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Wednesday, June 29, 2016

Mammals Evolved Three Times Faster after Dinosaur Extinction

     Our ancestors evolved three times faster in the 10 million years after the extinction of the dinosaurs than in the previous 80 million years, according to University College of London researchers.




     The research team found the speed of evolution of placental mammals (a group that today includes about 5000 species including humans) was constant before the extinction event but exploded after, resulting in the varied groups of mammals we see today.




     Lead (not lead ;-)) researcher, Dr. Thomas Halliday said: "Our ancestors, the early placental mammals, benefitted from the extinction of non-avian dinosaurs and dwindling numbers of competing groups of mammals. Once the pressure was off, placental mammals suddenly evolved rapidly into new forms."



     "In particular, we found a group called Laurasiatheria quickly increased their body size and ecological diversity, setting them on a path that would result in a modern group containing mammals as diverse as bats, cats, rhinos, whales, cows, pangolins, shrews and hedgehogs."

        Laurasiatheria is a superorder of placental mammals believed to have originated on the northern supercontinent of Laurasia. Thus it was the northern landmasses that produced much of the mammal explosion.



     The team found that the last common ancestor for all placental mammals lived in the late Cretaceous period, about three million years before the non-avian dinosaurs became extinct 66 million years ago. This date is about 20 million years younger than suggestions from previous studies which used molecular data from living mammals and assumed a near-constant rate of evolution.




     In this study the researchers analysed fossils from the Cretaceous to the present day, and used the dates of their occurrence in the fossil record to estimate the timing of divergences based on an updated tree of life. The new tree was released in 2015 and has the largest representation of Paleocene mammals to date.




     The scientists measured all the small changes in the bones and teeth of 904 placental fossils and mapped the anatomical differences between species on the tree of life. From measuring the number of character changes over time for each branch, they found the average rate of evolution for early placental mammals both before and after the dinosaur extinction event. They compared the average rate of evolution over the geological stages before the extinction and the geological stages after to see what impact it had.




     Senior author, Professor Anjali Goswami said, "Our findings refute those of other studies which overlooked the fossils of placental mammals present around the last mass extinction. Using rigorous methods, we've successfully tracked the evolution of early placental mammals and reconstructed how it changed over time. While the rate differed between species, we see a clear and massive spike in the rates of evolution right after the dinosaurs become extinct, suggesting our ancestors greatly benefitted from the demise of the dinosaurs. The huge impact of the dinosaur extinction on the evolution of our ancestors really shows how important this event was in shaping the modern world."




      Professor Paul Upchurch, co-author of the study, added: "Our large and refined data set allows us to build a clearer picture of evolutionary history. We plan on using it to study other large-scale evolutionary patterns such as how early placental mammals dispersed across the continents via land bridges that no longer exist today."



       I'd like to take that land bridge from South America to Africa in the southern land masses of Gondwanaland. 

      How about you? Does "Reunite Gondwanaland!" ring true to you?

Steph

19 comments:

  1. "The huge impact" [nice choice of words] "of the dinosaur extinction on the evolution of our ancestors really shows how important this event was in shaping the modern world." -- Why conclude that it was the dinosaur extinction that was pivotal, rather than the impact that caused the dinosaur extinction. I.e., rather than just removing the competing dinosaurs, the Chicxulub impact changed the planetary climate in a way that may have favored the mammalian explosion even if it hadn't wiped out the non-avian dinosaurs.

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    1. An important distinction. Thanks, jan.

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  2. yea..fossils is the greatest proof for evolution..i believe it..i believe you.

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  3. Forget Gondwanaland! How about reuniting Laurasia? "I think I'll make a road trip from Boston over to see the Louvre."

    In the illustration showing the Bering Strait land bridge, the yellow-framed detail in the lower-left inset looks like a detail from the Creation scene on the Sistine Chapel.

    LegoDenizenOfLuke&Laurasia

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    1. Forget Gondwanaland, Lego? Jamais! ;-)

      The Creation scene does look like the Bering Strait land bridge. Wonder what bearing it has to Laurasia?. . .

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  4. What would Donald Trump do about all those land bridges?

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    1. He might think about giant Wall-O-Waters near the land bridges, eh?

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    2. Or perhaps moats or ha-has.

      LegoWhoIsAFanOfTheGreenBayPackersHahaClintonDix

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    3. Yes, a ha-ha would be doubly appropriate for someone widely considered a joke, who objected to wind turbines in Scotland off the coast of his golf course, as they would spoil the view.

      Speaking of which, I love the cover of this week's New Yorker.

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  6. Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo. Bison bison bison.

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    1. Just saw this, jan. Great article and wonderful black and white photography.

      I, too, had an encounter with a bbb one winter in Yelliwstone. We were both using a cross-country trail when I came upon a large male bison. I said something like "You stay just there and I'll just mosey on my way." And he did. . . and I did.

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    2. Yeah, my wife used her soothing therapist voice on another (or the same?) one in Yellowstone when we were there. A ranger in Grand Teton had told us to use a low, calm tone if we encounter large animals in the wild. Same uneventful outcome.

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    3. My encounter was in 1987, but I suppose it could be the same fellow.

      The big guy turned his head side to side, munching on some hay or grass, and agreed to just co-exist. I wasn't really scared, just fascinated.

      On the other hand, our 16-year-old Japanese student went charging up to a bull moose at Snow Mountain Ranch before we could stop her. The moose just walked into the nearby pond and started swimming away so effortlessly.

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  7. New post on "Bac(teria) To The Future: Two Bacterial Types Helpful in Vaccine Transport and in Blocking Zika Transmission" is now up.

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