Yes, it's remarkable what we can learn from the outliers and anomalies. I have been fascinated by studies that have been conducted on people with only one lobe - yet, somehow their brain compensates for missing an entire lobe - and the person can still be highly functioning!A lot of advances in psychology came from observing people with brain damage
Selecting for, or modifying allele frequency (or introducing new alleles), is the basis for the business of genetically modified organisms. Most of the food you eat has been genetically modified in some way, to make fruit grow faster or bigger, etc. In terms of evolutionary studies of species change over time, a few cell biologists have experimented with this in bacteria. They can test for allele frequency changes over time in different cultured mediums. Because bacteria replicate so frequently they can actually see evolutionary change in weeks and months. Of course this is impossible to do in organisms with longer reproductive periods.