Like a Virgin by Prasad, Aarathi (recommended reading txt) 📕

that a mutant animal is born, quite by chance, which is able to reproduce all on its own. This asexual female could give twice as many genes to its offspring as compared to a female having babies only through sex, providing a better chance for these genes to survive. The asexual animal’s descendants would get to keep those genes that made their mother (or grandmother) well adapted to the environment – there would be no random mixing and matching with a father’s DNA. If that mutant female was particularly well suited to the environment, its descendants would quickly take over. And in fact, this has happened, creating species in which there are no longer any males at all.

The classic example is the whiptail lizard. In one species of whiptail, known as Cnemidophorus uniparens, there are no males – and there never have been. The lizards were created when a male and female of two different whiptail species mated, forming a mutant offspring that could reproduce without sex; the eggs of the animal develop into female baby lizards via parthenogenesis. Curiously, to activate fertilization, the females still need to ‘mate’, and to look at, it seems just like the elaborate ritual one witnesses when a male whiptail courts a female. First, the ‘courting’ female lunges at and bites her targeted female. The attacked female is at first defensive, and attempts to bite back, but this behaviour rapidly dissolves into a more passive stance. The aggressor then grips the responsive female’s tail or leg with its jaws, and then mounts it for two to three minutes. While the lizard is on top of its target, it will intermittently rub its cloaca (that’s the one orifice that serves as the sole opening for the lizard’s anus, genitals, and urinary tracts) against the back of the passive female, stroking the back and neck with its jaws and forelimbs. The active female then grasps the back of the neck or shoulder of the passive female in its jaws and begins to curve and force its tail beneath the other’s tail, so that the cloacae of both are brought into close contact, somewhat as a male lizard would do in order to erect one of its two penises through its own cloaca. Once the orifices of both females are in contact, the courting female shifts its jaw to grip the lower half of the mounted female’s body. This forces the couple to adopt a contorted posture characteristic of mating lizards of opposite sexes. Now, if you were to dissect lizards post-‘coitus’, you would find something quite interesting: the female doing the courting has ovaries containing only small, or immature, eggs, while the passive female hosts several large eggs, each ready to develop into an embryo – almost as though the eggs had just been ‘fertilized’ by mating with the other lizard. It’s not known how the courting activates the egg to divide.

A number of other all-female species have been created by chance, when distinct but related male and female ancestors happened to mate. These include species of snails, crustaceans, and insects, including weevils, stick insects, and grasshoppers (not just aphids). Among other animals, the ability to have virgin births has occurred spontaneously, as happens quite naturally, for instance, in around one in ten fruit-fly eggs.

But for animals for which there are no males in the species, reproducing can be a little tricky at times. One tactic that has developed to get around this is known as kleptogenesis – where members of some all-female species, such as mole salamanders (Ambystoma), ‘borrow’ sperm from the males of related species in order to stimulate egg development, but without allowing the sperm to contribute to the genetic make-up of the offspring. The borrowed sperm kick-starts the eggs into action, and even fuses with the egg nucleus; however, unlike when a human egg is fertilized, the father’s and mother’s genomes do not combine. Occasionally, the father salamander’s genetic attributes will show up in some offspring, but only the mother’s DNA is transmitted to the next generation: when the offspring produce their own eggs, the chromosomes they got from the father are dumped and replaced by material stolen from the next sperm donor.

It is among insects, though, that virgin births probably exhibit the most diverse array of genetic strategies of animal reproduction, including some extremely rare mechanisms. Take the electric ant, Wasmannia auropunctata, a tiny ant that lives deep in the rainforests of Brazil and French Guiana, though it has now spread around the globe. Commonly known as the ‘little fire ant’, it is ranked among the world’s most invasive species. Some populations of the ant reproduce through normal sex. But for others, the females can make babies without the males – through a rather unusual process. The virgin females produce males, which then fertilize the eggs, though biologists do not understand how they do so. In any case, the fertilized eggs grow into more females – workers that are all sterile.

What is especially odd about the little fire ant is that it isn’t just the females that clone themselves; the males can do it too. This indicates that virgin birth in little fire ants probably developed spontaneously, as a result of mutations in their DNA. The males of the species are able to clone themselves by eliminating their maternal genes, so that they only ever pass on their father’s genes – the reverse of the scenario when females produce offspring through virgin birth. When scientists first discovered this detail, they assumed that the female DNA was discarded from the egg during fertilization, just as happens in reverse with sperm in female virgin births. It seemed as though the ants were waging a war of eugenics – the females dumping male DNA, with the males doing it right back.

In further studies, it has