In addition to moving the world, sex is a source of diversity because with sexual reproduction the genes of the parents are combined and recombined in each generation, producing a unique genetic configuration. Of course it has its drawbacks. The biggest is the loss of immortality. If we reproduced asexually, we would be like bacteria, which remain much the same as they were billions of years ago. Sex makes us mortal .
That mortality forces us to flirt. It does not matter if you are the fastest, the best forager or the most skillful in avoiding predators: if you are unable to seduce a mate, your genes will be lost like drops of water in the rain . The need to reproduce exerts a very high pressure on animal behavior, to the point that some strategies conflict with the individual’s own survival. It is well known that the praying mantis has the unpleasant habit of ripping off the head of the male in a kind of sexual cannibalism . Thus, in 60% of copulations, the male ends up decapitated and devoured. Hence, the male sneaks up on females from behind or, like the springbok mantis -also known as Miomantis caffra , native to southern Africa- tries to subdue her by immobilizing her after a violent struggle. In this case, if the male is faster and manages to grab her with his front legs, he has a 78% chance of escaping unharmed . But if she is the one who catches him, may God catch him confessed.
Sex to death
The one who has no chance of getting out of sex alive is the male bee: when he reaches climax his genitals are torn from his body emitting a loud snapping sound. The reason for this sexual suicide is none other than blocking the queen’s conduit to prevent other males from mating with her: an organic chastity belt , after all. Of course, the competition is fierce: up to 25,000 males fight to copulate with a queen during the few days that she is accessible, because the rest of the time she will be preoccupied with producing offspring, up to half a million bees. Copulation takes place in full flight: the queen goes out into the open and mates with any male that approaches her, although she does not usually do so more than 20 times. That means that 99.92% of male bees will die virgins .
We must take into account that not all living beings understand sex as we do . Although it essentially involves joining the male and female gametes, the way it is done differs greatly from one species to another. Let’s start with the stick insect, which copulates non-stop for more than ten weeks , but not because it is immersed in irrepressible lasciviousness, but because doing so non-stop prevents any other male from having the opportunity to approach the female. Of course, for jealousy, those of the male Idaho squirrel, who does not leave the female in the sun or in the shade: he follows her everywhere and when he returns to the burrow he stands guard at the entrance. Why such a level of jealousy?
Are males womanizers and females castes?
In 1948 AJ Bateman published an article in Heredity magazine that was destined to become famous. In it he argued that males had evolved for sex and females for motherhood. Known since then as Bateman’s principle -which basically means that males are womanizers and females are chastes-, he deduced it after observing for a few days one of the model animals of biology, the fly of the fruit or Drosophila melanogaster . He observed that the males strived to mate as many times as they could while the females tended to be more reluctant and refused the invitations of various suitors. In addition, Bateman observed that the most promiscuous males were those that had the most offspring , while the same was not true for females. The conclusion he reached was that this behavior stemmed from a simple energetic calculation: it takes very little for males to produce large quantities of their tiny sperm, but it is energetically very expensive for females to produce an egg.
Admittedly, the argument seems sensible enough, but further research has shown that Bateman’s principle is anything but a principle. Because as the biologist Olivia Hudson says, “in most species, females are more lewd than holy.” Furthermore, and to the horror of the Puritans, disorderly promiscuity is not a “malfunction”; the females reap huge benefits from such behavior. For example, when in heat, female rabbits have higher conception rates if they mate with multiple males, and the female European agile lizard ( Lacerta agilis ) lays more eggs the more lovers she has had. And let’s keep one thing in mind: As far as we know, the females of the most promiscuous primate species have a greater capacity for orgasm .
female promiscuity
If we were to point to the most promiscuous females among the higher animals, all fingers would point to our cousin-brother the chimpanzee. What we don’t know is why. Some biologists think that this is how they provoke sperm competition (the best sperm will fertilize the egg) while others are inclined to think of the so-called obfuscation theory: by mating with a large number of males, none can know if the child is not theirs – not even her-, and taking into account that infanticide is a clear and real risk in chimpanzee populations, the female prevents any male from killing the little one because it could be the father.
A totally different behavior is that of the California field mice ( Peromyscus californicus), faithful to their mate until exhaustion: they are genuinely monogamous. A behavior that contrasts with its closest mouse relatives, the deer mouse ( Peromyscus maniculatus ) cheats up to the ears. The only explanation is evolutionary: in this case the faithful mouse leaves more descendants than the promiscuous one. As this fidelity has a genetic component , these genes ended up spreading throughout the population and this behavior became dominant.
The promiscuity of the females remains unknown , however everything indicates – or at least that is what most researchers think – that they try to avoid possible genetic incompatibilities as much as possible. This idea has not been verified except in some species, such as the honey bee. For some biologists, incompatibilities between male and female genes are more common than we might imagine. On the other hand, we know that genetic incompatibility is a cause of infertility in quite a few species. In humans, for example, one in ten couples are infertile and of these between 10 and 20% of cases are due to genetic incompatibility.
References:
Judson, O. (2011) Sex office for all species, Critical Ed.
