Human Evolution

Posted: January 23, 2008 in Science

The BBC News has an article reporting that scientists have found evidence to suggest that human evolution is “speeding up.” Scare quotes are used for speeding up in the title of the article for good reason: it’s a reckless remark that can’t be proffered with a straight face. The study on which the article is based

looked specifically at genetic variations called “single nucleotide polymorphisms,” or SNPs. These are single-point mutations, or changes, in the genetic sequence of DNA on chromosomes.

If the mutation is advantageous then it will spread rapidly in the population, along with DNA on either side of the mutation.

It’s unclear to me whether it’s fair to conclude that evidence of a few changes in genetic sequence is tantamount to evolutionary change on the order of species change, which the article never states. Is there a term that describes minor genetic changes without meaningful change in the species? Put another way, isn’t a wide range of genetic variation within the species pretty normal without being evolutionary?

Researchers found evidence of recent selection in 7% of all human genes, including lighter skin and blue eyes in northern Europe and partial resistance to diseases, such as malaria, among some African populations.

This makes me wonder if the usual four mechanisms influencing evolution — natural selection, mutation, random genetic drift, and gene flow — shouldn’t be amended to include cultural election in the case of culturally preferred attributes such as skin type and eye color. (Nope, no suggestion of cultural bias or racial preference there. Move along.)

Also, if I’m not mistaken, when human evolution is discussed by regular folks without specialized training in genetics, the usual context is science fiction and the mode of evolution is either cultural (evolved minds) or biological (evolved bodies) or both. These are wildly divergent from a more narrowly defined science of genetic evolution, which apparently considers even modest change or variation evolutionary.

Without providing suitable context for the science and disclaiming the obvious associations with science fiction, the article invites credulous readers to infer that we’re pointed toward an a evolutionary breakthrough of some sort. What else could “speed up” suggest? The article muddies the waters further with these poorly framed quotes by Steve Jones, a genetics professor at of University College London:

“The general picture that evolution has speeded up in the last 10,000 years as we change from, to put it bluntly, being animals to being humans is clearly true,” he explained. “To suggest it is happening at this instant, I would suggest, is probably wrong.”

“At the moment we are in an evolutionary interval. We are in between two storms. One storm has more or less blown itself out, the storm of farming.”

I won’t bother to comment on the idiotic suggestion that humans aren’t animals. The more immediate problem is timescale. In evolutionary time, 10,000 years is almost nothing. Whether you believe in gradualism or punctuated equilibrium or some blend of both, it typically takes tens of thousands of years to observe changes to the genotype that aren’t merely chromosomal variations. Evolution is happening now, this instant; it’s always happening. But it isn’t instantaneous. Neither is a sunrise. Disclaiming such a thing is absurd to even a novice.

Perhaps it’s worthwhile to remind gentle readers not to get science news from the popular press. Whereas the study may have uncovered something meaningful to a geneticist, it holds almost no value to the general public the way it is reported and veers dangerously toward suggesting things from the realm of science fiction. Science is very good at discovering how things work. It’s not so good at predicting things or even extrapolating trends more than one step beyond the evidence. Take the “suggestion” of human evolution “speeding up” with a sizeable grain of salt.

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Comments
  1. Interesting article. I hadn’t heard that about human evolution before. I hope our brain size changes dramatically in either direction. As Kurt Vonnegut noted long ago (in Galapagos, if I remember correctly), humans have exactly the wrong size brain.

    If we had larger brains (or more accurately were smarter), we might be smart enough not to get into all the trouble we do. If we had smaller brains, we wouldn’t be able to do so. More likely, we’re breeding stupider without the high rate of predation and other accidents that would happen in a hunter gatherer society. In modern society, even those who walk out in front of buses are normally spared by alert drivers.

    With respect to the usefulness of this information to a general audience, it probably depends on the level of general. Most of the minority of the general public that actually believes evolution is real, still believes it to be either directional or worse, directed by god.

    For the reasonably educated who know that evolution is neither directed toward greater complexity nor directed towards a particular goal by a deity, it is interesting information.

    This can point to a reason for interesting facts such as high incidence of type 2 diabetes in hunter gatherer societies that have recently made the switch to agrarian sedentary lives. The gene for type 2 diabetes happens to provide greater ability to survive the binge-starve cycle of the hunter gatherer lifestyle, so is more common there.

    Since agriculture has only been around for about 10,000 years or so, the relatively reduced incidence of type 2 diabetes in people descended from older agrarian societies shows that some evolution has taken place. Of course, even without the high genetic tendency, McDs is capable of causing diabetes in the increasingly obese population of the U.S.

    I’d love to hear about more differences that can be explained by this relatively rapid evolution.

    Perhaps, if we don’t kill ourselves off too quickly, we’ll evolve teeth that are more resilient to current diets. Pre-agrarian societies did not have tooth decay according to paleopathologists. (The source of that is probably The Third Chimpanzee by Jared Diamond. I can try to find a web source if anyone doubts it. I realize it seems fairly incredible.)

  2. Brutus says:

    Misanthropic Scott wrote:

    Since agriculture has only been around for about 10,000 years or so, the relatively reduced incidence of type 2 diabetes in people descended from older agrarian societies shows that some evolution has taken place. Of course, even without the high genetic tendency, McDs is capable of causing diabetes in the increasingly obese population of the U.S.

    I’d love to hear about more differences that can be explained by this relatively rapid evolution.

    I’ve been puzzling for a couple days about how to respond to your comment. I’m certainly no expert on theories of evolution, and I don’t track research reports on the subject. So please don’t expect that I can or will follow up in answer to your desire for more info.

    I’ll say this much more, though: the four mechanisms influencing evolution may be inadequate to explain influences felt in the modern era. When a fast food chain or an invention like the television is able to exert so much influence single handedly that our evolutionary path is altered (only truly discoverable in hindsight), those influences don’t fit too well within the classical theory. Because of our relatively high standard of living and the ability of even weak or compromised specimens to procreate, the sense that survival of the fittest drives natural selection may be misguided, at least in terms of human evolution. Further, the growing number of extirpated species resulting from human influence on the environment doesn’t strike me as a natural process but as a system wildly out of balance. Perhaps that’s really about how one defines one’s terms.

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