126 Will Robots Inherit the Earth? – or extensive, constant treatment using future regenerative medicine. In computer programs it is easy to install such redun- dancy. Many computers maintain unused copies of their most critical ‘system’ programs, and routinely check their integrity. However,  no  animals  have  evolved  like  schemes,  presum- ably because such algorithms cannot develop through natural selection. The trouble is that error correction then would stop mutation – which would ultimately slow the rate of evolu- tion of an animal’s descendants so much that they would be unable to adapt to changes in their environments. Could we live for several centuries simply by changing some number of genes? After all, we now differ from our evolu- tionary relatives, the gorillas and chimpanzees, by only a few thousand genes – and yet we live almost twice as long. If we assume that only a small fraction of those new genes caused that increase in life span, then perhaps no more than a hun- dred  or  so  of  those  genes  were  involved.  Still,  even  if  this turned out to be true, it would not guarantee that we could gain  another  century  by  changing  another  hundred  genes. We might need to change only a few of them – or we might have to change a good many more. Making new genes and installing them is slowly becoming feasible. But we are already exploiting another approach to combat biological wear and tear: replacing each organ that threatens to fail with a biological or artificial substitute. Some replacements have already become routine, while others are on the horizon. Hearts are merely clever pumps. Muscles and bones are motors and beams. Digestive systems are chemi- cal reactors. Eventually, we will solve the problems associated with transplanting or replacing all of these parts. When we consider replacing a brain though, a transplant will not work. You cannot simply exchange your brain for another  and  remain  the  same  person.  You  would  lose  the knowledge  and  the  processes  that  constitute  your  identity.