The evolutionary advantage of cats' retractable claws is that they allow cats to be more efficient hunters and climbers. Retractable claws allow cats to keep their claws sharp and ready for use when needed, while also protecting them from wear and tear when not in use. Additionally, retractable claws allow cats to have a better grip on surfaces, which helps them to climb more efficiently and to catch their prey more easily. Finally, retractable claws help cats to defend themselves against predators and to protect their territory.