(I loved the days when I could look at any paper on anything, anywhere, anytime - I really miss it.)
Were Fundamental Constants Different in the Past?
Atomic physics, nuclear physics, and cosmology enable physicists to probe changes in the fine-structure constant over time scales ranging from a few years to nearly the age of the universe.
Keith Olive is the director of the William I. Fine Theoretical Physics Institute and a Distinguished McKnight University Professor and Yong-Zhong Qian is an associate professor and a McKnight Presidential Fellow; both are in the school of physics and astronomy at the University of Minnesota, Minneapolis.
The general point is that scientists would be extremely interested to know that physics was different only a few thousand years ago. But if it was, it would be very obvious and we would see the evidence everywhere.
One pretty catastrophic piece of evidence is that for the radiodating regimes to be wron radioactive decay rates had to speed up. As decay rates increase so does heat. It's estimated that to change decay rates to make it look like the earth was 6,000 years old, the temperature of the earth would then be 65,000C/km. Rock would be liquid.
Apparently, dating cave paintings is quite difficult; carbon dating requires the destruction of at least some of the painting and can give quite a range. Also many paintings use pigments that don't contain carbon.
Sometimes bones, fires and other signs of human habitation are found in the caves that can also be dated but you then have to assume that those inhabitants also made the paintings.
They also use uranium dating as sometimes calcite forms over or under the painting. (The beginnings of stalagmites). QI