Poachers killed so many elephants for their ivory during the 1977-1992 Mozambican civil war that elephants rapidly evolved to be naturally tuskless. Male and female elephants usually have tusks, but a few are born without. Because so many of the species were killed during the war the tuskless were much more likely to pass on their genes. Researchers have found that the proportion of tuskless females rose from 19% to 51% during the conflict.

They also found that the genetic mutation for tusklessness is lethal to males, and that those who have it die, sometimes before birth. The speed at which this happened shocked experts. Although the loss of tusks may stop females being poached, it denies them a tool used to strip bark off a tree for food, dig holes for water, and defend themselves. (Source: Shane Campbell-Staton, lead author of report in New Scientist)

My comment: And all for the sake of carved ornaments for well-off Chinese.