Modern europeans may have acquired genes that them adapt to the cold and absorb more vitamin d through interbreeding with:

Around 100,000 years ago there was a second hominine species closely related to modern humans,  Homo neanderthalensis, or commonly called the Neanderthal. Recent studies of neanderthal DNA have shown that there is 3-4% of their genes in modern humans outside of Africa, mostly from Europe, including the ones for adapting to the cold and vitamin D absorption. 

Cis the right answere

Nerves are problay the number 1 thing in the body