Since everyone carries some adverse genes, there is no clear line between selecting against a child with above-average risks of contracting a disease and selecting for a child with unusually rosy health prospects. Thus, genetic selection will inevitably move towards genetic enhancement.
由于每个人都有这样那样的不良基因，因此，在 淘汰 患病风险高于平均水平的子女，和 挑选 健康前景特别乐观的子女之间，不存在一条清晰的界线。有鉴于此，基因筛选必将发展成基因优化。