Evolution does not necessarily favor the longest-lived. It doesn't necessarily favor the biggest or the strongest or the fastest, and not even the smartest. Evolution favors those creatures best adapted to their environment. That is the sole test of survival and success.

This quote is saying that evolution does not always reward the longest-living or biggest or strongest or fastest creatures. Instead, evolution rewards the creatures that are the most adaptable to their environment. In other words, evolution only cares about how well a creature can survive in its environment and successfully pass on its genes to the next generation. The only way for a creature to be successful over time is if it can properly adapt to changes in its environment.