If you thought that a long extinct and fabulous beast that roamed the Earth thousands of years ago doesn’t have much relevance to what’s happening now, then be prepared to think again.
A team of researchers has discovered that the American mastodon, which died out 11,000 years ago, holds important clues about our understanding of climate change.
Reporting the findings in Nature Communications, the team describes that not only did the mastodons move thousands of miles up and down North America with the ebb and flow of ice ages, but they also became less genetically diverse, leaving them vulnerable to extinction.
American mastodons, or Mammut americanus to give them their proper species name, were around 10 feet tall, shaggy and stocky elephantine creatures. Once one of the largest land mammals on the planet, The Washington Post describes them as towering over other animals. They lived around 3.5 million years ago, making their homes in forests and swampy areas that held bountiful foods. According to Wired, they went extinct 11,000 years ago, presumably through a combination of pressure from climate change and being hunted by humans.
Although fossil remains of the American mastodon exist, the recent study reveals how the various populations developed. Using mitochondrial DNA (mtDNA), the scientists examined the family trees of around 33 individual mastodons to tease out the different lineages. They found several distinct populations, with evidence suggesting that migrations took place as the climate warmed and food became abundant further north. Over around 800,000 years ago, these large creatures moved up and down the continent in search of new ranges, being forced back as the ice sheets froze again.
MtDNA are the intracellular organelles that convert food energy into cell blocks, called ATP (adenosine triphosphate), which cells use to power themselves. Scitable describes how they not only contain the proteins required for oxidative phosphorylation that builds ATP but also their own distinct genome.
Unlike nuclear DNA, mtDNA is circular rather than helical and is inherited only from the mother. It also contains fewer base pairs (bp) of genomic materials. For example, human mtDNA contains only 16,569 bp whereas nuclear genome comprises 3.3 billion bp. The smaller mitochondrial genome rapid mutation rate is exploited when looking at phylogeny, the relatedness in populations.
Using mtDNA to trace the American mastodon family tree, the researchers found that not only were the northern groups distinct, representing the results of numerous migrations as the ice sheets grew and receded, but they were also less diverse. In terms of hybrid vigor, the northern American mastodons were much weaker than their southern counterparts and succumbed more easily to disease and food scarcity.
Prehistoric Climate Change Relevance to Modern Day
Biodiversity is under threat. Citing reports from the World Wildlife Fund and the Royal Botanic Gardens at Kew, CNN notes that two thirds of our wildlife vanished over the past 50 years and around 40% of plant species are at risk of extinction. Human pressure from hunting, development and agriculture is making life almost impossible for many species.
Anthropogenic climate change is making it worse.
Ice-bound areas of the globe are warming and melting, opening up polar regions to exploration and resource extraction. We already know that climate change can dramatically affect habitats. Core samples drilled from beneath the Antarctic show that past global warming episodes created a lush temperate rainforest over the south pole.
Furthermore, evidence from National Parks records shows that, with habitat change, species are moving north with their food sources. Brown bears are heading into the Arctic, and moose and beavers are making their way north in search of food.
The evidence found by the researchers shows that the American mastodon also moved as the climate changed in search of new food sources. However, northward migration came at the cost of reduced diversity and weakened resilience. Northern populations died out faster. Under climate change, our planet won’t be as abundant as it was in our recent past.