IIRC the light coming from in front of you gets blue shifted, each photon increasing in energy, and the count increases because of the geometric changes you see in the video (the angles in front seem to shrink).
Light from the rear red shifts (each photon has less energy), and there are fewer as some of the (formerly incident) photons "rotated" to the front.
(edit: typo)
(edit: didn't read the question closely, this is about approaching c, not exceeding it)
This image [1] comes from "Converson to Islam in the Medieval Period" by Richard Bulliet [2]. The percentages inferred by Bulliet roughly track a sigmoidal curve. He makes an argument in analogy to the spread of a disease through a social network.
It should be noted that the deta is from Iran, but presumably the same arguments apply for Southeast Asia.
Do you have references for the multiple migrations, especially from India? I know there was this paper: http://www.pnas.org/content/110/5/1803, but I had the impression that hadn't been replicated.
