Monday, April 21, 2014

Epigenetic study narrows (and erases?) the gap between Neanderthals and modern humans

Skeleton of a Neanderthal (foreground) near the
skeleton of a modern human (background) at the
Museum of Natural History in New York.
Image source.
"DNA Study Shows Why Neanderthals, Modern Humans Are So Different," proclaimed a Huffington Post headline on Friday.  In light of the new study, however, I think the headline was quite misleading in emphasizing the differences.  Rather, we have found that there is almost no difference between the two at all.

Admittedly, Neanderthals do appear slightly different superficially.  They were somewhat shorter and much more robust than the average modern humans, and they had larger braincases.  Looking deeper, however, reveals what caused these differences.  A team of scientists from various universities around the world studied and compared the DNA of Neanderthals, Denisovans, and modern humans.  Their results, published April 17 in the Science journal, reveal that the key differences lie not in the genetic code, but in the epigenetic factors.

The study of epigenetics is quite recent.  Whereas the genes in a DNA sequence give the "recipe" for the proteins made by your body's cells, the epigenetic proteins regulate when and how frequently other proteins are made, or if they are made at all, making them the "on/off" switch for each section of your DNA.  The authors of the recent study have found that about 2000 regions in the genomes were "differentially methylated;" that is, some genes that are active in modern humans were deactivated in Neanderthals, while other genes that were activated in Neanderthals have been deactivated in modern humans.  In particular, a DNA region that controls shape and size of limbs was turned off in Neanderthals, giving them slightly shorter and more curved arms and legs.  It is significant to note that the genes themselves were identical; the only difference was whether they were turned on or off.

It is also important to note that epigenetic differences need not result from differential evolution.  Unlike genes, epigenetic systems are affected by external factors such as diet and climate, which may partially explain the differences between identical twins.  The implication is that Neanderthals may have been completely genetically human1, but particular diets and climatic conditions resulted in their slightly different morphology.  Creationists generally consider Neanderthals to be human descendants of Noah who adapted to the harsh conditions of northern Europe and Asia during the Ice Age, becoming more robust to conserve body heat.  This latest study indicates that such adaptations need not have resulted from natural selection of numerous generations, but could have been achieved within a single generation.  Likewise, these adaptations could have reverted almost immediately upon either southerly migration or warmer climatic conditions.

Though Neanderthals were once seen as ape-like mindless brutes due to evolutionary presumption, in-depth studies of these beings have demonstrated more and more that they are entirely human, just as creationists have claimed.  They looked like us, they had culture like us, and they have the same DNA as us.  I think it is reasonable to say that they are us, descendants of Adam with hope of salvation from the evils of the world (and of ourselves!) by God through Jesus Christ.

1As was noted in the comments, epigenetic differences are still considered to be genetic differences, so this statement was misleading.  The distinction between species is not well-defined at the moment.  However, this does not affect the possibility that Neanderthals were descended from Noah.

3 comments:

  1. To say epigenetic factors have no genetic basis is outright false-- there's a whole load of DNA methylation patterns determined by how the mother's egg's chromosomes are methylated.

    Sure, epigenetic factors can change by environmental effects, but the very term "Epigenetics" refers to genetic (i.e, traits inherited from parents) factors that aren't included in the DNA.

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    Replies
    1. I'm sorry, I didn't mean to imply that epigenetic states weren't inherited at all, only that they can be affected within an individual by environmental factors. However, I don't think I ever said that "epigenetic factors have no genetic basis." If you would point out the specific false statements in the article, I will gladly fix them.

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    2. You said that "The implication is that Neanderthals may have been completely genetically human, but particular diets and climatic conditions resulted in their slightly different morphology"

      The phrase "completely genetically human" is misleading, as it suggests that all genetic factors, including epigenetics, were identical. DNA plays a large part in genetics, but we're only starting to uncover a bunch more factors, such as methylation or histone patterns, which have a part to play in increasing heritable variation. This suggests that maybe it's not just a % DNA difference which makes 2 species different, but a bunch of other factors as well.

      Although, whenever we talk about distinction between 2 species, that's always a tough issue, because there's not really an agreed objective standard for what constitutes two different species-- it's simply when a large majority of experts in a field come to a consensus that the two specimens are different enough to call different species. There was talk of using % DNA differences for this a couple years ago, but our discoveries in epigenetics have made that seem not as viable, as we'd need to have standardized metrics for other factors, like DNA methylation, histone modification, protein concentration in the developing environment, and a whole slew of other things, and somehow mix together the impact each of those factors have on the organism, and decide what % difference constitutes a new species.

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