A History of Science, vol 4 by Henry Smith Williams (best novels to read for beginners txt) đź“–
- Author: Henry Smith Williams
- Performer: -
Book online «A History of Science, vol 4 by Henry Smith Williams (best novels to read for beginners txt) 📖». Author Henry Smith Williams
like other sets is of course patent, but this only means, said
Lamarck, that these similar groups have had comparatively recent
common ancestors, while dissimilar sets of beings are more
remotely related in consanguinity. But trace back the lines of
descent far enough, and all will culminate in one original stock.
All forms of life whatsoever are modified descendants of an
original organism. From lowest to highest, then, there is but one
race, one species, just as all the multitudinous branches and
twigs from one root are but one tree. For purposes of convenience
of description, we may divide organisms into orders, families,
genera, species, just as we divide a tree into root, trunk,
branches, twigs, leaves; but in the one case, as in the other,
the division is arbitrary and artificial.
In Philosophie Zoologique (1809), Lamarck first explicitly
formulated his ideas as to the transmutation of species, though
he had outlined them as early as 1801. In this memorable
publication not only did he state his belief more explicitly and
in fuller detail than the idea had been expressed by any
predecessor, but he took another long forward step, carrying him
far beyond all his forerunners except Darwin, in that he made an
attempt to explain the way in which the transmutation of species
had been brought about. The changes have been wrought, he said,
through the unceasing efforts of each organism to meet the needs
imposed upon it by its environment. Constant striving means the
constant use of certain organs. Thus a bird running by the
seashore is constantly tempted to wade deeper and deeper in
pursuit of food; its incessant efforts tend to develop its legs,
in accordance with the observed principle that the use of any
organ tends to strengthen and develop it. But such slightly
increased development of the legs is transmitted to the off
spring of the bird, which in turn develops its already improved
legs by its individual efforts, and transmits the improved
tendency. Generation after generation this is repeated, until the
sum of the infinitesimal variations, all in the same direction,
results in the production of the long-legged wading-bird. In a
similar way, through individual effort and transmitted tendency,
all the diversified organs of all creatures have been
developed—the fin of the fish, the wing of the bird, the hand of
man; nay, more, the fish itself, the bird, the man, even.
Collectively the organs make up the entire organism; and what is
true of the individual organs must be true also of their
ensemble, the living being.
Whatever might be thought of Lamarck’s explanation of the cause
of transmutation—which really was that already suggested by
Erasmus Darwin—the idea of the evolution for which he contended
was but the logical extension of the conception that American
animals are the modified and degenerated descendants of European
animals. But people as a rule are little prone to follow ideas to
their logical conclusions, and in this case the conclusions were
so utterly opposed to the proximal bearings of the idea that the
whole thinking world repudiated them with acclaim. The very
persons who had most eagerly accepted the idea of transmutation
of European species into American species, and similar limited
variations through changed environment, because of the relief
thus given the otherwise overcrowded ark, were now foremost in
denouncing such an extension of the doctrine of transmutation as
Lamarck proposed.
And, for that matter, the leaders of the scientific world were
equally antagonistic to the Lamarckian hypothesis. Cuvier in
particular, once the pupil of Lamarck, but now his colleague, and
in authority more than his peer, stood out against the
transmutation doctrine with all his force. He argued for the
absolute fixity of species, bringing to bear the resources of a
mind which, as a mere repository of facts, perhaps never was
excelled. As a final and tangible proof of his position, he
brought forward the bodies of ibises that had been embalmed by
the ancient Egyptians, and showed by comparison that these do not
differ in the slightest particular from the ibises that visit the
Nile to-day.
Cuvier’s reasoning has such great historical interest—being the
argument of the greatest opponent of evolution of that day—that
we quote it at some length.
“The following objections,” he says, “have already been started
against my conclusions. Why may not the presently existing races
of mammiferous land quadrupeds be mere modifications or varieties
of those ancient races which we now find in the fossil state,
which modifications may have been produced by change of climate
and other local circumstances, and since raised to the present
excessive difference by the operations of similar causes during a
long period of ages?
“This objection may appear strong to those who believe in the
indefinite possibility of change of form in organized bodies, and
think that, during a succession of ages and by alterations of
habitudes, all the species may change into one another, or one of
them give birth to all the rest. Yet to these persons the
following answer may be given from their own system: If the
species have changed by degrees, as they assume, we ought to find
traces of this gradual modification. Thus, between the
palaeotherium and the species of our own day, we should be able
to discover some intermediate forms; and yet no such discovery
has ever been made. Since the bowels of the earth have not
preserved monuments of this strange genealogy, we have no right
to conclude that the ancient and now extinct species were as
permanent in their forms and characters as those which exist at
present; or, at least, that the catastrophe which destroyed them
did not leave sufficient time for the productions of the changes
that are alleged to have taken place.
“In order to reply to those naturalists who acknowledge that the
varieties of animals are restrained by nature within certain
limits, it would be necessary to examine how far these limits
extend. This is a very curious inquiry, and in itself exceedingly
interesting under a variety of relations, but has been hitherto
very little attended to… … …
Wild animals which subsist upon herbage feel the influence of
climate a little more extensively, because there is added to it
the influence of food, both in regard to its abundance and its
quality. Thus the elephants of one forest are larger than those
of another; their tusks also grow somewhat longer in places where
their food may happen to be more favorable for the production of
the substance of ivory. The same may take place in regard to the
horns of stags and reindeer. But let us examine two elephants,
the most dissimilar that can be conceived, we shall not discover
the smallest difference in the number and articulations of the
bones, the structure of the teeth, etc. … … . .
“Nature appears also to have guarded against the alterations of
species which might proceed from mixture of breeds by influencing
the various species of animals with mutual aversion from one
another. Hence all the cunning and all the force that man is able
to exert is necessary to accomplish such unions, even between
species that have the nearest resemblances. And when the mule
breeds that are thus produced by these forced conjunctions happen
to be fruitful, which is seldom the case, this fecundity never
continues beyond a few generations, and would not probably
proceed so far without a continuance of the same cares which
excited it at first. Thus we never see in a wild state
intermediate productions between the hare and the rabbit, between
the stag and the doe, or between the marten and the weasel. But
the power of man changes this established order, and continues to
produce all these intermixtures of which the various species are
susceptible, but which they would never produce if left to
themselves.
“The degrees of these variations are proportional to the
intensity of the causes that produced them—namely, the slavery
or subjection under which those animals are to man. They do not
proceed far in half-domesticated species. In the cat, for
example, a softer or harsher fur, more brilliant or more varied
colors, greater or less size—these form the whole extent of
variety in the species; the skeleton of the cat of Angora differs
in no regular and constant circumstances from the wild-cat of
Europe… … . .
The most remarkable effects of the influence of man are produced
upon that animal which he has reduced most completely under
subjection. Dogs have been transported by mankind into every part
of the world and have submitted their action to his entire
direction. Regulated in their unions by the pleasure or caprice
of their masters, the almost endless varieties of dogs differ
from one another in color, in length, and abundance of hair,
which is sometimes entirely wanting; in their natural instincts;
in size, which varies in measure as one to five, mounting in some
instances to more than a hundredfold in bulk; in the form of
their ears, noses, and tails; in the relative length of their
legs; in the progressive development of the brain, in several of
the domesticated varieties occasioning alterations even in the
form of the head, some of them having long, slender muzzles with
a flat forehead, others having short muzzles with a forehead
convex, etc., insomuch that the apparent difference between a
mastiff and a water-spaniel and between a greyhound and a pugdog
are even more striking than between almost any of the wild
species of a genus… … . .
It follows from these observations that animals have certain
fixed and natural characters which resist the effects of every
kind of influence, whether proceeding from natural causes or
human interference; and we have not the smallest reason to
suspect that time has any more effect on them than climate.
“I am aware that some naturalists lay prodigious stress upon the
thousands which they can call into action by a dash of their
pens. In such matters, however, our only way of judging as to the
effects which may be produced by a long period of time is by
multiplying, as it were, such as are produced by a shorter time.
With this view I have endeavored to collect all the ancient
documents respecting the forms of animals; and there are none
equal to those furnished by the Egyptians, both in regard to
their antiquity and abundance. They have not only left us
representatives of animals, but even their identical bodies
embalmed and preserved in the catacombs.
“I have examined, with the greatest attention, the engraved
figures of quadrupeds and birds brought from Egypt to ancient
Rome, and all these figures, one with another, have a perfect
resemblance to their intended objects, such as they still are
to-day.
“From all these established facts, there does not seem to be the
smallest foundation for supposing that the new genera which I
have discovered or established among extraneous fossils, such as
the paleoetherium, anoplotherium, megalonyx, mastodon,
pterodactylis, etc., have ever been the sources of any of our
present animals, which only differ so far as they are influenced
by time or climate. Even if it should prove true, which I am far
from believing to be the case, that the fossil elephants,
rhinoceroses, elks, and bears do not differ further from the
existing species of the same genera than the present races of
dogs differ among themselves, this would by no means be a
sufficient reason to conclude that they were of the same species;
since the races or varieties of dogs have been influenced by the
trammels of domesticity, which those other animals never did, and
indeed never could, experience.”[3]
To Cuvier’s argument from the fixity of Egyptian mummified birds
and animals, as above stated, Lamarck replied that this proved
nothing except that the ibis had become
Comments (0)