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Originally Posted by tom sawyer
We all know the reasoning behind the success of the various low carb diets. Its because our ancestors ate this way and we are adapted well to it, modern agriculture and the advent of plentiful carbs being a relatively recent development (10,000 years give or take). We also hear a lot that genetic adaptation takes much longer than this, like 100s of thousands of years.
My question is this. If it takes so long to develop and adapt, why has there been such a large change in the looks of man over the last 100,000 years? And how is it that we have adapted such different features in the various cultures across the world? It would seem to me, that the differences in how we look from each other, and from our distant ancestors, says something about the rapidity of genetic change.
Whats more, we have cultural groups who have been at dairy farming in some form or fashion for thousands of years, and these folks are better adapted to these sorts of foodstuffs. Thsi also seems to fly in the face of the notion that it takes hundreds of thouisands of years to adapt to changes in our environment.
I'm not questioning the idea that low carb is the way we are adapted to eat. That seems obvious based on what it does for your body. But I'm wondering if we aren't capable of adapting to grains faster than people want us to believe. Certainly not within any one person's lifetime of course.
Anybody other amateur evolutionary biologists have opinions on this subject? It would seem to be an area of the philosophy behind low carb, that is open to criticism.
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Here is how I understand it...
Of our genetic material there are genotype traits (your species) and phenotype traits (variance among members of a species).
The genotype is everything that all members of a species have in common. Because you can assume how difficult and time consuming it must be to spread a trait and cement it so deeply, an evolution in genotype and the evolution of species takes thousands and thousands of years of selection.
Phenotype is everything "else" in our genes, the subtle variances that makes us individuals. Changes in phenotype tend to be relatively insignificant, they may give an advantage or disadvantage relative to other members of your species (i.e. those with the same genotype) in varying environments, but generally speaking phenotype differences are small. The more related you are to another member of your species, the more insignificant the difference in phenotype will exist. For example, members of a nuclear family are very very similar and have relatively small differences in phenotype. They are so closely related they often can be mistaken for twins (like me and my sister often are). Then there are collections of families within a race. Families of humans which come from similar environments have more significant differences than related individuals, but they are still relatively small. Finally there is race. The difference between collections of families from different environments have an even more significant difference, but still in the grand scheme of things even racial differences are relatively insignificant. They are still confined to things like skin, eyes, hair, and other slight and/or superficial variances.
In other words, all ways in which humans are different among themselves is a phenotype difference. Changes in phenotype come about in response to recent (well recent on the evolutionary timeline) and/or subtle changes in environment. Blacks have dark skin because of the strong african sun. Higher melanin concentration works like built in sunscreen to protect them from it. On the other hand, whites have light skin because the frigid north did not give them enough sunlight, so they adapted by selecting for a paler complexion more sensitive to sun. The significant lack of melanin in the european complexion was an advantage... it allowed him to make the most of the sunlight he did get. The recessive nature of a light complexion implies that it is a more recent change, which implies that the phenotype of europeans (and all associated traits) are relatively new.
So you see human groups selected for different complexions due to the different environmental pressures in the regions where they lived, but these changes are so small and transient that they are not characteristic of an evolutionary branch off into two separate species. Despite superficial differences, blacks and whites share the same genome and are most definitely the same species.
Metabolic preference among races/families/individuals is also reflected by phenotype. Africans, native americans, australian aborigines and other newly modernized hunter gatherer peoples do very poorly with the grain based diet that european man eats. They never were exposed to it before, so they have a very low tolerance for these insulin spiking foods. Unsurprisingly their rates of obesity, diabetes, and heart disease are much much higher than white man. The insulin-sensitive phenotype is much more prevalent in the white racial group as it was an evolutionary advantage, since white people switched over to a very grain based diet.
Even though grain dependent cultures did start to partially adapt to the diet, we've been introduced to grain so recently that we, the human species, mostly still can't do well on it. Some phenotypes (those that descended from grain dependent cultures in particular) are very insulin sensitive and have a very low susceptibility to obesity, diabetes, and heart disease. For most of humanity this is not true.
The difference between genotype and phenotype is kind of like other classifications systems invented by man - it tries to make exact something which in nature is not exact and is far to expansive to ever be classified and organized. There is no hard line objective difference at which point a change is so prevalent and so intrinsic and so crucial that you have "old species" and then "new species". Humans invented the definition of a "species" and "genotype" and "phenotype". It is an entirely subjective classification. In nature there is no such thing as a "carnivore" and an "omnivore" and a "herbivore". There are no hard lines. For example, almost all carnivores eat some vegetation. Many herbivores eat insects and will eat meat if they can. Many if not most omnivores are not as unbiased as the label would imply, for example human beings have a distinct metabolic preference for a primarily meat based diet.
This is just of course my largely uneducated opinion on the subject so take this with a hearty grain of salt
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