# That's a knee-slapper!

**URL:** <https://boards.straightdope.com/t/thats-a-knee-slapper/106747>\
**Category:** Factual Questions\
**Created:** [May 1, 2002, 11:29pm UTC](https://boards.straightdope.com/t/thats-a-knee-slapper/106747 "2002-05-01T23:29:38Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![effiesmom](https://avatars.discourse-cdn.com/v4/letter/e/b5e925/32.png) [@effiesmom](https://boards.straightdope.com/u/effiesmom)\
**Post date:** [May 1, 2002, 11:29pm UTC](https://boards.straightdope.com/t/thats-a-knee-slapper/106747/1 "2002-05-01T23:29:38Z")

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Why do people slap their knees when they laugh hard? What evolutionary purpose could this serve?