“just as tusks evolved because they provide a number of benefits, a striking new study shows that somepopulations of African elephants have rapidly evolved to become tusk–less. Published in the journal Science, the paper’s authors found that many elephants in a park in Mozambique, which were heavily hunted for their ivory during a civil war a few decades ago, have lost their tusks — presumably because tuskless elephants are more likely to survive and pass the trait on to their offspring.”
…
“In theory, it’s advantageousto be born without tusks in areas where poachers are active, Hendry said. But tusklessness also has its downsides. Elephants need their tusks to dig, lift objects, and defend themselves. The hulking incisors are not useless appendages.
The genes that seem to make female elephants tuskless also appear to prevent mothers from giving birth to male calves — that’s why all the tuskless elephants in the park are female, Pringle said. (Some mothers did give birth to males with tusks, who likely didn’t inherit the gene.) Over time, a shift in the sex of elephants could have consequences for population growth.
There are also potential costs to African grasslands, which are among the rarest and most biodiverse ecosystems on Earth, the study authors write. By turning over soil in search of food and minerals and gouging trees with their tusks, African savanna elephants prevent forests from growing too denseand help maintain grasslands. That’s why they’re considered “engineers” of the ecosystem. If they lose their tusks, a whole web of plants and animals may feel the impact.“This evolutionary change could have massive cascading ecological influences,” Hendry said.”
https://www.vox.com/down-to-earth/22735163/elephant-tusks-genetics-evolution-adaptation-hunting