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 February 12.

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.

We are not there yet -- but this vision clearly does not belong to...