From a bit of google research it seems that the brains individuals with differing handedness are not just mirrored versions of each other. There also appears to be some link between left/right handed and ambidextrous and different traits that are presumably a result of their different brain structures.

It also seems likely that there would be archaeological evidence of handedness throughout history either e.g. asymmetrical bone structures or tools that appear biased.

Has any evidence been found for different ratios of right/left/ambi throughout our evolution and are there any correlations between these changes and the evolutionary pressures at the time?