In the far future, it may be possible to prevent genetic diseases from being inherited by cutting them out of the gene pool once and for all, so-called germline engineering.

BBC: What the genome can do for you

Such diseases could not have a genetic cause, because genes that negatively impact reproduction would have disappeared from the gene pool by now.

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Now come two unconventional thinkers, a physicist in New Mexico and a biologist in Massachusetts, with an arresting question: If such diseases are indeed genetic, and if they impair reproductive success, why haven't the traits disappeared from the gene pool by now?

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