Although it covers many die-offs old and new (especially the current demise of frogs and bats -- perversely, I wanted more catastrophe), Elizabeth Kolbert's ripping good read The Sixth Extinction: An Unnatural History [and Kindle] really is more interested in trickier questions like how people notice mass events that might be very quick in geologic time -- a couple hundred years -- given that each generation accepts its circumstances as baseline normal. Perception is crucial. She opens chapter five recounting a 1949 Harvard experiment that flashed regular playing cards with two alterations in the deck: a red spade and a black diamond. Students could not figure out what they were seeing. They couldn't determine the color ("purple," "brown," "rusty") or the suit of the changed cards. Inspired by that work, Thomas Kuhn studied how people deal with disruptive information. "Their first impulse is to force it into a familiar framework... Signs of mismatch are disregarded..."
"The pattern was, Kuhn argued, so basic that it shaped not only individual perceptions but entire fields of inquiry. Data that did not fit the commonly accepted assumptions of a discipline would either be discounted or explained away for as long as possible. The more contradictions accumulated, the more convoluted the rationalizations became. 'In science, as in the playing card experiment, novelty emerges only with difficulty,' Kuhn wrote."
To my mind nowhere is this syndrome more obvious or more prevalent than when historians or scientists are confronted with gay material. Scholars read Shakespeare's love sonnets to a young man and, exactly as Kuhn notes, they force it into a familiar framework ("friendship") and the more contradictions that accumulate (126 loving sonnets to him and the book dedicated to him vs. only 26 angry and unhappy sonnets to the dark lady), the more convoluted their rationalizations become. Historians find Lincoln in bed with a handsome young soldier while his wife is away or they read one of Eleanor Roosevelt's few surviving love letters to lesbian journalist Lorena Hickok, and suddenly they can't see what they're seeing. Even worse is scientists' global disregard of the 1,500 species of animals that engage in foreplay, mounting, penetration, pair-bonding, or co-parenting in same-sex couples. Rather than create outlandish excuses why some animals primarily have sex and pair with their own gender when the opposite gender is available, heteroists simply erase it. A profound and entertaining rescue is Bruce Bagemihl's phenomenal book, Biological Exuberance: Animal Homosexuality and Natural Diversity.