We Homo Sapiens Sapiens have only been around for about 100-120,000 years; there have recently been some good series on both Discovery and National Geographic Channel regarding our evolution. It seems whilst anthropologists agree we have evolved from Homo Sapiens there are two schools of thought as to how we did so.
The traditional school of thought sees Africa as the cradle of modern man with the entire world population having evolved from Homo Sapiens there and spread across the planet. Others believe modern man evolved from Homo Sapiens in Africa, Asia, and Europe at the same time. From what I have read and seen in documentaries it seems irrelevant which school of thought you belong to as both agree Homo Sapiens evolved from Homo Erectus in Africa who first evolved himself some 1.8 million years ago.
A recent documentary series that looked into genes found the largest diversity was found in Africa which tended to show it was where we origianted from, but ultimately all of mankind could trace their origins back to just five mothers. This did not mean there were only five original female humans simply that only the offspring of those five has survived through the past 100,000 odd years.
Regional differences are normally explained in several ways – the first the Darwinian theory the fittest evolve to survive in their given surroundings with climate, diet, lifestyle etc all affecting evolution. This is relatively easy to prove, go to any museum and look at clothes from just 200 years ago, most of us today are far to big to fit into them mainly due to diet, healthcare and our living conditions.
The other rationale (which some people find harder to accept) is that some of the differences came about through inter breeding with other humanoid species. It is argued there was inter breeding between Humans and Neanderthals, which goes to explain the heavy brow ridges of some individuals. In Asia it is argued Humans inter bred with Homo Erectus (No pun intended) as they have the same shovel shaped incisors as found in Homo Erectus fossils.
Again through inter marriage there has been cross mutation of genes worldwide throughout recorded history, which have kept humans as a whole similar in structure, development etc. An exception to this is the aboriginal people of Australia who became isolated on their arrival there and thus kept their gene pool pure for 50,000 years without any outside influence.
Of course not all humans have evolved and developed at the same rate as this we photo shows: -
http://politicalhumor.about.com/library/images/blbushignoramus.htm?iam=momma_100_SKD&terms=homo+sapiens+sapiens
Sorry I could not resist that one! So interesting all of our studies show we all come from a common gene pool of five mothers yet many of us are stupid enough to behave in a racist manner to anyone who looks different to us!