Evolution happens through reproduction, which tends to happen earlier in life. So if some gene confers an advantage in early life but a disadvantage later on, i

Evolution happens through reproduction, which tends to happen earlier in life. So if some gene confers an advantage in early life but a disadvantage later on, it's likely the disadvantage won't stop it from spreading. If it's not widespread, it's either not an advantage that "matters" or maybe it possibly has some negative interaction with other traits that matter for reproduction.