Mason  🏃‍♂️ ✂️

Earlier theories related to the Damorian variability hypothesis were along the lines of head size and phrenology. All shared the common feature of working backwards from the desired conclusion.

And all failed to correctly predict the dramatic shift in demographics of the scientific community, or to explain why the variability hypothesis only seems to apply to humans and not other animals.

For example, there's no observed difference in intelligence or learning ability across dog breeds, despite the size of dog breeds ranging between 4 lbs (Chihuahua) and 250 lbs (English Mastiff).

Where are you getting that from? This may be true for social memory or very simple, discrete tasks, but there are certainly some varieties of work and competition that require the dog to make quick judgments, and there are typically a small handful of breeds that excel.

That's folklore. Working dogs are traditionally chosen for very simple reasons, including tradition, size and strength.