↑In today's Mozambique, a large number of female elephants are born without ivory.
A new report published oct. 21 in Science magazine shows that African elephants have undergone an amazing evolution, with a large number of female elephants born without ivory, and this evolution is caused by the slaughter of humans who frantically plunder ivory.
The researchers found that at least 50 percent of the female elephants in Gorongosa National Park in Mozambique have no tusks. These female elephants seem to survive due to rapid evolution, but in fact they are only temporary, which affects not only the female elephants, but also the death of the male elephants and even the survival crisis of the entire elephant herd.
Why did the evolution of the female elephant lead to the death of the male elephant? Does this phenomenon occur in humans and other animals?
The loss of the tusks of the mother elephant is an existential crisis that hangs above the heads of the entire herd
During the Mozambican Civil War from 1977 to 1992, both sides killed 90% of the local elephants for their precious tusks. As a result of this slaughter, a large number of female elephants are now born without ivory, because these are the female offspring of those female elephants who survived without ivory during the war.
Mathematical models show that such changes are almost certainly the result of natural selection and are not accidental. During the Civil War, female elephants without ivory were more than five times more likely to survive. Dr. Shane Campbell-Stanton, an evolutionary biologist at Princeton University, and his team studied long-term data and found that at least 20 percent of female elephants had no tusks before the war, reflecting the effects of earlier poaching stress groups, compared with only 2 percent of well-protected elephants without tusks.
Scientists' intuition was confirmed by the results of genetic studies in families of ivory-free elephants. As Dr. Stanton's team predicted, a gene called AMELX carried by the maternal X chromosome is key. Ivory-free is a dominant genetic trait that is carried by females. Half of the female cubs without ivory gene mother elephants have no tusks and the other half have tusks; the male offspring of this mother elephant have half ivory, and the other half may die of genetic defects and incomplete development before they are born.
Dr Stanton points out that this genetic variant is killing the male elephant: some will die from birth defects, and the other part will also be a more concentrated target after birth because of the rarer tusks.
↑ Elephants without ivory may temporarily "steal life", but will endanger the survival of the entire herd.
Although evolving into elephants without ivory allows them to temporarily escape poachers, this has serious long-term consequences for elephants.
What's even more amazing is that the same class of genes can also cause humans to suffer from a rare condition that causes women's teeth to be small or deformed, and it also appears between the front teeth and the upper teeth of the canine teeth – that is, the position of the ivory. Moreover, this condition in humans can also lead to the death of their male offspring, because this genetic mutation can lead to the loss of some DNA, in addition to the genes for tooth growth, other key genes near it will also be missing.
The price of "evolution" is life
Elephants often use their tusks to break tree trunks in search of food, or to dig pits for water, and to defend themselves. "When you don't have this critical tool, how are you going to debug the behavior and compensate for the lack of this part?" Dr Stanton noted that scientists are now trying to figure out how elephants without ivory live. He also pointed out that with the increase in the number of elephants without ivory, this will not only affect the lives of this part of the elephant, but also affect the survival of the entire herd, because the number of newborn male elephants will be less and less.
Usually, African elephants, both male and female, have tusks. However, some elephants now have no tusks. As severe poaching continues, elephants with ivory will continue to be slaughtered, while elephants without ivory are more likely to survive and pass on their genes from generation to generation.
There are other cases of this in the biological world. Fanny Pelletier, a population biologist at the University of Sherbrooke in Canada, has found a similar phenomenon in her study of Canadian pan sheep: hunters like to hunt the males with the largest horns, causing the sheep to evolve smaller horns than before. But the effect of this change is much smaller than that of elephants that have completely lost their tusks.
"When you hear stories like this, it's easy to think, 'Oh, everything's all right. They have evolved, and they can cope. Professor Pertier says the fact is that species have to pay a price for this rapid evolution, "natural selection always has a price, and this price is life." ”
Professor Pelletier also stressed that even if poaching stops tomorrow, the genetic phenomenon of no ivory genes will continue to lead to the death of male elephants.
Red Star News reporter Lin Rong
Edited by Zhang Xun
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