Given populations of primates who use rocks to break nuts and shellfish open, I would not be shocked if this is a trait that primates evolved many times in vari

Given populations of primates who use rocks to break nuts and shellfish open, I would not be shocked if this is a trait that primates evolved many times in various contexts. Still, most felids and canids (as others point out) crush bones routinely for marrow. Between that and the likelihood of more than just one ancestral tool users I’m skeptical anytime claims of one major factor leading to big brains come out. I bet more than one factor was at play, and it probably involved some early forms of coordination through communication, the ability to carry things in hands while running, tool use, diet, and selection pressures.