Gee. Maybe they were all designed that way from the start. Did evolutionists watch this "mutation" take place from one species to the next?
A completely worthless "explanation." This would explain the opposite too. The entire Creation-ID-Post-Modern nexus has zero explanatory power precicely because "designed that way" can be said of anything. It is the agressive denial of knowledge.
The other problem is that there are not only shared mutations among primates, but shared viral genes incorporated into primate genomes. These are in the "non-coding" regions and thus seem not to be subject to selection pressure. There are those shared by chimps, gorillas, and humans but not by orang-utans. The chances of this happening are coecively less that 1^720.
It is a durned good thing we finally caught up technologically with the design so we could finally safely pull out each others' wisdom teeth and prevent infection. Wouldn't the designer be upset that we are improving upon his design when we do such things? Oh well, I'm leaving 'em in my kids then.