Robots
[ Edit (Sep 2020) : I no longer entirely agree with everything I wrote 2009 below. I don't think we should subscribe to any view that appears to almost romanticize or frame human obsolescence in an almost sort of 'positive' light, or to fatalistically accept it as any supposed 'inevitability'. Even if we eventually invent "superior" machines, we can and should assert our right to exist, and can and should do what it takes to survive and thrive in such a hypothetical world [notwithstanding our own obligations to uphold rational ethical principles - the existing of violators of ethical rights are not a reason to end the species, rather, we have a justice system for that]. Also, we could improve ourselves in various ways to remain 'competitive' with increasingly better machines, for example through augmentation (e.g. systems like what Neuralink aims to be), or perhaps in future through genetic modification. Furthermore, there are also two different c...