The Chain of Life in Geological Time: A Sketch of the Origin and Succession of Animals and PlantsDawson, John William, Sir
Science
The Chain of Life in Geological Time: A Sketch of the Origin and Succession of Animals and Plants
Dawson, John William, Sir
Paleobotany; Paleontology
(5) Many allied species, constituting groups of animals and plants, have
made their appearance at once in various parts of the earth, and these
groups have obeyed the same laws with the individual and the species in
culminating rapidly, and then slowly diminishing, though a large group
once introduced has rarely disappeared altogether.
(6) Groups of species, as genera and orders, do not usually begin with
their highest or lowest forms, but with intermediate and generalised
types, and they show a capacity for both elevation and degradation in
their subsequent history.
(7) The history of life presents a progress from the lower to the
higher, and from the simpler to the more complex, and from the more
generalised to the more specialised. In this progress new types are
introduced, and take the place of the older ones, which sink to a
relatively subordinate place, and become thus degraded. But the physical
and organic changes have been so correlated and adjusted that life has
not only always maintained its existence, but has been enabled to assume
more complex forms, and that older forms have been made to prepare the
way for newer, so that there has been on the whole a steady elevation
culminating in man himself. Elevation and specialisation have, however,
been secured at the expense of vital energy and range of adaptation,
until the new element of a rational and inventive nature was introduced
in the case of man.
(8) In regard to the larger and more distinct types, we cannot find
evidence that they have, in their introduction, been preceded by similar
forms connecting them with previous groups; but there is reason to
believe that many supposed representative species in successive
formations are really only races or varieties.
(9) In so far as we can trace their history, specific types are
permanent in their characters from their introduction to their
extinction, and their earlier varietal forms are similar to their later
ones.
(10) Palæontology furnishes no direct evidence, perhaps never can
furnish any, as to the actual transformation of one species into
another, or as to the actual circumstances of creation of a species, but
the drift of its testimony is to show that species come in _per saltum_,
rather than by any slow and gradual process.
(11) The origin and history of life cannot, any more than the origin and
determination of matter and force, be explained on purely material
grounds, but involve the consideration of power referable to the unseen
and spiritual world.
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