Thanks, I'll look more into it. This is an area of active debate and research. Estimates have gone as far back as 7 Ma (e.g. this 2002 NYTimes article[0] says 5-7 Ma). Even the origins of Homo sapiens gets pushed around every other year (e.g. [1]).

[0] https://www.nytimes.com/2002/02/26/science/when-humans-becam...

[1] https://www.vox.com/science-and-health/2017/6/7/15745714/nat...