Editing Exaptation (section)

===Jury-rigged design===
Darwin explained how the traits of living organisms are well-designed for their environment, but he also recognized that many traits are imperfectly designed. They appear to have been made from available material, that is, [[jury-rigged]].{{efn|Jacob (1977)<ref name=Jacob1977/> sees much of evolution as "tinkering," that is, working with available traits. "Tinkering" includes (but is not limited to) shifts in function.}} Understanding exaptations may suggest hypotheses regarding subtleties in the adaptation. For instance, that feathers evolved initially for thermal regulation may help to explain some of their features unrelated to flight.<ref name=M&L>{{cite journal |pmid=15740417|year=2005 |last1=MacDonald |first1=G. |last2=Leary |first2=M.R. |title=Why does social exclusion hurt? The relationship between social and physical pain |volume=131 |issue=2 |pages=202–23 |doi=10.1037/0033-2909.131.2.202 |journal=Psychological Bulletin|citeseerx=10.1.1.335.4272 |s2cid=10540325 }}</ref>  However, this is readily explained by the fact that they serve a dual purpose.

Some of the chemical pathways for physical pain and pain from [[social exclusion]] overlap.<ref name=M&L/> The physical pain system may have been co-opted to motivate social animals to respond to threats to their inclusion in the group.