On this particular thread, someone answered that the fact that there are diseases that only Blacks suffer from demonstrates that there are many races.
Whether the member of whom you speak was motivated by a racist attitude, or merely ignorance, cannot said with any reliability. However, this canard has been trotted out many, many times, and tends to get repeated, uncritically, because of ignorance. The big claim of this type centers around sickle-cell anemia. This condition is prevalent in west African negroes, and by sheerly evolutionary means, tended to get centered in blacks who were used as slaves in the New World--the plasmodium which is responsible for malaria colonizes red blood cells in the quaternary stage of its life cycle, and therefore, is at a disadvantage in persons with sickle cell anemia. People with that condition have a greatly probability of surviving malaria, and being (somewhat) productive workers thereafter. Slavery did not immediately take hold in the mainland North American colonies, until heavy competition in monocultures became common in the 18th century--tobacco, rice, cotton. It was not until the late 17th and early 18th century that slaves were commonly purchased in the mainland colonies (Virginia, Maryland, the Carolinas and Georgia), and they then tended to be purchased in the West Indies--the islands to which west African negroes had been brought by slave traders. Therefore, sickle cell anemia was "selected" by the concommitant prevelance of malaria (brought to the New World by Spanish soldiers who had served in Italy at the end of the 15th and beginning of the 16th centuries), and therefore, Americans of African descent have a high probability of sickle cell anemia.
But sickle cell anemia does not occur only in west African blacks--it is also known in some people of the north African coast, and in the middle east. From an original population with the trait, it might have spread to these other populations. But the problem the racist point of view has is that racists consider blacks ("negroid" people) to be a separate race from the Berbers of north Africa, and the Semitic peoples of the middle east. Compounding the problem for this racist fairy tale, is that sickle cell anemia is also common in east Asia, and Polynesia. It is not terribly common in Polynesia, but it is there--and the history of the settlement of Polynesia suggests that it was present in the oldest population to colonize those islands. It is most common in east Asia in the Korean penninsula, and it is thought that the prevelance of the disease in China and Japan results from Korean migration. For the racists to claim that diseases are race-centered, they must ignore mountains of contradictory data--which is why i say that anyone making such claims is either ignorant, or racist.
Diseases are often not
hereditary, and only appear to haunt a particular race or ethnic group. So, to return to the Koreans, a common disease in the Korean penninsula is epidemic hemmorrhagic fever. It has been alleged (by racists) that this is a disease which has an ethnic origin. But EHF can be caused by several pathogens, and it has been known for centuries to be common in the Korean penninsula and
the Crimean penninsula. EHF is actually a description of the rapid, sympotomatic decline of the victim, and the most recent version of the disease was first identified as EHF, before it was know that the west African variety is caused by the Ebola virus--in Asia, it is caused by a hantavirus.
Generally speaking, claims about race-centered diseases are evidence not simply of the ignorance of those who actually believe that separate races exist, but their ignorance of diseases and epidemiology.