Researchers discovered that an extinct species of dwarf elephant from Sicily halved in height and shrunk by about 85 percent in body mass in just 350,000 years after developing from one of the largest terrestrial mammals that ever existed.
Palaeoloxodon mnaidriensis became extinct some 19,000 years ago after evolving from the much larger straight-tusked elephant Palaeoloxodon antiquus, which stood over 4 metres tall and weighed 10,000 kilograms.
An international team of researchers used DNA evidence from the remains of a dwarf elephant discovered in Sicily, Italy’s Puntali cave to assess the species’ dwarfing rate.
Between 50,000 and 175,000 years old, the specimen is believed to be. The researchers analyzed a sample of petrous bone – the region of the skull that contains the inner ear – which is known to store DNA more effectively than other areas of the skeleton.
They discovered that during a maximum span of around 352,000 years, the dwarf elephant lost up to 200 kilograms and 4 centimetres in weight and height per generation.
To put this into context, the researchers note that P. mnaidriensis’s size reduction is akin to modern humans shrinking to the size of a rhesus monkey. “The magnitude of dwarfing caused by this rapid evolutionary process is truly remarkable, resulting in a nearly 85 percent loss of body mass in one of the largest terrestrial mammals ever,” says study member Axel Barlow of Nottingham Trent University in the United Kingdom. “As giants’ descendants, extinct dwarf elephants are among the most fascinating examples of island evolution,” he argues.
Between 40,000 and 800,000 years ago, P. antiquus lived on the European continent and is believed to have colonized Sicily between 70,000 and 200,000 years ago.
According to the experts, the process of dwarfing began when the Sicilian elephant separated from its mainland counterpart. Living in an insular and secluded habitat hastened the evolution of island organisms, and a new species, P. mnaidriensis, developed shortly thereafter.
“By combining ancient DNA with palaeontological evidence, we can more precisely date observable evolutionary changes,” Barlow explains.
According to previous study, mammals on islands evolve almost three times faster than their continental counterparts. This quick evolution may be explained by small initial populations and distinct selection pressures than those seen on the mainland.