There will be parallel and simultaneous changes, but the interaction has to be explored in models.
Not all changes in the evolution of skills go in the same direction. For instance, a calf can stand up, walk to its mother, and feed within minutes. Human babies have lesser locomotion skills at birth, but can handle more complex movements later.
For the species of interest for this study of skills, i.e. vertebrates or more narrowly mammals, the cooperation of two individuals in the parent population is required to produce offspring. Communication and cooperation may also be required to bring the offspring to maturity, and in transferring skills.