What We Learned About Human Origins In 2013 Will Blow Your Mind

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The existence of a mysterious ancient human lineage and the possibility that the earliest humans were actually all one species were among the human-evolution-related discoveries of 2013. 

Other breakthroughs include the sequencing of the oldest human DNA yet.

Here's a look at what scientists learned about humanity and human origins this year:

Mystery lineage

Recent analyses of fossil DNA have revealed that modern humans occasionally had sex and produced offspring not only with Neanderthals but also with Denisovans, a relatively newfound lineage whosegenetic signatureapparently extended from Siberia to the Pacific islands of Oceania.

This year, hints began emerging that another mystery human lineage was part of this genetic mix as well. Now, the first high-quality genome sequence from a Neanderthal has confirmed those suspicions.

These findings come from Denisova Cave in southern Siberia, where the first evidence of Denisovans was discovered in 2008. To learn more about the Denisovans, scientists examined DNA from a toe bone unearthed there in 2010.

The researchers found that the fossil belonged to a Neanderthal woman. Her DNA helped refine the human family tree, as it revealed that about 1.5 to 2.1 percent of the DNA of modern people outside Africa is Neanderthal in origin, whereas about 0.2 percent of DNA of mainland Asians and Native Americans is Denisovan in origin. 

Written By: Charles Q. Choi
continue to source article at huffingtonpost.com

15 COMMENTS

  1. @OP – The researchers found that the fossil belonged to a Neanderthal woman. Her DNA helped refine the human family tree, as it revealed that about 1.5 to 2.1 percent of the DNA of modern people outside Africa is Neanderthal in origin, whereas about 0.2 percent of DNA of mainland Asians and Native Americans is Denisovan in origin.

    This essentially says that these classifications were sub-species, not species, so had not separated enough to prevent recombination of populations within the wider diversity from the localised genotypes. In other words, humans were distributed like a ring or line species during these times.

    If someone in the future, found fossils without DNA evidence,of African Pygmy Bushmen and Zulus, they could easily mistake them for separate species.

    • In reply to #1 by Alan4discussion:

      From Wikipedia:

      The Westermarck effect, or reverse sexual imprinting, is a hypothetical psychological effect through which people who live in close domestic proximity during the first few years of their lives become desensitized to later sexual attraction. This phenomenon, one explanation for the incest taboo, was first hypothesized by Finnish anthropologist Edvard Westermarck in his book The History of Human Marriage (1891). Observations interpreted as evidence for the Westermarck effect have since been made in many places and cultures, including in the Israeli kibbutz system, and the Chinese Shim-pua marriage customs, as well as in biological-related families.

      From the article above:

      (Inbreeding may have been common among early humans — it remains uncertain as to whether it was some kind of cultural practice or whether it was unavoidable due to small community populations at the time.)

      Alan, do you have any thoughts on how these two statements can be reconciled?

      • In reply to #3 by LaurieB:

        In reply to #1 by Alan4discussion:

        From Wikipedia:

        The Westermarck effect, or reverse sexual imprinting, is a hypothetical psychological effect through which people who live in close domestic proximity during the first few years of their lives become desensitized to later sexual attraction. This p…

        “…do you have any thoughts on how these two statements can be reconciled?”

        Politics!!

        Pharaohs married siblings and were probably not the only culture to do so. In a political/dynastic marriage little account would be taken of any taboo induced revulsion.

        I find it plausible that in small early human groups incest was common. I suspect that this added to the short-life expectancy and the fluctuations in population size leading to some of the famous “bottlenecks”. Those matings between more distantly related partners would seem to have a good chance of being positively selected. A more diverse gene pool would reduce incest necessity to a status of “speciality”.

        • In reply to #4 by Philoctetes:

          “…do you have any thoughts on how these two statements can be reconciled?”
          Politics!!

          haha. Right. Before I wrote the comment above I read quickly through a few pages of the book Consilience by E.O. Wilson, which is here on my shelf and contains some discussion of Westermarck effect. He does mention the cases of exceptions to the incest taboo in the following cultures: Incas, Hawaiians, Thais, ancient Egyptians, Nkole (Uganda), Bunyoro (Uganda), Ganda (Uganda), Zande (Sudan), and Dahomeyans of West Africa. Wilsons writes:

          In each case the practice is (or in most instances was, having been discontinued) surrounded by ritual and limited to royalty or other groups of high status. In all the incestuous arrangements the male also consorted with other women, fathering outbred children in addition to “pure” progeny. he ruling families are or were Patrilineal. The strategy yielding maximum genetic fitness for a high-ranking male is to mate with his own sister, producing children who share with him 75 percent of their genes by common descent, instead of the usual 50 percent, and also to mate with women who are genetically unrelated and more likely t give birth to normal children. Less easily explained are the common and well-documented cases of brother-sister marriages among commoners in Roman Egypt, from about 30B.C. to A.D. 324. Papyrus texts from the period reveal beyond reasonable doubt that at least some of the siblings engaged in full and unabashed sexual relations.

          Consilience, E.O.Wilson, 1999. Paperback chaper 8, page 193.

          Here’s the sentence that really grabbed me -

          The strategy yielding maximum genetic fitness for a high-ranking male is to mate with his own sister, producing children who share with him 75 percent of their genes by common descent,

          75 percent! From a gene’s point of view, that’s damn attractive!

      • In reply to #3 by LaurieB:

        In reply to #1 by Alan4discussion:

        I don’t know just how much of a turn-off the Westermarck Effect would be. Perhaps in only operates when there a varied opportunities to select unrelated mates. I think the aversion to closely related mates is due to the similarity of one’s immune system, if I remember correctly.

        In a situation where the survival of the group depends on interbreeding with one’s close relatives, I would expect such niceties to be disregarded.

      • In reply to #3 by LaurieB:
        >

        (Inbreeding may have been common among early humans — it remains uncertain as to whether it was some kind of cultural practice or whether it was unavoidable due to small community populations at the time.)

        Alan, do you have any thoughts on how these two statements can be reconciled?

        I do not have studied this enough to have a definitive answer, but my feeling is that this is just speculation by the author.
        Hunter-gatherer tribes tend to exchange brides with neighbouring families/ communities/ villages/ camps, while pack animals like chimps, meerkats, wolves, and lion prides avoid breeding between closely related individuals within the group, using various social structures.

  2. Genetic analysis also revealed that the parents of this Neanderthal woman were closely related — possibly half-siblings, or another close relative. (Inbreeding may have been common among early humans — it remains uncertain as to whether it was some kind of cultural practice or whether it was unavoidable due to small community populations at the time.)

    Can’t you just imagine the Huff-Po readers swooning and dropping like flies?

  3. In reply to #6 by Nitya:

    I think the aversion to closely related mates is due to the similarity of one’s immune system, if I remember correctly.

    Yes, I remember reading an article about that some time ago. However, here’s a strange state of affairs from the same chapter, page 190, in Consilience by Wilson, that doesn’t seem to involve immune systems at least on the face of it:

    The existence of the phenomenon has gained increasing support from many sources in the intervening years. None is more persuasive than the study of “minor marriages” in Taiwan by Arthur P. Wolf of Stanford University. Minor marriages, formerly widespread in southern China, are those in which unrelated infant girls are adopted by families, raised with the biological sons in an ordinary brother-sister relationship, and later married to the sons. The motivation for the practice appears to be to insure partners for sons when an unbalanced sex ratio and economic prosperity combine to create a highly competitive marriage market.

    Across four decades, from 1957 to 1995, Wolf studied the histories of 14,200 Taiwanese women contracted for minor marriage during the late nineteenth and early twentieth centuries. The statistics were supplemented by personal interviews with many of these “little daughters-in-law” or sim-pua, as they are known in the Hokkien language, as well as with their friends and relatives.

    What Wolf had hit upon was a controlled-if unintended-experiment in the origins of a major piece of human social behavior. The sim-pua and their husbands were not biologically related, thus taking away all of the conceivable factors due to close genetic similarity. Yet they were raised in a proximity as intimate as that experienced by brothers and sisters in Taiwanese households.

    The results unequivocally favor the Westermarck hypothesis. When the future wife was adopted before thirty months of age, she usually resisted later marriage with her de facto brother. The parents often had to coerce the couple to consummate the marriage, in some cases by threat of physical punishment. The marriages ended in divorce three times more often than “major marriages” in the same communities. They produced nearly 40 percent fewer children, and a third of the women were reported to have committed adultery, as opposed to about 10 percent of wives in major marriages.

    I do agree that in the interest of group survival that everyone would be fair game.

    • In reply to #7 by LaurieB:

      In reply to #6 by Nitya:

      That’s a great, practical example. I hadn’t read that, but it sounds convincing. It would also explain the fact that adopted siblings are not attracted to one another ( as far as I know) even though their immune systems would be completely different. I’m not surprised that the females in the situation require coercion. The tendency to be more selective about potential mates is in evidence here. ( not meaning to sound sexist, of course.;-)

      I’d like to add the fact that an incest taboo was in operation in traditional aboriginal societies as well.

      • In reply to #8 by Nitya:

        The tendency to be more selective about potential mates is in evidence here. ( not meaning to sound sexist, of course.;-)

        Nothing sexist about it! I can’t imagine any argument to that statement!

        I’d like to add the fact that an incest taboo was in operation in traditional aboriginal societies as well.

        I wonder if it was just parents and siblings or did it include cousins too? Wilson points out that siblings are usually included in the taboo but cousins are often fair game. It could be a murky delineation if they were all brought up in an extended family together.

        • In reply to #9 by LaurieB:
          >

          I wonder if it was just parents and siblings or did it include cousins too? Wilson points out that siblings are usually included in the taboo but cousins are often fair game. It could be a murky delineation if they were all brought up in an extended family together.

          Yes I was wondering how it worked in small hunter gatherer tribes. Pity we don’t seem to have Helga Vieirch anymore.

          Michael

          • *In reply to #10 by mmurray:

            Yes I was wondering how it worked in small hunter gatherer tribes. Pity we don’t seem to have Helga Vieirch anymore.

            That’s right. I enjoyed some discussions I had with her.

  4. I wonder if it was just parents and siblings or did it include cousins too? Wilson points out that siblings are usually included in the taboo but cousins are often fair game. It could be a murky delineation if they were all brought up in an extended family together.>

    In reply to LaurieB# 9

    I’m not sure whether cousins were included as the system of taboos was highly complex. I suspect that some cousins would be okay ,whereas others would be off limits. The tribes were nomadic so it was not uncommon to come across different groups and select mates from a different ( though not completely different) gene pool. The various tribes practised a similar code of identifying members.

    IMO the early human communities in the article would have had much the same structure, though not the cultural aspect. The Australian Aboriginal culture remained unchanged for 40,000 years, so I think insights can be gleaned from their way of life although avoiding inbreeding was high on the list of priorities for the aboriginals.

  5. Aboriginal Culture – Traditional Life – Social Organisation
    http://www.aboriginalculture.com.au/socialorganisation.shtml
    They also have a complex kinship system where everyone is related to … Moieties. Throughout Australia the moiety system divides all the members of a tribe into …>

    This article describes the intricacies of the aboriginal moiety/totem/skin group organisation that made for the most diverse gene pool, in case anyone is interested in following it up. Sorry that I couldn’t make the link ‘clickable’.

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