Charles Lyell, Historian of Time's Cycle - Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time - page 138

top of the stratigraphic pile. Paleontologists had searched assiduously for
vertebrate remains. Could this literal appearance also be ascribed to
incompleteness of the record? Lyell quotes Sir Humphrey Davy on literal
appearance as confuting uniformities of both rate and state: "There seems, as
it were, a gradual approach to the present system of things, and a succession
of destructions and creations preparatory to the existence of man" (I, 145).
Lyell responds to this greatest challenge in chapter 9 of volume I: "theory of
the progressive development of organic life considered—evidences in its
support wholly inconclusive." He divides the attack on uniformity into two
separate questions requiring different responses: "First, that in the successive
groups of strata, from the oldest to the most recent, there is a progressive
development of organic life, from the simplest to the most complicated forms;
—secondly, that man is of comparatively recent origin" (I, 145). The first
claim, he argues, "has no foundation in fact"; the second, though
"indisputable," is not "inconsistent with the assumption, that the system of
the natural world has been uniform . . . from the era when the oldest rocks
hitherto discovered were formed" (I, 145).
Lyell uses two kinds of arguments to refute the first claim, that vertebrates
march up life's ladder in stratigraphic order. These arguments may not stand
formally in contradiction; but they certainly illustrate LyelTs willingness to
exploit both sides of a potential weakness.
First argument. Advanced vertebrates were present in the earliest strata as
well, but we haven't found their remains yet. Lyell here invokes his most
characteristic argument—the appearance of progress is caused by directional
biases in preservation, not by progressive trends in actual history. First of all,
apparent progress is not so marked or pervasive. Complex fish appear in the
earliest strata, reptiles soon after, and still in old rocks (now called
Paleozoic). The evidence for progress is entirely negative—the absence only
of birds and mammals in Paleozoic rocks. Birds so rarely fossilize that biases
of better preservation in more recent rocks might restrict