sex-featured

Here's why you really do need a man

Sep. 13, 2012 at 2:57 PM ET

Hanna Rosin’s new book, “The End of Men”, has people talking. In her book, Rosin argues that women are adapting better to modern society than men are – moving into new jobs and new careers.

It’s an issue that touches a lot of nerves. Are men really necessary? Despite research out this week that suggests the answer is no, scientists say males are vital to the survival of the human race.

The study in question found that some snakes sometimes have “virgin births” without any male input.

Teams at the Copperhead Institute and Wofford College in South Carolina and San Diego State University reported in the journal Biology Letters that they found copperhead and water moccasin snakes sometimes reproduce without males in a process known as parthenogenesis – literally, virgin birth.

Other snakes including boa constrictors have also been documented as reproducing asexually, as have sharks and birds including chickens and turkeys. Insects and bacteria do it frequently.

There are fears that advances in cloning technology could make the same true for humans. Farm animals are now frequently cloned. Why not people?

“Between cloning and cellular reprogramming, you probably don’t need men, at least not biologically speaking,” says Dr. Robert Lanza of Advanced Cell Technology, a company that uses cloning technology to make animals in the lab and also to make human embryonic stem cells. “But it wouldn’t be as fun.”

And the human race might become weaker, too.

Sexual reproduction makes plants, animals and other organisms stronger. Every time a new baby is born, half the genes come from mom and half from dad. It might be a roll of the dice, but over a population, this will give some of the new children an advantage growing up as the new genetic combinations help them survive new challenges.

One really good example of this is sickle cell disease. People who inherit two versions of a certain gene, one from mom and one from dad, get sickle cell disease, a painful and often fatal condition caused by misshapen red blood cells clogging things up. It affects 1 in 5,000 U.S. children, mostly African-Americans. But if you get just one version, it turns out that gene helps make their red blood cells resist infection by the malaria parasite. That explains why the gene is so common among people who live on the African continent and their descendants.

“This has saved literally hundreds of millions of people in the past,” says Lanza.

Lots of theories center around how the constant changes caused by sexual reproduction can help people live through outbreaks of disease and resist new challenges. For instance, the people who survived the “black plague” that wiped out populations across Europe and Asia hundreds of years ago probably inherited genes that helped protect them against plague germs. Because those people survived better and lived to have more children, those genes became more common in the population. But those same genes might not help a bit against new germs, like Ebola or AIDS. So the human population does better when DNA gets a little mixed up with every new generation.

However, there’s an even more compelling reason that explains why humans need sex, even if snakes and turkeys don’t.

Lanza said it became clear when his labs started cloning animals. Males carry genes important for a process called imprinting, and this DNA is extremely important for the proper development of mammals in the womb – especially humans.

In 2003, his lab cloned a rare animal called a banteng – an experiment meant to help preserve the endangered species of Asian cattle. One of the two animals had to be put down because it was twice the size of a normal banteng.

It turns out you need male DNA for the proper development of the placenta -- the organ that nourishes a developing embryo and fetus. Many cloned animals have been born large, which can lead to fatal heart conditions and failures of other organs.

Even companies that have successfully cloned pet cats and dogs have noted the process doesn’t work well – you must try many times to get a living animal.

So to try to make people would just be too dangerous, Lanza says. “I always say right now with the way the technology is, it would be like sending your kid up in a rocket with a 50-50 chance it’ll blow up,” he said. “With the bantengs we put one down, but you couldn’t do that with your child.”

And it’s not just the unnatural conditions involved in cloning an animal in the lab that are to blame. Every once in a while, a human woman’s body can start an egg developing without sperm having fertilized it. But Lanza says it doesn’t produce a baby. “Parthenogenesis in humans never produces a viable embryo,” he said. "They don’t implant in the uterus correctly.”

Even if it did work scientifically, there are lots of other arguments against cutting men out of the process of making babies. The debate really took off after Dolly the sheep became the first cloned mammal in 1996, and it became clear that someone, somewhere, someday, would clone a human being.

In theory, it would be possible to clone Einstein or Brad Pitt from a hair follicle. Scientists might perfect a technique for making sperm cells using cloning technology. “Everyone could have a child that was some percent Brad Pitt,” Lanza said. “You could see where that would cause very serious social issues.”

 

Related links:

 Clones, crooks and crazies

Religions don't agree on cloning

Why not clone people?

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