In Conjuring An Evolution To Serve You, Eliezer Yudkowsky compares using selective breeding or genetic algorithms to summoning a demon — an alien god, really — with its own intentions.
Commenter J. Thomas shares some examples:
There are lots of examples of unexpected selective outcomes.A story — a long time agon a swedish researcher tried to increase wheat yields by picking the biggest wheat kernels to plant. In only 5 generations he had a strain of wheat that produced 6 giant wheat kernels per stalk.
When scale insects were damaging citrus fruits, farmers tried to poison them with cyanide. They’d put a giant tent over the whole tree and pump in the cyanide and kill the scale insects. Plants can be immune to cyanide but no animal that depends on respiration can be. And yet in only 5 years or so they got resistant scale insects. The resistant insects would — when anything startling happen — sit very still and hold their breath for half an hour or so.