Swimmer's Body Illusion

We confuse selection factors with results. Pro swimmers have great bodies because of who is selected to become a pro swimmer, not because swimming produces great bodies.

• Harvard graduates are successful not necessarily because of what Harvard teaches, but because of who gets admitted in the first place.
• Models look stunning because of who is selected to model, not because the cosmetics they advertise will make you look that way.
• People think yoga makes you flexible — but flexible people are drawn into yoga. The sport selects for the trait it appears to produce.