Why might have people followed the rivers to find their way into asia

People might have noticed the geographical nature of the rivers, and probably knew there were mountainous regions of Asia of which lead to streams and rivers forming. I you are talking about exploration, Europeans couldn't get into Asia by foot because the trade routes were forbidden from the crusades.

I hope this helped!

answer; is roughly two weeks;

answer they showed that organic molecules such as amino acids could be produced from inoragnic molecules;