Source 136: The following quote is from Encyclopedia Britannica, cited on http://abyss.uoregon.edu/~js/glossary/primate.html. This link may or may not still be operational; if it isn't, we may have redirected it to the WayBackMachine archive.

‘The more sophisticated species also exhibit longer infant and juvenile stages, which are probably related to the time required for their more advanced mental development and their integration into complex social systems.’

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