Which Evolved First, The Human Skin, Blood, Or The Human Heart?

Discussion in 'Biology & Genetics' started by JBT, Aug 11, 2016.

  1. JBT Registered Member

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    I am in a discussion with a theist and he gave me a very weird question indeed.. one that I find a bit moronic and yet a bit interesting.. I then thought about it and I really don't know.. I am not a scientist but am interested in this area.. so if anybody has the slightest ides about this question.. much appreciated.

    Which evolved first, the human skin, blood, or the human heart?

    To me is seems like they all evolved together.. simple answer but from my current knowledge that seems correct.
     
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  3. billvon Valued Senior Member

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    The first thing that would be recognized as "skin" probably happened around the time we were simple multicellular organisms with specialized outer cells. So I'd say that would be first.
    The first thing that would be recognized as "blood" would have been intracellular fluid in a slightly more complex organism, where it served merely as a conduit for metabolic wastes (and some homeostasis.) So I'd say that was second.
    The heart was last - something that actively pumped that fluid.
     
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  5. Yazata Valued Senior Member

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    'Evolved first' how? In fetal development? In the evolutionary history of humanity's ancestors?

    Fetal development in pretty much all animals except sponges starts with what amounts to a disk (embryonic disc) or a hollow sack (gastrula) with two layers. (Ectoderm and endoderm.) Some very simple animals like the jellyfish (Cnidaria) and comb jellies (Ctenophora) develop from these two cell layers and remain two-layered hollow sacks into adulthood. All of their specialized tissues (sensory, motor, reproductive, digestive) develop from these two layers.

    https://en.wikipedia.org/wiki/Germ_layer

    https://en.wikipedia.org/wiki/Diploblasty

    But in all the more elaborate kinds of animals (from worms to man) a third layer of cells called the mesoderm develops between the ectoderm and the endoderm. All of our organs and body structures develop from these three original layers.

    https://en.wikipedia.org/wiki/Triploblasty

    In humans (and most other animals) the ectoderm develops into both the skin and the nervous system (including the brain). The muscles, heart, blood, blood vessels and bone develop from the mesoderm. The endoderm contributes the gut (and intestines, liver, pancreas, urinary bladder and the pharynx).

    So I guess that an argument can be made that the skin develops in man (and most animals) from a layer of cells that exists in the simplest animals that don't even possess the mesoderm that develops in man into the muscles and the circulatory system. That suggests to me that skin has earlier phylogenetic origins. (Of course everything has continued evolving ever since.)
     
    Last edited: Aug 11, 2016
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  7. spidergoat Valued Senior Member

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    What makes a human? The step before a human already had all those things.
     
  8. iceaura Valued Senior Member

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    This is a stalking horse for an incoming irreducible complexity "argument".
     
  9. Fraggle Rocker Staff Member

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    We generally distinguish modern humans (Homo sapiens) from the earlier species of genus Homo. However, since Neanderthals (Homo neanderthalensis) had a highly-developed culture and (apparently) lived in peace with the sapiens who migrated into Europe, as the ice age ended (and as we now know the two species even interbred, leaving lots of Neanderthal DNA in several European populations)... many scientists prefer to put the Neanderthals on the same plateau as our species.

    But if you're looking for the point in time, at which animals that we refer to as pre-modern humans first appeared on this planet, then you're looking at Ardipithecus. Ardi is the first Great Ape species that wandered off into a new evolutionary line, which continued to veer further and further off from all the other species of Great Ape (the 2 species of gorilla, the 2 species of chimpanzee and the 2 species of orangutan). Ardi had several anatomical features that placed her (the first specimen found was female) clearly on a new evolutionary path.

    She had only one prehensile toe on her feet (the hallux or "big toe"), which allowed her to use her feet to escape from predators, but otherwise the foot was built for both climbing and bipedal walking.

    So the answer to your question, "What makes a human," can be:
    • 1. Ardipithecus (which goes back about 7 million years) and all of the intermediate species between Ardi and our own species
    • 2. Or the two most recent species of genus Homo: neanderthalensis and sapiens.
    • 3. Or JUST Homo sapiens, the only member of the genus still in existence.
     
  10. origin Trump is the best argument against a democracy. Valued Senior Member

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    Since we evolved from animals that already had skin, blood and a heart, your question is absurd.
     
  11. Fraggle Rocker Staff Member

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    Indeed. The most primitive chordates, the cartilaginous fishes (skates, rays, sharks, eels, etc.) have hearts, blood and skin. However, their skeletons are comprised of cartilage, not bone.

    Octopuses, which are much more primitive than chordates, have skin and blood, and three hearts!
     
  12. Kristoffer Giant Hyrax Valued Senior Member

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    Useful information for those hunting vampire squid.

    Bring three stakes.
     
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  13. Fraggle Rocker Staff Member

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    While the various species of squid and the various species of octopus are related (both in the phylum of cephalopods), it's not a very close relationship.

    They're about as close as a human and a lizard.
     
  14. DaveC426913 Valued Senior Member

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    6,288
    Well....

    Cephalopod is a class. Squid and Octopus are the same class.
    Humans and lizards are class mammalia and reptilia, respectively.

    So, squid and octopus are about as close as humans and other mammals, such as, say, giraffes.
     

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