[beambot]

When our daughter was one year old, we gave her some child-safe finger paints. Finger prints and hand prints were some of the first "drawings" she made without any parental instruction. She does not have any inherent access to global information flows or other esoteric explanations that would bind her to her ancient relatives -- beyond a bunch of shared DNA and common physiology & brain development.

She also prefers bright colors, and red pigments are probably some of the most accessible in nature that might be more robust to the sands of time (i.e. survivorship bias).

[there_the_and]

It seems like a likely explanation is that these are primarily done by children and that this is a human universal / instinctual behavior during child development. Looking at google scholar there are at least a couple studies of hand print sizes estimating that in a few regions they were almost exclusively done by young people. That would seem to suggest a biological basis for this specific behavior.