Red Grouse

Males—now this might shock you—generally spend a lot of time and effort trying to convince females they're worth sleeping with. Whether it means building an ornate bower, shaking their tail feathers, or buying the biggest diamond ring, men put a lot of work into getting laid. And why do they go to such ridiculous and even dangerous lengths? Well, because we females demand it. Sexual selection is a process first coined by Darwin explaining how mate choice could drive evolutionary changes. Females pick guys that they think have the best package—of DNA, that is. The gals pick guys whose genes…