A comprehensive analysis conducted by researchers from the University of Bristol and the University of Fribourg suggests that placental mammals, including species such as humans, dogs, and bats, emerged during the Cretaceous period and lived alongside dinosaurs before their extinction. Contrary to popular depictions, the earliest placental mammals were believed to resemble tiny chipmunks.
The fossil record has shed light on the origin of placental mammals, encompassing humans, dogs, and bats, revealing their co-existence with dinosaurs for a brief period before the dinosaurs’ demise.
The catastrophic impact of an asteroid colliding with Earth resulted in the extinction of all non-avian dinosaurs, marking the Cretaceous-Paleogene (K-Pg) mass extinction event. Researchers have long debated whether placental mammals were present alongside dinosaurs prior to the mass extinction or if they only emerged afterward.
The discovery of placental mammal fossils exclusively in rocks younger than 66 million years, coinciding with the asteroid impact, suggests that the group evolved after the mass extinction. However, molecular data has consistently pointed to an older age for placental mammals.
In a recent publication in the journal Current Biology, a team of paleobiologists from the University of Bristol and the University of Fribourg utilized statistical analysis of the fossil record to determine that placental mammals originated before the mass extinction, indicating their co-existence with dinosaurs for a limited duration. However, it was only after the asteroid impact that modern lineages of placental mammals began to evolve, implying that their diversification was more successful once the dinosaurs were gone.
The researchers collected extensive fossil data from various placental mammal groups, spanning back to the mass extinction event 66 million years ago.
Lead author Emily Carlisle, from Bristol’s School of Earth Sciences, stated, “By compiling thousands of placental mammal fossils, we observed patterns of origin and extinction among different groups, enabling us to estimate the timeline of placental mammal evolution.”
Co-author Daniele Silvestro (University of Fribourg) explained the methodology employed, stating, “Our model estimates the age of origin based on when lineages first appear in the fossil record and the species diversity pattern over time. It can also determine the age of extinction based on the last appearances of the group when it is no longer extant.”
Co-author Professor Phil Donoghue, also from Bristol, added, “Through examining both origins and extinctions, we gain clearer insights into the impact of events such as the K-Pg mass extinction or the Paleocene-Eocene Thermal Maximum (PETM).”
The study revealed that primates, including the human lineage, along with Lagomorpha (rabbits and hares) and Carnivora (dogs and cats), evolved just before the K-Pg mass extinction, indicating that our ancestors co-existed with dinosaurs. Following their survival of the asteroid impact, placental mammals experienced rapid diversification, potentially facilitated by reduced competition from dinosaurs.
Reference: “A timescale for placental mammal diversification based on Bayesian modeling of the fossil record” by Emily Carlisle, Christine M. Janis, Davide Pisani, Philip C.J. Donoghue, and Daniele Silvestro, 27 June 2023, Current Biology.
DOI: 10.1016/j.cub.2023.06.016
The computational resources of the Advanced Computing Research Centre at the University of Bristol were utilized for this research.
Frequently Asked Questions (FAQs) about prehistoric co-existence
Q: What does the study reveal about the co-existence of humans’ ancestors and dinosaurs?
A: The study suggests that humans’ ancestors, known as placental mammals, lived alongside dinosaurs for a short period during the Cretaceous period before the dinosaurs went extinct.
More about prehistoric co-existence
- University of Bristol: Link
- University of Fribourg: Link
- Current Biology journal: Link
- Advanced Computing Research Centre, University of Bristol: Link
2 comments
omg! so crazy to think that our ancestors were hanging out with DINOSAURS! like tiny chipmunks or something lol. and then an ASTERIOD came and killed them all, but not our ancestors. so cool!
Fascinating study! Finally, some evidence showing the co-existence of placental mammals and dinosaurs. The fossil record can be tricky, but this research provides valuable insights into our evolutionary history. Kudos to the researchers!