It's a development that would have delighted Darwin.
African elephants are losing their tusks in an astonishing example of evolution by natural selection which protects them against ivory poachers.
Until the Nineties, around 2500 elephants lived in Gorongosa National Park in Mozambique, but 90 per cent were killed during the 15-year civil war which raged from 1977 to 1992 - with their ivory used to finance weapons.
Now scientists have noticed that nearly one third of the female elephants born since the war have lost their tusks.
Normally, fewer than four per cent of a population are born without tusks, but because tuskless animals were ignored by poachers, they gained a biological advantage and were able to mate, and pass on their genes. A team from the University of Kent is now carrying out genetic studies to learn more about the new traits.
Dominique D'Emille Correia Gonçalves, an ecologist and conservation biologist from the University of Kent who is studying the population, said: "The elephant population today is derived from most of the elephants who survived the war, where they were heavily poached for their tusks.
"The key explanation is that in Gorongosa National Park the tuskless elephants were the ones which eluded poaching and therefore passed this trait on to many of their daughters. We could be talking about the removal of certain genes from the population."
Even where the elephants are born with tusks they are often smaller than usual, again because poachers tended to pick out the animals with most ivory.
Poaching has also led to a decrease in tusk sizes in southern Kenya where survivors of a period of intense poaching had much smaller tusks, a pattern which was repeated in their offspring. And in Addo Elephant National Park in South Africa, 98 per cent of the females are now tuskless.
Researchers in Gorongosa have also noticed that the females have developed a "culture of aggression" and have a low tolerance to vehicles and people, which is likely to stem from a desire to protect their group against poachers, but also could be linked to the lack of tusks, which makes them vulnerable.
"This is a big change. Anecdotal records from people that have been in Gorongosa before the war suggest the family units used to be calm and almost indifferent to people presence," added Miss Gonçalves.
"Many of the matriarchs and lead females of the family units were alive during the slaughter and saw their families and friends being hunted.
"They are survivors and the trauma is still present, which would explain such intolerance to humans."
Ryan Long, a behavioural ecologist at the University of Idaho, told National Geographic: "The consequences of such dramatic changes in elephant populations are only just beginning to be explored."
Scientists are now monitoring the elephants by attaching GPS satellite collars to 10 females from different family units to find out if a lack of tusks affects their ability to feed and breed.
- The Daily Telegraph