Good question, ez3t1524! We need an evolutionary biologist to give us a detailed answer, but here’s a little bit of information about it. We know that the Earth formed about 4.6 billion years ago, so life couldn’t have existed here before then. We think that early forms of simple cell life started to form around 3.8 billions years ago, so it’s likely that our early, single- and multi-cellular ancestors appeared around then. Humans (as in Homo sapiens) appeared only around 200,000 years ago. So that means that it took about 3,799,800,000 (give or take a few thousand) years to go from early bacterial life to modern day humans!