Yes, you are referring to Malcolm Gladwell's books. He had looked at what month elite hockey players in Canada were born. I forget the exact details but almost all of them were born within 3 months of the start date- b/c then you had older kids (who were likely bigger and had better motor skills) starting; then those kids were naturally selected for elite teams; they developed faster, etc.
Obviously, every child is different.
Although I did read Outliers, I'm talking more about my crazy hockey family (in contrast to my overly cautious kid) and how things are around here for elite sports rather than the book. And if we were in Canada, my kiddo would be in the right month to be an elite player, but you can only lead a horse to water...
ETA: Also, if you don't start ANY sport young around here, there are very few simply fun, recreational opportunities to play sports when you decide you want to try it out later. Especially team sports.
