@Green
I'm sure he's talking about Sickle Cell Anemia. I'm no expert on genetics, but my understanding is that it's caused by a recessive gene, that is very common in people of West African descent. If two people of West African descent have children, there is a very good chance that both will at least be carrying the gene, and therefore pass it along to their offspring, who will have an increased chance of having a full blown case of the disease.
What this moron likely fails to comprehend is that sickle cell anemia was at one time beneficial, and in some parts of the world still is. People who have it, are far less susceptible to malaria, than those who don't, and therefore more likely to live long enough to have children.
It does shorten the life span, but a single malaria outbreak could kill off entire villages, many of whom would be well under 40--people with sickle cell anemia tend to die between the age of 45-50. People in developed nations take for granted living to reach their 60s, 70s, or beyond, but in in undeveloped parts of the world, living past your 30s is still a real achievement.
It's also not just a black thing. It was/is also common in the Mediterranean, Middle East, and India. As malaria has become less of a problem in those regions, sickle cell too has become far less common, because people not carrying the gene are also living long enough to reproduce. In fact, African-Americans today are less prone to it than people in West Africa, and the number of diagnosed cases continues to fall.
Also, I don't mean to sound like I'm saying sickle cell is a good thing per se. People that have it do have some very serious health issues because of it. It's just that from a evolutionary standpoint, their ancestors were the people who were better capable of long-term survival, which probably doesn't make them feel any better about having it.
