Standard Caveat - Even though this essay appears on the SAG website it is represented as solely the opinion of Mike Deering, and is not endorsed by the SAG organization or the individual members of the SAG Board of Directors. It is the policy of the SAG to present a diversity of opinion on the Singularity.
With the advent of neural scanning and functional duplication in silicon circuitry, a whole host of options become available. Undoubtedly, a large portion of mankind will decline any electronic augmentation, the total biologicals. But even the total biologicals will benefit greatly from the advances in nanomedicine.
Level one - natural humans with pre-nanotechnology medicine (us), and nanotechnology derived non-nanobot medicines and medical therapies. Level-one humans will not allow active nanobots to invade every part of their bodies. Level-one will consist of people with anti-technology philosophies, and members of some religions that will call nanobots the devil's minions, whose acceptance will constitute taking the "mark of the beast" as it is called in Revelations.
Level two - natural humans with medical nanobots to repair and assist natural biological mechanisms. Active nanobots will cruise the blood stream and enter every cell to repair and maintain all molecular biological processes. All damage will be corrected at the molecular level. All invading organisms will be attacked by hunter-killer nanobots, and all waste materials will be removed preventing accumulation. Medical nanobots will keep your neurons in tip-top shape, prevent your fat cells from bulging, maintain your metabolism in perfect working order, and sculpt your appearance to your ideal. Level-two's will never grow old, get sick, or suffer any physical imperfection. They will be thoroughly human, as all repair functions will be strictly limited to that which falls within the design specification of the human genome. Level-two's will enjoy all the advantages of medical nanobots while not wanting to give up their humanity.
Level three - transhumans, engineered biologicals. Level-three transhumans will use nanotechnology to re-engineer their biological mechanisms for greater functionality and new capabilities, while maintaining the biological paradigm. Biomolecules, cellular organelles, organ and tissue systems, and overall body design will be redesigned and optimized giving enhanced senses, adaptation to different environments, and radical aesthetic body forms. Level-three's will resist going to level-four because of beliefs about the biological basis of life and consciousness.
Level four - post-human non-biological life-forms, nano-electromechanical computational machine paradigm. The biological paradigm is abandoned, or, in the case of AGI's, never adopted. Whether a level-four is a former re-engineered human, and upload, or an AGI, the capabilities and limitations, if any, are the same. Level-four computational and physical capabilities are limited only by physical law. The forms and powers of a level-four are beyond level-one comprehension.
I have seen the future, and it is us. What do you want to be when you grow up? You may notice some correlation between these levels and Eliezer Yudkowsky's shock levels. The disparities in intelligence and powers between the levels will make contemporary democratic ideas obsolete. Verner Vinge in his novels finds it necessary to physically separate the different levels, limiting contact and communication between them. We will not have that luxury. Once we level-one's have created or become level-four's our evolutionary function will have been discharged. Those who decide to remain at the lower levels may spend eternity doing whatever pointless things amuse them.
Singularity Action Group website frames version.