Archive for the ‘The adaptationist programme’ Category

Filthy ideas

Monday, February 2nd, 2009

gorilladirt.jpgIt’s been a while since I grumbled about inappropriate evolution-speak in science writing in the NY Times. So at the risk of sounding shrill, I’m going to take another stab. Jane E. Brody has written about the immunological benefits of babies eating dirt. The idea that exposure to germs in early childhood can boost immune development and reduce risk of allergies and other auto-immune disorders has been around a while, and Brody’s article doesn’t really cover anything shocking. But this passage was annoying:

Since all instinctive behaviors have an evolutionary advantage or they would not have been retained for millions of years, chances are that [babies putting their grubby little hands in their mouths] has helped us survive as a species.

Do all instincts have an evolutionary advantage? Are all instincts adaptations? That opening line sounds irritatingly like another indiscriminate claim for adaptation. But in biological terms, instincts are hard-wired, not learned, and improve fitness. So I think by definition, instincts are adaptive. But has natural selection really favored babies putting things in their mouths, to increase exposure to germs and boost immunological development? (Is there variation in this? Have babies ever not eaten dirt?) I doubt it.

For most of human history, we didn’t have lysol antibacterial spray, soap, or running water. Babies, like the rest of us, were perpetually grubby and reliably teeming with microbes. So I can’t imagine that they needed an adaptation to increase exposure to germs. Only in our over-sanitized present does an instinct to seek and ingest dirt really make sense. So maybe this “instinct” is an adaptation—a really, really recent one. But… haven’t babies always eaten dirt?

Prehistoric women may not have had a passion for fashion

Wednesday, November 14th, 2007

passionfashion3.jpgAccording to Salon’s Broadsheet blog, I’m not the only graduate student frustrated by portrayals of scientific discoveries in the popular media. Anthropology student Allison Sherrill indicts MSNBC for spinning news from an archaeological dig into an entirely new story. Discovery of a small female figurine dressed in clothing prompted the MSNBC journalist to cry, “Prehistoric women had a passion for fashion.” The truth, in Sherrill’s words:

This type of news coverage typically frustrates archaeologists. Unfortunately very common — in order to make a better story, the media frequently portray a very tentative conclusion as well-supported truth, and furthermore, those hypotheses are often twisted into a meaning that the archaeologist never intended. In this case, some figurines that portray women in some kind of costume have been spun into a sweeping conclusion about women’s innate love to shop. The article even mentions that the archaeologists felt that their most important find had to do with early copper production, but obviously, that headline does not look nearly as exciting (or maybe they just couldn’t think of one that rhymed?).

Another naughty example by the NYTimes

Thursday, September 20th, 2007

This week The New York Times published an article by Nicholas Wade entitled “Is ‘Do Unto Others’ Written in Our Genes?” It reads like a parody of science writing, it’s so full of flimsy logic. Of course it’s just the latest article among many (e.g. 1,2,3) that have inappropriately invoked adaptive explanations for complex human characteristics.

The article describes the views of Jonathan Haidt, a psychologist at the University of Virginia who researches human emotions and morality. Haidt proposes that our morality is rooted in two fundamental structures, one “ancient” and one “modern.” Through cross-cultural research, he has also concluded that human morality is based on five moral systems, which may vary in importance but appear fundamental across most cultures. Some cultures emphasize the rights of the individual, for example, while others reinforce group cohesiveness. All this sounds interesting and enlightening, until the argument is overextended… and these moral structures become adaptations. “Religious behavior may be the result of natural selection,” according to Haidt, and “‘Those who found ways to bind themselves together were more successful.’” Haidt also claims that the “ancient” and “modern” moral structures evolved independently in humans, at different points in our history: before and after the emergence of language. Interesting speculation, but where’s the evidence?

To be honest, I’m more frustrated with the NYT‘s Nicholas Wade than I am with Haidt. I haven’t read Haidt’s research, so he very well may have been careful to explain the potential evolutionary implications to his anthropological and psychological findings. But consider the opening paragraph in the article:

Where do moral rules come from? From reason, some philosophers say. From God, say believers. Seldom considered is a source now being advocated by some biologists, that of evolution.

What biologists? Wade does not cite a single biologist, let alone an evolutionary biologist, in the article. For shame! This is downright inaccurate reporting.

So what’s the big deal? Two points. First, evolutionary biology is an actual field, in which empirical data are collected and theory is developed. Science has a method, in which hypotheses are formed and tested; you can’t just make up your own, convenient as it might be. This process generates evidence, which can support a claim. Without evidence, it is not science. Second, evolution is contentious in the public sphere. And small wonder! Haidt’s claims on the role of religion in human evolution—such as they might be—are absolutely, positively, not science (and not the first we’ve heard, either). Yet to a lay reader, the claim that morality is an evolutionary adaptation, proposed by someone with an academic degree and covered enthusiastically in the NYT science section, may seem like a perfectly legitimate representation of contemporary evolutionary theory. It’s not! Let’s not confuse titillating speculation with science, lest the power of basic science research to explain the world around us be destroyed.

Nothing in evolution makes sense except in light of population genetics

Tuesday, May 22nd, 2007

zebra.jpgEvolutionary biologist Michael Lynch has published a paper in PNAS this month in which he takes to task scientists in general, and evolutionary biologists in particular, for interpreting “virtually every aspect of biodiversity in adaptive terms.” His language is aggressive: he throws around words like “untenable” and likens the tendency of biologists to dramatize the power of natural selection to the invocation of an intelligent designer. At the end, he writes, “This tone of dissent is not meant to be disrespectful.” Given that he has specifically criticized some of his colleagues, it’s inevitable that some will be offended. But I love this paper, I’m thrilled it’s out there, and I hope it’s making a big splash.

For those interested in my wee little opinion, here’s why:


Thought experiment is not science

Tuesday, May 15th, 2007

wolpertbook.jpgToday’s cover story in Salon is an interview with biologist Lewis Wolpert, who argues that the propensity for religious belief is wired into our biology and is an evolutionary product of natural selection.

Wolpert is an atheist. He theorizes that the ability of early humans to understand causality—pounding this nut with this rock will break it open—enabled tool-making, which was an evolutionarily successful strategy. And thus the establishment of this causal worldview necessitated an explanation for everything:

Salon: So once you have an understanding of cause and effect, then ignorance is no longer tolerable? You want to explain everything.

Wolpert: Exactly. You know, we cannot tolerate not knowing the causes of things that affect our lives.

There’s a fairly logical flow of reason to this theory, and I’m all for thought experiments. But is this science? Perhaps Wolpert doesn’t claim any particular authority for this argument. But wait, right there in the title of his new book, Wolpert hauls in the “evolutionary explanation” juggernaut: Six Impossible Things Before Breakfast: the Evolutionary Origins of Belief. The problem here is that Wolpert’s ideas may be reasoned, but they are not evidenced. Science is an evidence-based discipline. The fact that Wolpert is an eminent (developmental) biologist may only exacerbate the problem, since so much authority is accorded to scientists. You know, because their discipline is so evidentiary.

Well, despite his training and esteemed contributions to science, perhaps Wolpert has relaxed his criteria for discerning facts. But what’s this about lack of evidence for qi, the energy manipulated by acupuncturists?

Salon: Maybe the scientific instruments that we have at our disposal just can’t detect anything about qi.

Wolpert: Sorry. When they invented qi, how in the hell did they know what an energy field was? They hardly had a concept of energy. I mean, if you go back and look at their evidence, I’m afraid it was a nice set of ideas, but I’m terribly sorry, evidence matters. And that’s what causal beliefs are really about. If we believe that something has a particular cause, we should be looking for the evidence.

So evidence does matter. But so, apparently, does hubris:

Wolpert: My argument is that causal understanding gave rise to toolmaking; that was the evolutionary advantage. It’s toolmaking that’s really driven human evolution. This is not widely accepted, I’m afraid, but there’s no question about it. It’s tools that really made us human. They may even have given rise to language.

No question about it? There must be a great deal of evidence for there to be no question about it… But if there were a great deal of evidence, it would be rather well-accepted, wouldn’t it? Let me be clear: intellectual discourse makes me happy. Let’s talk about the evolution of the psyche. But let’s not imply that it’s science. Evolution is such a fun explanation to invoke, but flinging around adaptive arguments willy-nilly just gets everyone into a lather and makes actual science that much more difficult to integrate into the popular consciousness.

Evolution of sex roles

Saturday, April 21st, 2007

invisiblesex1.jpgThe Philadelphia Inquirer published an article on April 2 reporting research findings on the sex roles of our hominid ancestors. It includes a reference to a new book, The Invisible Sex: Uncovering the True Roles of Women in Prehistory by James Adovasio, Olga Soffer and Jake Page. Perhaps the most prominent message in the article is that current paleoanthropology research is invested in studying human evolution from an equal-rights-minded perspective, while past research has chauvinistically and perhaps inaccurately emphasized the machismo of early man’s big-game hunting achievements. No doubt this enlightened effort to consider the importance of early woman’s labors to our extant existence reflects our recent cultural evolution towards gender equality. Bravo in this regard. And while I’ll never criticize the popular media for reporting on, nor researchers from researching, the evolutionary history of the species we’re all most interested in (our own), the fact remains that inferring evolutionary dynamics from ancient fragments of bones and tools is nearly impossible. The opacity of this problem is well illustrated by just how easily influenced the scientific perspective is by the social politics of our culture at large.

Still, there’s a big difference between making the most of the data you’ve got—and the validity of these researchers’ scientific conclusions should be evaluated by the rigor of their scientific method—and flat-out naivety or, worse, disingenuousness. At the end of the article, Stanford anthropologist Richard Klein is reported as saying that a mutation in the lineage of early humans may be responsible for our eventual success, as opposed to the eventual extinction of the related Neanderthal lineage. This point comes after a dramatic description of humans emerging into a “cultural” and “artistic” existence of sophisticated “conceptual thinking,” the implication being that our superior intellectual powers should be credited with saving us from extinction. (There’s no way to know this, either: another example of human bias?) But hand-waving aside, there are some things we DO understand rather well, and the extraordinarily complex, quantitative nature of human biology is one of them. No geneticist or evolutionary biologist would ever think that a single mutation could induce such a dramatic new phenotype, so why should an anthropologist (or reporter)? The truth is almost certainly that multiple mutations distinguished our early human ancestors from their Neanderthal neighbors. This may be less easily dramatized to a non-scientific audience, but I argue strenuously that an accurate representation of the scientific process is as critical in an agenda for general science education as is whether scientific research is reported at all.

Yup, still a problem

Thursday, April 19th, 2007

NOTE: This post was originally published on February 28, 2007, on an old version of this site.

In discussing Stephen Jay Gould and Richard Lewontin‘s article “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme” with a group of undergraduates the other day, one of the students asked if this critique, published in 1979, is still relevant. Gould and Lewontin’s basic thesis is that too many biologists fall prey to the seduction of describing everything they see as an adaptation. They accuse their colleagues of inappropriately dissecting organisms into discrete traits, then conjuring adaptive explanations for the existence of these traits—a process that not only neglects to provide evidence to justify such an adaptive explanation, but that also fails to consider how evolution is a whole-organism process. Well, today I have a definitive answer: it is as relevant as ever.

moalembook.jpgToday Marty Moss-Coane interviewed guest Sharon Moalem on her show Radio Times. Dr. Moalem, author of Survival of the Sickest, a book about how many human diseases are in fact adaptive “complicated blessings,” paraded a series of sophomoric explanations for how susceptabilities to many human diseases have in fact been selected for over our evolutionary history.

For example, Moalem argues that the relatively high frequency of genes that underlie the disease hemochromatosis in populations of European descendants may be the result of selection for these genes during the plagues of Europe. Hemochromatosis is a disorder in which iron accumulates in body tissue, and macrophages—which are a part of the immune system—suffer an iron deficiency. Because some pathogens may depend on iron to escape attack by the immune system, and because descendants from countries with high plague casualties show high frequencies of hemochromatosis, Moalem makes the argument that Europeans with iron-deficient macrophages were more likely to survive the plague… and thus we see a disproportionate representation of hemochromatosis in European descendants. But wait a minute! Correlation must not be confused with causation. If the genes that cause hemochromatosis are so detrimental, why were they not purged from the population before the plagues began? Maybe new mutations are popping up, or maybe selection is too weak to purge these alleles from the population. Or perhaps there has been positive selection for some of these genes, but we have no direct evidence that it was to avoid dying from the plague. It may be the case that the genes that underlie hemochromatosis also perform a beneficial function elsewhere in the body.

Furthermore, Moalem uses spurious scientific data to spin his adaptation stories. For example, he reports that fewer boy babies than girl babies were born in New York city after 9/11. Apparently there are some data suggesting that gestation of a male fetus incurs a higher cost to the mother, and that under stress, a mother will be more likely to miscarry if she’s carrying a high-cost son. Nevermind that this phenomenon deserves skeptical examination—the statistics that claim a significant gender skew in New York births can be easily dismissed, thus debunking Moalem’s claim that the 9/11 attacks stressed out pregnant mothers and caused a slight decrease in the boy/girl newborn ratio. The failure of this study is quite straightforward. The authors compute birth ratios for 81 different time intervals in New York city: 71 intervals leading up to 9/11, and 10 inervals after 9/11. The authors claim that the lowest boy/girl ratio occurred in one of the 10 post-9/11 intervals, and that it deviated “significantly” from the average ratio over all 81 intervals. Their data do show that the lowest ratio occurred post-9/11, but it is not significant. Fluctuations in birth ratios, just as in any natural phenomena, will occur due to randomness. (And in fact, the sex ratio went up more often than it when down in the 10 intervals after 9/11!) Statistics allow us to infer whether a fluctuation differs enough from the average to suggest something unusal, and when looking at multiple events, a statistician must correct for multiple tests. Quite simply, these authors performed the correct test but utterly failed to adjust the type I error value to accommodate the type of data they were examining. The truth is that there is absolutely no evidence that birth ratios changed at all in response to the 9/11 attacks. To see what p-values should have been reported, see this criticism.

Radio Times is broadcast every weekday from the Philadelphia NPR station WHYY, 90.9 FM. You can listen to this particular show from the Radio Times archive.