Death, sex and psychopaths... solutions to the same problem

There are few big questions as big as "Why death?" and "Why getting old?" and "Why sex?. And it's surprising that the answer is probably parasites.

After a lifetime of fighting disease and random damage, it becomes more efficient to give up and just start anew. Death comes just as a natural consequence of a body that has (or should have) achieved replication already and is out of warranty, so to speak.

Sex is similar. Once a parasite finds a way in, it makes a whole lot of other parasites that know that way, too. If an entire population is the same, clones of the same splitting creature, they are all just as vulnerable. Sexual reproduction mixes things up and leads to more variety, jump starts evolution and maximizes the chances that a portion of a population is immune to any one attack.

And I've been thinking today, as a tangent, that another big question might have the same answer: "Why are there sociopaths?". If societal development and cooperation is the solution for gaining supremacy over individualistic populations, why aren't we all social and empathetic and nice? And I am thinking: empathetic people want to help others, especially sick and hurting people. Instead, they get sick themselves and help spread the disease. It helps to have a small, but significant minority, of assholes who only care about themselves. In case of a major outbreak, they stay clear and survive.