Building Humans - ‘Unnatural’ Selection


Picture this: prospective parents excitedly clicking through an online catalogue, ticking off the optimal mix of traits for their yet-to-be-conceived child.

Will they opt for blue eyes or brown? Perhaps green, for a touch of originality? What colour skin? And do they want a boy or a girl?

Are they aiming for an Olympian athlete, or will they stack the deck in favour of intellectual prowess? Why not both?

For some people, this would be a dream come true. For others, a nightmare of widening inequality touching on eugenics.

For biologists, it raises acute questions about evolution.

The principle of species change through natural selection was set down by Charles Darwin, who was born 200 years ago on 12 February.

But what “natural selection” means when it comes to Homo sapiens is hard to define. It has already been challenged by medicine, habitat, diet and other factors that affect lifespan, reproduction and survivability.

Genetic selection means our species’ evolutionary path would be even more radically changed.

Building humans

We are not there yet – but this vision clearly does not belong to the hazy future of science fiction.

Dozens of clinics in the United States, one of the least regulated markets for fertility services, already provide would-be parents in-depth profiles of potential sperm and egg donors.

Atlanta-based Xytex Corporation, for example, offers a long list of genetically-coded physical attributes, right down to the length of eyelashes, the presence of freckles and whether ear lobes are detached.

There is also a summary of the donor’s medical history and – for an additional fee – personality and educational profiles, a personal essay and photos, as an adult and a baby.

Much of this information has no relation to genetic pedigree and even when it does, the result – a human child – may not come out as advertised. But that has not dampened enthusiasm for the tests.

Most heterosexual couples shop in this market to compensate for either male or female infertility.

But there is nothing – in science or, in some countries, law – to prevent matching a donor egg with donor sperm to create an embryo that can be purchased and implanted in the buyer’s womb.

This option was offered by at least one “embryo bank” in Texas before it reluctantly withdrew the procedure under an ethical firestorm.

Desirable traits

Even parents who don’t need outside help to procreate may soon be clamouring for “preimplantation genetic diagnosis” of embryos to check not only for genetic defects and disease – the original intent – but also for sex and desirable traits as well, experts say.

“We need to look carefully at these selection technologies,” said Marcy Darnovsky of the Center for Genetics and Society in Oakland, California.

“It is not bad to have a desire for a girl or a boy,” she said by phone. “But in chatrooms and on bulletin board you can find moms, for example, that don’t just want a girl, but a particular kind of girl – ‘I want to go shopping with her, play Barbie Dolls, paint her toenails pink’.”

“What are they going to do if they don’t get that kind of kid – take her back?” she said.

An even more problematic scenario for some is the leap from genetic selection to genetic engineering.

That can happen in two ways. Gene therapy alters genes, for example, in a diseased organ in order to affect a cure.

But changes wrought by so-called germ-line therapy alter the blueprint itself, the human genome, and would thus be passed on to offspring.

“The pressure to change genes will probably come from parents wanting to guarantee their child is a boy or a girl, or to endow them with beauty, intelligence, musical talent or a sweet nature,” notes Peter Ward, a scientist at the University of Washington and author of “Future Evolution”.

For now, germ-line therapy is out of reach. But were science to master the genome, the temptation to tweak it to increase smarts, looks and longevity would be overwhelming, Ward argued last month in Science.

“One day, we will have it in our power to bring a new human species into this world,” he said.

Not all researchers agree.

“I think that all of these worries are misplaced – genetics is far too complex to allow for easy manipulation of human traits,” said Steven Pinker, an evolutionary biologist at Harvard University.

Nearly all diseases and traits are determined not by one or two genes but the interaction of many, he pointed out.

There is no such thing, in other words, as a master gene for intelligence or musicality.

“I doubt that parents would take a risk greater than five percent that something would go wrong,” he told AFP. “Testing is easy and safe. Manipulation is hard and risky.”