I think this question has been answered for some time actually, and the narator at the end manages to get it 100% wrong in method even if the conclusion is correct. For all who are interested in this, please consider the excellent book, The Ancestors Tale by Richard Dawkins. He details an experiment by a Russian behaviourist who raised Silver fox for docility and within 20 years had animals who acted and even looked, complete with markings and colours, border collies, and only from breeding generations strictly on the basis of docility and hence, higher serotonin levels. However this is interesting in any case. Enjoy.