I'm far from an expert on this particular area of discussion but isn't the problem with interptive arguments that they hinge on thongs that are subjective to the author and current understanding.
100 years ago there were also the Dravidians and Sinhalese races of man, so that'd be 5 races rather than 3 - and as it stands currently there have been no where near enough studies done on the genetic make up of the native tribes of Austrailia, but considering how far divergent the rest of the mammals there are we could probably expect some interesting findings. Not to mention that there may be more similar folk hidden around the world that may have died out or been breed into obscurity long ago
Reason > Belief
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