Bacteria, protozoa and plants have genes in common with humans. Bacteria already have blood groups. Protozoa display in organelle form most of the functions present in humans as organs. Plants produce hemoglobin, sex hormones and neurotransmitters.
A metazoan may have been formed by mainly sorting out and rearranging the protozoan genes. All human cell types can be traced to only four basic tissues. Structures analogous to these tissues are already present in the protozoa.
The deer Muntiacus muntjak has only 3 chromosomes, but another species, M. reevesi, has as many chromosomes as humans (n=23). Thus, genes can be reorganized into 3 or 23 chromosomes to produce essentially similar animals. Human chromosomes could be compressed into a single chromosome in terms of their DNA content. A single chromosome of Tradescantia has more DNA than the 23 human chromosomes and behaves quite well at cell division.
To produce 106 functions, 106 genes are not necessary. One enzyme may have five functions, two genes may produce five enzymes, several messenger RNAs can be transcribed from a single DNA segment. Thus, 1000 primary genes may be quite enough, if not too many. There is experimental evidence that secondary genes can be produced by combination of the primary ones. From these genes multiple messenger RNAs, multiple enzymes and multiple functions can be obtained.