 Darwin believed, as do biologists today, that natural selection can explain the origin of many complex adaptive traits. In Darwin’s original presentation of natural selection, he requires that parent organisms differ in their abilities to survive and reproduce, and that offspring resemble their parents in terms of the traits that promote or inhibit these abilities (Darwin 1859). This explanatory schema is largely neutral regarding what mechanism accounts for parent-offspring resemblance. For example, offspring might learn skills from their parents, and thereby come to resemble them behaviourally. From the perspective of natural selection explanations, it does not matter why offspring resemble parents, only that they do resemble them.