Study shows early North Americans lived among giant beasts

by Danielle Torren

A new University of Florida study provides evidence that humans reached the Western Hemisphere during the last ice age and lived alongside giant extinct mammals.

The study published online in the Journal of Vertebrate Paleontology addresses the century-long debate among scientists about whether human and mammal remains found at Vero Beach, Fla., in the early 1900s date to the same time period. Using rare earth element analysis to measure the concentration of naturally occurring metals absorbed during fossilization, researchers show modern humans in North America co-existed with large extinct mammals about 13,000 years ago, including mammoths, mastodons and giant ground sloths.

“The Vero site is still the only site where there was an abundance of actual human bones, not just artifacts, associated with the animals,” said co-author Barbara Purdy, UF anthropology professor emeritus and archaeology curator emeritus at the Florida Museum of Natural History on the UF campus. “Scientists who disputed the age of the human remains in the early 20th century just did not want to believe that people were in the Western Hemisphere that early. And 100 years later, every single book written about the prehistory of North America includes this site and the controversy that still exists.”

Following discovery of the fossils in South Florida between 1913 and 1916, some prominent scientists convinced researchers the human skeletons were from more recent burials and not as old as the animals – a question that remained unanswered because radiocarbon dating required the presence of collagen in bones that did not exist.

“The uptake of rare earth elements is time-dependent, so an old fossil is going to have very different concentrations of rare earth elements than bones from a more recent human burial,” said lead author Bruce MacFadden, Florida Museum vertebrate paleontology curator. “We found the human remains have statistically the same concentrations of rare earth elements as the fossils.”

As bones begin to fossilize they absorb elements from the surrounding sediment, and analysis is effective in distinguishing different-aged fossils deposited in the same locality.

Researchers use mass spectrometry to analyze samples from 24 human bones and 48 animal fossils in the Florida Museum’s collections and determined the specimens were all from the late Pleistocene epoch about 13,000 years ago.

Bruce MacFadden, bmacfadd@flmnh.ufl.edu