What important conclusion does the Time Traveller reach after experiencing the monster among the ruins? Does this appear to be the central conflict of the novel?

This question relates to chapter 5. There are many things that the TT learns about the creatures in the ruins. The TT realizes that man has evolved into two distinct animals, the "Upperworld" creatures and the nocturnal ones below. Wondering what the relationships is between the two, he resolves to descend into the well, though he is afraid to do so. You can read about ch 5 at the GradeSaver link below: