This is classic Baxter. It spans millions of years, all the characters die, and by the end not only has everyone we know ceased to exist, the human race itself has de-evolved. No super-race of the future in Baxter's vision, humanity evolves eventually into little monkey like creatures that are symbiotic with trees.

Typical Stephen Baxter plotline:

author meets area of technology

author falls in love with technology

various characters appear and interact since publishers tend to want this

author kills off all people and goes into far future to be alone with technology (he doesn't actually dislike the people, so they all die quite happily, fascinated by the amazing walls of flame, vastnesses of space etc etc, and it hardly hurts at all)

author realises this is a bit boring for most readers, and resurrects some random people to admire mindboggling vastnesses of space and time

end