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View Diary: Evidence of Cerebral Reorganization in the Skull of a Seven Million Year Old Human Ancestor (65 comments)

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  •  Homo (2+ / 0-)

    I believe that there is really only one species of Homo and there has almost always been some gene flow (interbreeding) amongst regional populations since our too using genus first emerged approximately 2.6 million years ago.

    Marcel    

    •  Well, I don't want to get between what you (9+ / 0-)

      believe and what Scientific American says, so remember that I am only the messenger here. As you may know, the magazine often provides a brief summary of the key points of an article. Here is that summary for the article entitled, "Human Hybrids."

      A long-reigning theory of the origin of Homo sapiens holds that our species arose in a single locale--sub-Saharan Africa--and replaced archaic human species, such as the Neandertals, without interbreeding with them. But recent studies of modern and ancient DNA indicate that these modern humans from Africa did mate with archaic humans and hint that this interbreeding helped H. sapiens thrive as it colonized new lands.
      The foregoing quotation comes from page 66 of the paper version of the May 2013 magazine. I suppose that some might debate whether the Neandertals were "anatomically modern humans," but there is no argument about Denisovans or Archaic African hominims. Neither of the latter qualify as "anatomically modern," yet the authors contend on page 70 that interbreeding likely did take place with these early relatives. The Denisovans have been identified from archeological evidence, but apparently the interbreeding with the Archaic Africans comes from analysis of our own DNA. Certain portions of our DNA had to come from somewhere and interbreeding in Africa with other hominims seems to be the way.

      I think that this idea makes great sense, especially when one reviews the evolution of ideas over many decades that have purported to explain our evolution.

       

      Might and Right are always fighting, in our youth it seems exciting. Right is always nearly winning, Might can hardly keep from grinning. -- Clarence Day

      by hestal on Fri Apr 26, 2013 at 12:56:22 PM PDT

      [ Parent ]

      •  definitions get involved here because (10+ / 0-)

        interbreeding and species need to be clearly understood.

        It is most widely accepted that a definition of a species is that members are fertile with other members of the same species, but there can be many strains of the same species. Think dalmatians and collies.

        But how about horses and donkeys, which are close enough to produce mules, but the mules are sterile? Such details have to be taken to account in defining species.

        If homo sapiens could breed productively with neardertalis or erectus or whomever, one may reasonably say that we are therefore of the same species, just different strains in which some genetic drift occurred during long isolation from one another, but not enough to create a barrier to fertilization, just like coyotes and dogs can, with their 39 pairs of chromosomes.

        That said, this is a great diary topic and a fascinating find. And I had no idea about the Tuscany part of the story, so it's doubly cool.

        Fear is the mind-killer - Frank Herbert, Dune

        by p gorden lippy on Fri Apr 26, 2013 at 01:49:57 PM PDT

        [ Parent ]

        •  I agree that definitions do get involved, (4+ / 0-)

          but the definitions used by the authors of the article are the ones that are most widely accepted by specialists in the field.

          In the second chapter of his masterpiece, Origin of Species, “Variation Under Nature,” Charles Darwin attempted to separate individual differences, varieties, and species. He was trying mightily to establish some rule by which a group of individuals that differs from another group of individuals, yet both groups are clearly closely related, can be properly classified as a variety of a species or another distinct species. He failed to find the rule. My own reading, while by no means exhaustive or even broad, has failed to find the rule elsewhere. Darwin ended his discussion with this comment:

          Hence in determining whether a [life] form should be ranked as a species or a variety, the opinion of naturalists having sound judgment and wide experience seems to be the only guide to follow. … That varieties of this doubtful nature are far from uncommon cannot be disputed.
          So, I follow Darwin's advice on this perennial problem. I accept the conclusions of naturalists (scientists) who have sound judgment and wide experience. The authors of this article, to my mind, meet both those standards.

          Might and Right are always fighting, in our youth it seems exciting. Right is always nearly winning, Might can hardly keep from grinning. -- Clarence Day

          by hestal on Fri Apr 26, 2013 at 02:07:29 PM PDT

          [ Parent ]

          •  absolutely. Just trying to raise the question that (2+ / 0-)

            has plagued us for many years. Glad to have it discussed. There are simple rules such as what I listed, then you get all the gray stuff which means there can be no one-size-fits-all. The ability to interbreed is hugely important but not the only criterion, to be sure.  

            Fear is the mind-killer - Frank Herbert, Dune

            by p gorden lippy on Fri Apr 26, 2013 at 02:17:54 PM PDT

            [ Parent ]

        •  I am more often erectus than sapiens, you know (1+ / 0-)
          Recommended by:
          p gorden lippy

          and I'll breed with just about anything - female, I'm not really strong on the 'homo' part - that will breed with me ...

          [which ain't much, as it turns out]

          Too late for the simple life, too early for android love slaves - Savio

          by Clem Yeobright on Fri Apr 26, 2013 at 02:12:46 PM PDT

          [ Parent ]

      •  We know very little about Denisovans (3+ / 0-)
        Recommended by:
        triv33, gooderservice, Clem Yeobright

        and we know pretty much nothing about whatever archaic African populations contributed to the modern genome.

        Every thing we do know about them, however, strongly suggests that they were human, even if they may have been of another sub-species.

        These would be hybrids between human sub-species, not  evidence as you claim above that "human beings have be procreating with non-humans since the beginning of our time. "

        "Paid Activist" is an oxymoron.

        by JesseCW on Fri Apr 26, 2013 at 03:48:03 PM PDT

        [ Parent ]

        •  Just a little touchy, aren't we?... (0+ / 0-)

          Might and Right are always fighting, in our youth it seems exciting. Right is always nearly winning, Might can hardly keep from grinning. -- Clarence Day

          by hestal on Fri Apr 26, 2013 at 04:26:51 PM PDT

          [ Parent ]

          •  Erm. What? (4+ / 0-)
            A long-reigning theory of the origin of Homo sapiens holds that our species arose in a single locale--sub-Saharan Africa--and replaced archaic human species, such as the Neandertals, without interbreeding with them. But recent studies of modern and ancient DNA indicate that these modern humans from Africa did mate with archaic humans and hint that this interbreeding helped H. sapiens thrive as it colonized new lands.
            You just cited an article reporting overwhelming evidence that modern human populations interbred with archiac human populations, and tried to use it to support an argument that
            human beings have be procreating with non-humans
            It's staggering that you cannot see that you're trying to use evidence that is directly contrary to your assertion to support your assertion.

            "Paid Activist" is an oxymoron.

            by JesseCW on Fri Apr 26, 2013 at 05:15:46 PM PDT

            [ Parent ]

            •  plus (3+ / 0-)
              Recommended by:
              JesseCW, KenBee, triv33

              It's hominids not hominims.  A hominim is...oh forget it.  

              I one caught a STD and the doctor asked me if I had sex with monkeys, sheep or donkeys.  I replied that I wasn't from Stearns County.  

              I'll be here all week, be sure to tip your waitron.

              Bad things aren't bad! And anyway, there's mitigation!

              by Nada Lemming on Fri Apr 26, 2013 at 08:53:28 PM PDT

              [ Parent ]

              •  Hominini is a cladistic "tribe" that includes (3+ / 0-)
                Recommended by:
                triv33, Clem Yeobright, Nada Lemming

                the Genus Homo (us and our extinct kin) and the Genus Pan (the two kinds of Chimp).

                So, "we" have sex with other Hominins in the same sense that you could say we have sex with other Primates or other Vertebrates.

                But there's no evidence at all of hybridization of members of Pan and members of Homo, so there's no point to saying that "different Hominins interbred" when we can be far more specific and say that "different human species or sub-species interbred".

                Homo means "Human".  I mean, it's the literal definition of the word.  When two members of the genus Homo breed, this is definitionally two humans breeding.

                Hominid is a group that includes all the Great Apes.  

                A lot of these classifications have changed quite a bit since back in the bad old days of just 30 years ago, so a lot of folks learned different terms or different meanings for those terms in school.

                I know I'm no fun when I've got my "18 units of Anthropology spread out over 20 years" hat on 8P  

                It was funny.  

                "Paid Activist" is an oxymoron.

                by JesseCW on Fri Apr 26, 2013 at 10:29:02 PM PDT

                [ Parent ]

    •  the multiregional hypothesis was killed years ago (2+ / 0-)
      Recommended by:
      Clem Yeobright, RainyDay

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