1_ The title ¨Dumb Martian¨ is very ironic in my opinion, since Duncan treates in a bad way, insulting & abusing with violence to Lellie when actually she was smarter than what he thought. Lellie is the one who waits with a lot of patience the right moment to lock Duncan outside the house. I think the title has a moral, not everyone is the way you think.
2_ The story sais that the shape of their face and specially the eyes make them look dumb, but they weren’t. In my opinion, they were just different as the human. It also says that before the humans arrived to Mars, they were a very developed group.