Body-building might sound like a modern obsession — but for paleobiologist Paul Koch, it’s a window into the past. Based at the University of California, Santa Cruz, Koch is a visiting speaker with Utah State University’s Ecology Center.
“It was a play on words," Koch said. "I really mean, how does an animal build a body? What is a body made of?”
As a paleobiologist, Koch is focused on answering questions about extinct and extant animals.
“It's a way of thinking about animals or plants doing what animals or plants do in the world," he said, "as opposed to the way that some paleontologists use fossils to tell time.”
In his research, Koch ditches the pickaxe and shovel commonly associated with paleontology and instead uses something unexpected: chemistry. By analyzing tiny chemical signatures in bones, he can uncover details that fossils alone can’t show — like what an animal ate and how it lived.
Koch uses this chemical approach for his form of “body-building” — not lifting weights but explaining how animals literally build their bodies from the food they consume.
“How an herbivore take a blade of grass or a leaf which has lots of carbon in it and lots of oxygen and lots of hydrogen, but not so much nitrogen," he asked. "How does it take that food and turn it into a protein rich animal?”
Herbivores eat plants that are low in key nutrients. But microbes in their gut step in, helping make essential amino acids — the building blocks of protein. Those microbes leave behind chemical “fingerprints” that scientists like Koch can still detect thousands of years later.
That ability to analyze ancient chemical signatures has allowed Koch to focus on animals from the Pleistocene, a period spanning roughly 2.6 million to 11,700 years ago.
“I am also interested in the Pleistocene because it's sort of the last view of the world that was before the spread of agriculture,” Koch said.
Peering into the past, Koch has been able to work indirectly with mastodons, giant ground sloths, and helmeted musk ox. And while his work is rooted in ancient history, its implications are very modern.
“Fossils can tell us how these animals respond to events that we have not seen them respond to in the 500 years that humans have been studying animals closely,” Koch explained.
That includes periods of rapid warming events. Koch pointed to one in particular.
“It's called the Paleocene-Eocene Thermal Maximum. It’s a mouthful," Koch said, "It occurred 55 million years ago; it's known from deposits in Utah. The primates and the horses and the cloven-hooved animals show up about 20,000 years into the event, and the prior 20,000 years don't look great.”
For Koch, the big takeaway is this: The past isn’t just gone — it’s a guide. Hidden in bones and chemistry are clues about how life adapts, survives, and sometimes struggles in a changing world.
And those clues might help us better understand the changes happening today.