Friday, August 28, 2020

The Ancestor's Tale by Richard Dawkins -- The Big Intervals

The intervals:

  • 2000 mya (2 billion years ago) -- the first -- calls and microscopic animals
    • Eubacteria
    • archaea
    • eukaryocytes
  • 900 mya (it took another billion years to get to plants)
    • plants
    • amoebozoans
    • fungi
    • drips
    • choanoflagellates
  • 630 mya (intervals are shorter; less than 300 million years to get to sponges)
    • sponges
    • placozoans
    • ctenophores (look like, but are not, jellyfish
    • acoelomorph flatworms
  • 590 mya: deuterostomes appear (two sub-kingdoms: proterostomes and deuterostomes)
  • 565 mya: a chordate shows up
  • 530 mya ( only 100 million years to get from sponges to fish)
    • pivotal: the dawn of vertebrates
    • lampreys and hagfish
  • 460 mya (but it took 70 million years to get to things that really looked like modern fish)
    • sharks, rays
  • 440 mya (the huge jump; only 20 million years to get to ray-finned fish)
    • now we're cooking
    • in quick order, ray-finned fish will break off and three major groups will appear
    • coelacants (426 mya)
    • lungfish (417 mya)
    • everything else, sometime between 400 mya and 340 mya
  • 340 mya: a little bit of a lag, from 565 to 340 million years ago, we finally get from "fish" to amphibians; that's a long, long time
  • 310: Sauropods show up (once we get from fish to amphibians, things start to move quickly); after an incredibly long time where it as only fish or fish-like animals, it only took 30 million years to get from amphibians to reptiles
    • amphibians really were short-lived;
  • then, again, a long time for the next leap while reptiles dominated;
  • Permian: two dominant land land animals — sauropsids and synapsids;
  • 252 mya: Permian Mass Extinction
  • 180 mya  (long period of mammal evolution begins, placental animals show up):
    • first, monotremes showed up; and, then:
    • 140 mya: the marsupials showed up;
  • 25 mya: Old World monkeys; 100 million years to get from marsupials to monkeys)
  • 4 mya: ape-men; Australopithecus
  • 2 mya: Homo habilenes
  • 160,000 years ago: "modern" or "nearly modern" man

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