Lamarck, the Founder of Evolution Part 9

We now come to Lamarck's own time. He must have been familiar with the results of Pallas's travels in Russia and Siberia (1793-94). The distinguished German zoologist and geologist, besides working out the geology of the Ural Mountains, showed, in 1777, that there was a general law in the formation of all mountain chains composed chiefly of primary rocks;[70] the granitic axis being flanked by schists, and these by fossiliferous strata. From his observations made on the Volga and about its mouth, he presented proofs of the former extension, in comparatively recent times, of the Caspian Sea. But still more pregnant and remarkable was his discovery of an entire rhinoceros, with its flesh and skin, in the frozen soil of Siberia. His memoir on this animal places him among the forerunners of, if not within the ranks of, the founders of palaeontology.

Meanwhile Soldani, an Italian, had, in 1780, shown that the limestone strata of Italy had acc.u.mulated in a deep sea, at least far from land, and he was the first to observe the alternation of marine and fresh-water strata in the Paris basin.

Lamarck must have taken much interest in the famous controversy between the Vulcanists and Neptunists. He visited Freyburg in 1771; whether he met Werner is not known, as Werner began to lecture in 1775. He must have personally known Faujas of Paris, who, in 1779, published his description of the volcanoes of Vivarais and Velay; while Desmarest's (1725-1815) elaborate work on the volcanoes of Auvergne, published in 1774, in which he proved the igneous origin of basalt, was the best piece of geological exploration which had yet been accomplished, and is still a cla.s.sic.[71]

Werner (1750-1817), the propounder of the Neptunian theory, was one of the founders of modern geology and of palaeontology. His work ent.i.tled _Ueber die aussern Kennzeichen der Fossilien_ appeared in 1774; his _Kurze Kla.s.sifikation und Beschreibung der Gebirgsarten_ in 1787. He discovered the law of the superposition of stratified rocks, though he wrongly considered volcanic rocks, such as basalt, to be of aqueous origin, being as he supposed formed of chemical precipitates from water.

But he was the first to state that the age of different formations can be told by their fossils, certain species being confined to particular beds, while others ranged throughout whole formations, and others seemed to occur in several different formations; "the original species found in these formations appearing to have been so const.i.tuted as to live through a variety of changes which had destroyed hundreds of other species which we find confined to particular beds."[72] His views as regards fossils, as Jameson states, were probably not known to Cuvier, and it is more than doubtful whether Lamarck knew of them. He observed that fossils appear first in "transition" or palaeozoic strata, and were mainly corals and molluscs; that in the older carboniferous rocks the fossils are of higher types, such as fish and amphibious animals; while in the tertiary or alluvial strata occur the remains of birds and quadrupeds. He thought that marine plants were more ancient than land plants. His studies led him to infer that the fossils contained in the oldest rocks are very different from any of the species of the present time; that the newer the formation, the more do the remains approach in form to the organic beings of the present creation, and that in the very latest formations, fossil remains of species now existing occur.

Such advanced views as these would seem to ent.i.tle Werner to rank as one of the founders of palaeontology.[73]

Hutton's _Theory of the Earth_ appeared in 1785, and in a more developed state, as a separate work, in 1795.[74] "The ruins of an older world,"

he said, "are visible in the present structure of our planet, and the strata which now compose our continents have been once beneath the sea, and were formed out of the waste of preexisting continents. The same forces are still destroying, by chemical decomposition or mechanical violence, even the hardest rocks, and transporting the materials to the sea, where they are spread out and form strata a.n.a.logous to those of more ancient date. Although loosely deposited along the bottom of the ocean, they became afterwards altered and consolidated by volcanic heat, and were then heaved up, fractured, and contorted." Again he said: "In the economy of the world I can find no traces of a beginning, no prospect of an end." As Lyell remarks: "Hutton imagined that the continents were first gradually destroyed by aqueous degradation, and when their ruins had furnished materials for new continents, they were upheaved by violent convulsions. He therefore required alternate periods of general disturbance and repose."

To Hutton, therefore, we are indebted for the idea of the immensity of the duration of time. He was the forerunner of Lyell and of the uniformitarian school of geologists.

Hutton observed that fossils characterized certain strata, but the value of fossils as time-marks and the principle of the superposition of stratified fossiliferous rocks were still more clearly established by William Smith, an English surveyor, in 1790. Meanwhile the Abbe Hauy, the founder of crystallography, was in 1802 Professor of Mineralogy in the Jardin des Plantes.

_Lamarck's Contributions to Physical Geology; his Theory of the Earth._

Such were the amount and kind of knowledge regarding the origin and structure of our earth which existed at the close of the eighteenth century, while Lamarck was meditating his _Hydrogeologie_, and had begun to study the invertebrate fossils of the Paris tertiary basin.

His object, he says in his work, is to present certain considerations which he believed to be new and of the first order, which had escaped the notice of physicists, and which seemed to him should serve as the foundations for a good theory of the earth. His theses are:

1. What are the natural consequences of the influence and the movements of the waters on the surface of the globe?

2. Why does the sea constantly occupy a basin within the limits which contain it, and there separate the dry parts of the surface of the globe always projecting above it?

3. Has the ocean basin always existed where we actually see it, and if we find proofs of the sojourn of the sea in places where it no longer remains, by what cause was it found there, and why is it no longer there?

4. What influence have living bodies exerted on the substances found on the surface of the earth and which compose the crust which invests it, and what are the general results of this influence?

Lamarck then disclaims any intentions of framing brilliant hypotheses based on supposit.i.tious principles, but nevertheless, as we shall see, he falls into this same error, and like others of his period makes some preposterous hypotheses, though these are far less so than those of Cuvier's _Discours_. He distinguishes between the action of rivers or of fresh-water currents, torrents, storms, the melting of snow, and the work of the ocean. The rivers wear away and bear materials from the highlands to the lowlands, so that the plains are gradually elevated; ravines form and become immense valleys, and their sides form elevated crests and pa.s.s into mountain ranges.

He brings out and emphasizes the fact, now so well known, that the erosive action of rain and rivers has formed mountains of a certain cla.s.s.

"It is then evident to me, that every mountain which is not the result of a _volcanic irruption_ or of some local catastrophe, has been carved out from a plain, where its ma.s.s is gradually formed, and was a part of it; hence what in this case are the summits of the mountains are only the remains of the former level of the plain unless the process of washing away and other means of degradation have not since reduced its height."

Now this will apply perfectly well to our table-lands, mesas, the mountains of our bad-lands, even to our Catskills and to many elevations of this nature in France and in northern Africa. But Lamarck unfortunately does not stop here, but with the zeal of an innovator, by no means confined to his time alone, claims that the mountain ma.s.ses of the Alps and the Andes were carved out of plains which had been raised above the sea-level to the present heights of those mountains.

Two causes, he says, have concurred in forming these elevated plains.

"One consists in the continual acc.u.mulation of material filling the portion of the ocean-basin from which the same seas slowly retreat; for it does not abandon those parts of the ocean-basin which are situated nearer and nearer to the sh.o.r.es that it tends to leave, until after having filled its bottom and having gradually raised it.

It follows that the coasts which the sea is abandoning are never made by a very deep-lying formation, however often it appears to be such, for they are continually elevated as the result of the perpetual balancing of the sea, which casts off from its sh.o.r.es all the sediments brought down by the rivers; in such a way that the great depths of the ocean are not near the sh.o.r.e from which the sea retreats, but out in the middle of the ocean and near the opposite sh.o.r.es which the sea tends to invade.

"The other cause, as we shall see, is found in the detritus of organic bodies successively acc.u.mulated, which perpetually elevates, although with extreme slowness, the soil of the dry portions of the globe, and which does it all the more rapidly, as the situation of these parts gives less play to the degradation of the surface caused by the rivers.

"Doubtless a plain which is destined some day to furnish the mountains which the rivers will carve out from its ma.s.s would have, when still but a little way from the sea, but a moderate elevation above its river channels; but gradually as the ocean basin removed from this plain, this basin constantly sinking down into the interior (_epaisseur_) of the external crust of the globe, and the soil of the plain perpetually rising higher from the deposition of the detritus of organic bodies, it results that, after ages of elevation of the plain in question, it would be in the end sufficiently thick for high mountains to be shaped and carved out of its ma.s.s.

"Although the ephemeral length of life of man prevents his appreciation of this fact, it is certain that the soil of a plain unceasingly acquires a real increase in its elevation in proportion as it is covered with different plants and animals. Indeed the debris successively heaped up for numerous generations of all these beings which have by turns perished, and which, as the result of the action of their organs, have, during the course of this life, given rise to combinations which would never have existed without this means, most of the principles which have formed them not being borrowed from the soil; this debris, I say, wasting successively on the soil of the plain in question, gradually increases the thickness of its external bed, multiplies there the mineral matters of all kinds and gradually elevates the formation."

Our author, as is evident, had no conception, nor had any one else at the time he wrote, of the slow secular elevation of a continental plateau by crust-movements, and Lamarck's idea of the formation of elevated plains on land by the acc.u.mulation of debris of organisms is manifestly inadequate, our aerial or eolian rocks and loess being wind-deposits of sand and silt rather than matters of organic origin.

Thus he cites as an example of his theory the vast elevated plains of Tartary, which he thought had been dry land from time immemorable, though we now know that the rise took place in the quaternary or present period. On the other hand, given these vast elevated plains, he was correct in affirming that rivers flowing through them wore out enormous valleys and carved out high mountains, left standing by atmospheric erosion, for examples of such are to be seen in the valley of the Nile, the Colorado, the Upper Missouri, etc.

He then distinguishes between granitic or crystalline mountains, and those composed of stratified rocks and volcanic mountains.

The erosive action of rivers is thus discussed; they tend first, he says, to fill up the ocean basins, and second, to make the surface of the land broken and mountainous, by excavating and furrowing the plains.

Our author did not at all understand the causes of the inclination or tilting up of strata. Little close observation or field work had yet been done, and the rocks about Paris are but slightly if at all disturbed. He attributes the dipping down of strata to the inclination of the sh.o.r.es of the sea, though he adds that nevertheless it is often due to local subsidences. And then he remarks that "indeed in many mountains, and especially in the Pyrenees, in the very centre of these mountains, we observe that the strata are for the most part either vertical or so inclined that they more or less approach this direction."

"But," he asks, "should we conclude from this that there has necessarily occurred a universal catastrophe, a general overturning?

This a.s.sumption, so convenient for those naturalists who would explain all the facts of this kind without taking the trouble to observe and study the course which nature follows, is not at all necessary here; for it is easy to conceive that the inclined direction of the beds in the mountains may have been produced by other causes, and especially by causes more natural and less hypothetical than a general overturning of strata."

While streams of fresh water tend to fill up and destroy the ocean basins, he also insists that the movements of the sea, such as the tides, currents, storms, submarine volcanoes, etc., on the contrary, tend to unceasingly excavate and reestablish these basins. Of course we now know that tides and currents have no effect in the ocean depths, though their scouring effects near sh.o.r.e in shallow waters have locally had a marked effect in changing the relations of land and sea. Lamarck went so far as to insist that the ocean basin owes its existence and its preservation to the scouring action of the tides and currents.

The earth's interior was, in Lamarck's opinion, solid, formed of quartzose and silicious rocks, and its centre of gravity did not coincide with its geographical centre, or what he calls the _centre de forme_. He imagined also that the ocean revolved around the globe from east to west, and that this movement, by its continuity, displaced the ocean basin and made it pa.s.s successively over all the surface of the earth.

Then, in the third chapter, he asks if the basin of the sea has always been where we now actually see it, and whether we find proofs of the sojourn of the sea in the place where it is now absent; if so, what are the causes of these changes. He reiterates his strange idea of a general movement of the ocean from east to west, at the rate of at least three leagues in twenty-four hours and due to the moon's influence. And here Lamarck, in spite of his uniformitarian principles, is strongly cataclysmic. What he seems to have in mind is the great equatorial current between Africa and the West Indies. To this perpetual movement of the waters of the Atlantic Ocean he ventures to attribute the excavation of the Gulf of Mexico, and presumes that at the end of ages it will break through the Isthmus of Panama, and transform America into two great islands or two small continents. Not understanding that the islands are either the result of upheaval, or outliers of continents, due to subsidence, Lamarck supposed that his westward flow of the ocean, due to the moon's attraction, eroded the eastern sh.o.r.es of America, and the currents thus formed "in their efforts to move westward, arrested by America and by the eastern coasts of China, were in great part diverted towards the South Pole, and seeking to break through a pa.s.sage across the ancient continent have, a long time since, reduced the portion of this continent which united New Holland to Asia into an archipelago which comprises the Molucca, Philippine, and Mariana Islands." The West Indies and Windward Islands were formed by the same means, and the sea not breaking through the Isthmus of Panama was turned southward, and the action of its currents resulted in detaching the island of Tierra del Fuego from South America. In like manner New Zealand was separated from New Holland, Madagascar from Africa, and Ceylon from India.

He then refers to other "displacements of the ocean basin," to the shallowing of the Straits of Sunda, of the Baltic Sea, the ancient subsidence of the coast of Holland and Zealand, and states that Sweden offers all the appearance of having recently emerged from the sea, while the Caspian Sea, formerly much larger than at present, was once in communication with the Black Sea, and that some day the Straits of Sunda and the Straits of Dover will be dry land, so that the union of England and France will be formed anew.

Strangely enough, with these facts known to him, Lamarck did not see that such changes were due to changes of level of the land rather than to their being abandoned or invaded by the sea, but explained these by his bizarre hypothesis of westward-flowing currents due to the moon's action; though it should be in all fairness stated that down to recent times there have been those who believed that it is the sea and not the land which has changed its level.

This idea, that the sea and not the land has changed its level, was generally held at the time Lamarck wrote, though Strabo had made the shrewd observation that it was the land which moved. The Greek geographer threw aside the notion of some of his contemporaries, and with wonderful prevision, considering the time he wrote and the limited observations he could make, claimed that it is not the sea which has risen or fallen, but the land itself which is sometimes raised up and sometimes depressed, while the sea-bottom may also be elevated or sunk down. He refers to such facts as deluges, earthquakes, and volcanic eruptions, and sudden swellings of the land beneath the sea.

"And it is not merely the small, but the large islands also, not merely the islands, but the continents which can be lifted up together with the sea; and, too, the large and small tracts may subside, for habitations and cities, like Bure, Bizona, and many others, have been engulfed by earthquakes."[75]

But it was not until eighteen centuries later that this doctrine, under the teachings of Playfair, Leopold von Buch, and elie de Beaumont (1829-30) became generally accepted. In 1845 Humboldt remarked, "It is a fact to-day recognized by all geologists, that the rise of continents is due to an actual upheaval, and not to an apparent subsidence occasioned by a general depression of the level of the sea" (_Cosmos_, i). Yet as late as 1869 we have an essay by H. Trautschold[76] in which is a statement of the arguments which can be brought forward in favor of the doctrine that the increase of the land above sea level is due to the retirement of the sea.[77]

As authentic and unimpeachable proofs of the former existence of the sea where now it is absent, Lamarck cites the occurrence of fossils in rocks inland. Lamarck's first paper on fossils was read to the Inst.i.tute in 1799, or about three years previous to the publication of the _Hydrogeologie_. He restricts the term "fossils" to vegetable and animal remains, since the word in his time was by some loosely applied to minerals as well as fossils; to anything dug out of the earth. "We find fossils," he says, "on dry land, even in the middle of continents and large islands; and not only in places far removed from the sea, but even on mountains and in their bowels, at considerable heights, each part of the earth's surface having at some time been a veritable ocean bottom."

He then quotes at length accounts of such instances from Buffon, and notices their prodigious number, and that while the greater number are marine, others are fresh-water and terrestrial sh.e.l.ls, and the marine sh.e.l.ls may be divided into littoral and pelagic.

"This distinction is very important to make, because the consideration of fossils is, as we have already said, one of the princ.i.p.al means of knowing well the revolutions which have taken place on the surface of our globe. This subject is of great importance, and under this point of view it should lead naturalists to study fossil sh.e.l.ls, in order to compare them with their a.n.a.logues which we can discover in the sea; finally, to carefully seek the places where each species lives, the banks which are formed of them, the different beds which these banks may present, etc., etc., so that we do not believe it out of place to insert here the princ.i.p.al considerations which have already resulted from that which is known in this respect.

"_The fossils which are found in the dry parts of the surface of the globe are evident indications of a long sojourn of the sea in the very places where we observe them._" Under this heading, after repeating the statement previously made that fossils occur in all parts of the dry land, in the midst of the continents and on high mountains, he inquires _by what cause_ so many marine sh.e.l.ls could be found in the explored parts of the world. Discarding the old idea that they are monuments of the deluge, transformed into fossils, he denies that there was such a general catastrophe as a universal deluge, and goes on to say in his a.s.sured, but calm and philosophic way:

"On the globe which we inhabit, everything is submitted to continual and inevitable changes, which result from the essential order of things: they take place, in truth, with more or less prompt.i.tude or slowness, according to the nature, the condition, or the situation of the objects; nevertheless they are wrought in some time or other.

"To nature, time is nothing, and it never presents a difficulty; she always has it at her disposal, and it is for her a means without limit, with which she has made the greatest as well as the least things.

"The changes to which everything in this world is subjected are changes not only of form and of nature, but they are changes also of bulk, and even of situation.

"All the considerations stated in the preceding chapters should convince us that nothing on the surface of the terrestrial globe is immutable. They teach us that the vast ocean which occupies so great a part of the surface of our globe cannot have its bed constantly fixed in the same place; that the dry or exposed parts of this surface themselves undergo perpetual changes in their condition, and that they are in turn successively invaded and abandoned by the sea.

"There is, indeed, every evidence that these enormous ma.s.ses of water continually displace themselves, both their bed and their limits.

"In truth these displacements, which are never interrupted, are in general only made with extreme and almost inappreciable slowness, but they are in ceaseless operation, and with such constancy that the ocean bottom, which necessarily loses on one side while it gains on another, has already, without doubt, spread over not only once, but even several times, every point of the surface of the globe.

"If it is thus, if each point of the surface of the terrestrial globe has been in turn dominated by the seas--that is to say, has contributed to form the bed of those immense ma.s.ses of water which const.i.tute the ocean--it should result (1) that the insensible but uninterrupted transfer of the bed of the ocean over the whole surface of the globe has given place to deposits of the remains of marine animals which we should find in a fossil state; (2) that this translation of the ocean basin should be the reason why the dry portions of the earth are always more elevated than the level of the sea; so that the old ocean bed should become exposed without being elevated above the sea, and without consequently giving rise to the formation of mountains which we observe in so many different regions of the naked parts of our globe."