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Jun 162014

Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live, by Marlene Zuk

The myth of the golden age dies hard. People who espouse a Paleo lifestyle speak in terms of evolution, but the overall framework of their beliefs strikes me as being modeled surprisingly closely on earlier stories of a golden age, a fall, and attempts to live in accordance with the rules that will return us, at least to some degree, to the golden age. The complexities of evolution are smoothed out, and the story of human evolution is forced awkwardly into a much older narrative.

Marilyn Zuk’s book is a bracing corrective that explains how the Paleo picture is at odds with the way humans have really evolved (and continue to evolve). It’s not only informative but witty and even laugh-out-loud funny in spots.

Zuk begins by outlining the ways that human evolution is often misunderstood. The short version: Evolution is complicated. First, it can happen much more quickly than we often realize. Second, we never stopped evolving, although not everything about us is evolving at the same rate. We’re not really Fred Flintstone living in Manhattan, and we’re not “stuck with” a brain or a body or a set of genes that has been unable to “catch up” to current conditions. Different parts of the genome change at different rates under different circumstances.

It’s less meaningful, Zuk points out, to look at how genes differ or are the same between species of within a species over time than it is to ask which ones changed quickly, and why. The idea of a baseline human nature (or chimp or bonobo nature, for that matter) that we can use for comparison is not really all that helpful.

There’s also no reason to believe that humans were ever perfectly adapted to their environment. Zuk quotes François Jacob: “Nature is a tinkerer, not an engineer.” We’ve always been, and continue to be, a work in progress, with all the trade-offs involved in working within the limitations of what’s already there. Once you look at the story of human evolution that way, you see that it’s hard to put a finger on a perfect time when we were very well fitted to our environment and to try to replicate that environment. We’ve always been a series of kludges that worked well enough most of the time.

On top of that, because different parts of the genome evolve at different rates, there isn’t even a single environment that shaped all of our characteristics. Zuk argues that you need to think in terms of the environment that affected a particular trait rather than tracing everything back to the savanna. (Although it can be hard to pin down the landscape and circumstances in which a particular adaptation occurred because humans have lived in so many different environments, even before the advent of agriculture and the technologies that enabled us to live pretty much anywhere.)

Within this framework, Zuk examines diet, exercise, illness and health, how men and women behave and relate to each other, and how people raise families.

Regarding diet, for example, she discusses the relatively recent adaptation that enables adults to drink milk (which, I learned, is actually two different genetic changes in European and African populations, an example of convergent evolution). She also says that humans didn’t have a single diet between the emergence of the genus Homo and the rise of agriculture. In any case, it’s hard to draw a line regarding pre-agricultural and post-agricultural humanity because there are different types of agriculture—horticulture, pastoralism, and intensive agriculture—and it’s not clear when some of the changes in humans related to intensive agriculture began to appear.

Overall, this excellent book taught me a lot about the subtleties and complications of human evolution, and it was great fun to read. On a deeper level, I think it fosters a better understanding of the fuller implications of being evolved, and evolving, creatures for whom there was, and will be, no golden age.

 Posted by at 8:57 am
Mar 122014

A couple of years ago I reviewed Werner Herzog’s documentary Cave of Forgotten Dreams, a fascinating tour of the prehistoric art in Chauvet cave in southern France. The art, which was discovered in 1994, was notable not only for its beauty and variety, but also because it was thought to be the earliest cave art found to date. The oldest paintings were estimated to be as much as 36,000 years old; this placed them in the Aurignacian culture, which produced the earliest known human art.)

However, new research has examined the paintings in the context of other early art, and the results suggest that the bulk of the paintings may be no more than around 18,000 to 26,000 years old, which would put them in more recent periods.

Regardless of the age of the paintings, they are well worth exploring, either by watching Herzog’s film or visiting the French government’s Chauvet cave web site.

Mar 062014

In Washington Monthly, Chris Mooney has reviewed two new books that synthesize what we know to date about how our political outlooks are related to our personalities. The review is worth reading in its entirety, and it raises some interesting points about evolution, personality, and politics.

However, I was struck by one thing that I wanted to mention because it seems representative of a particular type of statement about evolution that really bugs me: the simplistic application of a single complex evolutionary phenomenon to some complex contemporary situation. To wit:

Again and again, when they take the widely accepted Big Five personality traits test, liberals tend to score higher on one of the five major dimensions—openness: the desire to explore, to try new things, to meet new people—and conservatives score higher on conscientiousness: the desire for order, structure, and stability. … And this finding is highly consequential, because as [both books] note, people tend to mate and have offspring with those who are similar to them on the openness measure—and therefore, with those who share their deeply rooted political outlook. It’s a process called “assortative mating,” and it will almost certainly exacerbate our current political divide.

It’s the last part of the last sentence that got to me. My gripe is essentially that assortative mating has, as far as we know, been going on for a very long time, through various kinds of political arrangements and balances of power between liberals and conservatives,1 and it’s hard to see how it could affect our current political divide except in the broadest sense that it presumably has some effect on what kind of species we are.

If it has produced a mixed bag of personality traits (not to mention physical traits) so far (as Mooney discusses later in the review), why should we believe that it’s going to somehow worsen a very recent (in evolutionary terms, not even the blink of an eye) situation that involves a very particular history and set of political institutions?

My point is not that assortative mating is unimportant to human societies, just that mate choice is complicated, and we don’t know enough right now to say anything meaningful about how it affects specific contemporary political situations (or maybe even broader questions of human nature overall). People may look for many types of similarity in a mate: other personality traits, looks, socioeconomic status, level of education, religion, and intelligence, for example. Not only that, but they may also sometimes look for dissimilarity, or things that aren’t really about similarity or difference.

People do try to educate their children according to their beliefs, but again, this has been going on forever, and the results are mixed. The apple sometimes does fall pretty far from the tree. More importantly, if this could be described as evolution at all, it’s cultural evolution, not biological evolution, and it’s got nothing to do with assortative mating.

I bring this up not just to vent, but also because this sort of oversimplification is an obstacle to fruitful discussion of how human evolution has affected human nature and the societies we create. This is a complex topic that involves aspects of our lives that we’re sensitive about; our data are limited at the moment. Still, it’s a subject of endless interest, which is all the more reason to be careful how we talk about it.

1 The liberal/conservative distinction has been used in most of the research into politics and personality that has hit the news, and it’s the focus of Mooney’s review, but it will be nice when the research has developed to the point where it can consider more sophisticated categories. It would be useful to have at least a second axis, as in the Political Compass system. Current research into personality and politics is fascinating, but it’s just beginning.

Mar 312013

I went to hear Dr. Kim Hill's talk on Thursday on the origins of human uniqueness. Hill began by framing our uniqueness in terms of our energy usage and biological dominance&emdash;for example, the fact that we cycle more nitrogen than all other terrestrial lifeforms combined, and we represent 10 times more biomass than any other large species that ever lived. We also exhibit extreme social complexity and specialization; no other species has anything remotely resembling the New York Stock Exchange or the NCAA basketball tournament, for example. Moreover, even before agriculture, we had colonized every landmass, and hunter-gatherers exhibited unusually complex social behavior compared to that of other animals. However, although we exhibit non-unique traits that arose through non-unique processes, we somehow turned into this distinctive species. The question is, how?

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Happy Darwin Day!

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Feb 122013

People around the world are celebrating the anniversary of Charles Darwin’s birth on February 12, 1809. (Maybe you can find a Darwin Day event near you.) To mark the day, I thought I’d share this quote from The Descent of Man, which has particular resonance for me because it seems related to what I’ve been reading in Steven Pinker’s The Better Angels of Our Nature: Why Violence Has Declined.

As man advances in civilization, and small tribes are united into larger communities, the simplest reason would tell each individual that he ought to extend his social instincts and sympathies to all the members of the same nation, though personally unknown to him. This point being once reached, there is only an artificial barrier to prevent his sympathies extending to the men of all nations and races. If, indeed, such men are separated from him by great differences in appearance or habits, experience unfortunately shews us how long it is, before we look at them as our fellow-creatures. Sympathy beyond the confines of man, that is, humanity to the lower animals, seems to be one of the latest moral acquisitions. It is apparently unfelt by savages, except towards their pets. How little the old Romans knew of it is shewn by their abhorrent gladiatorial exhibitions. The very idea of humanity, as far as I could observe, was new to most of the Gauchos of the Pampas. This virtue, one of the noblest with which man is endowed, seems to arise incidentally from our sympathies becoming more tender and more widely diffused, until they are extended to all sentient beings. As soon as this virtue is honoured and practised by some few men, it spreads through instruction and example to the young, and eventually becomes incorporated in public opinion.

The Descent of Man, Chapter III: Comparison Of The Mental Powers Of Man And The Lower Animals

Feb 062013

Like most thinking primates, I am sometimes baffled by my own behavior and reactions. As a result, I generally take an interest in research that explains otherwise puzzling behavior, particularly research involving subconscious influences. One type of study examines the effect of small, perhaps seemingly inconsequential, external events that prime people to behave in a certain way. The technical term for this is behavioral priming, and all sorts of fascinating results have been offered in recent decades. People who have been exposed to words associated with old age walk more slowly when leaving the psychology lab than those who have not, for example, and people who were asked to hold a warm drink as part of a lab experiment judged others more favorably than people who were handed a cold drink.

However, this work has been encountering problems lately, chiefly because it is hard to replicate, as described in this article by Tom Bartlett in the Chronicle of Higher Education. (You might also find an earlier article by Bartlett about the reproducibility of psychological research interesting.) Thus, the answer to the question in the title is that the jury is still out. Stay tuned.

Darwin Day

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Feb 052013

The realization that humans were produced by a long, ongoing evolutionary process, like every other living thing on the planet, suggested that many magical or supernatural creation stories are best considered as myths or metaphors rather than as literal truths. It also caused profound changes in our view of ourselves and our place in nature. On February 12, people around the world will celebrate the life and work of Charles Darwin, who was born on that date in 1809 and whose work was crucial to that realization. The Secular Alliance of Indiana University is celebrating Darwin Day with several events spread out over the week beginning on Sunday, February 10. Check it out at their Darwin Week page. For a list of events in other parts of the world, visit the International Darwin Day Foundation’s events page.

 Posted by at 11:34 pm
Nov 192012

I’m reading Steven Pinker’s The Better Angels of Our Nature: Why Violence Has Declined. I really like the book so far. For example, I liked what he had to say in a chapter on what he calls the humanitarian revolution in human history, in which humans came to treat their conspecifics with less violence. He talks about two factors in the decline in “institutionalized superstitious killing, whether in human sacrifice, blood libel, or witch persecution”:

One is intellectual: the realization that some events, even those with profound personal significance, must be attributed to impersonal physical forces and raw chance rather than the designs of other conscious beings. A great principle of moral advancement, on a par with “Love thy neighbor” and “All men are created equal,” is the one on the bumper sticker: “Shit happens.”

(The other factor, incidentally, is “an increased valuation of human life and happiness”—including that of other people.)