A word of explanation. When biologists speak of 'primitive' traits they mean traits that were inherited from earlier forms. That is to say that it is found in an earlier form, rather than being developed later. In this respect there is an article in Phys.Org about the development of the human hand.
Human hand more primitive than chimp's, study saysIt has been assumed that the human hand with its flexibility, particularly the ability to touch the tips of the fingers with the thumb, was developed in the context of stone tool making. The last common ancestor (LCA) of chimps and humans was assumed to have a rather chimplike hand. However the authors of the study reported in Phys.Org have studied the hands of humans and chimps and the hands of fossil ancestors. They have concluded that our modern human hand is more like the hand of the LCA than are the hands of chimps. Thus our hand is more primitive than the hand of a chimp.
The main import of this is that it was not the evolution of our hands that led to stone tool making, our hands were already set to make stone tools. Their conclusion is that there was some mental development that led to the production and use of stone tools rather than the physical capability.
Bill Gill
