For example, a typical E. coli bacterium has about 4,700 genes. At the other end of the evolutionary spectrum, the human genome has about six billion nucleotide pairs. Still, the number of genes in a human is estimated to be 100,000 or even 140,000. Humans have organs and systems that prokaryotes do not. These features are made possible by genetic instructions that humans have and prokaryotes do not.
Most human genes have no known analogs in the world of bacteria.
Compared with any prokaryotic gene, they have nucleotide differences in dozens to hundreds of essential positions. But the process has not been demonstrated in any experiment. In his analysis, a beneficial gene differing from an earlier gene by five nucleotide substitutions can be fixed in a species if the population is large enough, and if none of the intermediate genes is fatal. This method would require evolution to be ultragradual, which is not confirmed by the fossil record. Furthermore, it would require that there are gradual pathways, without any fatal intermediates, such that they lead from an original set of prokaryotic genes to, ultimately, all the genes employed by all higher life forms.