Like a Virgin (14 page)

Komodo dragons and sharks aren’t like whiptail lizards; they aren’t all females, and they don’t behave – as has been said of whiptails – ‘like
lesbians’. Flora the dragon and Tidbit the shark only experienced virgin births because they had no males to mate with. Theirs was an artificial situation, because they were living in zoos,
but sometimes the situation in the wild isn’t altogether different. Poaching and human encroachment have decimated the population of Komodo dragons in the wild. Sharks are also increasingly
overexploited: in the north-west Atlantic, there have been rapid declines in large coastal and oceanic shark populations – over a seventy-five percent decline, in fact, in the past twenty
years or so.

Usually, hammerhead sharks in the wild have litters of around fifteen pups, and blacktips have four to six. Of the two sharks that were found to have had virgin births in captivity, both only
had one pup. Having babies without a mate means that the offspring won’t enjoy as much genetic diversity as they would if
they had a father’s genes too. And low
genetic diversity is almost always a bad thing – something to be avoided in a population struggling for its existence; if every member of a family line has the same DNA, and that DNA is not
well suited to the existing environment, it could spell disaster. Then again, a Komodo mother creating a male with which it can breed doesn’t appear to be such a bad option, when faced with
extinction. And it’s not such a bad option to have just one shark daughter, instead of six, if the alternative is not reproducing at all.

Whether in situations where males are sparse, or simply as a matter of course, it is perfectly possible to create life from eggs alone – it’s a strategy that females of many species
have long exploited. And indeed, parthenogenesis in animals has even been exploited, in a more domestic context, by us humans.

After the war, the US Department of Agriculture and British animal research units sponsored some interesting experiments with the ostensible aim of improving the efficiency and
sustainability of animal husbandry. Then, in 1952, scientists at the Beltsville Agricultural Research Center in Maryland discovered parthenogenesis in turkey eggs. Immediately, selective breeding
programmes were launched in an attempt to intensify the trait in certain lines of turkeys and chickens – it was the hunt for the ultimate breeder.

Those turkeys that showed the greatest predisposition for reproducing without sex were crossed, and were a runaway success – the Beltsville Small White breed. The percentage of virgin
births in the turkeys increased from nearly seventeen percent to around forty-five percent in the space of a mere decade – a mote of evolutionary time.

Interestingly, parthenogenesis in the eggs of both chickens and turkeys was notable for the seeming lack of cell organization within the early embryos. A chaotic,
multi-layered mess of cells would develop, whether it was grown in a hen’s oviduct or in an incubator. This made the scientists at Beltsville wonder whether an infection could have triggered
the birds’ new mode of reproduction – an avian version of
Wolbachia
.

As a culprit, the researchers suspected a particular group of viruses, Rous sarcoma retrovirus, fowlpox virus, and Newcastle disease. Each of the viruses was found to enhance parthenogenesis; in
other words, they appeared to stimulate the egg to develop into an embryo, an effect that, as with
Wolbachia
, persisted in the eggs of the daughters and granddaughters produced through
virgin birth. Unlike with
Wolbachia
, however, virgin birth in the turkeys was not ‘curable’. If an already vaccinated turkey was infected with the fowlpox virus, the incidence of
parthenogenesis in the eggs of that same hen increased markedly over the level recorded for her eggs before she was vaccinated – the opposite to what the scientists had expected.

Still, the data indicated that parthenogenesis could be boosted by selective breeding. The team could identify the ‘high-incidence’ turkeys, those recorded to have the highest
predisposition for virgin birth, and keep the line going, without introducing sperm. The finding was backed by studies of fruit flies, among which it was observed that both males
and
females
could transmit the parthenogenetic trait to their offspring. Through cross-breeding these flies, scientists increased the rate of parthenogenesis by around thirty-four times, compared to unselected
fruit flies, in just twelve generations.

That, of course, leaves the question: if the birds and the bees can do it, why couldn’t
we
?

It was March 1984. In a small town in Lesotho, a fifteen-year-old girl walked to a local bar to start work for the day. At some point during her shift, her new boyfriend showed
up. Unfortunately, so did a jealous ex-lover – just in time to catch her with her boyfriend’s penis in her mouth: to the ex’s eye, in flagrante delicto. The details of the fight
that ensued are unclear, but it seems the girl tried to protect her boyfriend (and herself) from attack, because she ended up with lacerations on her hand; she also sustained two stab wounds to her
stomach.

Just over nine months after the doctors at Mafeteng District Hospital stitched up her wounds, the girl returned. This time she was much larger in girth and complained of acute, but unexplained,
pains in her lower abdomen. The possibility that she was pregnant had never occurred to her – not because she was naïve, but because she was well aware, as her doctors were soon to
discover, that she did not have a vagina.

In one sense, having sex and getting pregnant is as straightforward an event as any. You need a male and a female, they have sexual intercourse, sperm meets egg, and, some
time later, a baby is produced. All of this we take for granted, though not in a glib sense; as we have seen, much can go wrong along the way, and sometimes babies are born with debilitating
diseases and sometimes they are miscarried or emerge stillborn. Yet, in all these cases, we assume that at one point a sperm met an egg, thereby beginning a pregnancy. But step back from that
assumption and consider the circumstance within which sperm meets egg, and even whether or not sperm meets egg at all.

The Lesotho teenager was treated by Douwe Verkuyl, who reported on her predicament in the
British Journal of Obstetric Gynaecology
. Dr Verkuyl suggested that the pregnancy may have been
the first recorded case of ‘oral conception’: the knife wound to the stomach may have allowed the sperm the girl had swallowed to find its way from her gut to her womb. As unlikely as
it may seem, this is a strategy that has seen precedents in nature. There are animals in which fertilization can be achieved artificially by injecting sperm into the abdominal cavity, from where
they swim down a Fallopian tube to the egg. In fact, for some, like the blood-sucking African bat bug, impregnation via the abdomen is the standard mode of operation. Even though the females of the
species have not one but two vaginas – one real, one fake – the males use neither. Instead, a male will stab a female’s abdomen and inseminate the female’s blood. Of course,
just because a relative of the bed bug can do it doesn’t imply it can happen in humans too. But Verkuyl noted two conditions that she thought made the scenario more likely: when her young
patient arrived at hospital after the fracas, her stomach was devoid of food (and the gastrointestinal juices that are produced to digest it) and saliva itself tends to be alkaline (it has a high
pH). These things, she thought, helped the sperm survive
what would have otherwise been the hostile, acidic environment in the stomach.

Shortly after the child’s birth by Caesarean section, the families of the girl and her boyfriend exchanged cattle to seal their union. But the girl’s son, conceived from that
gruesome and bizarre violent encounter was to be her only child. Around the time her son reached the age of two and a half, the girl began to suffer crippling pains, because her menstrual blood,
which had no outlet, was collecting in the cavity of her uterus. Unable to stop her periods through drug treatments, doctors ordered a hysterectomy, the removal of the uterus. ‘By that
time,’ Verkuyl wrote, ‘the son looked very much like the legal father,’ a fact that ‘excludes an even more miraculous conception’. By which, one assumes, the doctor
was alluding to the conception of a child without the involvement of sperm at all.

Mission impossible? It should be. Yet, some animal eggs regularly manage to achieve virgin births – not just tiny insects, but large vertebrates, including fish, birds, and reptiles. And,
in fact, human eggs can work on their own too.

Most animals have eggs with a lot in common. Of the billion or so cells in our bodies, the egg is the largest cell that animals have. Among most amphibians and fish, an egg is
about as big as the full stop at the end of this sentence. If you divided that full stop into one hundred pieces, most other cells in their bodies would be about the size of just one of those bits.
Human eggs, by comparison, are the size of ten pieces. Reptiles and birds, of course, have immense eggs – each egg in the cardboard carton you bring home from the supermarket to scramble up
for your breakfast is essentially a single egg cell.

The mammalian egg is the site of a number of quite extraordinary biological processes, not least of which is the way the egg itself is produced. The first person to figure
out that there was something unusual about eggs was Edouard Van Beneden, in 1883. At the time, Van Beneden was studying how the cells in
Ascaris megalocephala
, a worm parasite of horses,
were made. By throwing live female worms into containers filled with diluted alcohol and leaving them there to ‘stew’ for several months, he was able to dissolve the worms’ cells
enough to reveal their components. (This method of damaging cells is still used in labs to isolate DNA and RNA; it’s also the reason why alcohol wipes are effective at killing bacteria.) Van
Beneden observed that the worms had four chromosomes in almost all of their cells. In their eggs, however, there were just two chromosomes. To Van Beneden, this made no sense: the eggs were made
from cells with four chromosomes, so two chromosomes had seemingly disappeared. He then noticed that the mother’s and the father’s chromosomes came together in the fertilized egg, thus
producing baby worm cells with four chromosomes. The contradiction puzzled him, and he did not publish any further work on the subject.

A year later, Van Beneden’s work came to the attention of the German biologist August Weismann. Alas, the esteemed professor was suffering from eye trouble. After many years of conducting
his groundbreaking scientific experiments in chemistry, biology, and medicine, he could no longer look down the microscope for himself, and he was forced to turn his attention to theoretical
questions. Still, he was not ready to give up experimentation altogether. Weismann asked his janitor to carry out the logistics of his experiments and assigned his students to do the microscopic
analysis. His wife, Marie, would read scientific papers aloud to him, so that he could keep up with the latest ideas. Among the papers Marie recited was Van Beneden’s work
on chromosomes in worm eggs. As Weismann listened to Van Beneden’s extensive observations, and Marie’s descriptions of the paper’s drawings, he came up with a
theory: a very special division happened exclusively in the sex – or germ – cells, that is, in eggs and sperm.