What does genetic determinism mean exactly? If it means genes determine physical and behavioral phenotypes, that is certainly true. However, if it means that genes alone determine phenotypes, that is a fallacy. As Philip Kitcher observes, in The Lives to Come, both genes and environments play critical roles in the formation of phenotypes (239). This is not as obvious as one might think. It appears that diseases like Huntington’s are dependent solely on the occurrence of particular combinations of alleles (in the case of Huntington’s an overlong CAG repeat). Environment seems to have little or no impact. There are quite a few cases like this.
However, in other cases, genetically determined diseases are clearly affected greatly by environment. A classic case mentioned by Kitcher is phenylketonuria. PKU is a genetic disorder characterized by a deficiency in the enzyme phenylalanine hydroxylase (which converts phenylalanine to tyrosine). This deficiency is genetically determined but it can be treated (with debatable efficacy) by creating an environment in which phenylalanine intake is drastically reduced. Genetic abnormalities can be responsible for hypercholesterolemia and cancer but these diseases can also be caused by environmental factors, poor dietary choices and exposure to radiation/pollutants respectively.
These examples are not very controversial. Where things get hairy, however, is when people try to prove that intelligence, aggressive tendencies, or sexual preference has a genetic basis. There is research out there that draws out causal connections. Here is one example: stimulation of the hypothalamus or amygdala and reduced activity in the prefrontal cortex causes or augments violent behavior. However, in all these cases, individual-specific environmental factors should also be taken into consideration. Assuming two children had a genetic susceptibility for the same disorder, a child raised in a nurturing, stable, affluent environment could potentially and would presumably be less affected or unaffected by the disorder than a child denied love/resources and exposed to negative influences/toxins.
There are other tricky issues. Problems arise when people use use genetic information to reinforce prejudices and carry out exclusionary policies against members of a particular gender, race, or creed. In fact, genetic discrimination has already been carried out against African-Americans (who have a high frequency of the sickle cell allele) and Ashkenazi Jews (who have a high frequency of the Tay-Sachs allele). Kitcher states, “it would be wrong to suppose that inequality in genetic distribution represented grades of superiority and inferiority among races” (154). I agree. The danger with the genetic determinism argument is that it transforms all difference into pathology and lessens our tolerance for the diversity of human life. However, for me, it is not wrong to take life away to ease or prevent suffering. A mother should have the option to abort a fetus that shows signs of a genetic disorder if it jeopardizes her health. A patient should have the option to request release from a terminal disease. Still, it’s not right to treat humans like commodities. Do we have the right to assign a value to human life and casually discard people with defective genes? Defective genes does not mean a person is automatically a failure. It does not mean that they will never make any significant contributions to humanity. Determination, hard work, and passion can make up for lack of natural ability. Genes cannot determine destiny… at least not completely.