Approximately 90 percent of the elephants in the present-day Gorongosa National Park, called one of the “last wild places” by National Geographic, were poached for ivory to finance the civil war in Mozambique from 1977 to 1992. Before the conflict, less than one-fifth of females were born without tusks. Now the number is closer to 50 percent. A study published in Science Friday reveals “smoking-gun evidence for genetic changes,” according to University of Victoria (Canada) conservation scientist Chris Darimont. He believes the study helps us understand how humans can have a major influence on evolution.

The same phenomenon has also been observed in Uganda, Tanzania and Kenya after periods of intense poaching. Although female and male elephants can be born with tusks, tusklessness occurs at around 2 percent in a well-protected population. Study co-author and Princeton evolutionary biologist Robert Pringle thinks the changes are reversible as the population recovers, saying, “There’s such a blizzard of depressing news about biodiversity and humans in the environment, and I think it’s important to emphasize that there are some bright spots in that picture.”