Could Mammoth Bones Reveal When Humans First Arrived in North America?

The horsemeat had a slightly cheesy flavor when Dan Fisher, a paleontologist at the University of Michigan, put it in his mouth. Every two weeks for the preceding six months, Fisher had pulled the carcass up from the bottom of a pond and cut off a hunk of flesh. His aim was to see how long it would keep in the cool waters. The tangy taste was the first sign of decay.

Half a year earlier, in February of 1993, fellow University of Michigan paleontologists Catherine Badgley and her husband Jerry Smith had found the draft horse dead on their farm. She, Smith, and Fisher skinned and butchered the animal, then sank parts of the horse in a shallow pond on the property. It kept for longer than anyone had expected. Surprised by the length of time the meat lasted, even Badgley, a vegetarian, tasted it.

The finding helped support a theory that Fisher had wanted to test: Humans may have used small ponds that dotted the Great Lakes region during the end of the Pleistocene epoch, some 10,000 years ago, as refrigerators. The water bodies formed across the landscape as glaciers receded, and Fisher reasoned that they offered storage for dead mastodons and woolly mammoths.

What Fisher saw happen to the meat is “very strong circumstantial evidence” for the idea that humans used ponds to cache their food, says Badgley. And that’s just one of the unconventional experiments Fisher has employed over his more than 40-year career.

The study of humanity is a diverse domain. To answer questions such as when people first came to the Americas and how they may have contributed to the demise of woolly mammoths and mastodons, anthropologists ally with experts in fields such as genetics and geology.

“Interdisciplinary teams are the best because you’re bringing in so many different perspectives,” says Michael Waters, an archaeologist at Texas A&M University who has collaborated with Fisher. Such partnerships, he adds, are the future.

Fisher has been blending disciplinary approaches throughout his career to add to knowledge about humankind and human history. He has a library of data, shelves upon shelves of ancient animal bones, molds and casts, and decades of experience studying the marks made on remains. He’s well-respected both by other paleontologists and by experts in other fields, such as anthropology, and is largely considered the leading expert on mammoths and mastodons.

Fisher’s known for pushing the envelope with his methods, but lately, his work has gone further still. He contributed to one of the most controversial papers to date on evidence indicating the presence of humans in the Americas, and he’s offered support for one of the main hypotheses on what caused the extinction of mammoths and mastodons, contributing to debates rippling through the field of anthropology.

Dan Fisher was just 15 years old when he joined his first international archaeological dig. His father, Loren Fisher, a professor of Semitic languages at Claremont Graduate University in California, traveled to Syria in the early 1960s with Dan to investigate clay tablets found in the ancient city of Ugarit. (They traveled by passenger ship to Europe, took a train to Belgium, purchased a Volkswagen van, and drove to their destination.) Shortly after they arrived, however, the scholar had to leave, but Dan Fisher stayed on. For the next four months, living mostly with Arab workmen at the site, Dan participated in the dig.

Inspired by early experiences investigating the natural world and human history, Fisher received his undergraduate degree and Ph.D. in geological sciences at Harvard University, where he studied horseshoe crabs. He went on to work at the University of Michigan’s Department of Geological Sciences and Museum of Paleontology. He began his career examining primitive echinoderms, predecessors to sea urchins, diving into work on their behavior and ecology. But when Fisher’s attention turned to mammoth and mastodon bones, he decided the other stuff could wait. He wanted to understand how these massive animals died and how their remains had been preserved over millennia.

Thus began a string of novel studies to help answer questions that pull at paleontologists’ and archaeologists’ minds alike. Paleontologists often conduct experiments to see how an environment may have affected fossils—floating bones down a river, for example. Fisher employed the tools he had.

In addition to sinking animal bodies in ponds, Fisher tested tools and methods he thought early people of the Americas may have used. When the Toledo Zoo in Ohio needed to exhume an elephant carcass in 1994 and called Fisher, he took the body back to Michigan. There, he butchered the animal using a stone knife that he fashioned himself, as well as ropes and tree branches to move the weighty body parts. Humans in the region could have used similar tools thousands of years ago. He found that one man (in this case, himself) needed three days to butcher an elephant. And he now had evidence of the markings such tools make on the bones.

But Fisher still had plenty of questions. If humans sank meat in water to protect it from scavengers, what did they do when ice covered the pond’s surface? How could early inhabitants melt it? Fisher used his children’s kiddie pool to find an answer. He put rocks on ice that formed in the water-filled plastic pool sitting in his backyard, observing the time it took for them to melt through. At more than one site, Fisher has found large rocks among the bones, which he believes could have been used to thaw the ice so people could reach meat caches below.

These patterns exist on many skeletons, says Fisher, and could help substantiate claims made in two major debates roiling among archaeologists, paleontologists, and other scholars who study the history of the American continents. First, when did humans come to these lands? And did they precipitate the demise of mammoths and mastodons?

Up until the 1970s, the established wisdom held that the peopling of the Americas began roughly 13,000 years ago, but mounting evidence has pushed that date further back. Many conventional estimates suggest people made their way onto the North American continent about 16,000 years ago. In Michigan alone, Fisher and other researchers have uncovered bones from more than 30 mammoths and 300 mastodons. The bones and tusks, some of which show evidence of human processing, suggest that humans existed in the region now known as the Midwest as far back as 15,000 years ago. But some scientists—including Fisher—suspect the timeline goes back even further.

In 2017, anthropologists at the University of Montreal presented evidence for humans living in the Yukon 24,000 years ago. And in perhaps the most controversial claim yet, published that same year in Nature, Fisher and a cast of scientists from various disciplines concluded that humans may have butchered a mastodon 130,000 years ago at what they call the Cerutti site near what is now San Diego, California. Many anthropologists questioned the findings, arguing in scientific journals about the validity of the paper’s conclusions.

“Things are more open and in a process of discovery than they’ve ever been, but we still are constrained by standards of evidence, and that site just doesn’t meet it,” says Todd Braje, the Irvine Chair of Anthropology and an associate curator at the California Academy of Sciences, who, with nine other scholars, wrote a response in the journal PaleoAmerica. Nature can cause the fractures seen on the bones, and the timeline itself doesn’t fit with what we know about human navigation, he says. Humans, or their ancestors, weren’t sophisticated mariners until roughly 50,000 years ago, 80,000 years after the Cerutti team claims people existed at the site.