I have had a chance to apply primer to my cavemen.
I call them cavemen because I use movies like One Million BC as one of my primary sources of information about prehistoric life.
There are very few actual "cavemen" in 1/72nd scale.
Phersu Miniatures makes very nice resin figures in 1/72nd scale.
I have re-purposed a number of other figure sets to get a pretty impressive range of figures.
By careful shopping and a few conversions you can get decent ancient megafauna too.
Soft plastic and resin figures are much cheaper than the metal 28mm alternatives.