The Future of Sex
Continued from previous page
There are these lizards called “lesbian lizards,” because they don’t have any males. They originally came about when a male from a related species and a female from another related species mated; their daughter was a mutant and she had the ability to reproduce without males. They do this strange mating ritual where one female mounts the other, and the female that mounts looks and acts very much like a related male would in a mating ritual, where she’s the aggressor and the other female is very passive. They rub their crocus together, which is their orifice that they use for reproduction. When you dissect them after that mating ritual, what you find is something very interesting: the female that was acting as the male, nothing much is going on with her eggs, but the female that was acting in the female role, her eggs were ready to become baby lizards.
A whole animal can be built from an egg — that’s why we see all-female species but you never find an all-male species; it’s not possible because the sperm is essentially packets of DNA, but an egg contains all the rest of what you need to create a new animal.
You can imagine that, yes, you have less genetic variety, but if the choice is to not reproduce at all or to reproduce with less genetic variety, than I guess for endangered species it’s probably a good strategy to have. There are all these strategies for reproduction in nature, and it’s something maybe we can learn from.
Is it possible, hypothetically, for human females to reproduce asexually?
Naturally? No, it’s absolutely impossible, because there is a genetic mechanism whereby certain genes in the male genome and the female genome are locked, and if they’re locked in the male genome then they’re not locked in the female, and vice versa. A lot of these genes that I’m talking about are important in the development of the placenta and the brain, so it’s absolutely necessary to have two parents — one male, one female — in order to get a viable child. If you try making a baby from two female eggs, and they did this with mice, the embryo would be OK but you’d never get a placenta because the DNA for the placenta actually comes from the father.
It’s almost like if you had two copies of a book and in one copy of the book page 9 and 11 were unreadable, so you had to turn to your second copy to read page 9 and 11. That means you need both books to decipher the entire narrative arc, and that’s what it’s like with humans — and all mammals, as far as we know. We think that’s the case because fathers in nature will come along and mate and then go off again so the investment in the baby is backed up if they are able to dictate the genes that nourish the baby. So they want the baby to grow bigger and healthier and stronger and take as much resources from the mother as possible, and the mother, on the other hand, doesn’t want one child to take too much of her resources because she needs it for herself and for other children that may have different fathers. So it’s a kind of battle for resources, that’s why they think it’s developed. That’s significant for humans, particularly, because we have very big brains and therefore the rationing of resources becomes very, very important.
There is these things called ovarian teratomas, which are essentially women’s eggs just going ahead and developing on their own — but they never get very far. In these ovarian teratomas, you get skin, you get hair, you get nails, you get all manner of body parts. But they never grow into real babies, because they will never be able to form a placenta because they have no father’s DNA.