Which differences there are evidence for

I have previously pointed out that human nature is the same everywhere.  This of cause does not mean we have not evolved at all.  Naturally there are differences in physical characteristics between different parts of the world.  But each of them is caused by one or a small number of genes.  This way they can arise much easier than new mental functions.  The later evolution has not had enough time for.

One example of this is how we do when we smile.  Originally, nearly all humans were more or less dark-skinned.  To show one’s teeth then makes it visible at a longer distance that one is friendly.  One does not even have to be particularly dark-skinned for this effect to occur.  It is enough to be on the darker half of the scale.  Now there are a large part of humanity which is unquestionably light-skilled.  However, all humans can still smile in the same way as the dark-skinned.  The only thing stopping you is thinking you have too ugly teeth.

Many differences in looks can be explained by genetic drift.  This applies to things like hair colour, eye colour and nose shape.  Likewise, small differences in head shape which I can see with my unaided eye belong to this category.  Such differences are too small to matter for the development of the brain.  Other differences can be beneficial in a certain environment.  This for example applies to immunity to different infections.  Other examples are:

• Digestion of lactose is strikingly new adoption.  This characteristic does not seem to have become common until some peoples become dependent on milk from certain animals.  Either they have suffered famines when fresh milk was the foodstuff there was the very most of.  Or they ended up living on keeping such animals.

• Digestion of starch is curiously due to a single gene.  It is just a matter of how many copies of the gene you have.  At some point in evolution this singe gene doubled.  Over the course of tens of thousands of years more and more copies arose.  The more copies you have the easier you can digest starch.  Peoples which historically have eaten much of starch tend to have more copies.  However, there are still people who just one of this gene.  They usually belong to populations which historically have eaten carbohydrates in the form of sugars.

• Hair texture was originally an adoption to a hot climate.  Curly hair help prevent the brain from getting too hot.  However, when humanity reached cooler climates, it did not matter anymore.  So other hair textures could arise and become the subject of regional sexual selection.  Otherwise, it is a bit hard to explain why strait hair is so common.

• Height matters for temperature regulation and how much people need to eat.  Short people have easier to keep warm.  This is why Eskimos and Tibetans are so short.  Pygmies are even shorter but this is due to shortage of life-forms eatable to humans.  They are not as common as one might think in a rainforest.

• Number of fat cells also varies between different populations.  Those which historically have run a higher risk of famine tend to have more fat cells.  This means you can cope with larger changes in weight over time.  Those peoples which historically have run lower risk of famine did not need to have as many.  On the other hand, this makes them more sensitive to cardiovascular disease.

• Skin colour varies from pink to dark brown.  Of cause, there are people which are claimed to be brownish black.  But I think this is due to suntan on their otherwise dark brown skin.  For the very purpose of protecting against ultraviolet light we originally evolved dark skin.  When humanity reached higher latitudes, it became more important for the skin to create vitamin D.  With less ultraviolet light, lighter skin become an advantage.  This evolution accelerated after the introduction of agriculture.  The diet of the farmers contained less vitamin D which increased the importance of skin colour.

• Sweating also varies by which climate you descend from.  Peoples which lived in hotter climates tend to sweat less at the same temperature.  They have historically had a need for saving water when sweating.  When people settled in cooler climate this need decreased.  For this reason, people who descend from higher latitudes tend to sweat more.  There is in fact a correlation between skin colour and sweating.  The light-skinned tend to sweat more than the dark-skinned.

Epicanthic folds may belong to this category but I am not sure.  This characteristic could be an advantage in bright, open landscapes.  However, it seems to have been common among the first farmers of southern China.  Otherwise, it is hard to explain why this characteristic is so common among present-day Southeast Asians.  At the same time, it seems to have been rare among the first farmers of West Asia.  This is why it is rare among the peoples around the Mediterranean.  Still, it is West Asia which has the drier climate.  It could be a founder effect but I don’t know.

Yet, there are limits to what humans could adopt to.  We still have a minimum need for different nutrients.  The size of it is only determined by how much the person weights.  We can survive on a diet consisting to 90% of maize.  However, it is not nutritionally optimal.  This is why Mesoamericans are so small and weak.  They have spent the last few millennia trying to survive on such a diet.

 

Uploaded on the 22nd of Mars 2023.