Like a Virgin Read online

  Since Jane had conceived all of her sons naturally with her husband (who DNA tests showed was definitely their father), the results effectively suggested that she had somehow given birth to another woman’s children. That, of course, she deemed an impossibility, especially since mistakenly swapping not one, but two, children at birth would have been a highly improbable coincidence. Further checks had to be done. Doctors tested DNA from other tissues, including Jane’s thyroid gland, mouth, and hair. And that was how they discovered that this woman’s body was composed of two genetically distinct groups of cells. Jane, like FD, appeared to be a mixture of two different people.

  The most likely explanation was that Jane’s own mother had conceived non-identical twin girls, who would have been no more alike genetically than two siblings conceived at separate times. At an early stage of the pregnancy, however, these twin embryos had fused, to form a single embryo. Because Jane’s blood cells presumably carried DNA from one twin, and her ovaries and the majority of her eggs carried DNA from the other, a quick DNA test threw out the result that she was not the mother of two of her own children. Speaking in terms of DNA only, Jane’s unborn twin was, in fact, the mother.

  Yet, in one very significant way, FD was not like Jane at all.

  Getting pregnant in the normal way is a hit-or-miss process; a couple has only around an eighteen percent chance that the man’s sperm will penetrate the woman’s egg at her peak period of fertility, assuming, of course, that they are having unprotected sex. Then, there are the odds that a fertilized egg will transform into an embryo, and make it to full term. Jane’s foetal life had been very rare – two different eggs developing into two different embryos and then fusing together. Which makes the way in which FD began life all the more incredible. FD had originated from only one egg. What is more, that egg had broken the laws of nature and developed into an embryo without waiting to be fertilized. His blood with its two X chromosomes was the product of parthenogenesis.

  How tiny is the likelihood of each single event in the sequence of events that brought FD to life! First, one of his mother’s eggs – the egg that would become him – was activated by some hormonal trigger, despite there being no sperm around to do the job. The activated egg then began dividing, the first steps towards becoming FD. The only DNA in FD’s embryo at that point was from his mother. Next, rather ‘miraculously’, along came a sperm – a single sperm, as far as the scientists can tell – from his father. It should have arrived too late to have any effect, since normally after an egg is activated, a cascade of chemical signals tells the egg’s outer layer to harden, making it impossible for ‘follow-on’ sperm to penetrate the egg and mess things up. An egg that accepts more than one sperm will form an embryo with too much DNA, and such embryos are normally destined for early termination – a miscarriage.

  If FD was the product of parthenogenesis, couldn’t Monica Jones have been a product of parthenogenesis, too? Unfortunately, scientists will probably never be able to answer definitively the question of Monica’s maternity and paternity; they just don’t have the information necessary to figure it out – the DNA of her mother’s parents. But there might be alternative circumstances in which a woman might give birth to a child, apparently unaided.

  Take, for instance, the best-known story of a virgin birth and consider how in the world such a miracle could have been effected – biologically rather than divinely speaking. In the third century ce, an influential Church father named Origen worked to promote belief in the virginity of Mary, mother of Jesus, in what sounds at times like evolutionary terms, to the modern ear. The evangelist wrote:

  For it is ascertained that there is a certain female animal which has no intercourse with the male (as writers on animals say is the case with vultures), and that this animal, without sexual intercourse, preserves the succession of the race. What incredibility, therefore, is there in supposing that, if God wished to send a divine teacher to the human race, He caused Him to be born in some manner different from the common!

  Origen argued that reproduction without a mortal man was very uncommon indeed; for instance, he dismissed the legend of his countryman Plato’s immaculate conception, as ‘veritable fables’ that did not demand such creative innovation. But what rare biology might have been involved in producing Jesus (or for that matter, FD)? To answer that question, an emeritus professor of genetics at University College London, Sam Berry, has worked out the biological possibilities for how Mary could have given birth to a son, while still remaining a virgin. Beyond the issue of activating the egg to develop into an embryo without a human sperm, there is another problem: the fact that Jesus was not Mary’s daughter.

  A woman alone should never be able to provide the genes needed to make a son. The Y chromosome, which carries the genes that dictate maleness, are normally only carried by men, so are passed on through a father. So if Mary had given birth to God’s divine daughter, the biology would make sense – she would have been able to provide all of the DNA, with the supernatural power activating the egg in some way. But Jesus was, as we know, God’s only son.

  To produce a son via virgin birth, Berry suggests that Mary may have suffered from one of the several chromosome abnormalities that cause testicular feminization, a condition which affects around one in thirteen thousand people. While women with testicular feminization have a Y chromosome, they ‘present’ as a girl at birth – with a vagina and no testes or penis. And throughout life, they appear to develop along female lines, growing breasts, for instance. Internally, however, their bodies tell a different story. The vagina is quite short, and leads to nowhere – neither to womb nor ovaries – and hidden away in the abdomen, there is a set of testes. Normally, testes make testosterone, the hormone that masculinizes the growing embryo and child, so that he develops the external genitals and other sexual characteristics of a typical male – such as more extensive body hair. Yet, even though a woman with this condition is exposed to the testosterone produced by her testes, the body seems to be insensitive to its effects. As a result, she will likely show off a luxuriant head of hair and never experience male-pattern balding – and further, she’ll never develop hair where you would expect it, in the armpit and pubic area.

  Essentially, Berry’s idea was that the only way a woman could have a son without input from a father is if she herself carried a Y chromosome. In fact, a son from a mother who carried a Y chromosome – most likely one that was not fully functional – might develop into a normal male, without issues of abnormal testosterone production or sensitivity, if, say, that chromosome mutated back into a functional state somewhere along the way.

  But what made this biologically plausible possibility highly improbable was the fact that a testes-carrying female virgin would have a very hard time getting pregnant in the first place: because people with testicular feminization cannot make eggs and have no womb in which a placenta could form, they are sterile.

  In theory, Mary of Nazareth might have been a genetic chimaera, rather like Jane of Boston – except that, to have any chance of fertilizing herself, Mary would need to have been formed from a set of twin embryos, one male and one female, who fused into a single body while maintaining both sets of chromosomes – Y and all. This is an intriguing thought experiment, in Berry’s view, but it is also an unlikely scenario, not least because Mary’s body would have to achieve a truly miraculous balance between male and female hormones and reproductive organs.

  It’s important to note, however, that in a purely physical sense this kind of sexual ambiguity is actually not that uncommon. As many as one in a hundred people are born with bodies that differ from the standard male or female package, and one in 1666 people are born with sex chromosomes that are not XX (normal female) or XY (normal male); one in a thousand carry XX chromosomes as well as a Y. Far more rare, and for our purposes, more interesting, are the one in every eighty-three thousand people who are born with ovotestes – gonads that are part ovary and part testes.

  Indeed,
another suggestion is that having ovotestes could explain how Jesus could have been born to a Virgin Mary. Genetically, Mary would carry two X chromosomes and appear to be a normal female – superficially. She would have had breasts (though she may not have been able to lactate), a uterus, Fallopian tubes, and a vagina. Her clitoris, though, would be enlarged, approximating a small penis – reminiscent of Aristotle’s hyenas. This larger clitoris would have been due to her anomalously high testosterone levels – produced by the incomplete testes inside of her perfect female form.

  Ovotestes result when a woman inherits from her father an X chromosome carrying SRY material, which is normally located on the Y chromosome. When cells divide – the process by which any fertilized egg multiplies into the millions of cells that make up a living animal – the cells’ chromosomes copy themselves in order to populate the new cells with genetic information. In this replication process, mistakes can and do happen; genes are exchanged between chromosomes quite regularly, and sometimes they are cut and pasted on to chromosomes where they are not supposed to be. So if a person has two X chromosomes, but one of them has acquired essential male genes from a Y chromosome, this would make her completely male.

  For the occasion of a Virgin Mary, we would have to go a step further, and imagine that when Mary was a developing embryo, her abnormal X chromosome in most of her tissues lost its male genes. Most, but not all. If the X chromosomes carrying SRY-containing genes were retained in some of those cells destined to become gonads, this would make Mary a genetic and sexual mosaic; she may even have had a beard. And depending on the balance of her mishmash of hormones, it would ‘simply’ be necessary for her ovotestes to produce both sperm and eggs when she reached puberty, and for these simultaneously to travel down the Fallopian tubes, and for the sperm to fertilize the egg, and for the fertilized egg to implant in the uterus. Voilà: virgin birth.

  This may sound far-fetched, but just such a case of hermaphroditism was described in 2000. The child, a one-year-old girl from Mexico, was reported to have ovotestes, and to have all the ingredients that might begin the chain of events necessary for an eventual virgin birth. But given her young age at the time of examination, it was not clear whether she would be able to produce viable sperm and eggs at puberty – a question that might very soon be answered, given her date of birth.

  You would be forgiven for thinking that these scientific scenarios are no more plausible than a miracle would be. Indeed, (rather like Monica Jones) misunderstanding, misdemeanour, or even mistranslation may be the real explanation behind the baby Jesus’s birth. The great irony, as we have seen in the previous chapter, is that it may, in fact, be almost more sensible to reproduce without males, because of all the drawbacks of sex for females.

  Nature has also shown on several occasions that mistakes in the DNA have allowed many animals that normally reproduce through sex to do without it. Sex is, after all, something that evolved only once, which means that those animals today that have the capacity to reproduce without sex regained this capacity relatively recently, through mutation. Switching between sexual reproduction and self-reproduction should, therefore, bring with it some evolutionary advantages. For example, imagine 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 D
NA. 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 been revealed that things are not so simple (or so very human). The male little fire ants appear to be clones, without any of their mother’s DNA, but this trait appears to be controlled by the females – or more specifically, by the queen ant. Only males mated to the queen can become clones of their fathers, which is to say that, if a son ditches its maternal DNA, it is because the mother has dictated it to do so.

  For the little fire ant, it seems there would be no male clones if the females themselves were not able to have virgin births. When the cells in a queen divide to produce parthenogenetic eggs, there is not an equal division. One of the two ‘daughter’ cells takes the DNA-containing nucleus in its entirety, while the other takes just the cell’s cytoplasm. So a queen lays some eggs that have a complete set of DNA and require no fertilization (and which become sterile daughters) and lays eggs that are ‘empty’, with no nucleus or DNA. Should these empty eggs be fertilized by sperm, the only DNA to be donated to the embryo comes solely from the male – there simply is no genetic information from the mother ant in the egg.

  In other species, parthenogenesis is triggered by the sort of hazard that some scientists believe gave rise to sex in the first place: a contagious infection. Believe it or not, this means that you might be able to ‘cure’ some animals from the plague of virgin births – animals like stingless wasps (Trichogramma). These tiny parasites make their living with some rather cunning tricks. The females attack the eggs of moths and other species, injecting their own eggs into those of their unsuspecting victims. In some cases, they find newly hatched eggs via some quite sophisticated chemical espionage. The wasps can sense anti-aphrodisiacs – the pheromones that many male insects pass to females to signal that mating has taken place, and which makes these females less attractive to other males, in an attempt to keep other males’ DNA from competing in a race to fertilize the egg. This may be a useful tactic to employ when there is competition for females, but it’s also a communication system prone to sabotage by the stingless wasp. By following the scent of these pheromones, the wasps can locate a female butterfly, moth, or other insect that has just mated and is poised to lay a clutch of eggs. The female wasp then hitches a ride on her hostess insect, until the host lands on a plant to lay its eggs. The parasitic passenger hops off and quickly injects its own eggs inside the fresh host eggs, so that when the wasp’s larvae develop, they are perfectly placed to eat the contents of the victim eggs. And these host insects are not the only victims. For the female wasps themselves play host to another parasite, one yet more brilliant. When this parasite infects its target, the males of its host species become infertile, or are killed while they are still developing as embryos. And as the males are eradicated, their females begin having virgin births. This is probably how stingless wasps began to reproduce in this way – and why they may yet be kept from transforming into an all-female species.