Where does Ancient Astronomy Begin?

If you know nothing of astronomy: The first thing you notice (after day/night, of course) is the phases of the moon. That's pretty easy to figure out. Eclipses happen now and then--without a little math and a lot of measurements over time it's hard to predict those, and maybe they don't matter a lot, since everything seems fine afterwards. (I'm not talking about seasons and weather--you learn subtle signs about those independently of understanding the sky.)

The next thing you notice--if you are far enough north--is that the days aren't the same length all the time. At 5 degrees north or south, the difference is about an hour. That may or may not be very noticeable, but by 10 degrees it is 2 hours and I think that's enough of a difference that you can tell. The Sun isn't always in the same position when it sets, though if you live in a forest you might not be able to see that. If you live in the mountains it can be very obvious that sunset is at a different place on the distant slope than it was last month.

The ancient "observatory" closest to the equator seems to be the Chankillo towers at about 9.56 degrees away--and it is in an area with high hills and mountains.

If you live at the equator, unless someone has given you a reason to look, I don't think you'd spontaneously notice the changes with the sun. The planets are another matter, of course.