No, the reason is that they dispersed from the Middle East by sea and overland, when the sea level was lower during the Ice Age.
According to who exactly? And is this to state that you disagree that floods occur all over the planet?
Further to which, if you were to assume that all the ancient flood stories are based upon an actual global flood then it stands to reason that the oldest such story, (the original if you like), would be more accurate than any account given thousands of years after the actual event. In saying, the biblical flood account will lose out to the Utnapishtim version which was written a good 1,500 years before the biblical version. You can't tell someone a story now without it being prone to chinese whispers after 10 minutes let alone one and a half millennia.
Finally, these ancient cultures would have had no way to tell that the flood was global. It might have seemed so from their very limited perspective, but there's no valid reason to accept their stories as factual - unless of course science was to concur, which it does not.
Almost all geologists admit...
Kindly provide a source for this data.