Monthly Archives: May 2012

Dr. Pangloss runs a marathon

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Runners in the 2009 New York Marathon. Photo by Whiskeygonebad.

ResearchBlogging.orgThis just came over Twitter (hat tip to @DLiancourt): NPR is running a story claiming that the “runner’s high” some of us feel after a good workout is an adaptation to prompt us to keep fit, or something.

When people exercise aerobically, their bodies can actually make drugs—cannabinoids, the same kind of chemicals in marijuana. [University of Ariona anthropologist David] Raichlen wondered if other distance-running animals also produced those drugs. If so, maybe runner’s high is not some peculiar thing with humans. Maybe it’s an evolutionary payoff for doing something hard and painful, that also helps them survive better, be healthier, hunt better or have more offspring.

So, in a study [$a] pubished in The Journal of Experimental Biology, Raichlen tested this adaptive hypothesis by comparing the levels of these “endogenous cannabinoids” in the blood of humans, dogs, and ferrets after running on a treadmill. The idea being that the ancestors of dogs, like ours, made a living by running—chasing down prey—while ferrets don’t.

So it’s kind of nice to see that Raichlen and his coauthors did, indeed, find that humans and dogs both had higher levels of endogenous cannabinoids in their blood after a run, and the ferrets didn’t. That’s a useful evolutionary data point: it suggests that whatever physiological system prompts endogenous cannabinoid production in connection with exercise dates to (at least) the common ancestor of dogs and humans, and that its preservation in both species may be linked to our shared ability to run long distances.

But it really doesn’t show that this cannabinoid response is an adaptation to reward us for putting in our daily miles.

To really show that the runner’s high is an adaptation, of course, we’d need data that showed (1) observed variation in the runner’s high response has a genetic basis, and (2) people who had get stronger runner’s highs have more babies. But even apart from that, the understanding of what is good for us today—getting off our butts and going for a run—isn’t particularly that well connencted to the lives of our proto-human ancestors. Does Raichlen really think that early humans (or dogs, or any other animal that chases down prey) would just sit around and go hungry if we didn’t have a cannabinoid payoff at the end of the hunt?

And then, in the text of the very same NPR article, an orthopedic surgeon is quoted saying that the “runner’s high” can actually be a problem:

[Dr. Christina] Morganti treats runners for injuries and she says they’re the worst patients. “The treatment is to stop running,” she says. “They won’t. They don’t want to. A lot of the behavior is not unlike the patients we have who are seeking drugs. It’s really similar. It’s an addiction.”

So … a physiological response that prompts some of us to run even when running is likely to exacerbate injury is a good thing? How, exactly, would giving yourself shin splints lead to greater reproductive fitness if you’re making a living hunting gazelles on the savannah? I’m going to go out on a limb and say it wouldn’t.

Here’s an alternative hypothesis, which I freely admit is no better supported by the available data: the endogenous cannabinoid response isn’t a “reward” for running. Instead, it helped our ancestors tolerate the stress of running when they needed to, by letting them ignore minor pains and press on after that one elusive, tasty antelope. For our ancestors, dinner was the reward for running, not the cannabinoids. In the modern world, where we don’t run for our dinners, we’ve re-purposed the pleasant persistance of those cannabinoids as a motivation to replace that original life-or-death need.

Whatever the actual evolutionary origins of the “runner’s high,” the idea that it’s an adaptive reward for exercise is nothing more than adaptive storytelling filtered through the lens of our modern, very unnatural, lives. Don’t get me wrong—I love to run, and in fact I’m a month away from my fourth marathon. But I’m not going to pretend that I’ll be running those 26.2 miles because natural selection wants me to.◼

Reference

Raichlen, D., Foster, A., Gerdeman, G., Seillier, A., & Giuffrida, A. (2012). Wired to run: exercise-induced endocannabinoid signaling in humans and cursorial mammals with implications for the ‘runner’s high’ Journal of Experimental Biology, 215 (8), 1331-6 DOI: 10.1242/jeb.063677

The living rainbow: The selective benefit of a fa’afafine in the family

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ResearchBlogging.orgOne of the key evolutionary puzzles of same-sex sexuality, as it manifests in modern, Western human societies, is that those of us attracted to members of our own biological sex don’t make a lot of babies. I’ve already spent a lot of pixels on the question of how genes for same-sex attraction might persist in human populations in the face of that selective cost—but a paper just published in PLoS ONE adds some evidence in favor of one popular hypothesis: that gene variants that make men more likely to be gay could also make their straight relatives more fertile.

The new paper presents data from Samoa, where the traditional culture has long had a place for men who are attracted to other men, in the role of fa’afafine—literally, men who “live in the manner of women.” Samoan boys who show interest in feminine activities are recognized by their families as members of this “third gender,” which is more like the modern Western conception of transgender identity than what we call “gay.” Fa’afafine often present and dress like straight women, and as adults, they generally have relationships with straight-identified men. But fa’afafine aren’t exactly “transgendered” as we understand that concept in the West—they don’t have the sense that their bodies don’t match their gender identity.

The fact that Samoan culture accommodates and accepts same-sex sexuality makes it an especially interesting context for testing hypotheses about the evolution of queer sexuality, including the idea that relatives of fa’afafine might be more fertile than people with no fa’afafine in the family. The study’s coauthors surveyed Samoan fa’afafine and straight men, asking how many children their grandmothers, aunts, and uncles had had. And they found that grandmothers of fa’afafine—both maternal and paternal grandmothers—had more children than grandmothers of the straight-identified men they interviewed.◼

Reference

VanderLaan, D., Forrester, D., Petterson, L., & Vasey, P. (2012). Offspring production among the extended relatives of Samoan men and fa’afafine. PLoS ONE, 7 (4) DOI: 10.1371/journal.pone.0036088

Science online, diverse botanical evolution edition

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Wind turbines. Photo by ali_pk.

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Carnival of Evolution, May 2012

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Photo by NS Newsflash.

This month’s issue of the Carnival of Evolution, which collects online writing about Darwin’s dangerous idea and all its variously modified descendents, is online over at John S. Wilkins’s blog Evolving Thoughts. Highlights include, but are not limited to, an attempt to trace the origin of the phrase “social Darwinism,” discussion of how sloths and turtles evolved to move slowly, and whether the diet of early humans was more healthy than ours. Go now and read the whole thing.◼

Be advised

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It is mean and insulting and completely outside of the realm of polite behavior to ask that fundamentalist Christians explain why the “plain text” of the book they use to justify treating queer people as second-class citizens is different from the plain text of the same book that enthusiastically endorses slavery, genocide, and apalling mistreatment of women.

Especially when, as Dan Savage did, you have the nerve to call that hateful interpretive double-standard “bullshit.”

Dan’s apologized exactly to the extent he ought (which isn’t much) and come out with guns a-blazing against the fundamentalist fish in the theological barrel that is modern “Biblical literalism.”

Of course, the point of all this is not that it was rude for him to use the word “bullshit,” or even to describe those poor, defenseless Christian teenagers who walked out rather than engage with a perfectly legitimate theological question as “pansy-assed.” It was rude of Dan to confront those kids—and, now, the universe of fundamentalist offense-addicts who are giving him their undivided attention—with the fact that no matter what they claim, their “literalism” is a tangled mess of specific interpretive decisions that have nothing to do with the “plain text” of the Bible. It’s never been about adhering to the superficial meaning of the King James (or any other) text; it’s about putting their own mean little prejudices in the mouth of an unassailable, inaccessible, invisible Creator.

In other words, Dan told those kids that if they’ve been mean to gay people, it’s because they wanted to be mean to gay people. And they didn’t have a word to say in their own defense.◼

Almost immediately updated to add of course Fred Clark and John Shore are all over this.

Nothing in Biology Makes Sense: The link between science and religious (un)belief

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The Thinker. Photo by marttj.

This week at the collaborative science blog Nothing in Biology Makes Sense, guest contributor Amy Dapper takes on a recent psychological study showing that people prompted to think analytically were subsequently reported less likely to report religious belief.

Their first study establishes a correlational relationship between analytic thinking and religious belief by asking participants to answer three clever questions that have an immediate intuitive, but incorrect, answer and a correct answer that requires deeper analytical processing. These questions, and their answers, can be found in the table below. The study participants then answered a survey about their religious beliefs. The results show that participants that arrive at the correct, analytical answers to the first set of questions also tend to exhibit more religious disbelief in their responses to the survey.

The results would seem to confirm the experiences of many of us working in science: when you think analytically Monday through Friday, it can be difficult to stop thinking that way on Sunday morning. For more detail on the experiments, go read the whole thing.◼