Tuesday, June 7, 2011

Random Thought: Genetics, Evolution, & Eugenics

A recent slew of articles in Science caught my attention. All the papers highlight the effect of epistatic interactions between beneficial mutations can cause a decline in the rate of increase of fitness of the population1,2,3.

A little background first. Evolution is the process by which a population changes in order to adapt to some selective pressure. This usually occurs by the weeding out of individuals who are not as fit as the others. As this occurs the fitness of the population as a whole increases.

In the lab we can study evolution in bacteria. We expose bacteria to a selective pressure and see how they adapt and evolve. With gene sequences we can tell exactly which genes have been altered/selected. The researchers of these papers did exactly this. In the one paper, researchers took, the bacteria and exposed it to low glucose (main food source) environment and looked at the adaptations that resulted2. The saw that there were five mutations that were being incorporated into the bacteria.  They showed that the decreases in the increases in the fitness could be attributed to negative epistatic (gene-gene interactions) effects between the beneficial. While I did read the paper I didn't really understand, it seems they did some math magic and some other stuff (not an evolutionary biologist, didn't really get everything they were talking about).

Anyways, this got me thinking about the current state of human evolution. In my opinion, humans are currently in a state of evolutionary limbo. Our technology, medicine (courtesy of our intellect) have overcome any environmental stimulus in place of any biological adaptations.People of all shapes, sizes, intellects, colours, dispositions, et cetera are breeding without regard to the increasing fitness of the human population (some breed merely for the concept of 'love'). There could, of course, be selective pressures that I am not taking into account (irony will probably have radio waves or some such man-made thing become our next selective pressure). Some have presented the solution to this problem: artificial selection.

Eugenics is process by which humans select traits that they wish future populations to have and breed accordingly. Eugenics also includes the selective breeding out of certain traits/diseases. Using this, we could theoretically, artificially evolve humanity. This is an impractical method though, for all of humanity would have to abide by the eugenics program (or at least one large enough to branch off into its own species). I'm of two minds on this topic.

On one hand, I wouldn't mind humanity evolving into a bunch of beautiful genius olympic-level athletes. By doing this we could accelerate our technological advancements as well as increase our physical preparedness for disaster. One of my fears is that our brains will become a limiting factor in our technological development. What happens when to advance the current state of science we have to study for 40 or 50 years just to get caught up. What happens when the 'basics' are beyond the capacity of the human brain. If we do not either become more intelligent and have higher brain capacity, eventually our technological development may not grow either. We could also rid ourselves of a number of genetic diseases, securing the medical future of our race.

On the other hand, I fear the repercussions. Evolution itself requires that there be variability in a population. Eugenics, is in essence a program in which we decrease the variability of our population. We remove those traits that we dislike or find unattractive and we keep only those that we like. Should we take this too far, we may face the same problems that our monoculture crops currently face. If a disease or other selective pressure comes in the future and we've removed so much variability in our species that no one individual has an immunity, we will have caused our own extinction. Furthermore, I don't believe we have enough knowledge of our bodies that we can make educated assumptions about what traits are truly beneficial. On its face, sickle cell anemia is a very detrimental disease, whereby red blood cells are deformed. This causes poor oxygen transport, which leads to a wide variety of symptoms. However, it does confer upon the individual an increased immunity to malaria. What if, in some future we discover that a gene that increases the risk of leukemia actually grants protection against HIV (or some other disease), but we've eliminated it from our population. We'd have lost a valuable, yet seemingly negative trait.

The obvious solution to this would be genetic engineering (another way we could artificially evolve). We keep track of all current traits and their various genetic permutations, and when we find one we want tor bring back, we just engineer it into our populations again. I didn't mention gene therapy/engineering in the same breath as eugenics due to the fact that the technology just isn't on par. We can and are (sperm/ova banks) implementing eugenics, but gene therapy for the purposes of evolution are far beyond our current capabilities. Setting aside the moral dilemmas that eugenics might create, I think we should hold off until we require it, or until we have a near complete understanding of the human body at a molecular level (all pathways mapped).
    1. Kryazhimskiy, S; Draghi, JA; and Plotkin, JB. 2011. In Evolution, the Sum is Less than its Parts. Science. 322:1160-1161
    2.Chou, HH; Chui, HC; Delaney, NF; Segre, D; and Marx, CJ. 2011. Diminishing Returns Among Beneficial Mutations Decelerates Adaptation. Science. 322:1190-1192
    3. Khan, AI; Dinh, DM; Schneider, D; Lenski, RE; Cooper, TF. 2011. Negative Epistasis Between Beneficial Mutations in an Evolving Bacterial Population. Science. 322:1193-1196