Durables

It is a shame that civilization seems to rise and fall based immunity to random disease outbreaks. Plague has had more influence on civilization than anything except perhaps drought/famine. Which humans end up in charge of civilization depends almost entirely which ones are lucky enough to get a reliable supply of food AND have the right kind of immunity. All the other traits we find so useful, i.e. intelligence, beauty, strength, compassion, musical talent, analytical ability, etc. mean nothing unless you win the immunity lottery. In short, we are selected not for how good we are, but how durable our immune system happens to be.