Written By:
lprent - Date published:
11:08 am, December 23rd, 2009 - 12 comments
Categories: racism, science -
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Poring around the nets while I’m on holiday is turning out to be quite interesting looking at summaries of science. I’ve been picking out some for discussion here. Here is a post from Knol with a summary on why Europeans are so pale.
They discuss well-known ultraviolet / vitamin D linkage with the consequent diseases.
UV rays produce vitamin D and reduce folate when they hit naked skin. And embryos are terribly vulnerable to both substances in the mother. When it comes to sunlight and skin tone, furless humans are balanced on a knife-blade.
Too much UV penetrating the skin (too pale-skinned under intense sunlight) increases Vitamin D but reduces folate. Lack of folate causes neural tube defects in the fetus, causing such congenital abnormalities as craniorachischisis, anencephalus, and spina bifida, leading to many miscarriages.
On the other hand, too little UV penetrating the skin (too dark-skinned under dim sunlight) increases folate but reduces vitamin D. Lack of vitamin D causes skeletal neonatal abnormalities (skull, chest, and leg malformations), rickets being the best known. Again, this causes miscarriages.
And so, humans adapt very quickly to solar UV. Prehistoric groups that migrated towards the equator got darker. Prehistoric groups that migrated away from the equator got lighter.
Some foods that are eaten also contain vitamin D and therefore break the dependence on the sun. So people like the Inuit, Sammi, Chukchi and Aleut in the north have far darker skins than would be expected because a high proportion of their diet is seafoods.
People who eat grains do not get vitamin D from food; they must get it from sunlight.
This usually works out fine because grains grow only where it is warm. And this means only in latitudes with bright sunlight, with one exception.
People who live in low latitudes, where they can live off grains, get plenty of sunlight. People who live in dim sunlight cannot grow grains, and so they get vitamin D from the meat and fish that they eat.
But this is unsatisfactory for explaining the historical paleness of Northern Europeans who are very pale in skin and hair tones, live inland, and live in a latitude that grains should be hard to grow without high levels of farming technology.
However grains do grow in Northern Europe easily. A climatological quirk explains why. The Gulf stream delivers warmth further north than the latitude would normally allow. This is about the only place where there has been grain grown for a long time in high latitudes. But eating these foods, while good for diet, would cause severe neonatal abnormalities and therefore a severe evolutionary pressure.
Now this is where it gets interesting to me because it is something that I hadn’t realized previously. Because children are not reproductively active, there is less evolutionary pressure on them for vitamin D. So all populations have some children who have lighter hair colour. My hair was quite blond and my skin tone was much fairer when I was child, and then darkened as I hit puberty. My hair went to a dark brown/black and is now going lighter as it goes grey, presumably because by my age my female counterparts would have stopped having children.
This is more pronounced when you look at the children of human populations living closer to the tropics as the photos above display for hair colour. So for Europeans..
When the inhabitants of this region switched to grain about 6 KYA, they suddenly got insufficient vitamin D to survive. They had stopped eating mostly meat and fish in a place where sunlight was too dim to produce vitamin D in normally pigmented skin.
And so they adapted by retaining into adulthood the infantile trait of extreme paleness. Blonde hair and blue eyes were other infantile traits that were just swept along accidentally.For the detailed text of this topic, complete with footnoted references, citations, and all the peer-reviewed material, visit The Paleo-Etiology of Human Skin Tone.
So Europeans have infantile traits from a neoteny adaption because of a climate quirk. I’m sure that will impress the ‘white’ racists who persist in perpetuating some other childish traits.
The current rise of populism challenges the way we think about people’s relationship to the economy.We seem to be entering an era of populism, in which leadership in a democracy is based on preferences of the population which do not seem entirely rational nor serving their longer interests. ...
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The links in the first four thumbnails are broke.
Damn – fixed.
Oh neato.
And thinking about it, if you mapped out centers of historical grain-based agriculture (or diet low in vit D) vs skin colour, you’d probably see a strong correlation right off.
fascinating post.
I wonder how eye colour fits in. There’s no reason it ought to be tied to skin-colour and hair-colour but brown eyes seem nearly universial apart from northern europe. My blonde, blue-eyed girlfriend seems to find bright light far harder to deal with than myself with dark brown eyes. You would think that would be tied to latitude as well but inuit seem to have mostly dark eyes.. of course, it’s often actually very bright in high latitudes with snow.
oh, the clicks to enlarge the pics don’t work
If you right click and select “view image” you will get them at the large size, although the vitamin D in food one is quite blurry.
lprent
All this points to one thing. Humans, like all complex life forms, are highly adaptable and conventional wisdom that evolution is a series of small random changes looks less and less likely. I read a book once that coined the name ‘envolution’ which examined the theory that all life adapts to take advantage of the environment it is in, and that there was nothing random about it.
Evolution describes life adapting to it’s environment. The only way it couldn’t be random is if someone went and did the changes and, as this isn’t happening, the changes must therefore be random.
….
Pick up on of Dawkin’s evolutionary biology books (say Climbing Mount Improbable, or the latest) or go grab a recent evolutionary biology text book and read up primarily on “mutations” and “genetic drift” (linked to because most books are a bit crap on it). Both processes are random, but the results are modified by non-random selection.
However, this does not mean that evolution is “non-random”, as the variation required for selection to work on is created by random processes, instead it’s obviously a mix of random and non-random processes.
Which also means Draco’s wrong-ish.
Evolution a series of random changes? Huh? Evolution as described by Darwin is adaptive.
Evolution (i.e. the change in the relative frequency of genotypes in a population) can occur by many mechanisms. One in which is truly random would be genetic drift, which can be a strong force in small populations and changes occur entirely be chance. Evolution can also occur by natural selection where individuals that are better adapted to the environment survive and reproduce better than others, and therefore the genotypes of these individuals become more common in the population in future generations. Of course this depends on adaptable traits being heritable and other such factors. Needless to say, natural selection is NOT a series of random changes. Of course in real life there is a combination of random changes and adaptation occurring, and there is a strong stochastic component to evolution. The adaptations of life to the environment can be clearly seen everywhere, but one must always be careful to not assume that EVERYTHING you see in nature is adaptive, as some things happen just by chance.
You forgot spandrels and selective sweeps 😛
Also, you can get neutral and seemingly maladaptive traits due to either the above, canalisation and/or lack of exposure to selection via low fitness cost, r.e. non-coding DNA.
And on randomness, it’s mutation rate/location + stochastic loss of individuals that are the main random elements in evolutionary biology, but in turn of course that’s shaped by selection, a non-random process.
/evo.bio-nerd
This is probably the best post I’ve read on a political blog for a while – very interesting. Thanks!