. The single jawbone is a defining characteristic of a mammal and that happened far back in our past when our synapsid ancestors became mammalian.
Modern Humans don’t have room for wisdom teeth because we have smaller jaws. One of the differences between human and the other great apes is that our smaller jaw muscles don’t attach to the top of out head,they attach at the side . ( You can feel this if you chew) This was due to a mutation in the genes that lead to smaller jaw muscles . The smaller jaw muscles lead to our brain having room to grow larger .
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You can easily see the Sagittal crest on this gorilla skull where the huge jaw muscles attached at the top of the head