Humans' ancestors survived the asteroid impact that killed the dinosaurs


Date:
June 27, 2023
Source:
University of Bristol
Summary:
A Cretaceous origin for placental mammals, the group that includes
humans, dogs and bats, has been revealed by in-depth analysis of
the fossil record, showing they co-existed with dinosaurs for a
short time before the dinosaurs went extinct.


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FULL STORY ==========================================================================
A Cretaceous origin for placental mammals, the group that includes
humans, dogs and bats, has been revealed by in-depth analysis of the
fossil record, showing they co-existed with dinosaurs for a short time
before the dinosaurs went extinct.

The catastrophic destruction triggered by the asteroid hitting the Earth resulted in the death of all non-avian dinosaurs in an event termed
the Cretaceous-Paleogene (K-Pg) mass extinction. Debate has long raged
among researchers over whether placental mammals were present alongside
the dinosaurs before the mass extinction, or whether they only evolved
after the dinosaurs were done away with. Fossils of placental mammals
are only found in rocks younger than 66 million years old, which is when
the asteroid hit Earth, suggesting that the group evolved after the mass extinction. However, molecular data has long suggested an older age for placental mammals.

In a new paper published in the journal Current Biology, a team of palaeobiologists from the University of Bristol and the University of
Fribourg used statistical analysis of the fossil record to determine
that placental mammals originated before the mass extinction, meaning
they co-existed with dinosaurs for a short time. However, it was only
after the asteroid impact that modern lineages of placental mammals began
to evolve, suggesting that they were better able to diversify once the dinosaurs were gone.

The researchers collected extensive fossil data from placental mammal
groups extending all the way back to the mass extinction 66 million
years ago.

Lead author Emily Carlisle of Bristol's School of Earth Sciences said:
"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." Co-author Daniele Silvestro (University of Fribourg) explained:
"The model we used estimates origination ages based on when lineages
first appear in the fossil record and the pattern of species diversity
through time for the lineage. It can also estimate extinction ages based
on last appearances when the group is extinct." Co-author Professor
Phil Donoghue, also from Bristol, added: "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)."
Primates, the group that includes the human lineage, 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. After they survived the asteroid impact, placental mammals rapidly diversified, perhaps spurred on by the loss
of competition from the dinosaurs.

* RELATED_TOPICS
o Plants_&_Animals
# Extinction # Endangered_Animals # Evolutionary_Biology
o Earth_&_Climate
# Near-Earth_Object_Impacts # Global_Warming # Weather
o Fossils_&_Ruins
# Early_Mammals # Dinosaurs # Paleontology
* RELATED_TERMS
o Hadrosaurid o Dinosaur o Feathered_dinosaurs o Paralititan
o Ichthyosaur o Fossil o Archaeopteryx o Brachiosaurus

========================================================================== Story Source: Materials provided by University_of_Bristol. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Emily Carlisle, Christine M. Janis, Davide Pisani, Philip
C.J. Donoghue,
Daniele Silvestro. A timescale for placental mammal diversification
based on Bayesian modeling of the fossil record. Current Biology,
2023; DOI: 10.1016/j.cub.2023.06.016 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230627123015.htm

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