Elephants' extinct relatives once roamed far and wide across the planet. When they settled onto islands, some species' evolutionary course changed direction in a dramatic fashion.
In a paper published this month, scientists found clues to just how much island living can rapidly alter the evolution of these animals.
"Evolution on islands is a quite intriguing field of science, since it can be seen as an experiment of nature or evolution in action," said Sina Baleka, the paper's lead author and a paleogeneticist at McMaster University in Canada. She and her co-authors hope their findings can offer insights into how species living today are affected by geographic isolation on islands and in other habitats.
Evidence of smaller versions of extinct elephants has been found worldwide. But much remains to be learned about how many millenniums of evolution it may take for mammals as massive as elephants to shrink to a horse-like size. To make sense of this mystery, the scientists focused on fossils of a species of dwarf elephant from Sicily that are believed to be 50,000 to 175,000 years old.
Baleka and her colleagues used a variety of techniques to study the rate at which the species' ancestors became dwarves, including paleogenetics, geochronology and other dating methods.
At the higher end, that rate was less than 352,000 years. But it might have occurred within 1,300 years, which equates to "about 40 generations" of elephants, said Victoria Herridge, a co-author and evolutionary biologist at the Natural History Museum, London.
Ancient DNA from the elephant's fossilized petrous bone indicated it descended from a mainland counterpart, Palaeoloxodon antiquus, around 400,000 years ago. Those beasts weighed an estimated 10 tons each and were about 12 feet tall.
Descendants of the large elephants that colonized Sicily were almost 6.5 feet smaller, and almost 8 tons lighter. That change is comparable to a human becoming the size of a Rhesus monkey.
