The only way to know for sure is to find M45 indicators in Ainu. However, if the emergence of M45 really did take place 40K years ago, there would have been significant evolutionary divergence since then. In fact, that is believed to be the time when Caucasoids and Mongoloids split from a common ancestral population. Perhaps this common ancestral population was similar to the long-isolated Ainu, who anyway appear to share genetic and physical traits with Southeast Asians and Australoids.
Click on the various dates at the top then move your curser over the arrow/trail to get the dna type. DNA will eventually solve all these questions but appears to be a little murky yet.