Yeah, their face shields were unconvincingly fragile throughout. The storyline of why the monkeys were there is what the other poster said, that they were conducting experiments on animals in space. There have been enough movies with animals turning powerful and smart (think: The Secret of Nimh, every single freakin' Planet of the Apes movie, etc.) that I guess they figured the audience didn't need more than that.

But from an analytic perspective, I think the apes were there to suggest that humans derived from exactly those kinds of raging beasts, things that kill because a desire for killing occurred spontaneously due to a genetic error, and that desire to kill and effectiveness at killing caused them to survive and multiply. Then the question becomes, have we gone beyond that? He made a direct comparison of his father to those apes: "I've seen that same look of anger in my father. I've seen it in me." and his father was costumed/made-up to look hairy and blotchy, and his father committed unjustifiable homicide in gruesome ways (note the other shattered face-mask with the head wrapped in webbing of some sort that was likely a call-back to the face attack by the ape). A possible point from all this is, if we humans are "all that we have," we have to figure out how to be human in spite of our biology that demands we act in ways that kill humanity (even our own, personal humanity), we must choose to move beyond reacting to what has happened to us, we must choose to make ourselves vulnerable to other humans who also have these powerful evolutionarily-successful aberrant passions which they only bridle to varying degrees of success.

The whole mythic archetype of "the son must kill the tyrant father" was a drawn into this theme, too, but that's another analytical path.