Why did caucasians develop longer larger torsos and shorter limbs on average after moving out of Africa

Statistically blacks have shorter torsos, and longer arms and legs.

While whites etc have longer larger torsos and shorter arms and legs.

Why did we evolve this way?

Europeans, or the descendants of Cro-Magnon man, invaded Europe about 35,000 years ago, during the last ice age. Modern humans, however, had begun migrating out of Africa about 60,000-80,000 years ago. The earliest archaeological evidence of human beings outside of Africa is in Australia, not Europe, even though Europe was much closer. Why did it take so much longer for modern humans to occupy Europe compared to, say, Asia and Australia? The answer is that Europe was in the depths of an ice age (which causes droughts in Africa and which in turn drove the Africans into migration out of Africa searching for food), and there were Neandertals in Europe, and they were superbly adapted to the cold climate. Modern humans that had just migrated out of Africa were adapted to a dry tropical climate. Y chromosome genetic markers show that the Europeans originated in the Steppes of Central Asia. After migrating out of Africa, a group of humans spent tens of thousands of years in the Steppes, adapting to a cool climate, before they were able to conquer the ice age climate of Europe.

It is true that Europeans have shorter limbs than Africans. This is known as Allen's rule:

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Allen's Rule

In 1877, the American biologist Joel Allen went further than Bergmann in observing that the length of arms, legs, and other appendages also has an effect on the amount of heat lost to the surrounding environment. He noted that among warm-blooded animals, individuals in populations of the same species living in warm climates near the equator tend to have longer limbs than do populations living further away from the equator in colder environments. This is due to the fact that a body with relatively long appendages is less compact and subsequently has more surface area. The greater the surface area, the faster body heat will be lost to the environment.