The whole of evolutionary biology is based on survival of the fittest. The above notion is absurd and rather false, therefore. For example, infanticide was widely practised in both palaeo times and until recently. Infanticide was, in some ways, a form of abortion during times when contraception and abortion were not available. The disabled offspring are therefore highly unlikely to have been specially kept alive, especially given circumstances where food was scarce(which was most of the time).
I note how desperate they are in one section in the article, to claim that human chins evolved as a result of cooking. In actual fact, Neanderthals went in for cooking but did not ever develop chins, so it is a bogus theory. Cooking is one of the few aspects that separate humans from wild animals, and there is no real logical explanation for cooking, so no wonder scientists are trying to justify cooking by linking it to the advent of bigger brains and similiar nonsense.