The final straw that killed off the mammoth was likely excessive inbreeding. Using new DNA sequencing techniques researchers compared two ancient DNA sequences from different Mammoth populations, one from a congested mainland mammoth population from 45,000 years ago and one from a more recent population on Wrangel island that was dwindling rapidly 4300 years ago.
The researchers found that the mammoth DNA from the island showed greater signs of genetic disease — a buildup of excessive mutations and deletions — due to a small population size (inbreeding). For the Wrangel island mammoths, these deletions lead to a loss of smell and poor mating signals among other problems.
“We observe an excess of detrimental mutations, consistent with genomic meltdown in woolly mammoths on Wrangel Island just prior to extinction. We observe an excess of deletions, an increase in the proportion of deletions affecting gene sequences, and an excess of premature stop codons in response to evolution under low effective population sizes. Large numbers of olfactory receptors appear to have loss of function mutations in the island mammoth. These results offer genetic support within a single species for nearly-neutral theories of genome evolution. We also observe two independent loss of function mutations at the FOXQ1 locus, likely conferring a satin coat in this unusual woolly mammoth.”
Researchers noticed that big chunks of the genome were missing which affected the animal’s functionality and survival.
Large Populations vs Small Populations
In large animal populations beneficial mutations tend to spread across the population’s genome over time. At the same time harmful mutations are weeded out through predation, disease and environmental factors, making larger populations more resilient.
Smaller groups suffer the most because there is a higher chance that both parents carry the harmful genes, and with no source of diversity to rescue the population’s “corrupt genome”, the population is likely to implode.
The same problems occur in modern species where population numbers are low, making animal conservation efforts difficult as the genome degrades with further inbreeding.
This inbreeding problem may cause some skeptics to doubt the Bible story which offers a simplified “Adam and Eve” inbreeding narrative to explain the origin of all humankind.
For many skeptics the bigger problem with the Bible comes from the difficulty in believing Noah’s animals could carry enough genetic diversity to prevent extinction.
For the mammoths on Wrangel island at least, 300 was not a sufficient population to sustain the species.
Share your thoughts in the comments below!