Tuskless elephant females may be about to become the norm for the species, if it survives the environmental pressure of poaching that’s pushing it that way.

In African elephants, the tusks serve an important purpose. Actually, many–they’re a natural multitool. Elephants use them to dig for roots, to shift logs to find tender grass underneath, to scrape bark off of trees. They also protect the mouth and the tender underside of the trunk from attack by predators or other elephants.

Despite all this, historically a fifth of elephant females have lacked any tusks at all. It’s not a matter of loss, but of genetics.

Poaching for ivory has been a problem in every elephant population remaining, but nowhere has it been so heavy a pressure as it has been in Mozambique. From 1977 to 1992, a war in that country was financed almost purely by elephant ivory. Nearly 90 percent of all elephants in the region now known as Gorongosa National Park were killed.

The survivors? Mostly those tuskless elephant females. The next generation saw a strange consequence. Not only were half of all females born after the war were tuskless, up from approximately 20 percent, but fewer males were being born. Many fewer males. And in the next generation, the imbalance grew even further.

Researchers in Mozambique studied the park’s population of nearly 800 elephants through the 2000s, and have come to a few conclusions.

First, they confirmed that yes, the tuskless elephant trait is genetic. And it’s X-linked, meaning it’s found specifically on the X chromosome, half of the pair of chromosomes that determines sex. It’s dominant, so a female embryo only needs inherit the tuskless gene from one parent. And it is incompatible with a Y chromosome, meaning any male embryo with the tuskless X chromosome will miscarry.

The long-term concerns of this evolution – and it is evolution – in Mozambique’s elephants in direct response to human action could mean that the population is now on an inevitable path to breeding itself into extinction.

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