The explanation that best explains the trends seen in the data is:
Individuals with thicker fur had a survival advantage in the cold environment, allowing these individuals to reproduce more often and create more offspring.
This statement aligns with the principles of natural selection, where individuals with advantageous traits (in this case, thicker fur in a cold environment) are more likely to survive, reproduce, and pass those traits on to future generations. This would lead to an increase in the frequency of the trait within the population over time.