natural selection

n. [生]自然选择,物竞天择说

A systematic long-term change of this kind suggests the action of natural selection and indicates that female skeletal characteristics confer greater fitness. But is this the whole story.

这种长期的系统变化说明自然选择的作用，并表明女性骨骼的特性较大的适应性。但是，情况完全是这样的吗？