Are men necessary?
Not if you're a shark, a lizard or any one of a number of invertebrate species. Females of many species can procreate perfectly well without a male, thank you very much.
A Komodo dragon named Flora gave birth to asexually produced hatchlings at a British zoo earlier this year, and scientists recently confirmed that a hammerhead shark in a Nebraska zoo had reproduced asexually. Bees, lizards, fish, snakes and sometimes turkey have been known to do it too.
With the virgin birth trend sweeping through the animal kingdom, is it just a matter of time before human females follow their shark sisters into a man-less future? It's been 2,007 years since a human virgin birth was reported - an extensively documented yet still scientifically unconfirmed event. But with scientists hard at work decoding our genetic mysteries, virgin birth isn't just the stuff of religious texts and science fiction any more.
"There is no reason that it couldn't be done in humans," said Vett Lloyd, a Mount Allison University professor of genetics, discussing recent experiments in which scientists successfully combined eggs from two female mice to create healthy offspring.
"Well," she corrected herself, "no technical reasons. There may be ethical and moral reasons."
Already, scientists seeking options for infertile couples have discovered a way to create sperm cells out of a man's bone marrow. Pioneering biologist Karim Nayernia isolated adult stem cells from bone marrow samples and stimulated them with vitamin A, causing some of the bone marrow cells to develop into immature sperm cells. (Immature sperm cells, in this context, mean cells that have the potential to develop into sperm cells, not cells that fear commitment or never call when they say they will.)
Prof. Nayernia is now seeking permission from British officials to try similar experiments with female bone marrow, raising the possibility that lesbian couples could one day have their own biological daughters.
Scientists are also investigating parthenogenesis - the term for what happens when an egg "activates" on its own and starts to divide - as a way to create stem cells for medical use without generating controversy. Most of the research in this field involves animals - livestock that reproduce parthenogenetically would save farmers a lot of time and trouble. But Advanced Cell Technology of Worcester, Mass., has developed various specialized cell types through parthenogenesis in monkeys, advances they hope to extend eventually to humans.
Parthenogenesis, the key to virgin birth for both the hammerhead shark and the Komodo dragon, sometimes happens naturally in humans and other mammals but the resulting embryos don't survive past a few days. (The term comes from the Greek words for virgin, parthenos, and creation, genesis.)
That hasn't stopped some futurists from seeing possibilities in parthenogenesis. Oxford University geneticist Bryan Sykes predicted in his 2003 book Adam's Curse that men will go extinct in about 5,000 generations, or 125,000 years, done in by their weakening Y chromosomes and replaced by asexually reproducing females.
"I see a slow decline in men's fertility until, eventually, men can no longer breed naturally," Prof. Sykes told The New York Times in 2004. "... I feel sure that humans will one day be able to reproduce by the fusion of two eggs. The children will always be girls, and they will have the same genetic mix as any other girl. This is very feasible, and I think will happen in my lifetime."
Male pundits around the globe have taken the recent spate of virgin births a bit personally.
"This is bone-chilling news to every man on the planet, every XY clinging to the fragile cliché of male necessity," wrote John MacDonald for The Arizona Republic.
"Where sharks have boldly gone, female humans will surely follow. Men could soon be as pointless as a bathing costume in the Antarctic," Eilis O'Hanlon predicted in The Independent of Ireland.
But most scientists say men shouldn't fear being made redundant.
"I think it's complete and utter rubbish," Queen's University evolutionary biologist Adam Chippindale said of Prof. Sykes's theory. The Y chromosome will likely change over time, he said, but it will survive.
Still, the continued existence of both sex and males is one of the surprises of evolution, he noted. Parthenogenesis is a more efficient way of procreating than sex, and in most species the male doesn't contribute much more than sperm to the whole child-rearing process.
"Males are essentially a big waste of time. We don't do anything useful, we just fertilize the eggs," Prof. Chippindale said.
And yet, even in species that sometimes reproduce parthenogenetically, sex usually makes a comeback. Some female lizards, for example, will reproduce asexually in harsh conditions or when there are no males to be found, and then they'll go back to sexual reproduction once their environment improves. There's something to be said for the genetic shuffling that happens with sex, even if scientists aren't yet sure what it is.
"It's a huge riddle in biology," Prof. Chippindale said.
