The paper that you sourced but did not understand compared the gene for p53 in eleven different species and discussed the differences.
Are those differences due to mutation?
CAN YOU ANSWER THE QUESTION?
WHY NOT????
Of course it is.
"Did these differences between humans chimps and gorillas arise by mutation or were they designed differently from the beginning?"
Please show how we would distinguish between created differences and differences that arose later through mutation. Can you show that all of the differences can either be only the cause of created differences or only the cause of mutation with no combination of the two? All one way or all the other. If you cannot, then you have used the fallacy of the false dilemma.
"Are those differences due to mutation?"
Just how would you tell the difference between a created difference and a mutation after-the-fact with no original DNA to compare? Having original DNA to compare would be science. Assumed logical fallacies like 'false dilemma' and 'affirming the consequent' are not a substitute for science.
This is why fallacies cause so much trouble in evolutionary-thinking. Unfortunately, most adherents cannot recognize how completely fallacies are ingrained in evolution.