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September 01, 2004

Mother Nature: a complicated and morally ambivalent tale

Of all the books on the sidebar, Steven Pinker's The Blank Slate is the most "clicked." It deserves the accolades it receives, but perfection is generally an ideal, not an attainment. You can read my review of Pinker's book from 2 years ago, but I have to say that there were two problems I had with The Blank Slate:


  • Instead of demolishing one idol, Pinker decided to also topple "The Ghost In The Machine" and "The Noble Savage." I think that this distracted from the main aim of the book, that is, introducing the general public to advances in evolutionary psychology, behavorial genetics and the "study of human nature" in in the broad sweep.
  • The second problem, when viewed in light of the "core" audience of this blog is that the book is aimed toward the general public. Very few people adhere to a genuine "blank slate" paradigm anymore, but GNXP readers are more likely to be open to biologistic causes and underpinnings to phenomena traditionally explained or assumed without recourse to natural science. Additionally, most of the readers of this blog are surely somewhat cynical about "The Noble Savage," while a poll I took a year back indicated that about 3/4 of of readers are religious unbelievers (ergo, no need for "The Ghost In the Machine").

The Language Instinct on the other hand is a more tightly focused book, that nevertheless can offer insight into the general framework Pinker brings to the table and is involved in fleshing out through his research. It is in this spirit that I highly recommend Mother Nature: Maternal Instincts and How They Shape the Human Species, by Sarah Blaffer Hrdy. The title alone tells you what you are in for, an ostensibly tight beam that manages to shed light on the broader human condition. 500 pages of text and 50 pages of notes assault you with data point after data point, yet all the while Hrdy manages to interject both amusing anecdotes about the scientists that have shaped our understanding of human evolution & nature (eg; Robert Trivers' ganja habit) and more serious reflections on the personal & private factors that mold the form of scientific knowledge (the juggling of work & family that many female scientists must accept figures importantly in her narrative).

This is not a dry text, rather, it reads like a scientific autobiography. In the main the author neither explicitly advocates her social & ethical norms nor does she make a great attempt to mask the assumptions that form the basis of her world-view. Blaffer strikes me as a moderate liberal, and I feel she injects her own experiences and values in framing the arguments in her book respectfully. The argumentation rarely turns into polemics or advocacy. I will admit that I tend to share her moderate social liberalism, so I found the occasional tincture of sermonizing innocuous. But even if you sharply disagree with her politics, you shouldn't pass up opportunity to feast upon the data Blaffer presents you.

There are three threads in Mother Nature that I want to focus on:


  • Stepping beyond simplistic "genetic determinism" or "essentialism."
  • Contingency in human behavior.
  • And the naturalistic fallacy.

Much of Hrdy's book takes shape as a counterpoint to the conception of a simple "Maternal Instinct." The colloquial phraseology is somewhat imprecise as to what "instinct" is. Nevertheless, most people generally agree that women are characterized by strong tendency toward nurturing their offspring. Not only is this the norm, Hrdy argues that people tend to conceive of this instinct as a monolithic phenotype that has one "normal" expression. If a woman does not adhere to the expectations set by her essence, many might wonder if she is ill, that is, malfunctioning.

By analogy, it is as if those who possess the maternal instinct had the conventional complement of fingers, while women who do not display the requisite behavorial patterns are lacking in some essential digits, the exact number being irrelevant because the dichotomy is between "normal" and "abnormal." In other words, the maternal instinct is conceptualized as a class genetic trait, likely with a low heritability. The predominant phenotype is so much more "fit" than the alternatives that they are trivialities.

Hrdy would disagree with this assumption. In many ways, she is repackaging in scientific language what many people already assume. Genes can express themselves in different ways depending on their environmental context, polyphenism. Not only can a variety of contextually dependent behavioral patterns be on display within a given population, Hrdy argues that the mother-child interaction is characterized by co-adaptation. Adaptation implies evolutionary change, and usually evolutionary change implies some variance within the population of the phenotype due to variance in genotype, that is, a continuous heritable trait.

Hrdy does not limit herself to one layer of illustration. Much of her work (she is a primatologist) focuses on ethology, behaviors, and ultimate evolutionary ends. Nevertheless, she often tunnels down to the molecular & physiological level, spending a considerable amount of time discussing the work of David Haig, the Harvard biologist whose reasearch on genomic imprinting and the "tug of war" that goes on between the fetus and the mother during pregnancy that have made him rather well known to the lay audience. With her focus on the relationship between mothers and their offspring, Hrdy touches upon the reccuring tendency toward infanticide that characterizes humans, and to marshall her argument she draws upon the works of historians who suggest child abandonment has been an endemic feature of our species and fully expressed in many cultures, to the point where at any given time 1/2 of adults might have given up a child, likely to destitution or certain death (from the Romans to the early modern French).

Yes, human females have a tendency toward nurturing their youth, but Hrdy points out that in many ways our species has a more tense mother-infant dynamic than that that characterizes monkeys. Evolution might not be an ascending ladder that we scale in the moral realm. To her liberal readers who support abortion rights, she broaches the fact that in many ways the newborn infant can be thought of as a fetus, and that many cultures do not imbue the newborn with "personhood." Hrdy notes, with some obvious concern, the fact that some hunter-gatherer people who are characterized by relative health and prosperity also engage in high levels infanticide as a form of rational family planning, taking the phrase "no child should be born unwanted" to a new level. Variability is a constant in human evolutionary history. If one personality type, one behavior, one cultural tradition, was ideally "fit," it seems implausible that 1/3 of humans are "introverts" to some extent, or that polygyny and monogamy are both common features of the species. Multiple strategies seem to coexist in response to varying environmental and social inputs. Concise and succinct narratives are difficult to extract from the Ph.D. theses of thousands of scientists who study how we tick. Trying to extract or map conventional ethics is a tricky business in this area. Where someone like Margaret Mead might see in various behavorial and cultural adaptations creativity and an outward bound spirit, Hrdy sees rational and evolutionary reactions to constrains and competition, all is not possible, but many options and equilibria are probable.

The author also notes that there are many misconceptions about the pace of evolution in humans and emphasizes that adaptation did not stop 10,000 years ago at the end of the last Ice Age. Standard arguments like the spread of lactose tolerance are highlighted, but she also is bold enough to offer that women of Southeastern European heritage tend to begin their menses earlier than women of Northwest European heritage, and she does not flinch from a biological possibility as the root of the variance. Hrdy also leaves broaches the idea that the sex skew among East Asians is a result of thousands of years of cultural norms that favored sons. These topics are not so provocative when set against chapters that discuss infanticide and euthanasia as social and biological "adaptations."

She has enough on her plate, disabusing the public of simplistic notions of motherhood, that I don't want to mislead that the book is about inter-group variation. Rather, it is about variation, complexity and the unpredictability (from the human standpoint) of adaptation. Varied populations react to selection pressure more readily (there is more variation to select from), ergo adaptation. This sort of knowledge is a consiliated whole, the same variables and inputs that shape mothers also shape various groups and families. Typologies have their own internal topography, and making language map well to the reality of this diversity can be an arduous task.

Not only are there a host of factors that result in any given behavior and its various morphs, there is the issue of the serial nature of our psychology, that is, input leads to response which might elicit a certain specific range inputs from another individual. Human behaviors are contingent upon each other, and etch out probabilistic pathways. Not only do humans display multiple phenotypes, in the realm of behavior these phenotypes smear into each other in the same individual over time. That is, an introverted individual is sometimes extroverted, which might lead this person down a peculiar behavioral pathway that they have never experienced before. Nevertheless, this might not be the human norm, or the norm for the individual. Data needs to be viewed within its context, not in a standalone fashion.

Hrdy points out that the essentialist vs. environmentalist dichotomy benefits adherents of both positions, who are disadvantaged against those who would take the more factually supported position that one has to be cautious about making perfect generalizations and accept the fuzzines of the phenomena in question as a fact of nature. A French feminist falsifying biological explanations for motherhood by pointing to counterexamples simply won't cut it, because human behavior is not deterministic, it is probabilistic and it is contingent upon internal and external variables. This is plain to common sense and statistical modelling, but reframing it in elegant prose can be rather difficult, especially in contrast to the categorical and logically tight (though not empirically sound) oppositional viewpoints.

Elegant typologies in the domain of psychology has left the public aware of concepts like the conscious and subconscious, and for those more evolutionarily inclined, "the swiss army knife mind." But these are metaphors and analogies, imperfect models of reality. Conscious decisions trigger probable pathways and "hard-wired" response patterns within the mind, resulting in a certain range of conscious decisions which might in their turn trigger "mental reflexes" and be shaped by hard-wired biases informed by our evolutionary past. Might, likely, possible, trend, in general, all of these are wimp words, but they are all so appropriate when talking about our self-conception.

This leads me to the "naturalistic falllacy," drawing ought from is. To some extent, one might think this is a strawman, after all, our ought is somewhat constrained by the is. Reality is a given, how we respond to it limited by its bounds. But the line between the fuzzy spaghetti of hyopthesis, theory and data within a probabilistic framework and a axiomatic system of social organization is frought with assumptions, the very squishy bane of surety. As I noted earlier, Hrdy brings her own history as a working female scientist, a person of somewhat liberal views, all the while conscious of the negative reaction some feminists have toward biology.

Of course there are limits to these prevarications. There are some truths that can't be dodged. Men and women are different. Even in the most anti-biological mode, ignoring the reality that it is the female that gestates is folly. That very experience will cause an average difference between males and females. If 1 out of 1 million women were strong enough to join the military, it seems plausible that building ladies' restrooms in military facilities is silly. If on the other hand 40% of women were strong enough, vs. say 60% over men, the difference is small and the overlap great enough, that many people would dispute female exclusion on the grounds of physical strength alone (I am going to leave the complexity of that specific argument out of it). Women by their essence are more qualified to be "Hooters Girls." If only life were so easy! But how can one justify excluding women from the professions when their mean intelligence is basically the same as men? (though there might be more male variance, the difference does not show up until rather high in the percentiles, or rather low)

These are complex questions, and biology alone will not answer them, at least for now. A field dominated, at this point, by speculative models, hedges and qualifications is a shaky explicit guide for norms [1]. Nevertheless, biology does point strongly to certain human constraints. No matter Sarah Blaffer Hrdy's feminist orientation, one can sense anguish as she speaks of the difficulties that intellectually gifted women must make when it comes to a career or a child.

You get the feeling after 500 pages that the author has still left much unsaid, that she wishes she could explore and exhaust every accessible nuance. That which is dearest to us, a complete understanding of our nature and the natures of those we love and care about to some extent eludes our grasp (for now!). But striving does not hurt, and knowledge is always to the benefit in allowing us the greatest freedom in the portion of our world where consciousness and volition reigns supreme.

[1] I am thinking more of organismic than molecular biology in this context.

Posted by razib at 03:45 AM