The authors used museum samples in order to get around the fact that some modern Andamanese may have mixtures from non-indigenous groups, and that some of their tribes (like the Sentinelese) resist all direct contact with outsiders and would certainly not allow blood or other tissue to be sampled.
Genetic studies often seem to me to conflict with each other.
As to San being ancestral to us honkies, see my post about the Venus of Willendorf.
Can't tell you the reference at the moment but a couple of months ago I ran across a discussion of the "race" of the people who did the cave paintings in France. Turned out that you could estimate their height, and the relative proportions of their long bones to their torsos by making measurements of the distance from their handprints on the ceiling to the floor.
They still had tropical proportions but were roughly as tall as modern Negro people in Africa ~ and were clearly NOT white folk!
Remember, during the period of maximum glaciation in an ice age you have recurring periods of warmer weather where the ice may well melt allowing plants and animals to return.
Our early European ancestors supposedly walked into Europe about 35,000 years ago, just about when many of those cave paintings were being made. It is entirely possible that other people had gotten to Europe earlier, while the descendants of the San people in Africa (guys with the straight hair) simply arrived later.
Actually according to the study the Andamanese are close cousins of the Ancestral Southern Indians i.e they have a common ancestors. However Andamanes are NOT actually ASIs. They are used as proxies for the absence of pure Ancestral Southern Indians in today's mainland India.