Scientists have reconstructed the genomes of the extinct giant short-faced bear (Arctodus simus) and the American black bear (Ursus americanus) using environmental DNA fragments from the remote Chiquihuite Cave in Mexico. Reconstruction of the giant, short-faced North American bear Arctodus simus. Image credit: Daniel Reed / CC BY-SA 3.0. Fossil records are incomplete, and many species of mammals, in particular those that lived at low population densities,...