We show that the rate of gene expression evolution varies among organs, lineages and chromosomes, owing to differences in selective pressures: transcriptome change was slow in nervous tissues and rapid in testes, slower in rodents than in apes and monotremes, and rapid for the X chromosome right after its formation.
Of course there is no such thing as “selective pressure.” This phrase is commonly used to envision an active process that responds to environmental challenges. If natural selection shapes and designs the species according to need, then it sounds more plausible. In reality, all natural selection does is kill off the bad designs.
Although gene expression evolution in mammals was strongly shaped by purifying selection, …
Translation: The evolutionists found that many cases similar genes have similar expression rates.
we identify numerous potentially selectively driven expression switches, which occurred at different rates across lineages and tissues and which probably contributed to the specific organ biology of various mammals.
In other words, the evolutionists also found some similar genes that have significantly different expression rates. So the evolutionists must infer a new kind of evolution. Instead of mutations grinding away which, on rare occasion, provide a slightly better design (in terms of reproduction of course), the new kind of evolution states that the genes and their regulation mechanisms are generally already in place. What changes is their expression rates. So evolution created all these genes and regulation mechanisms, no knowing that it had just created the building blocks for all massive biological complexity. All that was needed was some expression rate changes.
Aside from being unlikely, evolution calls for massive serendipity. As usual, it is presented in teleological terms.