Mutations turn individual cells into parasites all the time; We call it "Cancer". With how many roles and profiles that our cells can adopt, I'm incredibly unsu

Mutations turn individual cells into parasites all the time; We call it "Cancer". With how many roles and profiles that our cells can adopt, I'm incredibly unsurprised that there's modes and forms that are purely parasitic, I would imagine that in most large populations, there are a decent number of parasites. The simple answer is this - Everyone it a "parasite" sometimes. Everyone is sometimes sick, wounded, or simply unlucky and requiring help. It's a standard part of living. In brutal nature, the sick and injured simply die. In social species, though, the sick and injured are cared for, with other members of the group, tribe, society or species giving It's of little surprise, then, that the genes and regulation that control "Where to signal for help" can become corrupted or overactive". In large, complex species, you'll see the groups carrying out a balancing act. Packs of dogs can both nurse members back to health and exile unproductive members. But at the larger by count scale, it's harder to rack the individual, so I'm not surprised that the systems break down somewhat more.