Oh! Not now, no. No it is all bad. Definitely maladaptive. But how did it make its way through the millennia without killing everyone it touched and disappearin

Oh! Not now, no. No it is all bad. Definitely maladaptive. But how did it make its way through the millennia without killing everyone it touched and disappearing? Because a lot of the carriers survived, and maybe because of it, or - more likely - because of some trait related to it, like fat metabolism or some form of environmental tolerance. Sickle cell is the poster boy for this kind of thing - we though it was just all bad, it turned out to be adaptive for a particular environmnt.