It’s been suggested that, given the seriousness of climate change, we ought to adopt something like China’s one child policy. There was a group of doctors in Britain who recently advocated a two-child maximum. But at the end of the day those are crude prescriptions—-what we really care about is some kind of fixed allocation of greenhouse gas emissions per family. If that’s the case, given certain fixed allocations of greenhouse gas emissions, human engineering could give families the choice between two medium sized children, or three small sized children. From our perspective that would be more liberty enhancing than a policy that says “you can only have one or two children.” A family might want a really good basketball player, and so they could use human engineering to have one really large child.