Never? I'll admit that my threshold for taking this stuff to heart is very high, but I think to rule out the possibility no matter the potential evidence isn't intellectually honest. Measuring something like "intelligence" is extremely difficult if not impossible. The same goes for defining it. Each depends on our societal values and is subject to endless confounding. But one cannot deny that there is a definable set of skills which makes some individuals more likely to succeed (in terms of wealth, safety, longevity, etc.).