It's like saying that you can make everyone on earth black within one generation. You just kill every nonblack person.

(Indeed, many of the attempts to use evolutionary psychology as prescriptive rather than descriptive come across to me like ‘people have dark skin, because they evolved in Africa where there was lots of sunshine, so you should spend plenty of time in the sunshine or you will get vitamin D deficiency’ when nowadays there are plenty of people who have pale skin and would get sunburns as a result of following that advice -- and can digest lactose so they can get the vitamin D they need from dairy products. And then when a fair-skinned person would point out that they've never got vitamin D deficiency and they've got quite a few sunburns, they are accused of lying, or of being inferior mutants rather than Real People. See e.g. some of the comments on Yvain's blog post about polyamory.)