XKCD Isn't Funny - #1545 - Strengths and Weaknesses
That's an interesting choice of staging in the first panel, it's like the fact that it's Bald on the other side of the desk is supposed to be a reveal. Or maybe, since we perceive time spatially when we read comics, he's trying to show that the dialogue in that panel took less time to say? I'm not outright criticizing the choice, but I don't understand why he did it.
Bald's first line is the best joke, but it's brought down a lot by the execution. As Shakespeare once said, "Words, words, words". He knew that you should get to the point as fast as possible, which is why all his plays are under five minutes long. And while complicated phrasing can be funny if done properly, this comes off more like Randy's trying too hard to seem quirky. A more direct, almost deadpan "Probably that I'm a fragile mortal that can die easily" would be better overall. Also, how is the human body a tangle?
The problems with the second punchline are more obvious. The answer doesn't match the question. "I'm a fragile mortal" is a genuine, albeit standard, weakness, but there's no circumstance under which the ancestor thing would be useful. Having a lot of relatives, maybe, but that's really a stretch from the actual line. And even if say he did intend the relative meaning, why would he mention that there's a possibility of it not even happening?
I kinda like the ending, how it implies he's either going to have all the sex ever or kill everybody, but again he doesn't answer her question, he just continues on from panel three.