Human behavior is "literally changing the anatomy of animals," according to the author of a new study that finds decades of ivory poaching in Mozambique has encouraged the evolution of elephants without tusks. What was once a rare genetic mutation causing tusklessness in female elephants at Mozambique's Gorongosa National Park has become more common in recent decades, following widespread poaching during a civil war that stretched from 1977 to 1992, the Guardian reports. Armed forces on both sides funded the conflict in part by hunting elephants for their ivory. Some 90% of the park's 2,500 elephants were killed, but those without tusks went untouched.
Princeton University evolutionary biologist Robert Pringle, co-author of the study published Thursday in Science, had heard that the rate of females born tuskless within the park had increased from 18.5% before the war to 33% after it, per Nature, but it was unclear why. In sequencing the genomes of tusked and tuskless elephants, he and his team discovered a genetic mutation on the X chromosome—reportedly in the genes AMELX and MEP1a, which are involved in the growth of incisor teeth in humans—that is believed to keep female elephants from developing tusks.
The downside is that the mutation appears to be fatal to male elephants, which do not develop properly as fetuses. About 50% of male calves born to tuskless mothers carry the mutation. With fewer males, there will be fewer elephants born overall, which isn't great for population recovery. With time, however, "we actually expect that this syndrome will decrease in frequency in our study population, provided that the conservation picture continues to stay as positive as it has been recently," Pringle tells the Guardian. The park's herd has more than tripled in number since the war, rising from 200 elephants in the 1990s to 700 today. (These elephants shrunk nearly 85% in size over generations.)
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