Poaching for ivory over decades has led to the evolution of tuskless elephants, researchers have found, showing that humans are “literally changing the anatomy” of wild animals.
A previously rare genetic mutation that caused the lack of tusks has become very common in some groups of African elephants after a period in which many were killed for their tusks, according to A study published in the journal Science.
The researchers analyzed why female elephants in Mozambique’s Gorongosa National Park were frequently born without tusks, and found that the animals were genetically modified through mass poaching for ivory.
Tusked elephants were most likely hunted during Mozambique’s civil war from 1977 to 1992, when 90% of the elephant population was slaughtered by armed forces on both sides to produce ivory that was sold to finance the conflict. Those without fangs were left alone, increasing the likelihood that they would reproduce and pass the fanged trait on to their descendants.
A couple of generations later, the effects of this are still visible in the group of some 700 elephants that live in the national park. Robert Pringle of the department of ecology and evolutionary biology at Princeton University, who led the study, said it showed the impact of human interference on nature.
He said: “What I think this study shows is that it is more than numbers. The impacts that people have, we are literally changing the anatomy of animals. “
Pringle said that Gorongosa National Park had always interested researchers, who suspected that historical poaching was the cause of this anomaly, although the exact mechanics of the problem were unknown.
He said: “One of the most striking characteristics is that many of the female elephants do not have tusks and this phenomenon intrigued us. We realized that even though a lot of people had written observing the fact that elephants sometimes didn’t have tusks, especially in places where there had been a lot of poaching, no one really understood why. And no one had really quantified or documented the phenomenon and been able to attribute it to a cause, rather than just speculate on the origins. “
The team suspected that the phenomenon had a genetic cause, and the fact that it was rarely seen in men suggested it was related to sex. After sequencing the genomes of the elephants with and without tusks, the researchers found a genetic difference between the two.
The analysis revealed a pair of candidate genes on the X chromosome, including one with known roles in the development of mammalian teeth. In humans, these genes are associated with an X-linked dominant syndrome that stops the lateral incisors from growing.
The presumed mutation in one or more genes ends up protecting female elephants from poaching, but is fatal to male elephants, who do not develop properly in utero.
About half of male elephant calves with a tuskless mother will have this genetic abnormality, meaning that elephant herds where there has been a lot of poaching can end up severely depleted of males. But this problem is reversible over time, Pringle said, as populations have been growing for two decades and have more than tripled since the 1990s, when they were pushed to the brink of elimination.
“Therefore, we expect this syndrome to decrease in frequency in our study population, as long as the conservation landscape continues to be as positive as it has been recently,” he said. “There is a huge storm of depressing news about biodiversity and humans in the environment and I think it is important to emphasize that there are some bright spots in that picture.”
George is Digismak’s reported cum editor with 13 years of experience in Journalism