Scientific research on the squatting position
Dov Sikirov, an Israeli doctor, wanted to check what was the best position for stool . He asked 28 volunteers to test several different positions.
Result: In a squatting position, doing one's needs took on average 50 seconds, with the added bonus of the feeling of an effective evacuation. In sitting position, it took on average 2 minutes 10 seconds, as we usually do on our toilets.
The exit door of the digestive system is naturally designed to open when squatting and not when sitting or standing. In these two positions, a muscle encloses our intestine like a lasso and pulls it so that an elbow is created.
And it seems logical enough: in the middle of nature, squatting is the simplest way to defecate (and without getting dirty).
Japanese researchers validated the explanation with the following experiments : they asked volunteers to swallow fluorescent substances and then X-rayed their defecation in both positions.
Result: in a squatting position, the intestinal canal is straight like a highway.
For further information, hemorrhoids and diverticula exist almost only in countries where one sits to defecate.
 Dov Sikirov, Comparison of Straining During Defecation in Three Positions: Results and Implications for Human Health – Digestive Diseases and Sciences July 2003, Volume 48, Issue 7, pp 1201–1205. 11.
 Sakakibara R, Tsunoyama K, Hosoi H, Takahashi O, Sugiyama M, Kishi M, Ogawa E, Terada H, Uchiyama T, Yamanishi T. Influence of Body Position on Defecation in Humans. Low Urin Tract Symptoms. 2010 April 2(1):16-21.