First of all evolutionary fitness is not about individuals, but about groups of organisms, such as species with different DNA.
Fitness is not physical fitness, but the ability to pass along to the next generation one’s DNA.
If a person is better prepared for a difficult task such as mountain climbing that is a strong indication that he or she engages in cooperative behavior, such as seeking out advice from experienced climbers, going through training, and using guides. Cooperation has much to do with the success of each climber.