Anyone with a clever mind and funded time can develop many wonderful graphs.
Doesn't make them plausible, though. It begs an explanation for the varied colors of man, blacks in Austrialia and India, Negroes in central Africa, a different race in southern Africa, without mentioning the rest of the world.
All of this is well understood. There are many excellent works on human races.
For example, if you had read one of these books you would know that Australoids are a distinct race, quite different from Negroids.
The dark skin is an adaptation to intense sunlight.
This distribution of skin color and its geographic patterning—with people whose ancestors lived predominantly near the equator having darker skin than those with ancestors who lived predominantly in higher latitudes—indicate that this attribute has been under strong selective pressure. Darker skin appears to be strongly selected for in equatorial regions to prevent sunburn, skin cancer, the photolysis of folate, and damage to sweat glands (Sturm et al. 2001; Rees 2003). Source