Brendan Zietsch of the Queensland Institute of Medical Research in Brisbane, Australia, and his colleagues have, however, come up with a twist on this idea.

• 一种提议是，未婚单身的叔叔阿姨们在关怀和照顾他们侄子侄女时所提供的帮助可能就足以说明为什么这种基因会得以延续。