New studies have pushed it back to around 200,000 years ago but there have been several out of Aftica migrations,130,000 and 60,000 years ago as well,but I believe there would have been a steady trickle out of Africa as well.some to Europe,Asia and Middle East etc.

Science in itself is always thinking about today versus tomorrow. We are were we are and know we are not yet where we will be. It is a continuum of discovery
Never is science wrong nor 100% on target, it is always on though

They left when continental shift allowed it to happen, there they encountered the non contaminated species of humans, Adaptation and cross breeding and here we are

Was watching a good tv show last night about pre Homo sapians(Homo Erectus).One scientist has found cooked food particles going back over a million years before it was previously thought that food was cooked. That's a staggering difference. If they can get that so wrong its not surprising we wil get unexpected finds like this.

The cooked food is thought to allow the homo erectus species gut to shrink,and allow more food to be absorbed and thus evolved a bigger brain.

A similar sort of change of thought is occurring regarding when modern man first entered the Americas.

[independent.co.uk]

Its hard to determine this.... seems like the scientists find new information every 10 to 20 years... I wish they could tell me how they set the stones to make a pyramids?

One can only rely on research provided by scholarly professionals to know this and as with all science research, it changes as new evidence, facts and data are acquired. (IMHO)