Remember the big excitement when the first sequence of the human genome was announced in 2000? It was hailed as the “book of Life”, and the proof that humans are 99.9% genetically identical, regardless of race. Well, not so fast. If we are 99.9% identical, how come we are so different from each other? How is it that Caucasians, Chinese, and blacks are so different not only in the pigmentation of their skin, but also in susceptibility to diseases, for instance?
The genetic belief in “liberté, égalité, fraternité” quickly gave way to a more nuanced view of human diversity, when a new set of data was published recently.
It turns out that the metaphor of a “Book of Life” does not really capture what is going on in our genomes. As Erika Hayden wrote in Nature, the wiki, constantly being modified, corrected and updated, is a more apt metaphor. This new view is the result of a project, called the HapMap, which catalogs the variation seen in 270 people from America, Japan, China, and West Africa. These variations are called SNPs (pronounced “snips”), and what these “single nucleotide polymorphisms” represent are variations in a single nucleotide in a single place in the gene sequence. For instance, amino acid F (phenylalanine) may change in a certain population to Y (Tyrosine). Now, if this change happens to be in a gene that codes for an enzyme that is making melanin, for instance, people with F will have the original amount of melanin synthesized, whereas people who have the Y version, which happens to be less active than the F version, will have less of it. This is the genetic basis for the difference in skin pigmentation between blacks and Caucasians. Truly amazing how such a minute change, one base pair change out of 600,000 base pairs in our genome, can cause such a remarkable change, and so much injustice and suffering.
The benefits of the HapMap
Some benefits fall in the realm of satisfying curiosity. A growing cottage industry is providing customers with information about what percentage of their ancestry is African, Asian, European, or from the Americas. But there is also very useful information in the medical field. Blacks suffer from a very specific, genetically determined cause of hypertension. Now, there is a tailor-made drug, BiDil, to treat it. Jews of Eastern European ancestry suffer from a mutation that was traced to a 17th century Polish family. The disease is called Tay-Sachs disease, and Ashkenazi Jews are offered prenatal tests for the genetic disorder. The list goes on and on. The one that I like the most because it has the potential to transcend the strictly medical field is called G6PD deficiency. This is a point mutation, another name for SNP, that results in a metabolic disorder of glucose metabolism that results in hemolysis (breakdown of red blood cells), which usually occurs under stress of infection, fever, etc. The disease is painful and life-threatening if not treated. So guess who is susceptible? People of Eastern Mediterranean ancestry. In other words, Sephardic Jews and Arabs. Now, can you think of a better indicator of common origin? Or a more humane, and human, unifying concern than health? Could a peace talk conference begin by discussing this common concern, and the Israeli side offering its know-how, gratis? This is the hopeful side of human genetics.
The dangerous aspect
Wouldn’t you expect non-scientists with an agenda to pounce on this treasure trove of new genetic information and mine it for support of theories they are bent on proving? Indeed, all you have to do is trawl the web and find bloggers who are at best uninformed, and at worst malignant, pure, and simple, claiming that blacks are less intelligent than Caucasians. Indeed, one of the facts they cite is the publication by geneticist Bruce Lahn from the University of Chicago claiming that two genes linked to cerebral cortex volume had evolved rapidly in groups that migrated out of Africa about 45,000 years ago. His results met with withering criticism from scientists because he simply didn’t have the evidence for such a claim. Indeed, these genes have not turned up in the HapMap, another nail in the coffin for his unfounded claims.
But even if his claims were true, they prove absolutely nothing. Here is why:
- Intelligence is a multigenic trait, meaning that it is controlled by many genes; we don’t even know how many are involved.
- There are many types of intelligence: cognitive, emotional, social. It is quite unlikely that the same genes control all types of intelligence.
- Genes don’t act in isolation—they interact. Imagine the complexity of unraveling those interactions if there are only 2 genes involved. Now imagine 3 genes: gene 1 interacting with gene 2 and 3, gene 2 interacting with gene 3, and all three genes interacting with each other simultaneously. Quite complex. But this is really just a simplified example because the likely number of genes involved is bound to be closer to ten than to two; each of the ten interacting with the other nine. The level of complexity is mind-numbing.
- The environment is interacting with each of those genes, modifying to different degrees the action of each gene in isolation, and the interaction of each gene with the other genes.
Can you see the level of complexity we are dealing with when it comes to multigenic traits like intelligence?
The danger of people of ill-will using snippets of genetic information for their malignant purposes reminds me of the Eugenics movement, which claimed that one could enhance the health and well-being of the human race by “breeding out” unwanted traits. The logical conclusion of such misreading of Darwin was the Nazi concentration camps and the ovens, where over 6 million Jews, Gypsies, Slavs, homosexuals, and the “mentally deficient” were incinerated on the altar of the Aryan race.
Science will march on, it is unstoppable. Indeed, we cannot and should not muzzle the truth. But it behooves us to be vigilant that facts should not be twisted to deform the truth.