or anything; I’m just thinking out loud. Let me know what you think in the comment board.
Dairy, as I’ve discussed, is a somewhat hazy matter in the Primal Blueprint. With adequate reasons from solid thinkers both for and against, I’ve relegated dairy to the provisional, the peripheral, the speculative even as I choose to modestly indulge in it. As with most Primal gray areas, some forms appear less controversial than others. Raw, fermented, full fat dairy offers much more health benefit with fewer reservations than processed, low fat renderings. (Isn’t that always the case?) From a Primal perspective, however, dairy still remains somewhat of an enigma. Hardly one of the original, universal foods in human evolution, milk entered the scene at a surprisingly late date – only some 9,000 years ago with the advent of animal domestication. Researchers have long traced the “progression” of Grok‘s dairy intake from the Middle East into Europe, where milk actually became an unusually significant dietary staple. New research into the dairy “drift” now offers more details than ever surrounding this relatively isolated, albeit dramatic, evolutionary event.
When we think of Grok, we often imagine him in full-fledged hunting action – spear in hand, muscles in action, eyes on the latest prize prey. (Hence, the logo.) But such dramatic displays of power and prowess were fairly limited engagements. Grok, of course, had no full-time job. The lives of hunter-gatherers entailed much more than our label for them suggests. Experts who have studied modern hunter-gatherer societies estimate that most members of these communities spend about 3-5 hours a day “working,” which included all the basics of their food preparation. So, what else did Grok and his contemporaries do with their time? Could it be that hunter-gatherers weren’t poor slugs incessantly roaming and writhing in near starvation? Could it be that most of the time they actually had ample leisure time – to play, create, decorate, imagine and invent? Yes. Now ain’t that a kick in the head?
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