The debate about when the key traits that define placental mammals appeared is on its way to resolution. A recent study by scientists from the University of Bristol and the University of Fribourg provides new evidence that suggests that a major human ancestor existed at the same time as dinosaurs.
The researchers found no fossils of placental mammals before the mass extinction of dinosaurs 66 million years ago. However, analysis of molecular clock data has allowed scientists to suggest that the lineage of placental mammals extends even further back in time, all the way back to the dinosaur age.
Using a new approach of statistical analysis, the researchers were able to determine that the earliest forms of placental mammals probably appeared during the Cretaceous period and mingled with dinosaurs for a short period of time. This means that placental mammals existed simultaneously with dinosaurs and possibly even interacted with them.
The model used by the researchers shows that after the asteroid fell and the dinosaurs died out, more modern lines of placental mammals began to appear. This could mean that conditions for evolution and diversification were better after the dinosaurs went extinct.
The study also confirms previous molecular clock data, which indicate that placental mammals had ancient origins. The researchers estimate that about 21.3 percent of the placental mammal families may go back to the Cretaceous period. This includes groups such as primates, dogs and cats, as well as rabbits and hares.
This study offers a new approach to determining the age of origin of species. It is based on an analysis of the annals of fossils and the nature of species diversity over time. Scientists believe this approach is more accurate, especially when the number of fossils available is limited.
Thus, the new data indicate that a major human ancestor existed at the same time as dinosaurs. This opens up new perspectives for studying human evolution and origins.