just read beyond infinity by gregory benford. borrowed many themes and ideas from "a fire upon the deep" by vernor vinge. notable ideas i hadn't encountered before:

• "original" humans, i.e. raw homo sapiens without genetic modification, no longer exist either as organisms or as DNA on file. Cley, the main character, is called "original", but has extra capabilities (her nostrils close camel-style to shut out foreign bodies, her eyes can zoom and select alternative wavelengths, she can extrude swiss-army-style tools from her finger-tips), some of which she and other characters conclude could not have evolved on the plains of "Afrik" millions of years ago.
• it led me to a classification of life i hadn't thought through before:
  • Physical (i.e. based on some physical substrate)
    • chemical (built from chemical building blocks (which are in turn elementary particles and so-on and so forth; perhaps this is really a distinction of "level"?) )
    • magnetic (patterns of magnetic field)
    • other (? based on other physical substrata)
  • Nonphysical (i.e. not based on any physical substrate)
    • conscious substrate (a living creature existing on a substrate of conscious thought, e.g. a simulated earthworm's nervous system being "run" by a person who conceives of the entire state of the nervous system and steps forwards through time by applying physical law to the current state of the system)
    • non-conscious substrate (a living creating existing on a non-physical, non-conscious substrate, e.g. a simulated earthworm's nervous system being run in software on a conventional CPU)
    Note that these two (assuming the rules of the emulator are enforced equally well) have much in common; if one could be considered life, it'd be difficult to argue that the other should not.