“There is a reflex called the Gastrocolic Reflex. When you eat, your stomach sends a signal to your colon, especially telling it “hey, you gotta make room!” giving you the urge to defecate. Some foods stimulate the reflex more strongly than others, that is why sometimes it feels like food “went through you” after you eat.”
#12 I’m sure it’s more conditioning than evolution. If you hold one of their newborns under water for a couple of minutes, it probably won’t come up breathing.