During the end of the last ice age, wooly mammoths occupied territories that spread across most the cold weather climates of North America and Siberia.[1] However, between then and about 4,000 years ago populations of wooly mammoths began to decline.[1] Although there are many theories as to why wooly mammoths eventually went extinct, one of the most recent theories is that they died of thirst.[2] Due to an increase in temperatures that followed the Ice Age, sea levels rose and fresh water lakes decreased in size. This shrunk the territories and fresh water sources available to wooly mammoths. Wooly mammoths then put too much pressure on the vegetation surrounding the remaining watering holes, which further hurt their chances of survival.[2] However there was a population of wooly mammoths that were lived on an isolated island off the coast of Siberia, Wrangel Island. some time after the last of the inland wooly mammoths had all died off.[1]
Researchers discovered the remains of these wooly mammoths and ran series of genetics tests on these specimens. What they found was shocking to the scientific community. These wooly mammoths were very different than their mainland-dwelling ancestors. They had translucent coats and decreased sensory capacities. This was due to several deletions and premature stop codons in the mammoth’s genetic code. These deletions and stop codons left the Wrangel Island mammoths with a decreased capacity to smell. Scientist deduce from modern elephant behaviors that this would have led to decreased mate selectivity and a breakdown in the signaling of social hierarchy.
Biologist Rebekah Rodgers, who worked on the analysis of the Wrangel mammoth DNA believes that this genetic problem was due to more than inbreeding alone. She describes that the genetic marker is different. The problem is from a small population size that led to a decrease in selective breeding behavior by the mammoths. This allowed for previously negatively selected for phenotypes to propagate in the population.
Although this information does not definitively link these genetic alterations to the extinction of the mammoths it does suggest a decreased ability to survive for the population as a whole. Also this also provides critical warnings for modern day endangered species that have low genetic diversity.
Modern conservation efforts include artificial insemination and other nonnatural selective behaviors to try to increase the number of individuals of an endangered species. However, this study with wooly mammoths may show that these efforts may not be enough. By performing these techniques, conservationists are still limited by a small gene pool and breeding these individuals together may allow for a similar breakdown in the genetics that was observed in the Wrangle Island mammoths.
Sources:
[1] Switek, Brian . "Dying woolly mammoths were in 'genetic meltdown'" Nature News. March 2, 2017. Accessed March 13, 2017. http://www.nature.com/news/dying-woolly-mammoths-were-in-genetic-meltdown-1.21575.
[2] Morelle, Rebecca. "Last woolly mammoths 'died of thirst'" BBC News. August 02, 2016. Accessed March 13, 2017. http://www.bbc.com/news/science-environment-36945909.