Recent research has unveiled critical discoveries about the mastodon, one of the largest land animals during the Ice Age, revealing its complex family structure and migrations influenced by climate change. The study highlights how mastodons roamed vast regions from Beringia, encompassing present-day Alaska and the Yukon, to Nova Scotia in the east and Central Mexico in the south.
Once classified into several distinct species, mastodons have ultimately been reclassified as Mammut americanum. However, new findings indicate that researchers may need to revise this classification to include at least two distinct species: the American mastodon and the Pacific mastodon (M. pacificus). This changing perception highlights the flexibility and ecological diversity of mastodons adapting to changing environmental conditions.
Migrations Shaped by Climate Change
This study shows that mastodons experienced several waves of migration due to several repeated cycles of climate warming. Though these cycles accelerated glacial melting, giving way to unoccupied territories for further northward expansion, they were not necessarily a boon to all peoples. Fossil evidence indicates that eastern species of mastodon had incredible diversity. They made it in clearly defined waves at least three times across North America.
As a co-corresponding researcher on the study, Hendrik Poinar pointed out how special Alberta is as a “hot spot” for mastodons. He noted, “The data shifts our view of the region today known as Alberta and the north more generally, from a marginal roaming ground to a repeatedly occupied migratory corridor and significant landscape for mastodons with possible interbreeding.”
Sure enough, Alberta’s role as a migratory corridor means that different mastodon species would have gathered there, allowing them the chance to interbreed. This astounding interaction to be uncovered leads us to fascinating questions about how these three very different species coexisted in their overlapping home ranges.
Genetic Diversity and New Discoveries
The research team identified two new genetic groups, or clades, of mastodons from specimens collected along the East Coast and in Northern Ontario. These unique clusters illustrate a layered history of diverse groups calling the same place home, but not necessarily at the same time. Scientists revealed an enigmatic genetic branch of Mexican mastodons. This lineage could be a more ancient outgroup of the western species M. pacificus, or it could indicate a completely different, yet unclassified, species.
For this study, scientists were able to take advantage of those fossilized specimens of teeth, tusks, and bones, which can date back hundreds of thousands of years. Novel genomic methods made it possible for scientists to piece together genomes from extremely small, degraded ancient DNA fragments. Among these specimens, you’ll discover eye-opening finds like the Middle River Mastodon femur, which dates to approximately 91,000 years ago! There’s the Windsor Sinkhole Mastodon tusk, approximately 178,000 years old and the Little Narrows Mastodon tibia, possibly the oldest mastodon with sequenced genetic data at an incredible 358,000 years old.
Unanswered Questions and Future Research
These findings not only increase our understanding of mastodon diversity, but raise dozens of unanswered questions about their interactions with each other and their environment. Emil Karpinski, the lead researcher on the study, expressed his enthusiasm. This study is a number of firsts, said him. He emphasized, “In addition to our work on the Pacific mastodon, it poses many new questions. For example, what was the interface between these far flung species of mastodon doing in Alberta? Did they compete for the same resources, or did they interbreed as our lab has done on mammoths before?
Researchers are deeply engaged in long-term investigations to better understand these complex interactions. Their hope is to find out how climate changes affected mastodon movement and/or their survival tactics during critical times in the Earth’s history.