Like a Virgin (27 page)

Should the Y chromosome crumble into scant genetic bits and bobs, and then disappear altogether, it would not necessarily mean the end of a species. There is hope. Some animals, such as the mole
vole (
Ellobius lutescens
) and the Japanese Ryukyu spiny rat (
Tokudaia osimensis
), have two sexes but no visible sex chromosomes. The voles, a rodent that burrows underground
throughout a wide swathe around the Caucasus mountains, are extremely interesting for one reason: it is impossible to distinguish a female from a male by looking at their chromosomes; both carry
only a single X. What is more, scientists have been unable to pick up any bits of
SRY
gene on any chromosome in the mole vole species. Since
SRY
normally acts as the primary switch
that initiates the development of a testis out of the undecided mass of cells in an embryo, you would expect to see it in an animal that looks male. It’s not there.

Unlike with the XX male cocker spaniels, pigs, and goats, sex reversal is the norm of the male mole vole, not the rare exception. How does the species survive? Male mole voles do have small
testes and problems in generating healthy sperm, but no hermaphrodites have ever been recorded in these animals. It appears, however, that testosterone is not very efficient in the males; the
prostate gland, in fact, seems to be insensitive to the effects of the hormone. Still, in captivity at least, mole
voles seem to have little problem breeding. Fifty percent
of early embryos perish, but certain mole vole couples have been seen to give birth to a litter of up to six pups – and they did that every four to six weeks, eleven times.

The mole vole story may give us a hint about the future of humanity. Even if the human Y were to disappear, it wouldn’t necessarily follow that men will vanish, too, though male fertility
would likely become substandard, adding another spanner in the works of making babies whenever you like. Infertility might one day affect all young, otherwise healthy men. And if the trend for
women having babies later and later in life continues, the health and quantity of their eggs will also be an issue. The limits of time is undeniably something we need to address, perhaps by
correcting genetic mistakes in embryos, a technique that is already being discussed but raises the spectre of eugenics in many circles.

Better answers will probably come from social policy rather than biology: discussing with young people the biologically optimal time to have babies, at the same time as they are taught how to
prevent pregnancies; more support for people who have children at a young age; more extensive childcare, benefits, and incentives to allow for family and work to exist side by side. After all,
right now, IVF treatments are invasive, difficult, and very expensive. For many people, however, ‘losing’ their youth to parenthood is neither an ideal nor a practical life choice.
It’s very hard to get away from the uncomfortable fact that it is educated women who tend to have babies later in life. It has even been suggested that an effective way to control
overpopulation would be to increase women’s rates of literacy. In any case, many women who have access to education and work opportunities are not going to turn them down in order to have
babies at a young age and at the risk of slipping behind their male colleagues on the career ladder. The goal

should be to give everyone these opportunities, not to snatch them away from those who have won them.

In a world where men and women now very often face the same social prospects, our reproductive biology has not kept pace. Normally, men produce sperm, women under thirty-five have eggs, women
bear children, and men cannot. There is a clear division between the sexes. That, however, is set to change.

In 2008, scientists at the New South Wales Department of Primary Industries, in Australia, developed the first artificial womb. It was a plastic container specially designed to
hold fluids, bacteria, and the other stuff that is needed to mimic the conditions found inside the mother as an embryo develops. It was a phenomenal breakthrough. Especially if you were a grey
nurse shark, the species for which the womb had been developed.

For aquatic ecosystems scientist Nick Otway, the artificial womb was a tool for addressing a terrible problem. The grey nurse shark, also known as the sand tiger shark, has roamed the
world’s oceans for more than seventy million years, but in the past century, the species has been decimated by increased fishing. Though it is not the target of the fishing itself, the
animals get tangled in commercial fishing nets or are mistakenly caught on hooks by recreational sportsmen. As a result, the shark is
now listed by the World Conservation
Union as globally vulnerable and as critically endangered in eastern Australian waters; its risk of extinction is high.

Part of the problem is the way in which grey nurse sharks reproduce in the wild. When a female becomes pregnant, dozens of embryos are produced. But at the end of a gestation of nine to twelve
months, the lengthy labour expels only two pups, each about one metre (just over three feet) long. The mother then enters a year-long rest before the next pregnancy. This means that the
shark’s birth rate is low, and births are few and far between. And it is lucky that the female produces two pups at all, and not just one – because the female grey nurse shark has not
one but a pair of separate wombs, so these offspring develop in isolation. And there is a reason for that.

The grey nurse shark is what most people think of when the word ‘shark’ is mentioned, despite the cinematic fame of the great white. In fact, historically, most sharks were labelled
the grey nurse – especially if they had taken a bite out of a person. It’s easy to see why – their menacing appearance is compounded by the fact that this is one of the few shark
species to display its impressive jaw of jagged teeth all the time. But most attacks attributed to the grey nurse are now considered to have been committed by other animals, and it is believed that
they have never actually been involved in a case of an unprovoked attack on a human. But while their savage reputation is unwarranted when it comes to humans, you can see how it might have been
earned when you consider exactly how grey nurse foetuses develop in their mothers’ wombs – through cannibalism.

Until they reach a length of about six centimetres (just over two inches), the embryonic grey nurses are nourished by the egg’s store of yolk. When they hatch from the egg, the foetal pups
swim into the so-called nurseries inside the mother’s body – what we would call the wombs – but very little nourishment
is left there. Luckily, by the time
the foetuses grow to about ten centimetres, they have developed a nice set of menacing jaws. To feed themselves, the foetuses begin to eat the remaining egg capsules, containing eggs and younger
embryos, and then, once they have consumed all of that, they attack the other foetuses in the womb – their siblings. The first foetuses to hatch will be the largest of the batch, so the baby
shark that manages to eat all of its siblings is likely to be the one that was fortunate enough to develop first. This cannibalism does mean, though, that out of the up to eighty embryos at the
beginning of the pregnancy, only one victorious pup is left in each womb at the end. As the other foetuses aren’t enough to feed the pup through to delivery, the mother shark nourishes the
two remaining pups, safely separated from each other’s jaws in their separate wombs, with a continuous supply of freshly produced eggs. Every grey nurse shark has survived at the expense of
dozens of its siblings – and thus no one female can produce more than two pups every two years.

These are not figures that can sustain an endangered species, and that’s how the idea of an artificial womb came about. The idea was suggested, in general terms, by an Australian
government minister in charge of fisheries but who was himself a farmer. As such, he was well versed in the manipulation of reproductive strategies, such as IVF, as a way of addressing breeding
problems in cattle and other livestock. He challenged scientists to create a similar intervention that might increase grey nurse shark numbers. Nick Otway answered the challenge by looking for a
means of pulling those dozens and dozens of shark embryos out of the mother and giving them a fair chance of coming to full term, away from the jaws of their siblings.

To create a successful surrogate for a shark womb, Otway, his research partner Megan Ellis, and their team first needed to figure out what a shark womb is like. What is the chemical
composition of the fluids in the womb, and of the eggs that the mother feeds the foetuses? What amount of oxygen exists in the womb, and what is the fluid’s temperature? Are
there types of bacteria that should be present, because they exist in the womb’s natural environment and might play some crucial role? What is the consistency of the walls of the womb, and
does the mother’s body allow extra nutrients to be supplied through it? Do any or all of these factors change at different stages in the course of a pregnancy? And could scientists invent an
artificial fluid to match the womb fluid, or re-create the overall environment?

To test the artificial womb prototype they developed, the scientists turned not to the endangered grey nurse, but instead to the related wobbegong, or carpet shark. The wobbegong is more docile
in outward appearance than its cousin: flat, sand-coloured, and patterned, with short catfish-like tentacles surrounding its mouth; it keeps its sharp teeth hidden from view. It’s also
smaller and easier to handle than the grey nurse. Internally, the wobbegong is simpler in structure, but there are similarities between the two species. Of special note to the research team, the
wobbegong reproduces more frequently than the grey nurse and was in no danger of dying out.

In a surgical procedure, Otway and the team removed six embryos from a wobbegong and placed them in their specially designed tank filled with some artificial womb fluid, some bacteria, and other
elements. After a normal period of gestation, the pups were ‘born’ through a tube that connected the grey box with another one containing ocean water, similar to that which would be
found where naturally developed pups would be born. The pups were reluctant to leave this rudimentary ‘womb’, even trying to swim back into the womb tank after making their initial
exit, but they eventually entered their new tank before being transferred into a more natural habitat. Proud as any new father, Otway said he was relieved, pleased, and even
amazed that everything had worked.

Next, Otway would focus on removing the embryos from the mother’s womb earlier and earlier – a move that would add layers of surgical complexity to the process, since the scientists
need to ensure that the delicate external yolk sac, as an essential source of nutrition, remains connected to the embryos as they are removed. Once this is accomplished, the embryos will also have
to be tethered to the artificial womb in some way, to stop them from detaching themselves and swimming away from their nourishment. If possible, Otway hopes to extract the embryos so early that one
day they might gestate completely in the artificial womb.

Otway’s artificial womb may be a novel idea for shark conservation, but bypassing a woman’s body is no new ambition when it comes to human reproduction. In 1924, evolutionary
biologist J. B. S. Haldane coined the term
ectogenesis
to describe how pregnancy in humans could be provided through an artificial womb. In a fictional account, he had two future scientists
describe the birth of the world’s first ectogenic child. ‘Now that the technique is fully developed, we can take an ovary from a woman, and keep it growing in a suitable fluid for as
long as twenty years,’ one of the characters announced. This, by the character’s calculations, would result in ‘a fresh ovum each month, of which 90 percent can be fertilized, and
the embryos grown successfully for nine months’, at which point they could be ‘brought out into the air’. Haldane imagined that artificial wombs might become so popular by 2074
that only a small minority, ‘less than 30 percent of children’, would then ‘be born of woman’.

Otway and Ellis finally reported the successful ‘artificial’ birth of their sharks late in 2011. But they had started the project early in 2008, and it had been a turbulent process,
with design failures along the way. Many embryos had perished. If creating such
a device for a shark has been challenging, could an artificial womb be viable for humans?

In some ways, the female grey nurse shark’s reproductive system is similar to a human’s, as eggs are produced in ovaries and pass down tubes towards the womb (whichever womb that may
be). As we saw, the pups first develop while still inside these eggs, surviving on the egg yolk, before the cycle of cannibalism begins.