Wolves.
There's a story among biological essentialists that wolves prove that humanity belongs in hierarchies determined by physical and social strength. The "alpha wolf." The alpha wolf is determined by which wolf of the pack is the toughest and which one can assert dominance over the rest of the pack. Through this, they determine the social order of the rest of the pack, in addition to his universal choice of mate.
Except, this isn't true. Or rather, it's only half true - it only applies to wolves in contrived, isolated situations, where they are confined to a small space, like a zoo, or if urban development has destroyed their habitat. In the true wild, there is no "alpha wolf" - wolves are relatively egalitarian. They roam, they have few hierarchies, and typically show little aggression outside of defending themselves and hunting. They're basically big happy dogs when they're in their element.
The same applies to other mammals. Rats in cages will do heroin until they die, but if you give them a playground to have fun in, they lose interest in heroin and play with other rats, for instance.
So, if you meet a biological essentialist, remind them: alpha wolves are effectively a reaction to slavery and theft of public property through horizontal violence (fighting other wolves in your pack rather than fighting the true oppressor, whatever that may be). How 'manly' and 'tough' is that?
Stop torturing human beings with capitalism, and likely the same trend will be seen. Animals, including humans, make self-sabotaging decisions when under large amounts of stress.
http://io9.com/why-everything-you-know-about-wolf-packs-is-wrong-502754629