While there isn't concrete evidence to back it up yet, other experts contend the feeling arises when your brain instinctually thinks you are liable to fal out of a tree-as may have been the case for some of our primate ancestors.这句话for some 的for怎么翻译,解析的翻译是就像我们的一些灵长类祖先可能遇到的情况那样。这个for怎么理解?