Positive Selection in Homo sapiens

Positive Selection in Homo sapiens

A look at my acadmic poster from last week showing some of the selective pressure on humans.


My first academic poster

I just wanted to share my first poster that I produced last week. If you have any questions please leave them in comments and I will do my best to answer them promptly. Just click on the thumbnail to see it at full size.

Stats Dept Presentation - Trinity 2013


I had a chance to explain this to a high schooler so I thought I would share it here.

HiĀ ,

I would be happy to help you understand what I do.

My research project is all about finding which mutations are beneficial to humans. The method that I am using is to look at the response to natural selection in human populations.

So what that means is that someone with a beneficial mutation should be in a better position to have children than someone that doesn’t have the mutations. One mutation that I mention in this poster is lactose tolerance in adults. In ages past the ability to digest milk as an adult gave some adults an advantage over other adults in that they had an additional food source. So because they had more sources of food they could provide for more children, therefore lactose tolerance spread through the populations of humans that raised cattle, sheep, and goats, if it appeared there. Europeans are by far the most lactose tolerant population in the world but there are some other populations that have evolved adult lactose tolerance. However in hunter gatherer populations the mutation will not provide a benefit and thus will not spread through the population.

So to look at this poster I want to start by looking at he ancestral graph under the methods. This is a look at one possible history of 120 people. On the left we have the modern people and as we move right we are going back in time watching as we find common ancestors to them all until at the very right we find the Most Recent Common Ancestor(MRCA). In an area of the genome that there is little selection we would expect each lineage to combine at about the same rate and have about the same number of descendants, however on this image we can see that the lines coloured red have a great number of descendants and we interpret that as evidence of natural selection. (Remember part of the definition of Natural Selection is that you have more children than other people.)

So on the left under results the first two images are showing that my method works. The Negative Control is showing that my method doesn’t show us false positives (where we think there is selection but there really isn’t) and the positive control is showing that I can detect the mutations for lactose tolerance in the population that I am studying. The second graph is showing a much higher resolution scan of the LCT (lactose tolerance) gene area to show that I can use a different data set with more information and the last image shows an area of selection that (I believe) no one else has discovered yet, that of MYT1L which is associated with the development of the central nervous system.

So the important points for my method are that it is low in false positives (though it is prone to false negatives where I say there isn’t enough evidence I could be wrong), it reproduces previously known information, and it discovers new areas that are under selective pressure.

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