i understand quite well how evolution is supposed to work i understand the capriciousness and contingencies in the workings of evolution it is the paragraph in question especially the example in that paragraph which distorts the workings of evolution the phrase it need only increase at a rate of cm per generation cm easily gives the impression of progressive linear change the anthropocentric notions of directionality and purpose often i assume inadvertently find their way into the writings of specialists who attempt to explain various forms of darwinian evolution from these i have often read how evolution invents various forms and functions carl sagan in my opinion one of the worst offenders in these matters injected anthropocentric notions on a massive scale so as to justify his idea of a million highly advanced technological civilizations in the galaxy i read your paragraph as suffering from the same notions of directionality