Depends on how you think about and define a 1% advantage. You are using the biological definition, which is that having the gene gives you 1% more offspring on average. If however my genes make me 1% faster than everyone else that is a 100% advantage in winning the race, which can lead to large advantage in reproductive success. In this way a gene that generates a minor performance advantage can spread rather quickly.
Depends on how you think about and define a 1% advantage. You are using the biological definition, which is that having the gene gives you 1% more offspring on average. If however my genes make me 1% faster than everyone else that is a 100% advantage in winning the race, which can lead to large advantage in reproductive success. In this way a gene that generates a minor performance advantage can spread rather quickly.