Maleness as quality control?

2009/04/14 § Leave a comment

The development of sex is a rather startling thing, that we still struggle to find good explanations for. It has been thought that sexual reproduction leads to more genetic stability, but counter evidence has been found. Mutation rates are not necessarily lower in sexually reproducing species. Additionally sex is a rather recent invention in evolutionary terms. If it were terribly necessary to keep mutation levels low we would have seen it sooner. However, it must be good for something, else it would not have developed.

When studying genetics I have been wondering why men are apparently the “weaker” sex. Men die earlier on average in every nation. Men suffer from a larger range of genetic disorders. Almost generally variation in men is larger than in women and leads to a variety of problems. The extremes in intelligence in men seem more pronounced.

It seems to also lead to men suffer from mental retardation more often, while on the other hand men are also found on the other side of the spectrum and are more often extraordinarily intelligent. Mens metabolism is more wasteful due to the fact that men are larger, stronger and faster than women, due to more muscle mass. It is also well-documented that more males die in childhood and before they are old enough to have children.

Why would it be like that? Why would evolution permit it? It is rather acceptable as a hypothesis that men underly a kind of “arms race” leading to the strength development. At the same time women, I.e. sexual selection, must have an influence on it. Aggression and physical strength must have been or still is a criteria for mate selection.

On the other hand there may be another mechanism at work too, as occurred to me the other day. The hypothesis is that the genetic overdrive in which males find themselves in might act as quality control. A “malfunctioning”, that means maladapted genome would more easily be revealed under harsh endogenous conditions.

We can find males under a performance stress (in a genetic sense that is) in various species. Many times males are bigger and stronger and have to produce either a energy consuming appearance- as in birds- or exhibit energy costly behavior as physical competition or behavior as collecting “goods” (as in some birds and humans).

Arguably maleness is a tougher test on a genome than femaleness, as reflected in the lower long term survival rates for males. Hence, is maleness a way of testing a genome under “extreme condition”? Has an advantage of sex been that one half of the species could be “sacrificed” to test the genome for its quality of adaptation? In this case a population with a less pronounced difference of male and female physique would eventually die off, as their genome becomes maladapted.

Now I must admit that I felt pretty smart to have come with that idea, especially since I at first did not find anything about it googling. But then I found a work that cites Charles Darwin for having the exact same idea some two hundred years ago [1]! Well, even though I was a bit late at least I am in good company. 😉

There is a reason why we celebrate Darwin this year [2], for he is for Biology what Einstein has been for physics. A great man with a great idea that is so powerful that it scares the living hell out of some people, who struggle accepting its possible implications (yes, I mean you, you creationists and un-intelligent designers)… Hail Darwin! 🙂



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