Statistically informed ideas on how to make the world work better.

Category: Ecology and Evolution

The costs of too much choice: How the science of evolutionary development justifies Obamacare

One of the more difficult and technical fields one could choose to study is Evo-Devo, or the evolution of development. Briefly, it is the field that studies how genetic programs determine the developmental process, how these programs evolve, and how the types of programs available constrain the directions evolution can take. For example, if humans were to evolve wings (an essential impossibility for many reasons), Evo-Devo lets us make the clear inference that we would not evolve them as sprouting from our shoulders like angels, but rather as modifications of our arms. Why? Because in all tetrapods (i.e., eptiles, amphibians, birds, and mammals) there is a developmental program to produce four limbs. Limbs can be lost (snakes, whales) and modified for flight (bats, birds), but they cannot be added.

One of the key insights to emerge from Evo-Devo is that developmental programs are highly organized. They have evolved ways to facilitate future evolution, called evolvability. They achieve this using mechanisms known as gene regulatory networks, compartmentalization, and canalization. While the details of these mechanisms are beyond the scope of this post, they have in common that they are ways to facilitate long-term evolution at the cost of flexibility. That is, they standardize the developmental process to give consistent results, but limit the forms that can be arrived at. Again, tetrapod limbs are a good example: if tetrapod limbs were not the result of a fairly standardized genetic module, we would be able to evolve them anywhere any time – the nose could become a hand, we could evolve rows of wings up and down our backs, etc. However, the  result would be chaos. It would be too easy for a minor mutation to mess up development, too easy for the final form to depend too heavily on what gene combinations one has (image if parents regularly “accidentally” gave birth to children with 6 or 10 limbs, just because of  how their genes got combined…), and too hard to control the evolution of limbs as the environment changed and a specific sort of form became necessary. In other words, we gave up flexibility for stability and predictability.

How does all this relate to Obamacare?  Read the rest of this entry »


What evolution can teach us about breastfeeding and natural childbirth

IMG_0109This little guy is my son, Soren, born March 13 (and the reason I haven’t posted for a while). In the photo, hours after birth, he is hooked up to electrodes, a blood pressure cuff, and various paraphernalia of the modern medical establishment, a result of having to undergo CPR to restart his heart and breathing as he emerged from a cesarian. He is doing great now, but it is clear that modern medicine saved his life (and possibly that of my wife), probably 2-3 times over between the long labor, the cesarian, and the resuscitation. (He is doing great now.)

Like many in our generation and social class, especially here in Quebec, we had wanted to have a “natural childbirth,” i.e., to see if we could deliver without any anaesthesia or other interventions of modern medicine. Unlike many of our friends, we had not signed up with a midwife or birthing center: the public hospital here in Sherbrooke has an excellent maternity ward, and nurses are trained to help with natural or medicalized childbirth, or any combination, depending on the wishes of the parents.

Despite my preference for “natural,” I was also acutely aware that childbirth is different than other aspects of nature: in this case, natural implies very high levels of both infant and maternal mortality. In contrast to breastfeeding, where all the evidence points to breast milk being superior to any technologically developed infant formula, “natural” childbirth does not always equate to good childbirth. As is often the case, this is clearer when seen in the light of evolution:

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Prediction and truth: two ways to measure scientific progress

Samuel Arbesman has a really interesting piece in Slate today about scientific progress and computers that may make discoveries that humans can’t understand. One of the issues he raises is that science sometimes overhauls what is considered as “truth,” but nonetheless we continue to make progress, despite the fact that everything we believe today may be considered false tomorrow.

Perhaps the classic example of this is Newton’s laws of motion, which were overturned by Einstein. Einstein showed that Newton’s laws were good approximations at low speeds, but that as objects approached the speed of light they broke down; Einstein’s special relativity theory proposed equations that are valid at all speeds. Einstein not only proposed better equations; those equations implied a different understanding of the universe, an understanding that allowed scientists to pursue new avenues of inquiry.

This example is famous, and shows two important principles. First, as science progresses, prediction gets better and better. In terms of predictive power, Einstein’s contribution was an incremental one, not a revolutionary one. Newton’s laws still apply nearly perfectly at most speeds experienced in daily life, though many cosmological and sub-atomic phenomena can only be predicted with Einstein’s equations.

Second, in terms of our fundamental understanding of what the universe is like, Einstein’s theory was revolutionary. But there is always the possibility that it will be completely overturned by the next revolutionary theory. In this sense, the paradigm shift of Einstein is perhaps most useful in that it opened up new avenues for research, not in that it is a better approximation of the truth itself.

A relativist or a critic of science can always claim, correctly, that the current scientific consensus risks being overturned by the next big discovery, and that therefore scientific claims to understand the truth of the universe are weak. What is harder for a relativist to critique is the improvement in predictive capacity that has been achieved over the course of science history. That should count for something, even if the “truth” of science is at risk of being overturned.

However, the discussion above is predicated on a model of science that originates largely in physics. It is striking to me how many lay discussions of the philosophy of science assume that all science is like physics, that the best scientific design is always a controlled experiment, and that Karl Popper’s idea of falsification of hypotheses is supposed to be the one true scientific method (as mentioned in the Arbesman article, to my chagrin).

In fact, there has been no major paradigm shift in biology since Darwin, despite many in physics. And unlike in physics, where it seems the next great theory might overturn everything we think, in biology it is clearer and clearer that the work that remains is to iron out the details, not find the next grand theory. Yes, evolutionary theory has been gradually refined, and we have largely rejected some spurious ideas such as widespread group selection. Yes, biology is still informed by theory, and sometimes a creative new theory can change a field. But the fields that get changed are narrower and narrower, as the high level theories become more strongly confirmed.

Likewise, controlled experiments are rare in fields such as ecology and evolution, where it is generally impossible to rewind history: most of our knowledge of these fields is based on observational data and on a gradual accumulation of evidence rather than clear yes-no, up-or-down tests of hypotheses.

We never know what tomorrow will bring, and in a formal sense no aspect of scientific theory can be considered to be 100% proven beyond all doubt. (Perhaps God is faking our data for reasons unknown to us, after all…). But it seems less and less likely that there are any impending scientific revolutions outside physics. So, while we can certainly measure scientific progress as an increase in our predictive power (regardless of the underlying truth), it is also probable that in many domains we are not too far off from an accurate description of “truth,” even if we will never know for certain.

Thoughts on science, truth, and prediction? Leave them in the comments and I’ll respond…

What Todd Akin gets right about rape and evolution

OK, I’m about to piss a lot of people off. Here goes…

US Senate candidate Todd Akin said, “It seems to me, from what I understand from doctors, [pregnancy from rape is] really rare. If it’s a legitimate rape, the female body has ways to try to shut that whole thing down.”

Todd Akin is an idiot. Tood Akin is ignorant. Todd Akin is insensitive to women. Todd Akin is a religious lunatic. All true. But Tood Akin is also (a little bit) right about rape, and about evolution (which I presume he doesn’t believe in).

Hear me out. I’m not saying no one gets pregnant from rape. I’m not saying we can distinguish between “legitimate” and “illegitimate” rape legally or morally. But I do think that women’s own perceptions of rape can be more or less severe, and that there are biological mechanisms to reduce the probability of pregnancy following a rape.

There is only one fundamental law of biology, and it is this: whenever you think you understand something, it’s more complex than that. Almost every major principle of biology has later been shown to have exceptions or caveats. One example of a simplistic principle is that once sperm are released, nothing the woman does affects the probability of fertilization. In fact, it is well-established that muscular contractions during a woman’s orgasm help draw in sperm and increase the probability of fertilization. During rape, no orgasm. No orgasm, no contractions. No contractions, lower probability of fertilization.

I do not know if other potential mechanisms for avoiding pregnancy from rape have been discovered, but I would bet they exist. It’s not hard to imagine that acute psychological trauma could release hormones that would reduce the probability of implantation, for example. Natural selection should fairly strongly favor avoidance of pregnancy via rape – the psychological trauma caused by rape is itself presumably the result of strong evolutionary pressure on women to make them avoid rape as much as possible.

And if psychological trauma does reduce the chances of pregnancy (I’m not saying it does, I’m saying it might), it is likely that the degree of trauma affects the probability of getting pregnant: more trauma, less probability of getting pregnant. So then we have the question: is all rape equally traumatic? I have no idea. I’m not a woman and I can’t say. But my guess (please, women, correct me if I’m wrong) is that it would be possible to imagine various rape scenarios, some more traumatic and some less. I’m not saying the different scenarios are morally different or legally different; I’m saying that the woman would perceive them as more or less traumatic. Todd Akin was 100% wrong to try to distinguish legitimate and illegitimate rape, but many commentators may have also been wrong to assert that, biologically speaking, all rape (or all insemination) is equivalent.

So let’s criticize Tood Akin for the many things he is guilty of, not for being wrong about biology when the biology is not necessarily well-known, and when his statement contains at least a grain of truth. And let’s take pleasure in the fact that even this religious nutcase has inadvertently invoked evolution in his understanding of rape!

The evolution of homosexuality

With this post, I’m going to get back to my roots as an evolutionary biologist, as well as wade into a controversial subject: how could evolution produce homosexuality? (At first glance evolution and homosexuality appear to be contradictory, since lacking a sex drive for the opposite sex should decrease reproductive success.) I am certainly not the first to write or speculate on this topic, and I cannot profess to have read in depth what most other writers are saying. But when the question came up casually the other day, I realized that simple application of evolutionary principles can lead to a fairly nuanced understanding of how this could happen. It’s also a good way to demonstrate the complexity of evolution with a subject likely to pique people’s interest.

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What we really know about nutrition, part 2

In the last installment of this series on nutrition and science, I argued that epidemiological studies on associations between diet and health are extremely difficult to conduct well. But aren’t there other ways we can get information on how to eat well? Yes. We know the biochemistry of molecules such as vitamin E relatively well, and we know a lot of what they do and why they are essential in the body. We have lots of animal studies on nutrition, both in mice as model organisms, and for domesticated animals such as dogs, chickens, cows, and so forth. These animal studies do what human studies can’t: they perform controlled experiments to identify causal relationships.

In addition to these basic science studies, there is also a lot of circumstantial evidence about nutrition. For example, there are studies that measure the nutritional content of hunter-gatherer diets. There are studies comparing the intake of different nutrients across species. And there are some lessons from basic evolutionary principles that can be applied to nutrition.

What can we learn from all this? The take-home message is that the details are very complicated and poorly understood, but there are some broad brush recommendations we can make. In my opinion, most of the basic science does little more than generate confusion about the details, and the most useful lessons come from the circumstantial evidence.

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