Hello Neil and Everyone
From what I have read it appears that a number of different groups of humans are being "found". It is quite probable that some of the DNA of all theses tribes, for want of a better collective noun, can be found in our current population. I find this quite fascinating.
It also appears that we can trace our humanity back, via DNA, to an original woman in Africa. Can't say the same for an original man though. Precisely how this has been accomplished and proven is beyond my grasp of science but I am willing to take the scientists word for it. After all our evolution had to have some form of common denominator.
In terms of population groups existing at the same time in different parts of the world Neil, this is what I understand happened. These groups either failed to thrive and so died out or they integrated with other groups. Don't know. It does appear that humans as we know ourselves now, did originate in Africa. The current widespread divergence of shape, size and colour is mainly due to climate. eg dark skin to combat exposure to sun, retention of hair to keep warm, eye shape and skin folds to protect against the wind. Also the adaptation of body shape and size due to the available type of food.
Geoff, it's amazing how long life can remain dormant until the right conditions trigger the next stage of development. Just a small amount of moisture underground can sustain frog spawn until the rains come.
Life in all its varieties is amazing and tenacious, adaptive and creative. Those species that do not adapt die out. So like all of us, it's a case of change or die.
What is our next incarnation?
By the way, I heard a quote the other day which I found quite scary. Can't remember who said it, but then I never can. The quote is, "The internet is the only invention of man that we do not understand" I have no idea what is meant by not understanding. Sounds quite menacing though.