A mastodon bone sat in a museum drawer with a single species name on the label.
Then a research team began pulling DNA from teeth, tusks and bone so old and degraded the fragments were barely readable.
What came out did not match the label.
Remains from Nova Scotia, the eastern seaboard and an Oregon river valley did not all belong to the same animal.
So how did one skeleton from Oregon change a species count that had held for decades?
Why one skeleton from Oregon changed the picture
The analysis places Pacific mastodons on a deeply divergent mitochondrial branch, an old and well established lineage separate from the American mastodon of the east. Tooth shape alone had never settled whether the Pacific mastodon was a full species or a regional variant. Genetic distance offers a different kind of evidence: two maternal lines that stopped exchanging DNA a very long time ago.
The Oregon animal was recovered along the Tualatin River and had been identified as a Pacific mastodon by the proportions of its molars. Its DNA agreed with that identification, and the results push the known range of the branch deeper into the Pacific Northwest, as far north as Alberta and possibly as far south as Mexico. That is a considerably wider map than the species previously had.
Mastodons were first split into numerous species, then consolidated back into one, and more recently revised to potentially include at least two. The debate over that split has not closed entirely, and this work adds genetic weight to the two species reading rather than declaring the matter finished.
What the bones actually are, and where they came from
Mastodons were not mammoths. They were stockier animals that browsed shrubs and low tree branches in forests and wetlands rather than grazing open grassland, and their cusped teeth were built for crushing browse rather than grinding grass. A full grown American mastodon stood roughly 10 feet at the shoulder, and the species disappeared around 10,500 years ago.
The gypsum sinkholes of Nova Scotia are worth pausing on. Gypsum dissolves in groundwater and leaves cavities underground, animals fall in, and bone that ends up in one is sealed away under conditions very different from open soil. Without that accident of geology, far less of this material would still be readable.
One of those finds came out of a working quarry at Little Narrows, where a limb bone was spotted protruding from rubble after a routine blast. The Nova Scotia Museum moved in to excavate it and sift loose material for fragments. Bones recovered that way are cleaned, conserved and catalogued, then sit in collections for years, and that is exactly where this project started.
Three waves where one steady population was assumed
The eastern mastodons arrived in at least three distinct waves, a pattern the team ties to repeated cycles of warming that melted glaciers and opened new territory to the north. When the climate cooled and glaciers expanded again, mastodons were driven south or went locally extinct. What reads in the fossil record as one continuous presence was a sequence of genetically different groups occupying the same region at different times.
The work rests on mitochondrial genomes from seven animals: five from Nova Scotia and the eastern seaboard, a partial genome from northern Ontario and, for the first time, a Pacific mastodon from Tualatin, Oregon. Subsamples were sent to a dedicated ancient DNA centre and processed in dedicated clean rooms. One of the eastern specimens may date to approximately 500,000 years ago.
Lead author Emil Karpinski framed the next question as how these distant species interacted in Alberta, whether they competed for resources or interbred as the same lab has previously shown for mammoths. The senior author, Hendrik Poinar, describes Alberta as a repeatedly occupied migratory corridor rather than marginal roaming ground. The team does not yet know which answer is right.
The number that was wrong, and what replaces it
For a long stretch, the count stood at one species. Work on Pacific records is a reminder of how an assumption baked into textbooks can persist simply because nobody goes back to look. Here the assumption was species unity, and mastodon ancient dna work is precisely what dislodged it.
The published findings put the count at at least two species and three eastern migration waves, against the single species and undifferentiated population most of the past century assumed. Both figures came from bones already sitting in museum collections, already catalogued, waiting for sequencing technology to catch up.
A tibia from Little Narrows, Nova Scotia, estimated at roughly 358,000 years old and likely the oldest mastodon with genetic data available, anchors one end of that record. A drone survey of chinstrap nests made a similar point elsewhere, where newer equipment revised numbers that earlier ground counts had fixed in place.
What is still open, and what the bones cannot say
The study is clear about its own limits. Mitochondrial DNA travels through the maternal line only, which means it captures movement and divergence but misses much of the picture of interbreeding between lineages. Nuclear genome sequencing would add the paternal side, but ancient nuclear DNA from material this old is far harder to recover cleanly.
The extinction itself is untouched by this work. Three waves of expansion across hundreds of thousands of years of glacial cycling make the final disappearance look odder, not less mysterious. A lineage that had rebuilt itself from southern ground at least three times did not manage a fourth.
Yet what the bones do say is worth sitting with. Sinkholes in eastern Canada were preserving a record of how the continent worked, and it went unread until a team brought the right technology to it. More bones, already collected, are sitting in museum drawers now, and most of them have never been sequenced.
