Toronto Subway Deer Mystery Revealed Using DNA Analysis

In 1976, as jackhammers and backhoes dug a subway tunnel through the glacial clays beneath Canada’s largest city, construction crews unearthed a surprise: the skull and partial antlers of a mysterious prehistoric deer.

The fossil, taken from an excavation pit near Islington train station west of Toronto, contained antler beams so thick and strangely horizontal that no scientist could associate them with a living species. Eventually, some paleontologists named it Torontoceros hypogaeus, meaning “Toronto horned deer from underground.” More commonly, it was called the Toronto Subway Deer.

But the specimen, estimated to be at least 11,000 years old, sparked decades of debate. Was this animal a strange relative of the caribou? Or evidence of a completely different deer that found itself in an evolutionary dead end?

After almost 50 years, the deer has revealed its secrets. Using ancient DNA extracted from the fossil, the researchers showed that, despite its size and large antlers with a caribou-like branching tip, the metropolitan deer was most closely related to mule deer and white-tailed deer, two smaller deer still common in North America.

The study’s authors, led by Aaron Shafer, a population geneticist at Trent University in Ontario, and Camille Kessler, a graduate student he worked with now at Ludwig Maximilian University in Munich, published their results online in September. The article is expected to be published soon in the journal Biology Letters.

“It’s very exciting,” said Roman Croitor, a paleontologist at the State University of Moldova who specializes in deer fossils. In his own research, he grouped Torontoceros and caribou together. If he had suggested, based on the shape of its antlers, that they were closer to mule deer or white-tailed deer, “people would have said I’m crazy,” he said.

But just as DNA evidence can invalidate the flimsy accounts of witnesses in a murder case, so does it. Does genetic analysis deliver the final verdict in paleontology, Dr. Croitor agreed.

According to DNA, the Torontoceros most likely split from a tangle of evolving deer lineages about two million years ago and took shape as a distinct species. He roamed the open landscapes around the Great Lakes alongside mammoths, mastodons and other Ice Age giants. But as the climate warmed and forests invaded the plains, its habitat disappeared and, with it, almost all traces of the species itself.

The metro’s only deer specimen, housed at the Royal Ontario Museum in Toronto, is now all that remains. An artist’s rendering included in Dr. Shafer’s article depicts the deer as a cross between Sven from Disney’s “Frozen” and the deer from HBO’s “Game of Thrones.”

While a single specimen is only a starting point for reconstructing its place in evolution, experts believe there could be related samples hiding in museum drawers – mislabeled, neglected or unidentified, and waiting for the tools of modern genetics to reveal their true identities..

“It’s possible that there are other skeletal remains from this distinct lineage,” said Charlotte Lindqvist, an evolutionary geneticist at the University at Buffalo who was not involved in the study.

A precedent for this type of fossil reclassification came recently from a human skull discovered in China. Initially described as a species in its own right, the fossil was re-identified through molecular analysis as Denisovan, a lineage of ancient humans that diverged from Neanderthals and persisted in Asia for hundreds of thousands of years before disappearing. A similar twist could yet happen with the Toronto subway deer’s long-lost relatives.

CS “Rufus” Churcher, the University of Toronto paleontologist who first characterized the fossil, finds the prospect appealing – and he is encouraged by the potential of genetic technologies to clarify lingering uncertainties around the deer’s origins and evolutionary connections.

“The fact that we only have one animal is frustrating beyond belief,” said Dr. Churcher, now 97 and retired. “We would like to have more pieces so we can attach it more securely.”

However, investigating the ancestry of the lost deer is about more than solving a paleontological puzzle. “It’s a tangible link to the distant past,” said Rob MacDonald, president of ASI, an archeology consulting firm in Ontario — and its story is a reminder of the risks species face as the climate changes again.

The Royal Ontario Museum is in the middle of a major renovation project. But when his mammal fossil gallery reopens in a year or two, Burton Lim, curator of mammal collections and co-author of the study, said he plans to highlight the metro deer.

Buoyed by the new DNA discoveries, Dr Lim hopes the exhibition will spark public interest, highlighting how a single local fossil, discovered by chance during subway excavations, preserved for decades in a museum and re-examined with modern technology, can reshape understanding of the region’s natural history and past extinction events.

“It tells us a story that’s not often told,” Dr. Kessler said.