https://www.theatlantic.com/science/archive/2021/05/evolution-butts/618915/

https://my.clevelandclinic.org/health/body/24785-rectum-function
https://en.wikipedia.org/wiki/Deuterostome#:~:text=Formation%20of%20mouth%20and%20anus,-Main%20article%3A%20Embryological&text=For%20instance%2C%20humans%20have%20already,later%2C%20temporarily%20forming%20a%20cloaca.
https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works
https://www.ucsfbenioffchildrens.org/conditions/imperforate-anus#:~:text=If%20a%20newborn%20does%20not,an%20enlarged%20or%20swollen%20abdomen.

https://www.dailymail.co.uk/news/article-11562045/French-man-sparks-hospital-evacuation-arriving-WWI-artillery-shell-stuck-rectum.html