Smaller ears, thicker fur: A genome analysis shows how Woolly Mammoths have adapted to the climate over hundreds of thousands of years. A research team led by David Díez-del-Molino from the Center for Palaeogenetics in Stockholm reports that many characteristic features of the woolly mammoth (Mammuthus primigenius) were already genetically created around 700,000 years ago in the journal Current Biology. These included their woolly fur and considerable pads of fat. However, many characteristics became even more pronounced in the course of evolution.
“We wanted to know what makes a mammoth a woolly mammoth,” lead author Díez-del-Molino is quoted as saying in a statement from the journal. Based on many finds, it was already known that woolly Mammoths had thick fur, small ears and a short tail. “But there are also many other adaptations, such as fat metabolism and the perception of cold, that are not so obvious because they take place at the molecular level,” says Díez-del-Molino.
Overall, the team compared the DNA of 23 Siberian woolly mammoths with each other and with the genomes of 28 modern-day Asian and African ones elephants. Almost all of the mammoths studied lived during the past 100,000 years, with one exception: one genome comes from the woolly mammoth Chukochya, which lived around 700,000 years ago and was therefore a very early representative of this species.
This oldest genome served the team as a chronological starting point. The researchers found that, compared to elephants, almost 92 percent of those genetic changes that are involved in the building plan of proteins in later woolly mammoths already occurred in chukochya. Thus, these systems were probably already present when the species evolved from its ancestor, the steppe mammoth (Mammuthus trogontherii).
Different species adapted to the cold in similar ways
Conversely, the good 8 percent of these mutations that do not match came later. “The very first woolly mammoths were not fully developed,” says study leader Love Dalén, also from the Stockholm Center for Paleogenetics. “They may have had larger ears, and their wool was different – perhaps less insulating and fluffy than that of later woolly mammoths.”
The denser wool could have evolved either continuously as improved protection against the cold or as a deliberate response to several ice ages. The team points out that even during the ice ages, woolly mammoths inhabited areas as far north as 80 degrees latitude. This corresponds to the extreme north of the Siberian mainland.
So it’s not surprising that the group found many different genes in the woolly mammoths that are linked to living in extreme cold, such as lipid metabolism and fat storage. The fact that other Arctic inhabitants such as reindeer and polar bears also have similar systems indicates that different species have undergone a similar development to adapt to the living conditions.
In addition, the researchers found changes in several genes involved in the immune system in more recent finds – probably a reaction to newly emerged pathogens.
Woolly mammoths emerged more than 700,000 years ago and were extinct on the mainland by about 10,000 years ago. The last common ancestor of mammoths and elephants lived several million years ago.
