Maybe if you're constraining 'general purpose manipulation' to mean 'rearranging blocks'. I'm thinking more along the lines of "can build a PC" or "repair a ma

Maybe if you're constraining 'general purpose manipulation' to mean 'rearranging blocks'. I'm thinking more along the lines of "can build a PC" or "repair a machine." I don't think we'll need to lap flint spearheads in 2018 and beyond. I don't think we need to have repair bots play the fiddle so much on the surface of Mars. I do think that the manipulation tasks useful to a 21st century civilization are "within the grasp" of simpler manipulators than the human hand. The human hand is freakishly complex. If we can get 80% of the functionality for 25% the cost, that will be a win. (For the most difficult 20%, there are still humans.) That complexity (and especially the extra brain power to run it) costs energy. If it wasn't useful, we wouldn't have it. Of course it's useful! No one disputes that! It doesn't matter. You're fallacious in supposing that 1) all of the complexity and capability is absolutely essential in current and future contexts and 2) that evolution had bought it with maximal possible efficiency. What we understand about evolution tells us that the 1st isn't necessarily true, and that the 2nd is probably not! Yes, there will be a place for human hands. But some huge fraction of the current uses of human hands will probably be replaced by very capable but much simpler manipulators -- simply due to economics!