What is one lesson the narrator and his world learned from the attack of the Martians?

The narrator muses on the lessons learned from the Martian invasion. The Martians taught them a great deal about science, though humanity has not been able to figure out the mechanisms behind the Black Smoke or the heat ray. One Martian body was recovered from autopsy, and science is learning a great deal about this species. More significantly, humanity has learned that they are not alone in the universe: there are other intelligent beings in the universe, and some of them are malicious towards humanity. He notes that there is some evidence that the Martians have gone to Venus, and he ponders the fact that humans could potentially do the same thing after the sun cools.