I'll just mention the Cambrian explosion is not as big a deal as some people make it out to be. It appears many phyla were present before the Cambrian. It may be more an explosion of decent fossils than phyla. If human activity ends up destroying a lot of fossil sites before we go extinct, then in a billion years time sentiant cockroaches will be amazed at the diversity of lifeforms suddenly appearing in the 21st century. (And maybe the sentient cockroaches will conclude that it takes five billion years for intelligent life to emerge.)