The races, so called, emerged from a common ancestry through adaptation, or the survival of the fittest. Those possessing the genetic traits best suited to the conditions of the place that they found themselves.
Up north, the ability to ingest milk and cheese as an adult was important for survival during the winter when food was scarce and you had to rely on stored food (e.g., cheese) and milk from livestock. Accordingly, the humans with this trait tended to survived to reproductive age, and their genes were passed on. In the tropical zone, the ability to ingest milk as an adult wasn’t significant. So, the trait enabling the ingestion of milk as an adult did not come to dominate.
In terms of “master race,” each race was the master race of its local conditions.
There are other genetic traits and cultural norms that differentiate humans by latitude. For example, immunity or lack of immunity to diseases of the jungle, skin pigmentation (since we are mostly hairless), certain kinds of muscularity. I don’t know that anybody has a complete list.
Nowadays, such differences are of little consequence. We have taken control of local conditions, e.g., heating and air conditioning. Pale-skinned humans can put on sun block or stay indoors most of the time when in the south. Lactose-intolerant humans - like other humans - can eat any kind of food they like in the north, through purchase of food at a supermarket.
But, instead of studying race from a scientific perspective, progressive-socialists choose to politicalize the subject because it’s in their political advantage to sow hatred and to pit us against each other.
This reminds me of some black woman forty years ago complaining she could not give her kids milk because they could not digest it.
Then she went into a rant on how if White people had the same problem “they” (who the Hell is they) would make milk tolerant for the white folks, there fore they were racist not to make milk for blacks to digest.
At that time Acidophilus and lactose free milk was beginning to hit the shelves.
This reminds me of the first meeting between VIKINGS and Indians(Skraelings) about 1100 years ago.
They shared food and got along fine, then the Vikings broke out the milk products they had in their ship and shared. All was well.
Several hours later, the Indians started vomiting up the milk and knew they had been poisoned so they attacked and drove away the Vikings.