INTERRACIAL VOICE

Essay

Genetic Closeness Belies Racial Separateness
By Emory Curtis

It is hard to believe that President Clinton expected Professor John Hope Franklin's committee to do the impossible and bring races together by talking a talk that started in the early sixties. It didn't work in the early sixties and it won't work in the late nineties.

For talking to work, the talk has to spring from a different premise than the equal rights premise of the sixties. Molecular biology offers a premise with hope; molecular biologists have found that there is less genetic differences within the human race than there is between two gorillas in an African forest.

Amazingly, scientists have used messages in our DNA strings to pinpoint those most suspectable to certain diseases and those with immunity to certain diseases. In court cases the DNA message has been used to positively state whether or not the accused fathered the child and whether a drop of blood at the crime scene came from the accused or not. Also DNA technology is the base of the new approaches to fighting old diseases that is so much in the news today.

Decoding DNA messages in the remains of the supposedly Unknown Soldier in the Washington, D. C. crypt has moved those remains from the ranks of the unknown to the knowns. The ability to read DNA messages long after the body has left the realm of the living makes it unlikely for any new Unknown Soldier's remains to be put in the crypt.

DNA's (deoxyribonucleic acid) thin cobweb-like strands consists of individual chemical bases of adenine (A), cytosine (C), guanine (G) and thymine (T). We have two kind of DNA -- mitochondrial and nuclear -- within our bodies.

Within the nucleus of each cell in our body there is a six foot double helical strand of DNA that consists of about three billion bases packaged into twenty-three pairs of chromosomes numbered from one to twenty-two plus a couple of X chromosomes (female) or an X and Y pair (male). When a cell divides, the strands separate and each grows a second chain that is an exact duplicate of the original strand.

When the egg meets a sperm and becomes fertilized, that single fertilized cell has DNA that comes equally from the father and mother. That single cell has all of the information needed to make a unique individual. Developed human bodies have a hundred million million cells of all types and every single one of them have all of the information that was carried by the DNA in that first fertilized cell.

The other set of DNA in our bodies, mitochondrial DNA, is within each cell but outside its nucleus. That is the embryo's energy source. Both the egg and the sperm have mitochondrial DNA but, when they combine, only the egg's mitochondrial DNA is kept and passed on from mother to daughter to granddaughter, etc.

With all of the copying and replications of DNA over the millennia as cells combine, there are occasional errors made where, for example, a C replaces a T or a sequence is dropped. Scientists have a handle on how often mutations occur in both mitochondrial and nuclear DNA.

The longer a population group has existed, the more diverse will be their DNA because more mutations will have occurred. Gorillas have been on this earth longer than man; that is why the mitochondrial DNA of an Eskimo in Alaska and an Australian Aborigine are less diverse from each other than the mitochondrial DNA of two gorillas from the same forest in Africa.

Studies of mitochondrial DNA have been made that traces the origins of all humans on this earth to a small band of hominid who lived in sub equatorial Africa about 200,000 years ago. About 100,000 years ago some of those early humans began moving out of Africa to populate this earth.

Interestingly, Yale scientists have searched nuclear DNA to find variations peculiar to different populations. On chromosome 12 they found interesting variations in the genetic material called polymorphisms which often serve no purpose.

They found that some people lack a long piece of DNA that contains 250 of A, C, G and T bases. That is called a deletion. They also found that people had four to fifteen repetitions of a CTTTT base. None of those variations had anything to do with the genetic well-being of the individuals.

In sub-Saharan Africa individuals were found with every variation of repetitions and deletions in their DNA. However, in the rest of the world, a very different pattern evolved. Chromosome 12s with deletions had only one pattern of CTTTT repeats, a sixfold one. Chromosome 12s without that deletion only had CTTTTs reiterated five or ten times.

The only feasible explanation for that finding is that a small group of sub-Saharan Homo Sapiens left Africa about 90 to 100,000 years ago and ended up conquering the world. That group, which includes us, has little genetic diversity and wide geographic diversity.

The presidential mandated conversation on race is a focus on our geographic diversity of origin (a focus on differences); that in itself is divisive. The focus ought to be on the closeness of our genetic heritage. Over time, that can be a healing process.

Don't for one moment think I'm a genetic or DNA expert. For this column I drew heavily from an excellent book, African Exodus by Christopher Stringer and Robin McKie. I highly recommend it. Contact me by phone (916-988-4439), FAX (916-988-5928) or e-mail (eccurtis@earthlink.com).