I used to live nextdoor to some former missionaries.

They spent 5 years in Indonesia.

When they first moved in nextdoor, their DD1 was potty trained.

Where they worked in Irian Jaya the natives just held the kid out at arms length and let them do their thing.

By 3 mos their DD was trained just as well as a native kid.

Right before they came back, they trained her to use a toilet.