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Joan Roughgarden – Evolution’s Rainbow

I learned many things from this book, on the biology side. Roughgarden’s case studies of varied gender expression and sexuality in animals are fascinating, and she is careful to take you through what they might “mean”–the function of third (and further) genders, the failures of “deceit theory” to account for the presence of “effeminate males” (since birds can verifiably tell the difference between females and female-looking males), the usefulness of cooperation as a valid concept in evolutionary theory. Colorful examples abound: fishes (wrasses) that change sex based on environment (open sea or reef), plants that change sex based on time of day (with the excellent name “flexistyly”). I’m willing to allow the possibility that, to use her example, different species of Idaho squirrel have different mating habits during their 20-minute mating window (with the male inserting a sperm plug or not) according as which the female prefers, or is more pleasured by.

There are other interesting ideas to perhaps add to our thinking on mate choice: how can we study whether animals in a population acquire a “reputation”? It’s certainly true that courtship behavior and parental care is frequently carried out in full view of others in the group. The idea of a population’s reproductive skew as partially determined by the level of distributional inequity in reproductive opportunity is appealing, especially as an alternative to the pure selfish rhetoric in traditional literature: “stealing” mates, “wasting” resources on others, etc. Family structure does seem to be fluid in the animal world, and behavior towards other animals partially governed by the best strategy for getting others to help. There are detailed discussions of “extended families” in tamarins, African hunting dogs, birds, and several other groups: the tamarins in particular exemplify how polyandry can be necessary to raising young in a cooperative setting–matings take place in view of other males with no sign of aggression, and males cooperate to take care of the young. And maybe it couldn’t be another way: mothers usually birth twins, and they are each 50% of her weight by the time they can walk or climb on their own–a monogamous couple isn’t enough to raise them.

The point is also well taken that the words we use to describe animal behavior reflect entrenched beliefs, so that males can be described as “cuckolded” in peer-reviewed publications in respectable journals, and everyone deceives each other. This was partly affirmation of my confusion over the so-called “problem of cooperation” and why it’s a problem at all. I do find it hard to subscribe to Dawkins’ “genes are the fundamental unit of selection” selfish-gene model. There’s just too much going on in the environment, and I want a theory that imputes meaning to our time on Earth…

To me personally, the book was most disappointing in its discussion of homosexuality in humans–just because that’s what I was most looking forward to in it, I think. She’s unwilling to speculate much there (despite wild speculation re: trans issues), and her belief that there’ll never be a biological theory of homosexuality seems to run counter to the call for more study of homosexuality in other animals and for more nuanced studies in the social sciences.

But there was a lot to make up for that. The stories of animal homosexuality were delightful and convincing (even excluding “homosexual, heterogendered” courtship between individuals of the same sex and different genders). I don’t believe cohabitation and the alternating assumption of the “male” role in courtship qualifies certain asexual anolis species to be called “lesbian lizards” (too much human/social baggage there), but it’s fascinating of itself. And it’s nice to see the doubters get hit where it hurts: she points out that even geese marriages, the poster children for lifelong stable, monogamous couplings, are 15% male-male. (And they love each other, too: the male shows despondent grief after his partner dies, just as in straight couples.)

On the function of feminine males, I’m not sure I think Roughgarden’s theories are totally plausible, but they seem to be a good counterbalance to the deceit theorists. And at least they make nice stories (not, of course, a criterion for a good scientific theory): Consider the red-sided garter snake that makes Manitoba’s interlake region a hotbed of snake-watching. (There’s even a monument to garter snakes in the town!) Thousands of garter snakes live in a single den in the winter, then emerge, mate and disperse; mating occurs in “mating balls” with one snake courted by many others. At the den entrances, the ratio of males to females is 10:1. It turns out all males secrete feminine hormones: Roughgarden’s theory is that male garter snakes just emerging from the den want to roll around in the sun and “wake up,” so they can signal with female hormones–and males watching  this would rather welcome this new guy than attack him, with so many others around who could jump on you. (Notable here is the lack of deceit theory–the males know the feminine male is indeed a male).

Part 2 of the book goes into development, where I think the treatment is a little weaker (it’s farther from Roughgarden’s area of expertise, which is ecology.) The most interesting thing I got from this was a BIOLOGICAL definition of gender: I’m used to thinking of “sex = biological characteristics, gender = how you feel.” Roughgarden takes the female to be the one with the larger gamete size, and that’s it. She then traces how sex (how a gamete matures) is influenced by gender (what type of tissue the gonad it lands in has) and vice-versa, and the complicated role of SRY in gender determination. She also solved a big mystery for me: how males and females can be so different while having only about 60 genes on their sex chromosomes (and about 4x that between two people on nonsex chromosomes). Two main culprits–evolution on the Y chromosome, and the extent of X inactivation–if there’s not much, the females have most of another chromosome to work with to effect these differences.

Continuing the theme of biological gender differences, the discussion of birds had a lot to offer: e.g. in speciese where males sing and females don’t, there’s a marked difference in the size of nerve cell clusters for learning and making song. Moreover, hormones control the size of these nerve cell clusters, varying with both age and time in the breeding season; they also control aspects of personality, often in very simple ways. Overall, the development section made me appreciate transgenderism as a biologically-based phenomenon, and not just something about “how you feel inside.”

The last thing of note for me was perhaps the “gay gene” discussion–basically, most biologists agree that homosexuality has some genetic basis, and the search for one gene is kind of pointless for a complex trait like this–we’ve only found things that sometimes make tiny differences.

Ultimately, though, despite all the things I learned about the biology, this book drove me a little crazy. Roughgarden has a clear axe to grind, and I think it weakens her book.  What could’ve been a solid, scientifically-based, well-researched book of half the size on a coherent chunk of material became a bloated thing that’s half science and half poorly-defended manifesto. Sure, it’s good to challenge the social sciences to take a broader view of sex and gender, and to point out biases in the literature. But Roughgarden pulls some stunts that really weaken her credibility for me: for example, calling theories “diversity-repressing” as if that were the end of their credibility, bringing in the Bible, arbitrarily focusing on the T in LGBT, and laying out a trans agenda. When she does these things, suddenly the copious footnotes vanish. I’d rather she have done more with the science and less explicitly with a “feminist critique,” or that she publish the political implications as she sees them separately.

As it is, I can recommend the scientific insights, but not much of  the editorializing woven in. And ultimately I’m not convinced that Darwinian sexual selection theory needs to be wholly overthrown: to me, its strongest point is that reproductive success can be selected for independently of survival probability, and we should look for reproductive explanations when a trait seems like it wouldn’t be naturally selected for. Yes, Darwin speaks of universal gender types; but he spoke of blending inheritance too, and the Modern Synthesis simply updated him with our new understanding of genetics; we could do the same with our understanding of sex and sexuality.


My favorite factoid: gay people’s otoacoustic emissions (little sounds emitted from our ears) are different than straight peoples’. Hello, gaydar! 😉


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