Were talking 18 years a few bears and no alternatives considered like the body fat changes with the severity of winters, family traits, type of food eaten etc. How do we know his first sample weren't from a particulary fat family that could not run very fast and his initial sample was just ones that moved slower ?
Too many factors other than global warming.
It is always possible to critique on the basis of incomplete knowledge of the data. I don't know the answers to your questions and whether or not the data is accurate or not. I only find information which pertains to the question you asked.