According to Alfred Russel Wallace, disadvantageous traits are eliminated from the population by natural selection. This is the process of evolution as only the dominant individuals are able to reproduce successfully and their traits passed down generations.
However, today in the advent of improved technology in healthcare, more and more ‘disadvantageous traits’ are being maintained in the population due to advances in medicine that improve the survivability of these individuals – such as people with genetic disease like Parkinson’s.