Thecommon ancestor of placental mammalsAmong which are rodents, whales and humans, it was a tiny insectivore that diversified after the extinction of the dinosaurs 65 million years ago. It is the conclusion reached by American scientists after reconstructing the appearance of the ancestors of many of today’s living mammals.
The finding contradicts the theory that the group diversified after the extinction of the large reptiles. “Species such as rodents and primates did not share the Earth with non-avian dinosaurs, but arose from a common ancestor, – a small and fast animal that fed on insects, shortly after the disappearance of the dinosaurs” in the Cretaceous-Palaeogenic period, says Maureen O’Leary, co-author of the work. The discovery could help understand how mammals survived previous climatic changes and how future changes in environmental conditions might affect them.
According to O’Leary and his colleagues in the magazineScience, the visual reconstruction of the ancestor of the placental animals was possible thanks to the work during six years with a database “in the cloud”, of public access, calledMorphobank. Unlike previous reconstructions, this study combines two types of data: genomic sequences from multiple species and anatomical and behavioral aspects. In total, they used traits from 86 species of placental mammals, 40 of them fossils, and analyzed more than 12,000 images. “Discovering the tree of life is like putting the pieces of a crime scene together: it is a story that happened in the past and that you can repeat “, emphasizes O? Leary, adding that, as at a crime scene,” the new tools that analyze DNA provide information, but physical evidence such as a body or, its equivalent in the scientific field, fossils and their anatomy “.
