Status Updates From The Red Queen: Sex and the ...

The process of choosing somebody to have sex with, which used to be known as falling in love, is mysterious, cerebral, and highly selective: We do not regard any and all members of the opposite sex as adequate partners. We consciously decide whether to consider people, we fall in love despite ourselves, we entirely fail to fall in love with people who fall in love with us. It is a mightily complicated business.

The fact that one segment of the population is having sons makes it rewarding for the other segment to have daughters. Every animal is the child of one male and one female. So if dominant animals are having sons, then it will pay subordinate ones to have daughters.

Lower down the social scale, daughters are preferred even today: A poor son is often forced to remain single, but a poor daughter can marry a rich man.

So human society, like ape society but unlike most monkey society, is a female-exogamous patriarchy, and sons inherit their father's (or mother's) status more than daughters inherit their parents' status. Therefore, says Trivers-Willard, it would pay dominant fathers and high-ranking mothers, or both, to have sons and subordinates to have daughters: Do they? The short answer is that nobody knows.

There are at least three different and better ways to determine your gender. The first is to choose the gender appropriate to your sexual opportunities.

A second way is to leave it to the environment.

A third way is for the mother to choose the sex of each child.

This, briefly, is the theory of sex allocation: animals choose the appropriate gender for their circumstances.

Far from settling down to a fair and reasonable way of determining gender, nature has to face an infinite series of rebellions: It suppresses one only to find it has opened the way to another: For this reason gender determination is a mechanism full of, in the words of Cosmides and Tooby, "meaningless complexity manifesting unreliability, aberrations, and (from the individual 's point of view) waste."

Maleness is a rather rare commodity at this stage. The few
remaining hermaphroditic mice are at a premium because only they
can produce the sperm that the all-female mice still need. The rarer
they get, the better they do. No longer does it pay to have the
male-killing mutation: Rather, the reverse. But if such a female
killing gene appeared, then the remaining hermaphrodites are no longer
at a premium.

Maleness is a rather rare commodity at this stage. The few
remaining hermaphroditic mice are at a premium because only they
can produce the sperm that the all-female mice still need. The rarer
they get, the better they do. No longer does it pay to have the
male-killing mutation: Rather, the reverse. But if such a female
killing gene appeared, then the remaining hermaphrodites are no longer
at a premium.

"Now a selfish gene might do rather well. Suppose it simply killed off its opposite number. Such a gene exists. Call such a gene Cain. The 'mask of Cain' protects him from the gas he uses against Abel. Cain becomes an ancestor, and Abel does not. Thus a gene for chromosomal fratricide will spread as surely as a murderer will inherit the Earth."

To be sexual does not necessarily imply the need for sexes, let alone for just two sexes, let alone for two sexes as different as men and women.

Indeed, at first sight, the most foolish system of all is two sexes because it means that fully 50 percent of the people you meet are incompatible as breeding partners.

The Red Queen's case is that an individual, by having sex, can produce
offspring more likely to survive than an individual that produces clones of itself. The advantage of sex can appear in a single generation because whatever lock is common in one generation will produce among the parasites the key that fits it.

The more successful the parasite's attack, the more the host 's chances of survival will depend on whether it can invent a defense. The better the host defends, the more natural selection will promote the parasites that can overcome the defense. The more dire the emergency for one, the better it will fight. This is truly the world of the Red Queen, where you never win, you only gain a temporary respite.

Pitted against a clone of asexual individuals, a sexual population must inevitably be driven extinct by the clone 's greater productivity unless the clone's genetic drawbacks can appear in time. Itis a race against time. For how long? Curtis Lively has calculated that for every tenfold increase in population size, the advantage of sex is granted six more generations to show its effects or sex will lose the game.

Sexual species shared their newly invented genes among all individuals; asexual ones did not. So sexual species were like groups of inventors pooling their resources.

Asexual ones behaved like groups of jealous inventors who never shared their knowledge, so that steam locomotives were used on roads and horses dragged carts along railways.

This concept, that all progress is relative, has come to be known in biology by the name of the Red Queen, after a chess piece that Alice meets in Through the Looking-Glass.

The faster you run, the more the world moves with you and the less you make progress. Life is a chess tournament in which if you win a game, you start the next game with the handicap of a missing pawn.