10,000 years ago, a small group of mammoths found themselves isolated on an island off the coast of Siberia. About 6,000 years later, they disappeared completely. Genetics may teach us why.
In 2017Researchers have suggested that the Wrangel Island mammoths were victims of genetic collapse, an accumulation of lethal mutations that would have led to their extinction. However, Swedish researchers A study has recently been published that casts doubt on this explanation.
The researchers analyzed the genetic evolution of these animals over 50,000 years, comparing the genomes of 14 mammoths native to the island with the genomes of seven mammoths that lived on the continent before the two groups separated. According to their analysis, Reports new worldA single herd of fewer than eight individuals originally settled on the island. This small number inevitably led to a significant reduction in genetic diversity. For example, the researchers observed the loss of many specific sections of DNA as well as an increase in homozygous genes, which exist in two identical copies.
However, the frequency of life-threatening mutations also decreased as the mammoths became isolated on the island. Since these types of mutations can have catastrophic effects on such a small population, they may have been wiped out after a few centuries. Scientists have concluded that genetic diseases were not responsible for the disappearance of these mammoths. In fact, the population is believed to have survived on the island for 200 generations, reaching a population of 200 to 300 mammoths.
However, although natural selection was effective in eliminating dangerous mutations, it did not eliminate several minor mutations that eventually accumulated in the mammoth genome. In addition, the reduced genetic diversity may have affected the effectiveness of their immune system.
Under normal circumstances, this loss of diversity would not have been a barrier to their survival. However, they likely found themselves vulnerable to rapid changes in their environment, such as a new disease or climate disruption. In other words, these mammoths may have been less equipped to respond to them, and that may have contributed to their extinction, the study authors suggest.
