A History of Science, vol 4 - Henry Smith Williams (epub e ink reader .txt) 📗

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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