This boy, found at Nariokotome on the banks of Lake Turkana, was athletically built, with a tall slim frame much like those of the people who live in the same region today. This build makes for a high surface area over which the body can be cooled by sweating. Sweating allows us to lose heat from the core of our bodies and keep ourselves at a healthy temperature. It is likely that the Nariokotome boy sweated to keep cool as well, since Sub-Saharan Africa was just as hot 1 million years ago as it is today. If he sweated, then he probably had little body hair.
Hair interferes with the sweating process, which works more efficiently through naked skin.
However, if Homo erectus had little hair, he may have burned in the hot sun. It is likely that his skin developed dark pigments to protect him from burning. This species was the product of millions of years of evolution in Africa, yet it left the continent soon after it evolved. The earliest members of Homo erectus are found in Africa at 1.8 million years ago, and in Asia 1.7 million years ago. It seems that one of the features of this new species was the ability to adapt to new places and new situations, an ability that we recognise as being fundamentally human.