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.
8
REAL MEN BEAR CHILDREN
Women’s liberation is just a lot of foolishness. It’s the men who are discriminated against. They can’t bear children. And no one’s likely to do anything about that.
Golda Meir, quoted in Newsweek, October 1972
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 f
luid 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.
But, in most ways, the grey nurse shark nurtures its foetuses in a far less complicated manner than humans; for whom getting nutrition is not as simple as ingesting egg yolk (or siblings). For a start, the shark does not have a placenta – the complex, specialized organ that is created from the fertilized mammal’s egg in order to sustain the embryo. Because the placenta is made from the fertilized egg, it contains both the mother’s and the father’s DNA. Very early in the pregnancy, the placenta sends out a system of blood vessels to penetrate and dock into the mother’s womb, through the umbilical cord. The foetus acquires oxygen and food – gets rid of its wastes – through the placenta, which should provide life support for forty weeks, until the foetus grows and develops to a stage where it is able to perform these functions on its own. A human artificial womb would need to replicate all of the placenta’s functions, not just the womb’s fluids, bacteria, and other stuff essential to the making of life.
Still, babies born prematurely have, for more than a century, been reared through several weeks of life despite being unable to live completely on their own. In 1975, Kim Bland became the first child to survive after being born just six months into pregnancy. He weighed little more than a couple of hundred paperclips – and had he been born ten years earlier, there would have been no medical efforts to keep him alive, because at that time, babies who weighed less than a kilogram (thirty-five ounces) were not considered to be viable outside of the womb. And on 24 October 2006, Amillia Sonja Taylor was born after less than twenty-two weeks in the womb, the youngest birth yet to survive. Born in Miami, Florida, where the law does not support the revival of a foetus less than twenty-four weeks, she owed her resuscitation to some ambiguity around her size (she appeared to be a bit older in the sonograms), and to the fact that her parents, Sonja and Eddie, were liberal with the truth surrounding her conception (the hospital was under the impression that Sonja was twenty-one weeks pregnant when she arrived for emergency delivery). At birth, though, Amillia was clearly tiny: weighing less than three hundred grams (ten ounces) and measuring only twenty-four centimetres (9.5 inches) long. Her body was a snug fit in the palms of an adult’s hands, and her feet were the size of one of the phalanges of an adult’s finger.
Both Amillia Taylor and Kim Bland were only able to survive because they were nurtured in an artificial environment already within our reach – the incubator. Like the stories of an artificial womb, the technology and benefits of the earliest incubators were a genuine marvel to the public when they initially came into use. But then again, they were brought to the world’s attention in a very bizarre manner.
In 1897, a German paediatrician named Dr Martin Arthur Couney moved his showcase of medical specimens from Coney Island in New York City to the Victorian Era Exhibition, at Earls Court, London. Rather than the usual monkeys, midgets, minstrels, and Moors, visitors to Couney’s were met with a true spectacle: a room neatly arranged full of large, glass-lidded wooden boxes, each containing a tiny baby, his ‘child-hatchery’.
The boxes were based on the original designs of the French obstetrician Etienne Stéphane Tarnier, who had realized that keeping premature babies warm was not enough; they had to be provided with isolation, excellent hygiene, appropriate feeding, and a warm, humid atmosphere in order to survive. Tarnier had studied a warming chamber used for rearing poultry at the Paris zoo. In 1880, he built his first enclosed wooden box for infants, outfitted with a compartment to hold a hot-water bottle that could warm the space without letting in germs. This crude incubator reduced the mortality of premature babies by nearly one third. Thirteen years later, Tarnier’s assistant, Pierre-Constant Budin, improved the basic contraption, adding a thermostat and natural-gas heating and more windows through which the babies could be observed – an innovation that his student, Martin Couney, must have applauded. Observed the babies certainly were – in Earls Court alone, the display drew crowds nearly four thousand strong.
The babies with whom Couney filled his incubators had been supplied by a Berlin hospital. As they were born prematurely, they were fully expected to die prematurely, too, which released the ‘incubator-doctor’ from liability for their deaths. Yet it was claimed that every one of the babies from his exhibitions had survived. With the money he made from his various circuses, Couney purchased more glass boxes for his hospital. His attempts to manufacture an artificial, independent environment for growing babies had proved a success.
A more technologicall
y sophisticated means of sustaining the premature was developed in the late 1950s. This comprised a mass of machinery – plates and gaskets clamped together, with connectors for blood and gas; stainless steel plates and bolts; fixed volume gas exchangers; pressure transducers; and water baths. This incubator was used in experiments conducted on lamb,
goat, and rabbit foetuses that were extracted very early from the mothers’ wombs. The incubator was meant to replicate the idealized environment within a mother’s body, and the age of foetuses for which this became possible was pushed further and further towards the beginning of life. The ultimate aim, of course, was to translate this technology into saving human babies’ lives.
A baby who is born full term, after spending thirty-seven to forty weeks in a woman’s body, should have lungs that are sufficiently developed to support breathing air by him- or herself. The lungs of babies born at around six months, however, are prone to collapsing between breaths. This problem can be overcome by providing the baby with a ventilator, which mechanically keeps the lungs slightly inflated between breaths, and by treating the lungs with a chemical called a pulmonary surfactant (which reduces the surface tension in the lungs) that would have been produced naturally, had the lungs been able to develop fully in the womb.
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