By Maciamo Hay,
on 6 May 2014
What physical or mental enhancements are possible through gene therapy ?
Altering our genes provides an enormous potential for personal enhancement, life extension and cosmetic modifications. But we are not entirely the products of our genes. The environment also plays a big part in modelling who we are. With this in mind, let's see how much we can expect from gene therapy to enhance our lives, or from genetic engineering to design future generations.
As a follow up of last week's article Fix diseases and improve yourself through gene therapy, I would like to review exactly what part of our health, intelligence, personality, physical appearance and psychological traits is rooted in our genes, and consequently can be altered through genetic engineering or gene therapy, and what part is environmental, and therefore cannot be modified by those methods.
Purely genetic factors
Fixing genetic disorders, especially single gene diseases like cystic fibrosis or Huntington's disease is the original aim of gene therapy. These conditions can in theory be completely cured by gene therapy.
Someone's physical appearance is almost 100% determined by genes, as demonstrated by the case of identical twins, who look, well, pretty much identical, apart from subtle differences. However the genetics of morphology is extremely complex. Genes only code for proteins and give very basic building instructions.
Altering one's eye or skin pigmentation is relatively straight-forward, but when it comes to modifying facial features or even body height or structure, it will probably takes several decades before we understand all the underlying genetic mechanisms and even longer before we can effectively determine how to apply them to redesign a person's traits. Even once this becomes possible for designer babies, there will still be obstacles in altering the morphology and facial traits of grown-up individuals.
Muscle mass, body fat, metabolism, skin tone and the like could all theoretically be changed by relatively simple genome editing procedures. In practice, it is doubtful that the bones of adults can change size and shape simply by modifying the DNA. The genes only provide the recipe for building a body. Once it has been built, changing the recipe won't alter it. Even if genes could be tricked into being reactivated, so as to restart the building process (e.g. using stem cells), there is no guarantee that this will be safe or pain-free.
Mixed genetic and environmental factors
A lot of diseases like cancer or cardiovascular diseases are not caused solely by genes, but depend on many environmental factors such as nutrition, stress, pollution, sleep deprivation, and so on. Some genes do confer a protective effect against some conditions, while others can moderately or greatly increase the risks of developing some diseases. Often these genes only affect disease risks indirectly, for example by increasing cholesterol levels or blood sugar levels.
The reason why some people have riskier versions of those genes is that human diets have evolved tremendously over the past 10,000 years. Genes that may have been beneficial with a hunter-gatherer's diet (much less caloric) and nomadic lifestyle (involving a lot of walking) in a cold environment (requiring to burn a lot of calories to keep warm), would become deleterious in people with a sedentary lifestyle with high-caloric intake.
Therefore it could be argued that humans ought to adapt their genes to their modern lifestyle, rather than wait tens of thousands of years for evolution and natural selection to do the job. In fact, natural selection wouldn't do the job anymore for the simple reason that virtually all humans live long enough to reproduce before succumbing to genetic maladaptations nowadays. As a result almost all genes get passed on to the next generation without selective pressures.
Intelligence can mean different things to different people. Looking only at IQ scores, the consensus in scientific research, notably identical twin studies, is that between 25% and 75%, is attributable to DNA. That's an average of 50%. The rest depends on environmental factors such as nutrition, education, motivation, opportunities, etc. In other words, altering our genes to increase our IQ would only partially work.
Someone with an IQ of 150 is 50 points higher than the population average (which by definition is 100, and is recalculated every year). It could be that that person really possesses exceptional genes while at the same time growing up in a terrible environment, in which case the genetic factors could be considered to represent most of the 50 extra IQ points. But conversely someone who grew up in an exceptionally nurturing and intellectually stimulating environment, with an ideal nutrition for brain development, could essentially have developed an IQ of 150 through environmental factors with very average genes for intelligence. Besides, there are many types of IQ tests (verbal, visuospatial, logic, problem-solving), and IQ only represents one fraction of our overall intellectual capabilities.
That is why it is so difficult to know at present what genes are truly associated with increased intelligence. Without knowing it, there is no way of enhancing the genes. Even if we could identify the right genes, given that the childhood environment plays such an important rile in brain formation, would it really have an effect on adult brains already filled with synaptic connections ?
If genes for intelligence increase the number of neurons or the brain structure during the embryonic development, then gene therapy on adults and even on children wouldn't have any effect. There may also be genes that modify the way neurotransmitters work, or help strengthen synaptic connections more quickly. Such genes could enhance mental faculties in adults, although the effects would probably be limited to having a better memory and thinking faster, rather than having great capacities at solving problems or having a musical aptitude.
Additionally, genes linked with better cognitive abilities can also cause negative psychological traits, such as higher anxiety, depression or schizophrenia. It would be inconsiderate to attempt to increase one's intelligence through gene therapy simply by getting as many genes as possible associated with higher intelligence. Working all together those genes may overshoot and cause crippling mental disabilities instead of a well-balanced intelligent person.
Mostly environmental factors
Identical twins, who possess virtually identical genomes (bar a few mutations), develop different personalities. They may share a similar temperament or similar political orientation or religiosity, all traits that have a moderately high genetic predisposition. It has been estimated that only about 20 to 40% of an individual's personality traits is set in his/her genetic code.