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And why has no animal species evolved into something new in the last five thousand years?
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Over the past 50 years, more than 2,500 cases of adaptation of insects to various pesticides have been recorded.

In the 1950s, the problem of bed bugs in the U.S. was practically solved by their eradication, but in the late 1990s in New York City appeared its new form resistant to the action of insecticides. These bugs have a thick wax-shaped cuticle, accelerated metabolism and dominant mutations that block the action of insecticides.

In the cave reservoirs live Mexican Pecilia (Poecilia mexicana Steindachner, 1863). These are fish of the family of viviparous (widespread among aquarians around the world). Aboriginal inhabitants of Southern Mexico have preserved one of the ancient religious rites of spelling the rain. They prepare a special paste from the root of local poisonous plants, and then submerge it in a cave lake for prayers.

The poison kills the Pecylia, which passes to the surface, and the peasants collect and eat them, calling for rain. By the way, the taste of Pecilia Mexican is just awful. The Mexican government banned this religious activity, however, nature also found a solution — many populations of the Mexican Pecilia evolved, developing resistance to the action of poison. It turned out that the cave forms of this species are able to withstand twice the concentration of poison than the cave forms, and accordingly their chances of survival are twice as high.