Katz had read extensively in popular sociobiology, and his understanding of the depressive personality type and its seemingly perverse persistence in the human gene pool was that depression was a successful adaptation to ceaseless pain and hardship. Pessimism, feelings of worthlessness and lack of entitlement, inability to derive satisfaction from pleasure, a tormenting awareness of the world’s general crappiness: for Katz’s Jewish paternal forebears, who’d been driven from shtetl to shtetl by implacable anti-Semites, as for the old Angles and Saxons on his mother’s side, who’d labored to grow rye and barley in the poor soils and short summers of northern Europe, feeling bad all the time and expecting the worst had been natural ways of equilibrating themselves with the lousiness of their circumstances. Few things gratified depressives, after all, more than really bad news. This obviously wasn’t an optimal way to live, but it had its evolutionary advantages. Depressive in grim situations handed down their genes, however despairingly, while the self-improvers converted to Christianity or moved to sunnier locales.

-excerpted from Freedom, Jonathan Franzen, p. 192.