The discovery of human remains in the same layer as fossil mammals, including mammoths and mastodons, at a site in Florida has generated debate about whether the species were contemporaneous. An analysis of rare earth elements suggests that they were.
Carbon dating of the fossils, found at Vero Beach, has not yielded conclusive answers, so Bruce MacFadden at the University of Florida in Gainesville and his team analysed levels of rare earth elements such as cerium to date the remains. The authors show that the levels of these elements are similar in both sets of remains, but are different from those in modern mammals. Assuming that the uptake of rare earth elements by fossils from surrounding groundwater is time-dependent, then the two sets of remains must have been laid down at the same time, probably around 12,000 years ago.