9.VIII: Human Ancestor Image Gallery

This image gallery closely tracks the table in the section “From Amoebas to Amniotes”.  These organisms are close representatives of what your ancestors looked like at critical stages of development.  Each successive taxon is a subset of the previous one, and humans belong to every taxon represented here.  That is, a human is a eukaryote, an opisthokont, an animal, etc., continuing to an amniote in this chapter of development.

2 BYA: Our single-celled ancestors were eukaryotes.  Despite the obvious changes since then, most of evolution’s hard work – the biochemistry – had already been done. 1

800 MYA (?): Our last unicellular ancestors were opisthokonts, from which sperm cells take their form.  Sponges only have a few cell types, one of which looks like this. 2



800 MYA (?):  The first animal was the sponge; many varieties are shown here. The “mouths” are not for feeding, as food is absorbed through the entire body.  3



800 MYA (?): The first metazoa was just a single layer of skin with a mouth that was used for feeding and excreting waste. 4


700 MYA (?): The deuterostome developed a more complex interior, including a through gut with anus. 5


600 MYA (?): The first chordate was a “fish shell” like this lancelet, with no eyes, heart, or brain.  This poor creature should have followed Dorothy to see the Wizard. 6



500 MYA: The first vertebrates, fishes like Myllokunmingia, made major advances in organ structure but still lacked a jaw. 7


More than 400 MYA:  Because we are gnathostomes, we have a face – two eyes, two nostrils, and a jaw. Let’s be glad faces have gotten prettier since they first appeared on this armored fish, the placoderm. 8



Less than 400 MYA: Tetrapods spent tens of millions of years at water’s edge, gradually going through the major adaptations required for life on land.  This species, Pederpes finneyae, is the first known animal with five-toed limbs. 9


More than 300 MYA: As amniotes, we are fully adapted to the terrestrial environment. 10



Back to Section 9.VII:  Chapter 9 Summary


Chapter 8 Human Ancestor Image Gallery

  1. Eukaryote photo: By Cymothoa exigua (Own work) CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0), https://commons.wikimedia.org/wiki/File%3AAmoeba_proteus.jpg (accessed 6/24/15)
  2.  Opisthokont photo: By Stephen Fairclough, CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5) or CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5), https://commons.wikimedia.org/wiki/File%3AMonosiga_Brevicollis_Phase.jpg (accessed 6/24/15)
  3.  Sponge photo by Twilight Zone Expedition Team 2007, NOAA-OE. (NOAA Photo Library: reef3859).  Public domain.
  4.  Comb jellyfish photo by NOAA / OAR / National Undersea Research Program (NURP), http://www.photolib.noaa.gov/htmls/nur01002.htm, public domain.
  5.  Sea cucumber image by NOAA, http://flowergarden.noaa.gov/image_library/inverts/threerowedcucumberelh.jpg , public domain.
  6.  Lancelet image © Hans Hillewaert, via Wikimedia Commons, https://commons.wikimedia.org/wiki/File%3ABranchiostoma_lanceolatum.jpg (accessed 7/02/15)   
  7.  Image of Myllokunmingia by Quade Paul, Echo Medical Media, http://www.echomedicalmedia.com/portfolio.html (accessed 7/02/15).  Reproduced with kind permission of Emiko Paul for the online version of TEOH.
  8.  Placoderm illustration by Nobu Tamura (http://spinops.blogspot.com) (Own work) GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY 3.0 (http://creativecommons.org/licenses/by/3.0), via Wikimedia Commons, https://upload.wikimedia.org/wikipedia/commons/9/95/Dunkleosteus_BW.jpg (accessed 6/20/15)
  9. Tetrapod image by DiBgd at the English language Wikipedia, license GFDL or CC-BY-SA-3.0, https://commons.wikimedia.org/wiki/File%3APederpes22small.jpg (accessed 7/02/15)
  10.  Amniote (casineria) illustration by ДиБгд (Own work) (CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)), https://commons.wikimedia.org/wiki/File%3ACasineria_kiddi_reconstruction.jpg
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