Hi, while you're waiting for replies here, you may be interested in a couple of threads in the FAQ, with answers by /u/lukeweiss and /u/darwinfish86. The posts are also linked in this thread, which includes a bit of follow-up discussion How did China and India wind up with such large populations compared to the rest of the world?.

Since these posts have been archived, if you have follow-up questions for any of the users, just ask here and tag their usernames to notify them.