There is no such biological evidence to prove such a statement. However, all humans represent a single species that is homo sapiens because they have a common body structure, physiology as well as metabolism. In genetic makeup too, they all carry 23 pairs of chromosomes and the fun fact is that 99.9%v of DNA of al the human beings is the same. Humans can inter-bred with each and produce offsprings. Although some of the early studies indicate that the evolution of human beings began from Africa and from that all of the other Asians, Americans and Europeans have evolved further from a common ancestor.