When similar characteristics occur because of environmental constraints and not due to a close evolutionary relationship, it is called an analogy or homoplasy. This usually happens because both organisms were in common adaptations that evolved within similar environmental conditions. Similarly, unrelated organisms may be distantly related, but appear very much alike. Some organisms may be very closely related, even though a minor genetic change caused a major morphological difference to make them look quite different. The same relationship between complexity and shared evolutionary history is true for homologous structures in organisms. However, if two people both invented a hammer, it would be reasonable to conclude that both could have the original idea without the help of the other. Imagine two people from different countries both inventing a car with all the same parts and in exactly the same arrangement without any previous or shared knowledge. The more complex the feature, the more likely any kind of overlap is due to a common evolutionary past.
Notice it is not simply a single bone, but rather a grouping of several bones arranged in a similar way. (credit a: modification of work by Steve Hillebrand, USFWS credit b: modification of work by U.S. Bat and bird wings are homologous structures, indicating that bats and birds share a common evolutionary past.
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