Straight-tusked elephants (Palaeoloxdon antiquus) were among the largest mammals to ever live during the Pleistocene era. The elephants were so massive they may have reached almost 15 feet tall and weighed over 30,864 pounds. To put that into perspective, they could have easily rested their chin on the back of the modern-day African savannah elephant, Josh Davis writes for the Natural History Museum.
However, new fossil analysis suggests that the descendants of these colossal mammals shrunk down to 15 percent of its size in 40 generations when they migrated into Sicily, an island off the toe of Italy's boot. The divergence created two types of miniature elephants—one species was as tiny as a Shetland pony. The study, published last month in Current Biology, showcases how rapid evolutionary changes can occur when animals are isolated on an island.
"Evolution on islands is a quite intriguing field of science since it can be seen as an experiment of nature or evolution in action," study author Sina Baleka, a paleogeneticist at McMaster University, tells the New York Times' Jeanne Timmons.
The researchers used 11 fossils from dwarf elephant specimens found on the island to find how the tiny elephants shrunk over time. One of the elephants' skulls, found in the Puntali cave in Sicily, was dated between 50,000 and 175,000 years old.
Surprisingly, the specimen provided enough genetic material to reconstruct its mitochondrial DNA. Hot and humid areas, like the Mediterranean, typically cause DNA to degrade over time, reports Ed Cara for Gizmodo. The DNA was found within the skull's petrous bone, a very small, dense bone that holds the inner ear. Petrous bones are known for their ability to preserve prehistoric DNA better than other parts of a skeleton, reports New Scientist and Press Association.
After analyzing the mitochondrial genome, the team determined the island-dwelling elephant is the descendant of gargantuan straight-tusked elephants. Based on paleontological and geological evidence, they estimate the species was possibly isolated on Sicily between 50,000 and 175,000 years ago, according to the Natural History Museum. Straight-tusked elephants may have migrated to Sicily between 70,000 and 200,000 years ago, the team explains in a statement. During that time, sea levels were low, and land bridges may have made it possible for the elephants to populate the islands. If a land bridge didn't exist, the elephants may have swam over to Sicily, the New York Times reports.
The dwarf elephant lost about 440 pounds and four centimeters per generation on average before finally shrinking down to a height of 6 feet tall and weight of 1.7 tons, Gizmodo reports. Scientists suggest the dwarf elephants reached this size in a short amount of time due to scarcity of resources, per Gizmodo.
"The magnitude of dwarfing resulting from this rapid evolutionary process is truly striking, resulting in a loss of body mass of almost 85% in one of the largest ever terrestrial mammals. As the descendants of giants, the extinct dwarf elephants are among the most intriguing examples of evolution on islands," Axel Barlow, a paleogenomics expert at Nottingham Trent University in the United Kingdom, says in a statement.
The team hopes other scientists can use their DNA extraction technique to study fossils from similarly warm regions, such as Africa and southern Europe, where the climate may degrade the genetic material, reports the New York Times. Currently, the Sicilan miniature elephant fossils are on display at the Gemmellaro Geological Museum in Palermo, Italy.