25 January 2010

Happy Roe v. Wade Day

Today is the day when pro-lifers nash their teeth in anguish over the 1973 Roe v. Wade decision, and when pro-choicers gnash their teeth in anguish over the fact that pro-lifers haven’t yet acquiesced to the Supreme Court’s ruling.

But I find the abortion debate particularly unenlightening. It consist of little more than two sides iteratively reciting a very limited set of very familiar arguments. There are no arguments pro or con which are less than 25 years old, yet each side continues to ritualistically invoke them as though mere repetition alone can change minds. My perspective is that neither side can convince the other because both side’s arguments have real power. Each has announced their own set of legitimate interests, but neither side has ever successfully rebutted the other side’s claim of legitimate interests, nor successfully demonstrated that their interests should always trump the other’s interests.

I want to examine the issue from a different perspective; a biological history perspective. I make no claim that this perspective will resolve the debate, but I believe both sides would benefit–intellectually, and perhaps morally, but not necessarily politically–from looking at abortion in this way. This is a bit long, as the biological argument requires quite a bit of setup, but if you’re game, please click the “continue reading” button.

The biological history perspective requires that we recognize abortion as a form of infanticide. Pro-lifers, of course, agree, but only because they see the term as having political power. Pro-choicers object, but only for the same reason. But as I repeat to my methods class daily, we are engaging in analysis here, not advocacy.

The historical fact is that infanticide has been practiced, with varying degrees of frequency and approval, in all cultures throughout history. For various reasons, mothers–and sometimes fathers–find the destruction of an infant to be in their own best interest. From a biological perspective, this is an interesting question because it means the destruction of their own genetic heritage, so it seems that evolution would tend to eliminate people with a tendency to do that, and favor those who are so attached to the concept of having children that they would never, under any circumstances, eliminate one of their own. The latter, after all, would leave more children, so their child-loving genes should, over time, come to dominate the population, while the child-killing parent’s genes should gradually diminish and disappear.

But that seemingly logical argument is superficial. It’s not simply quantity that matters evolutionarily, but quality. There are two approaches to reproductive success, the r and k strategies. The r strategy is to have very large numbers of offspring, but to put minimal parental investment into them. Sea turtles, for example, lay between 50 and 200 eggs (depending on the species) every few years, but after burying them in a sandy nest, leave them behind. Most of the babies are eaten shortly after hatching, but some survive to reproductive age. The k strategy is to have few offspring, but invest heavily in them. Orang-utans, for example, normally have one child at a time, which stays with the mother until sexual maturity at 6-7 years of age, during which time the mother will have no other offspring.

Human behavior is, compared to many species, very plastic, but it is nonetheless biologically based. We lack the reproductive capacity to be sea turtles, so we are clearly more toward the k end of the reproductive continuum, but even so there is great variability in human reproduction. In pre-technological agricultural societies, it was not uncommon for a woman to bear up to a dozen children (although rare for all of them to reach adulthood). In hunter-gatherer societies the average was considerably lower, and in contemporary western industrial societies the number is–from a historical perspective–shockingly low. In the EU, the average woman reportedly has only 1.5 children.

The lesson from this is that natural selection can favor having fewer children. The key to whether it is evolutionarily successful lies in understanding the life history of the parent. Orangutans live in different environments and have different social structures than sea turtles, so a different reproductive strategy is evolutionarily appropriate. Shifting our focus from a comparison between species, we can also compare individuals within a species. The specific life history of a particular human female may dictate having fewer, rather than more, children as the best reproductive strategy. If having fewer children gives them a better chance of surviving to reproductive age than does having more children, then the greatest expected value comes from having fewer children.

For example, if a mother has ten children, each of whom has a .01 chance of surviving to adulthood, her expected value is 10*.02 = 0.2. If she has only one child, which has a .3 chance of living to adulthood, her expected value is .3. Basic cost-benefit analysis tells us to take the highest expected value, so in this case having one child gives a better chance of passing one’s genes into future generations than having 10.

If a mother wants to limit her number of children, then she must sometimes make choices about whether to keep a particular child. Historically, and cross-culturally, women tend to commit infanticide under conditions that match up with the preceding logic, such as a) when a child is defective, b) when a child is born too soon after a previous child, c) when the father is unlikely to invest in the child (suspicion of adultery, for example, or actual absence), or d) when the mother is young and unprepared to raise a child. Supporting this argument is consistent evidence that the overwhelming majority of child killings occur in the first year of life. It’s as though children pass through an evaluation period during which parents decide whether they are a good vehicle for parental investment or not. (Although the empirical data tends not to differentiate within the first year, anecdotal data suggests that most of those first-year killings take place within the first few weeks or even days. It is likely that this evaluation period is quite brief, and the great majority of infants closing in on their first birthday are likely to enjoy many more.)

Obviously it would be even better for those mothers if they didn’t have to carry those to-be-discarded infants to full term. In the pre-technological era, however, means of abortion were rare and dangerous, limiting the rational use of this option. Today, however, abortion–while not without risk–is safer than pregnancy and childbirth, at least when performed before the third trimester. So women who, at least in a different time and place in history, would have committed infanticide now rationally choose to move the act forward to an early moment, limiting the overall cost of the undesired pregnancy.

Operating on the assumption that infanticide will occur–that social rules and norms can only reduce its frequency to some degree, but not eliminate it–we can see abortion (again, at least early term abortion) as a more human method of infanticide. In that respect, at least, abortion should be quietly celebrated.

General Sources:
Trivers, Robert. “Parental Investment and Sexual Selection,” in Trivers, Social Evolution (1985).

Daly, Martin, and Margo Wilson. “Killing Kinfolks,” in Daly and Wilson, Homicide (1988).

Scrimshaw, Susan C. M. “Infanticide in Human Populations: Societal and Individual Concerns,” in Glenn Hausfater and Sarah Hrdy, Infanticide: Comparative and Evolutionary Perspectives (1984).

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