Man adapted physically as well as culturally to the new surroundings into which he moved. Those who stayed in or moved to equatorial climates developed dark skin to protect them from the rays of the Sun. Those who moved to colder climates developed light skin to take advantage of the sunlight for the synthesis of vitamin D. People in cold dry climates became stocky, to conserve heat. People in hot dry climates tended to become tall and thin, to dissipate heat.
人们在身体和文化方面需要去适应新迁入的环境。 那些生活或迁入到赤道气候地区的人， 皮肤会变黑以抵抗太阳光线。 那些迁入到更冷气候地区的人， 皮肤颜色会变淡， 从而利用阳光合成维生素D。 生活在寒冷干燥地区的人变得矮壮， 以存储热量。 而炎热地区的人则更高更瘦， 以利于散热。