Page 126 - Once Upon a Time There Was Darwinism

Once Upon a Time
There Was Darwinism

tive photoreceptor cells of higher vertebrates with copious
quantities of oxygen and nutrients. 68
To understand this fact stressed by Professor Denton but

unnoticed by Dawkins, we must first recognize that the retina's
photoreceptor cells need a high level of energy and oxygen. While
our eyes are open to perceive light, these cells are the locus of very
complex chemical reactions every second. Photons, the smallest
particles of light, are perceived by the cells and, as a result of the
highly detailed chemical reactions begun by the photons, percep-
tion occurs and is repeated every instant. This reaction is so com-

plex and rapid that, in Denton's words, "the photoreceptor layer has
one of the highest metabolic rates of any known tissue." 69
To keep up this high rate of metabolism, of course, the retina
cells need a great deal of energy. A human being's retinal cells
consume 150% as much oxygen as renal cells, three

Michael Denton, professor of biology