Are there adult geniuses? I'm not sure either. Like I said, I can't remember the source, so now I can't validate anything, but I don't really ever hear of adult geniuses (if you prefer to call them that).
> Surely you believe there are people who are far more accomplished than 99.999% of the population that could be considered as such
This will obviously be a personal interpretation. One could consider the number 1 chess player an adult genius, but as I said, the article discussed that adults are no longer seen as such because the gap between the best and second best and everyone thereafter of similar training and experience is much smaller, so it no longer appears incredible, and people can very well imagine that someone else will soon come along and be even better than they are.
So it's not that there isn't ever one person arguably better at something than everyone else, but that they don't appear to be so due to a genius/prodigy gene, and they're no longer that much better that it seems impossible for anyone else to beat them ever.
Similarly, you'd expect that the best adults would likely have all been child prodigies no? And this appeared to be false based on my memory of that article.
