97 Essays on Infinite Lifespans   Raymond Kurzweil Once perfected, we will no longer need version 1.0 of our digestive system at all. I pointed out above that our adop- tion of these technologies will be cautious and incremental, so we will not dispense with the old-fashioned digestive pro- cess when these technologies are first introduced. Most of us will wait for digestive system version 2.1 or even 2.2 before being willing to dispense with version 1.0. After all, people didn’t  throw  away  their  typewriters  when  the  first  genera- tion  of  word  processors  was  introduced.  People  held  onto their vinyl record collections for many years after CDs came out  (I  still  have  mine).  People  are  still  holding  onto  their film  cameras,  although  the  tide  is  rapidly  turning  in  favor of digital cameras. However, these new technologies do ulti- mately dominate, and few people today still own a typewriter. The same phenomenon will happen with our reengineered bodies. Once we’ve worked out the inevitable complications that will arise with a radically reengineered gastrointestinal system, we will begin to rely on it more and more. PROGRAMMABLE BLOOD As we reverse-engineer (learn the principles of operation of) our various bodily systems, we will be in a position to engi- neer new systems that provide dramatic improvements. One pervasive system that has already been the subject of a com- prehensive conceptual redesign is our blood. One of the leading proponents of ‘nanomedicine’, (rede- signing  our  biological  systems  through  engineering  on  a molecular scale) and author of a book with the same name is Robert Freitas, Research Scientist at the nanotechnology firm Zyvex Corp. Freitas’ ambitious manuscript is a comprehen- sive road map to rearchitecting our biological heritage. One of Freitas’ designs is to replace (or augment) our red blood cells