The ancestors of humans, dogs, cats and bats briefly co-existed with dinosaurs before the giant reptiles went extinct.

Analysing fossils of placental mammals to estimate when they first appeared, researchers found evidence of their existence before the asteroid that is thought to caused a mass extinction hit Earth 66million years ago. This means our ancestors and the dinosaurs once lived side-by-side.

The study, published in the journal Current Biology, was conducted by a team of palaeobiologists from the University of Bristol and the University of Fribourg.

‘We pulled together thousands of fossils of placental mammals and were able to see the patterns of origination and extinction of the different groups. Based on this, we could estimate when placental mammals evolved,’ said Emily Carlisle, lead author of the study.

The earliest placental mammals were small, insect-eating animals that lived in trees. They survived the mass extinction because they were small and inconspicuous and lived in habitats that were not heavily impacted by the asteroid impact.

After the asteroid’s impact, placental mammals became bigger and more diverse as fewer big predators were around after the dinosaurs died out.

The study shows that placental mammals are more ancient than we thought. They also played a significant role in the recovery of life on Earth after the asteroid impact.

Scientists call this the ‘K-Pg mass extinction’, also known as the Cretaceous-Paleogene extinction event. This sudden and catastrophic event wiped out about 75% of all plant and animal species on Earth.

The impact of a giant asteroid or comet that struck the Earth in what is now Mexico’s Yucatán Peninsula is thought to have caused widespread environmental damage, including wildfires, tsunamis, and acid rain. The resulting climate change would have made survival difficult for many species.

Luckily, our ancestors made it, while the dinosaurs were not so lucky.

‘By examining both origins and extinctions, we can more clearly see the impact of events such as the K-Pg mass extinction or the Paleocene-Eocene Thermal Maximum (PETM),’ said co-author Professor Phil Donoghue, also from Bristol.

Primates, the ancestors of modern humans, as well as Lagomorpha (rabbits and hares) and Carnivora (dogs and cats), were shown to have evolved just before the K-Pg mass extinction, which means their ancestors were mingling with dinosaurs as well.

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