Why elephants are losing their tusks

Human activities have a substantial impact on nature, ever since humans began to cultivate its lands and hunt or domesticate wild animals. What is under the careful observation of scientists today is the important effect of human presence on the evolution of some species.

The pressure of humans on natural ecosystems has acquired dimensions that can be considered a real evolutionary factor. A study recently published in Science shows that it is precisely man’s fault that female Mozambican elephants are losing their tusks, and they’re not the only animals that change because of us.

Elephants are losing their tusks

Apparently, female elephants are evolving so they don’t retain their tusks. The cause of the phenomenon was intuitive, but the confirmation comes only from the research of Shane Campbell-Staton and colleagues, of Princeton University: elephants are losing their tusks to humans.

In particular, thanks to the study of historical videos that have been compared with the current situation, it was possible to quantify the phenomenon, and place it temporally in a period that would seem to leave no room for other hypotheses.

It turned out that between 1977 and 1992 the number of females born without tusks increased from 19 to 51%: these are the years of the Civil War in Mozambique, during which both sides in conflict were engaged in important poaching sessions intended for the collection of ivory, now illegal in much of the world.

Following the heavy hunting actions, the total elephant population in Gorongosa National Park decreased by 90% in those years: it is also for this reason that, according to the scientists, we can clearly speak of “developmental pressure“by the hand of man. Right after the end of the conflict, in fact, the number of female elephants born with tusks slowly started to increase.

The statistical analyzes conducted by the research team show that the emergence of a similar phenomenon is highly unlikely in the absence of an important trigger, such as selective pressure capable of modifying the evolution of elephants. So it is certain that the loss of fangs is linked to the human activity of hunting ivory, in this and other cases.

Man as an evolutionary pressure factor

Strangely, the research continues, the phenomenon studied in Mozambique involves only female elephants, and the reason lies in what is called a “genetic oddity”.

The genetic mutation underlying the loss of fangs would reside in one of the X chromosomes of elephants: Just like humans, female elephants have two X chromosomes, while males have only one.

The mutation of the only X chromosome is lethal for male elephants, while in females the presence of the second X chromosome allows the mutation to spread without affecting health.

This does not mean that ivory hunting has also had consequences on male elephant populations: today in Sri Lanka less than 5% of elephants are born with tusks. And thanks to Campbell-Staton’s research we know with certainty that the human activity of hunting ivory is at the basis of this genetic modification – in Sri Lanka as in Mozambique.

The genetic oddity that has so far “saved” the tusks of African male elephants, therefore, does not reassure the scientific community at all.

“Tusks are practically the elephant’s Swiss army knife,” says Campbell-Staton, which is why the loss of tusks can help elephants escape poachers, but seriously complicates the lives of animals, who get water and tusks with their tusks. food.

Many animals are indirectly dependent on elephant tusks: “this is what preserves the biodiversity“, concludes Campbell-Staton, and remembers that” our actions can have consequences like these “.

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