I'm wondering whether the Young Earth Creationism can be reconciled with the racial diversity found on the globe. How, can a young Earth accomedate, in a manner consistent with science, Noah's descendants going from being whatever race they were, (presumably of middle eastern appearance) and becoming of Chinese, Japanese Vietnamese & similar. Can environmental factors really account for such changes in such a short span of time? Would people of disparate races really return to the original race just from returning to its environment? Does this Creationist belief claim that all humans descend from the land of Israel?
First, Young Earth Creationism is a position officially invented and held by Christian Bible believers. However, it is true that many Jews do believe (based on Torah and tradition) in some form of limited history for the Earth. For instance, the Jewish calendar is now 5777 years since Creation (Anno Mundi).
But, many Jews will say that 5777 are the years since Adam was created, not since the world was created. Therefore, if you follow the interpretation that the 6 days of Genesis are not literal 24 hour periods, but rather epochs/stages called "days" then YEC is not needed for anything pre-Adam.
There are two approaches to your question (assuming we wish to examine a defense for YEC as applied to racial diversity presented in the OP):
1) The flood was a local Mesopotamian event (not covering the literal globe). The "whole Earth" of the flood was the portion of the planet that was populated by the evil descendants of Adam (except the righteous Noach etc.) Also, Adam may have been the first real full "man" with an intellectual soul. However, the species of man may have already existed earlier on the 6th day without a full human intellectual soul. Therefore, there were many more humans populating the world besides the "Adam's family".
For the former to be true, consider that the Talmud and Medrash explain that the dove sent by Noach found the olive branch in the land of Israel, because the flood did not reach there. Similarly, the sage Rabbi Yochanan says that Og escaped the flood by entering (the land that would become) Israel. There are other possible proofs to a local (or incomplete) flood.
For the latter idea to be true, consider Genesis 4:17 which tells us that Cain built a city. This guy was a farmer turned real estate developer? Cool. But who was he building condos for? He lived far away from his parents in eastern Nod and he killed his brother...is there anyone else left to sell the units to? :) There are more possible proofs that the "Adam's family" were unique among a larger human population around them.
These ideas in interpreting the Biblical narrative, would allow for the biological diversity and development noticed by scientists, who claim the races of mankind needed about 30,000 years, and a larger population, to develop.
2) The other approach is that the science of the human genome and racial anthropology etc. is a very new branch of research. It is constantly correcting itself and making new discoveries. No one knows if they can trace with accuracy, the exact number of years it would take for certain genes to change in the population.
Furthermore, G-d may have simply diversified Noah's three sons and increased their offspring supernaturally to make up for the flood and to provide faster racial diversity.
The Biblical account is primarily a spiritual teaching clothed in our reality. It may mention worldly events or scientific truths in passing, but it is not meant to be a historical or scientific textbook. So, it doesn't stop and explain itself like a manual. That doesn't mean it is a contradiction to anything.
However, it is interesting to note that "science" does say that humanity can be divided among three major races - Asian, sub Saharan African, and India/European. Many have pointed out the interesting correlation to Noah's three sons Shem (Middle East - Asia), Ham (Africa), and Yapheth (Indo-Euro).
Also, the origins of the Indian and European language connection was not known until the study of Sanskrit by Sir William Jones in 1786. He proved that the Europeans and Indians were descended from the same common people who spoke PIE (proto-Indo-European). Finally, in the 1980's Colin Renfrew, professor of Archaeology at the University of Cambridge, revealed that the best evidence suggests that the original speaker of PIE lived in Turkey.
If the mountains of Ararat (mentioned as the landing spot of the ark in Genesis) are in Turkey (as many believe) then your last question is also answered.
"All humans" (Noah's descendents) descend from the land of Turkey. :)
Hope this helps