Stapledon's posthuman vision

I'm almost three-quarters of the way through Olaf Stapledon's exploration into our posthuman future, Last and First Men, which was first published in 1930. From a 21st century perspective, it can be viewed as both insightful and naive. But the overall sense I get from the novel so far is that of Stapledon's quest to understand why humans, in their constant quest for perfection, continue to make the same errors that lead to their own downfall.

Stapledon approaches the evolution of humankind through various phases of posthumanity from physical, social, psychological and spiritual perspectives. However, his work is not prophetic in the way of some early 20th century science fiction, which foreshadowed various scientific and technological advancements. His posthuman approach is more focused on the human species search for continual improvement, for meaning, and to some degree for immortality. There is a strong focus on a search for spiritual meaning, and so far, most of the various evolutions of humans he describes have followed religions ranging from the profound to the nonsensical. (The exception to that are the 'fourth men' who are static superbrains who communicate telepathically; their sole concern is the intellect.)

One theme common to the various species of human and posthuman that people First and Last Men is self-destruction. No matter how much progress is made in intelligence, spirituality, art, intellect or humanity there is always conflict or crisis which results in the species' downfall. Sometimes this is deliberate, sometimes not. The 'third men', for example, aimed to create a form of human perfection that was able to achieve immortality. They eventually succeeded in  creating the 'fourth men', who were essentially giant brains without bodies that communicated telepathically, and who eventually enslaved the 'third men'. Thus the 'third men' achieved their goal of creating an immortal species, but in doing so destroyed themselves. In contrast, the giant-brained fourth men, realising the pointlessness of a life lacking in a value system, created the giant-sized, super-intelligent and gifted race of 'fifth men' to replace their physically restricted selves.

I'm interested to find out if, by the end of the novel, Stapledon creates a posthuman species that no longer strives for perfection, and if so, how these 'last men' find meaning in their lives. For all his posthuman creations - from standard sized humans who fight clouds of hive-minded martians, to small, six-fingered and big-eared creatures with a religious devotion to music and a penchant for creating art out of living things, to immobile brains housed in large buildings fuelled by radiation, to 3 metre-tall intellectually, artistically and psychologically gifted beings - have one thing in common. They search for knowledge, for perfection, for immortality but ultimately for meaning in their lives. The question I'm hoping Stapledon may try to answer is, once you've attained perfection, what's next?