So i figured, each of us belongs to a non-existing tribe (being in Portugal my anscestors might have been celts, though i can’t know for sure), and our bodies have evolved accordingly to what they ate, so it shouldn’t be so linear as the food piramid (http://www.hsph.harvard.edu/nutritionsource/images/pyramid215px.gif). Some people probably may be healthier only eating vegs, other eating mostly meat.
Does that make biological evolutionary sense?
Another question i have is, we have started drinking cow milk 10k years ago (according to wikipedia http://en.wikipedia.org/wiki/Milk), is that time enough for a tribe to evolve genes that make them capable of digesting cow milk?
What other foods have we never ate before, or started eating recently? ( and by recently 10k years should be the limit)
There are certain types of food tolerances/intolerances that are somewhat regional/racial, but I doubt if they would ever amount to so extreme a case as being better suited to eating entirely one thing or another. Generally speaking, we’re suited to eating a little bit of everything - with exceptions for individuals, regional food intolerances tend to reduce that to eating a little bit of most things, instead.
Lactose intolerance is an extremely simple issue biologically.
With a few exceptions (the monotremes, the pinnipedia), all mammals have lactose in their milks. And all mammals manufacture the enzyme lactase to digest (break down) the lactose into the simpler sugars glucose and galactose to digest mother’s milk. Since there’s no need for the continued manufacturing of lactase after the age of weaning, the body stops doing so.
However, the proteins that signal this change come from a single gene on chromosome 2 (in humans). All it takes is for a mutation to occur to this gene so that the signal never goes out. This is a mutation that happens regularly in humans. Gene studies have identified 43 separate variations in current humans. In addition, the never stop gene is dominant.
Despite what the anti-milk forces say, animal milk is an extremely good food in the greater scheme of things. It’s packed with nutrients and vitamins. It’s as adaptable as any type of food we know, creating everything from hundreds of cheeses to yogurt to whipped cream to chocolate milk. It can be dried. It can be turned into forms that will last for years.
The ability to digest lactose as an adult therefore has survival advantages. The extra calcium can make for better bones and can help woman survive childbirth. The advantage doesn’t have to be huge. Population genetic studies have found that a 3-5% survival advantage will spread the gene throughout a population in 5000 years, more than the time since the start of herding and dairying.
We started processing grains at about that time. Beverages like tea, coffee, and chocolate are recent. Lots of foods we take for granted today developed after the last ice age when conditions were right for humans to stop being nomadic hunter-gatherers and turn to agriculture and herding.
As for the rest of your question, while there are undoubtedly differences in the optimal diet for certain individuals, human are omnivores. There is literally no usable food that has not been part of some culture’s diet somewhere on the planet at some time in our history. Anthropological studies show that tribal diets vary from nearly all-meat to nearly all-plant depending on what foods are available locally, without the slightest sign that any particular diet is better overall for health.