The greater number of genetic changes in chimapanzees is relevant to the pope's soft attack on evolution? An oddity without a rock solid explanation shows evolution to be a worse explanation, despite over a century of gathered evidence, than an ancient myth contradicted by evidence? Even if this did show fundamental problems with evolution, the existing evidence shows the model has some worth and is still better than a story. It would still be better than the can't-prove-it's-wrong-therefore-it's-right of Intelligent Design. After all, claiming that I can fly because no one's recorded me 24/7 is rubbish.

This oddity is irrelevant anyway as the pope is refusing to state that evolution is a flawed model. He is implying it is unsupported, making it equal to other ideas. He would have a point except that it's wrong. Unless you're claiming an unknown is "not a complete, scientifically proven theory". If so, that's nonsense as science can only ever provide best-guess, working models, not absolute, unbendable certainty. Medical science hasn't the faintest idea how the Placebo Effect is possible but physiological models are retained as scientific anyway.

The sad thing is the pope could casually throw out the biblical creation as 'retired', dismiss accusations of being archaic and expound on the implications of new science and technology, such as genetic engineering. That'd shut up the critics.

The answer to your question is that it's unknown but probably the result of a low, human population at some time, which lost genes as the gene pool shrank.

That the question is asked implies a misunderstanding of mutations and evolution. Though change is driven by genetic mutation, a mutation does not always create a change that creates evolutionary superiority. Some mutations have no meaningful effect, such as eye colour. Indeed the benefits of a useful mutation is relative to an environment, relative to the existence of other genes and is, thus, random. A mutation for more sophisticated vocal chords works well with good hearing but doesn't combine with a stomach that can digest a greater variety of insects. Longer arms are good in a jungle but pointlessly costly in tundra. With random changes, comparisons are only vaguely useful.