https://www.vice.com/en_us/article/qjbdnp/rampant-poaching-forces-elephants-to-evolve-to-not-have-tusks-study-finds

Elephants in Mozambique are evolving away from having tusks due to pressure from rampant poaching over decades, according to a daunting new study. 

Published in the journal Science on Friday, the report from researchers across departments at Princeton University, the non-profit ElephantVoices, Gorongosa National Park in Mozambique, and the University of Idaho, analyzed survey data that suggests natural selection has favored tusklessness in female elephants—a rare genetic trait that has become more common—amid high rates of poaching and population decline.