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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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   
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   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   
      
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   Story Source: Materials provided by University_of_Bristol. Note: Content   
   may be edited for style and length.   
      
      
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   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   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230627123015.htm   
      
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