Opposable thumb in humans Adaptation for grasping objeccts. It is useful to grasp objects, e.g., spears used in hunting, bowls used for cooking. A characteristic is an adaptation if it is useful for some purpose. A characteristic is an adaptation if it arose through natural selection, and the purpose it serves is causally responsible for the increased fitness through which natural selection acted . Claims about adaptations are historical claims, i.e., claims about particular events that happened in the past.
Physical sciences seek to exclude particulars of time and place from their theories.
Certain aspects of evolutionary biology are bound to these particulars. No physical features suggesting slower rate of deposition. Explanans must contain general principles. Testability demarcates empirical knowledge from non-empirical knowledge.