See the Vortex

Hypothesis: White People are susceptible to commensural microbes that biohack their immune systems to adjust their metabolism to extremes in sunlight and weather.

I believe our metabolisms have been optimized (by microbes) for work in the summer and hibernation in the winter.

Way back when... let's say 20 or 30 thousand years ago, there were migrations of people going up into Northern Europe. Probably along the west coast, up to the North Sea and Scandanavia. (or it may have been from an earlier migration, and these were Caucasians coming back from the east)

It is clear that the people who survived are the ones who carried mutations for traits that were beneficial in high latitude areas-
Like lighter skin. And blue eyes. And more Vitamin D production. And lifelong lactose tolerance.
My theory is, they also have genes that promote tolerance for certain microbes. Some epithelial change that facilitates permanent colonization. (Nasal Strep is common, but Staph is too)

And the reason for this is because the immune system is triggered by light, and this modifies metabolic activity due to seasonal changes.
In specific, we predictably get sick in winter and that makes us tired. Which reduces activity and metabolic expenditure.

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This is how the yearly circadian cycle goes if you're a Neolithic Northern European:

When the sunlight lessens in Autumn, orexin levels lower and metabolism changes. Insulin resistance increases. The harvest season provides for carbohydrate loading and fat storage.

Then cold weather facilitates an initial viral infection which then lowers resistance to bacterial infection. And everyone goes inside and infects each other.  And becomes Vitamin D deficient.

The persistent bacterial infections lower orexin levels more and slows down metabolism and activity. Stored grains are more easily turned into body fat, and then burned slowly. But alcohol induces obsession, which facilitates repetitious tasks like weaving and tool making. Or storytelling and memorization.

When the days get longer- orexin levels increase, and the immune system ramps up again.
Metabolism increases and vitamin D levels too. The infections subside. By the time it's warm, people are active, and may even wash themselves.

Long days and lots of work and less available carbs promotes ketosis and mania. This is helpful if you have to farm and your warm season is only a few months long.

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We are slave zombies controlled by parasites.
(Parasites that like to eat bread and drink beer.)

Migration to sunnier places, or artificial light and temperature and a year-round constant schedule mess all this stuff up, of course. Not to mention modern diet, medicines and antibiotics. They turn this mechanism inside out.

See the Matrix.