Women After All: Sex, Evolution, and the End of Male Supremacy (9 page)

Without getting too much into the lizard sexual brain, both the mounting females and the males of their two-sex cousins have the same neural activity in the hypothalamus. This is the area at the base of the brain that interacts with the body, including sex hormones. The same locations are stimulated by testosterone and suppressed by estrogen in sexual males as in mounting asexual females; in fact, this happens even in mammals. Not only that, but studies by Brian Dias, in collaboration with Crews, showed basic biological similarities between the brain circuits that handle female-like and male-like sexual behavior. They wrote in 2008,

Given that the first “sex” was female, and [the estrogen] receptor is the most ancestral sex steroid hormone receptor, it is more appropriate to consider the female and [estrogen] as ancestral, and the male and androgen as derived, states. . . . [This concept] maintains the element of the “male phenotype” being imposed on what otherwise would be a “female phenotype” but extends research in new theoretical directions. If in fact males are the derived sex, it follows that males may be more like females than females are like males. . . . Several lines of evidence . . . support this idea, such as the relative ease of masculinizing animals compared with the difficulty of defeminizing animals and the [experimental] resurrection of males in parthenogenetic whiptails, indicating that the genes of male traits are present in this all-female species.

In other words, although the immediate ancestors of the whiptail parths were sexual, go back far enough and you find not only that the first sex was female but that her original, foundational existence left traces in the chemistry of the brain: estrogen first, androgens as
an afterthought, and the elimination of males as—for some lizards, at least—an even better
after
-afterthought. In a sense, the parth females were just using their brains, ancient hormonal adaptations, to recover their original condition.

As in all sorts of males, including human ones, castration in two-sex whiptails greatly reduces or eliminates male sexual behavior. But, oddly, many males of the two-sex form will respond to progesterone as well as testosterone. In fact, progesterone induces “the full suite of sexual behavior” in about a third of castrated males of the ancestral two-sex species. One of the brain chemicals involved in both cases is nitric oxide, the same molecule enhanced by Viagra. In the lizards, the effect is in the brain, not the penis, where Viagra causes erections. All-female whiptails have nothing to erect. Two put their genitals together—the lizard equivalent of rubbing vulvas—and it just takes a few minutes to set the otherwise asexual reproduction of the mountee in motion.

At this point, you may be wondering whether progesterone could help a male perform, which might be a boon to many men, despite perhaps (as with Viagra) being a bane to some women, who might prefer fewer male advances. In addition, if you are inclined to consider all possibilities, you may also be wondering whether, in the long run, we humans could follow an evolutionary path similar to that of the unisexual whiptails. Could
our
future evolution eliminate males, keeping female-only sexual connections? This is not just a science-fiction scenario, for two reasons.

First, we don’t have to wait millions of years. We are increasingly in charge of our own genes and will soon be able to guide our evolution. Enabling women to reproduce asexually, with or without intimate female contact, could be on our horizon, and if we are worried about reduced variation—losing the game to the Red Queen or overcrowding the tangled bank—we can always fertilize one woman’s eggs with genes from another woman’s or find new ways
of introducing genes to spice up the variation and avoid the risks of identical cloning.

Second, we might just be accelerating a process that has already begun. The Y chromosome has lost many genes over the last 300 million years, although it has given up just one since we split from monkeys, around 25 million years ago. Also, sperm counts were reported to be plunging worldwide during the 1990s, although this may have stabilized. But these uncertain biological trends aside, sociology and psychology seem to be evolving away from the need for males.

Almost twelve million U.S. families are headed by single parents, of which 85 percent are mothers. It is difficult to tease apart the effects of father absence from those of poverty and other deprivations, but the epidemic of psychopathology that some psychologists predicted in the wake of the absent fathers has not materialized. Fortunately, the declining significance of violence has removed part of the need for a woman to have a man around—although our society needs to do much better in protecting women from their own intimate partners as well as from strangers—and the huge influx of women into the workforce, combined with social safety nets, makes males even more dispensable. This is one of the reasons men in male-supremacist cultures are so queasy about current trends. Many single mothers have unintentionally ended up using men as sperm donors and not much else. And more women are
intentionally
putting males in an even more minimal role, through artificial insemination. Here female choice can come down to leafing through a book of stats on the IQ, height, weight, health, education, athletic history, and behavioral records of donor males—photos, but no strings, attached.

Traditional male activities like boxing and hunting are in decline, and the absence of the draft and growing roles for women in the military have badly dented men’s age-old claim to a special status as defenders. Machines have been replacing male muscle for centuries.
More girls than boys are entering college, and more women than men are finishing. If Olympian women can’t outrun, outswim, outplay, and outfight their male counterparts, they can easily beat
most
men at all those things and more. How long will it be before women can, for all intents and purposes, do everything men can do? How long a path is it, really, from artificial insemination with donated sperm to doing the same with synthetic sperm, preselected to have X chromosomes only, with future generations “fathered” by sperm carrying genes from another egg?

The legal, ethical, and social obstacles are greater than the technical ones, which will be overcome in decades, not centuries. But before we decide to go down that uncertain path, we should note that female-only whiptails and hermaphroditic garden snails, with their Cupid’s arrows, are not the only animal models we might emulate in a brave new world of guided evolution.

Most coral reef fish, although not simultaneously both male and female, can switch from one sex to the other during one reproductive career. This has been documented in many different species, including the gorgeous damselfishes and parrot fishes common in home aquariums. If a male is removed from an otherwise all-female group, hormonal processes kick in to turn the dominant female into a new male. Humans, in a future world, could perhaps stay all female, designating one of them to become male only when collectively wanted or needed.

Or consider the anglerfish, in which females are ten times as long as males and a thousand times heavier. The teensy male seeks a female out, sinks his teeth into her flank, and proceeds to fuse his flesh with hers. Then he withers away until he is little more than a sperm factory, ready to fertilize her eggs when she lays them. Seahorses have a neat arrangement where the female and male pair off, swim in synchrony for a few days, even tangle tails a bit, all of which is believed to coordinate their breeding states. They need to time it so that when the female lays her hundreds or thousands of
eggs, the male will be ready for her to squirt them into his brooding pouch, after which he will secrete sperm to fertilize them. Now
he
is pregnant, and she goes off to make some more eggs. It seems to be a roughly egalitarian relationship:
Okay, you get pregnant, I’ll drift off, ovulate awhile, and bring back some more eggs.
The male uses prolactin, the milk-making hormone in mammals, to help gestate the eggs, and when they are ready they are born live from his belly by the hundreds, a cloud of minute seahorses billowing in the deep.

There are a number of birds and mammals in which females are larger than males. In some cases, males serve and service females, take care of the young, and respect and fear female dominance and aggression. By mating with a harem of males, each female has offspring even more varied than she would have with one male. Women could achieve this kind of female-dominant reversal more easily than the other options we’ve considered, without getting rid of males.

But suppose future women don’t want a reversal, only real equality or, perhaps, a modest advantage over males, just to keep them in line—without major biological change? With that goal in mind, we will look at one of our ape cousins, the vulva-bumping bonobos, who, while keeping males around for
some
of their sexual dalliances, thus doubling their fun, also keep those same males well in line with the clout of female coalitions. This prevents all the hypermasculine menaces that befall their and our other cousins, the chimps. Yet before women try to choose from this bestiary banquet of future possibilities, they have to decide what males are good for.

Chapter 3

♦

Picky Females, Easy Males

C
harles Darwin, well into
The Origin of Species,
dropped “a few words about what I call sexual selection” that echo, often harshly, to this day:

This depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring. Sexual selection is, therefore, less rigorous than natural selection. Generally, the most vigorous males . . . will leave most progeny. But in many cases, victory will depend not on general vigor, but on having special weapons, confined to the male sex. A hornless stag or spurless cock would have a poor chance of leaving offspring.

Darwin clearly understood the consequences:

Sexual selection by always allowing the victor to breed might surely give indomitable courage, length to the spur, and strength to the wing to strike in the spurred leg, as well as the brutal cock-fighter,
who knows well that he can improve his breed by careful selection of the best cocks. How low in the scale of nature this law of battle descends, I know not; male alligators have been described as fighting, bellowing, and whirling round, like Indians in a war-dance, for the possession of the females; male salmons have been seen fighting all day long; male stag-beetles often bear wounds from the huge mandibles of other males. The war is, perhaps, severest between the males of polygamous animals, and these seem oftenest provided with special weapons. The males of carnivorous animals are already well armed; though to them and to others, special means of defense may be given through means of sexual selection, as the mane to the lion, the shoulder-pad to the boar, and the hooked jaw to the male salmon; for the shield may be as important for victory, as the sword or spear.

Now, there is plenty here to take issue with. Males struggle for
possession
of the females? The “best cocks” are the ones that are best at violence? Alligators are “like Indians in a war-dance”? None of this would pass in a work of science today. But Darwin offers an upside:

Amongst birds, the contest is often of a more peaceful character. . . . There is the severest rivalry between the males of many species to attract, by singing, the females. . . . Birds of paradise, and some others, congregate; and successive males display their gorgeous plumage and perform strange antics before the females, which standing by as spectators, at last choose the most attractive partner. . . . I cannot here enter on the details necessary to support this view; but if man can in a short time give elegant carriage and beauty to his bantams . . . I can see no good reason to doubt that female birds, by selecting, during thousands of generations, the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect.

So we have either the gladiator spectacle of males ripping each other to shreds, with the winner taking possession of passive females,
or hopeful auditioning males preening and strutting their best stuff, their destiny controlled by picky females. Either way, it’s a peculiar theater in which to play out the history of life—“strange antics,” indeed.

But tactless wording aside, was Darwin right? Well, there is one thing he was wrong about: sexual selection is
more
rigorous, not less. Of course, death by being snapped up by a predator, succumbing to a parasite, tumbling out of a tree, or starving can’t be pleasant. But for the arithmetic of evolutionary destiny, sexual selection is more severe than any of those fates, because you may have reproduced quite nicely, thank you, before you were gobbled up. Yet you can live long and fall short of the next generation’s gene pool, in which case (evolutionarily speaking) you might as well not have been born. Evolution is a struggle for reproduction, not existence, and the sole goal of survival is to get to reproduce (or to help close relatives do the same). Life is the handmaid, procreation the queen.

Consider a population of a thousand in which there is no differential survival. Everyone lives exactly sixty years and drops dead on that birthday. No evolution, right?

Wrong. Of the thousand, a hundred have ten offspring, a hundred have none, and the others have every gradation in between. To the extent that any feature even modestly genetic contributed to these differences, that trait and its underlying genes will spread. There doesn’t have to be variation in survival, although in real life there is, and it figures in evolution. But you don’t need it to evolve. What you need is variation in breeding success,
partly
determined by traits that are
partly
determined by genes. Ironically, the very process of domestication—artificial selection—which Darwin used as a model for his natural selection, does not work through differential survival at all. Farmers and trainers make fatter cattle, woollier sheep, faster horses, tamer dogs, and eggier hens just by deciding which ones to breed.