probably found adherents because it would deliver us from the
relationship to apes which many people so much dislike. In contrast to
it we have the second class of special hypotheses of descent, which
keeps strictly to the nearest structural relationship. This is the
only basis that justifies the drawing up of a special hypothesis of
descent. If this fundamental proposition be recognised, it will be
admitted that the doctrine of special descent upheld by Haeckel, and
set forth in Darwin's _Descent of Man_, is still valid to-day. In the
genealogical tree, man's place is quite close to the anthropoid apes;
these again have as their nearest relatives the lower Old World
monkeys, and their progenitors must be sought among the less
differentiated Platyrrhine monkeys, whose most important characters
have been handed on to the present day New World monkeys. How the
different genera are to be arranged within the general scheme
indicated depends in the main on the classificatory value attributed
to individual characters. This is particularly true in regard to
_Pithecanthropus_, which I consider as the root of a branch which has
sprung from the anthropoid ape root and has led up to man; the latter
I have designated the family of the Hominidae.
For the rest, there are, as we have said, various possible ways of
constructing the narrower genealogy within the limits of this branch
including men and apes, and these methods will probably continue to
change with the accumulation of new facts. Haeckel himself has
modified his genealogical tree of the Primates in certain details
since the publication of his _Generelle Morphologie_ in 1866, but its
general basis remains the same.[123] All the special genealogical
trees drawn up on the lines laid down by Haeckel and Darwin--and that
of Dubois may be specially mentioned--are based, in general, on the
close relationship of monkeys and men, although they may vary in
detail. Various hypotheses have been formulated on these lines, with
special reference to the evolution of man. _Pithecanthropus_ is
regarded by some authorities as the direct ancestor of man, by others
as a side-track failure in the attempt at the evolution of man. The
problem of the monophyletic or polyphyletic origin of the human race
has also been much discussed. Sergi[124] inclines towards the
assumption of a polyphyletic origin of the three main races of man,
the African primitive form of which has given rise also to the
gorilla and chimpanzee, the Asiatic to the Orang, the Gibbon, and
_Pithecanthropus_. Kollmann regards existing human races as derived
from small primitive races (pigmies), and considers that _Homo
primigenius_ must have arisen in a secondary and degenerative manner.
But this is not the place, nor have I the space to criticise the
various special theories of descent. One, however, must receive
particular notice. According to Ameghino, the South American monkeys
(_Pitheculites_) from the oldest Tertiary of the Pampas are the forms
from which have arisen the existing American monkeys on the one hand,
and on the other, the extinct South American Homunculidae, which are
also small forms. From these last, anthropoid apes and man have, he
believes, been evolved. Among the progenitors of man, Ameghino reckons
the form discovered by him (_Tetraprothomo_), from which a South
American primitive man, _Homo pampaeus_, might be directly evolved,
while on the other hand all the lower Old World monkeys may have
arisen from older fossil South American forms (Clenialitidae), the
distribution of which may be explained by the bridge formerly existing
between South America and Africa, as may be the derivation of all
existing human races from _Homo pampaeus_.[125] The fossil forms
discovered by Ameghino deserve the most minute investigation, as does
also the fossil man from South America of which Lehmann-Nitsche[126]
has made a thorough study.
It is obvious that, notwithstanding the necessity for fitting man's
line of descent into the genealogical tree of the Primates, especially
the apes, opinions in regard to it differ greatly in detail. This
could not be otherwise, since the different Primate forms, especially
the fossile forms, are still far from being exhaustively known. But
one thing remains certain,--the idea of the close relationship between
man and monkeys set forth in Darwin's _Descent of Man_. Only those who
deny the many points of agreement, the sole basis of classification,
and thus of a natural genealogical tree, can look upon the position of
Darwin and Haeckel as antiquated, or as standing on an insufficient
foundation. For such a genealogical tree is nothing more than a
summarised representation of what is known in regard to the degree of
resemblance between the different forms.
Darwin's work in regard to the descent of man has not been surpassed;
the more we immerse ourselves in the study of the structural
relationships between apes and man, the more is our path illumined by
the clear light radiating from him, and through his calm and
deliberate investigation, based on a mass of material in the
accumulation of which he has never had an equal. Darwin's fame will be
bound up for all time with the unprejudiced investigation of the
question of all questions, the descent of the human race.
FOOTNOTES:
[Footnote 75: _Life and Letters of Thomas Henry Huxley_, Vol. I. p.
171, London, 1900.]
[Footnote 76: _Ibid._, p. 363.]
[Footnote 77: No italics in original.]
[Footnote 78: _Life and Letters of Charles Darwin_, Vol. I. p. 93.]
[Footnote 79: _Ibid._ Vol. II. p. 263.]
[Footnote 80: _Ibid._ Vol. I. p. 94.]
[Footnote 81: _Life and Letters_, Vol. III. p. 175.]
[Footnote 82: _Ibid._ Vol. II. p. 109.]
[Footnote 83: _Ibid._ Vol. III. p. 112.]
[Footnote 84: _Ibid._ Vol. I. pp. 304-317.]
[Footnote 85: _Life and Letters_, Vol. I. p. 309.]
[Footnote 86: _Loc. cit._ p. 313.]
[Footnote 87: _Ibid._ Vol. II. p. 310.]
[Footnote 88: _Ibid._ Vol. III. p. 236. ["C. Ridley," Mr. Francis
Darwin points out to me, should be H. N. Ridley. A.C.S.]]
[Footnote 89: _Descent of Man_ (Popular Edit., 1901), fig. 1, p. 14.]
[Footnote 90: G. Schwalbe, "Das Darwin'sche Spitzohr beim menschlichen
Embryo," _Anatom. Anzeiger_, 1889, pp. 176-189, and other papers.]
[Footnote 91: _Descent of Man_, fig. 3, p. 24.]
[Footnote 92: _Descent of man_, p. 6.]
[Footnote 93: _Ibid._ p. 54.]
[Footnote 94: _Descent of Man_, p. 92.]
[Footnote 95: _Ibid._ p. 100.]
[Footnote 96: _Life and letters_, Vol. II. p. 161, June 22, 1859.]
[Footnote 97: _Ibid._ Vol. III. p. 15, March 17, 1863.]
[Footnote 98: _Descent of Man_, p. 132.]
[Footnote 99: _Ibid._ pp. 136, 137.]
[Footnote 100: _Ibid._ p. 143.]
[Footnote 101: _Ibid._ p. 193.]
[Footnote 102: _Descent of Man_, p. 231.]
[Footnote 103: _Descent of Man_, p. 308.]
[Footnote 104: _Life and Letters_, Vol. II. p. 23.]
[Footnote 105: _Loc. cit._ p. 39.]
[Footnote 106: _Loc. cit._ (1856), p. 82.]
[Footnote 107: _Ibid._ Vol. III p. 159.]
[Footnote 108: _Descent of Man_, p. 924.]
[Footnote 109: "Die Hautfarbe des Menschen," _Mitteilungen der
Anthropologischen Gessellschaft in Wien_, Vol. XXXIV. pp. 331-352.]
[Footnote 110: _Ibid._ p. 947.]
[Footnote 111: _Descent of Man_, p. 240.]
[Footnote 112: "Das geologische Alter der Pithecanthropus-Schichten
bei Trinil, Ost-Java." _Neues Jahrb. f. Mineralogie_. Festband, 1907.]
[Footnote 113: _Descent of Man_, p. 82.]
[Footnote 114: "La race humaine de Neanderthal ou de Canstatt en
Belgique." _Arch. de Biologie_, VII. 1887.]
[Footnote 115: Gorjanovic-Kramberger. _Der diluviale Mensch van
Krapina in Kroatien_, 1906.]
[Footnote 116: _Studien zur Vorgeschichte des Menschen_, 1906, pp. 154
ff.]
[Footnote 117: "On the cranial and facial characters of the Neandertal
Race." _Trans. R. Soc._ London, vol. 199, 1908, p. 281.]
[Footnote 118: Since this essay was written Schoetensack has
discovered near Heidelberg and briefly described an exceedingly
interesting lower jaw from rocks between the Pliocene and Diluvial
beds. This exhibits interesting differences from the forms of lower
jaw of _Homo primigenius_. (Schoetensack, _Der Unterkiefer des Homo
heidelbergensis_, Leipzig, 1908.) G. S.]
[Footnote 119: _Life and Letters of Thomas Henry Huxley_, Vol. II. p.
394.]
[Footnote 120: _Descent of Man_, p. 229.]
[Footnote 121: _Loc. cit._]
[Footnote 122: Klaatsch in his last publications speaks in the main
only of an ancestral form common to men and anthropoid apes.]
[Footnote 123: Haeckels latest genealogical tree is to be found in his
most recent work, _Unsere Ahnenreihe_. Jena, 1908.]
[Footnote 124: Sergi, G. _Europa_, 1908.]
[Footnote 125: _See_ Ameghino's latest paper, "_Notas preliminaries
sobre el Tetraprothomo argentinus_," etc. _Anales del Museo nacional
de Buenos Aires_, XVI. pp. 107-242, 1907.]
[Footnote 126: "Nouvelles recherches sur la formation pampeenne et
l'homme fossile de la Republique Argentine." _Rivista del Museo de la
Plata_, T. XIV. pp. 193-488.]
V
CHARLES DARWIN AS AN ANTHROPOLOGIST
BY ERNST HAECKEL
_Professor of Zoology in the University of Jena_
The great advance that anthropology has made in the second half of the
nineteenth century is due, in the first place, to Darwin's discovery
of the origin of man. No other problem in the whole field of research
is so momentous as that of "Man's place in nature," which was justly
described by Huxley (1863) as the most fundamental of all questions.
Yet the scientific solution of this problem was impossible until the
theory of descent had been established.
It is now a hundred years since the great French biologist Jean
Lamarck published his _Philosophie Zoologique_. By a remarkable
coincidence the year in which that work was issued, 1809, was the year
of the birth of his most distinguished successor, Charles Darwin.
Lamarck had already recognised that the descent of man from a series
of other Vertebrates--that is, from a series of Ape-like Primates--was
essentially involved in the general theory of transformation which he
had erected on a broad inductive basis; and he had sufficient
penetration to detect the agencies that had been at work in the
evolution of the erect bimanous man from the arboreal and quadrumanous
ape. He had, however, few empirical arguments to advance in support of
his hypothesis, and it could not be established until the further
development of the biological sciences--the founding of comparative
embryology by Baer (1828) and of the cell-theory by Schleiden and
Schwann (1838), the advance of physiology under Johannes Mueller
(1833), and the enormous progress of palaeontology and comparative
anatomy between 1820 and 1860--provided this necessary foundation.
Darwin was the first to coordinate the ample results of these lines of
research. With no less comprehensiveness than discrimination he
consolidated them as a basis of a modified theory of descent, and
associated with them his own theory of natural selection, which we
take to be distinctive of "Darwinism" in the stricter sense. The
illuminating truth of these cumulative arguments was so great in every
branch of biology that, in spite of the most vehement opposition, the
battle was won within a single decade, and Darwin secured the general
admiration and recognition that had been denied to his forerunner,
Lamarck, up to the hour of his death (1829).
Before, however, we consider the momentous influence that Darwinism
has had in anthropology, we shall find it useful to glance at its
history in the course of the last half century, and notice the various
theories that have contributed to its advance. The first attempt to
give extensive expression to the reform of biology by Darwin's work
will be found in my _Generelle Morphologie_ (1866)[127] which was
followed by a more popular treatment of the subject in my _Natuerliche
Schoepfungsgeschichte_ (1868),[128] a compilation from the earlier
work. In the first volume of the _Generelle Morphologie_ I endeavoured
to show the great importance of evolution in settling the fundamental
questions of biological philosophy, especially in regard to
comparative anatomy. In the second volume I dealt broadly with the
principle of evolution, distinguishing ontogeny and phylogeny as its
two coordinate main branches, and associating the two in the
Biogenetic Law. The Law may be formulated thus: "Ontogeny (embryology
or the development of the individual) is a concise and compressed
recapitulation of phylogeny (the palaeontological or genealogical
series) conditioned by laws of heredity and adaptation." The
"Systematic introduction to general evolution," with which the second
volume of the _Generelle Morphologie_ opens, was the first attempt to
draw up a natural system of organisms (in harmony with the principles
of Lamarck and Darwin) in the form of a hypothetical pedigree, and was
provisionally set forth in eight genealogical tables.
In the nineteenth chapter of the _Generelle Morphologie_--a part of
which has been republished, without any alteration, after a lapse of
forty years--I made a critical study of Lamarck's theory of descent
and of Darwin's theory of selection, and endeavoured to bring the
complex phenomena of heredity and adaptation under definite laws for
the first time. Heredity I divided into conservative and progressive:
adaptation into indirect (or potential) and direct (or actual). I then
found it possible to give some explanation of the correlation of the
two physiological functions in the struggle for life (selection), and
to indicate the important laws of divergence (or differentiation) and
complexity (or division of labor), which are the direct and inevitable
outcome of selection. Finally, I marked off dysteleology as the
science of the aimless (vestigial, abortive, atrophied, and useless)
organs and parts of the body. In all this I worked from a strictly
monistic standpoint, and sought to explain all biological phenomena on
the mechanical and naturalistic lines that had long been recognised in
the study of inorganic nature. Then (1866), as now, being convinced of
the unity of nature, the fundamental identity of the agencies at work
in the inorganic and the organic worlds, I discarded vitalism,
teleology, and all hypotheses of a mystic character.
It was clear from the first that it was essential, in the monistic
conception of evolution, to distinguish between the laws of
conservative and progressive heredity. Conservative heredity maintains
from generation to generation the enduring characters of the species.
Each organism transmits to its descendants a part of the morphological
and physiological qualities that it has received from its parents and
ancestors. On the other hand, progressive heredity brings new
characters to the species--characters that were not found in preceding
generations. Each organism may transmit to its offspring a part of the
morphological and physiological features that it has itself acquired,
by adaptation, in the course of its individual career, through the use
or disuse of particular organs, the influence of environment, climate,
nutrition, etc. At that time I gave the name of "progressive heredity"
to this inheritance of acquired characters, as a short and convenient
expression, but have since changed the term to "transformative
heredity" (as distinguished from conservative). This term is
preferable, as inherited regressive modifications (degeneration,
retrograde metamorphosis, etc.) come under the same head.
Transformative heredity--or the transmission of acquired
characters--is one of the most important principles in evolutionary
science. Unless we admit it most of the facts of comparative anatomy
and physiology are inexplicable. That was the conviction of Darwin no
less than of Lamarck, of Spencer as well as Virchow, of Huxley as well
as Gegenbaur, indeed of the great majority of speculative biologists.
This fundamental principle was for the first time called in question
and assailed in 1885 by August Weismann of Freiburg, the eminent
zoologist to whom the theory of evolution owes a great deal of
valuable support, and who has attained distinction by his extension of
the theory of selection. In explanation of the phenomena of heredity
he introduced a new theory, the "theory of the continuity of the
germ-plasm." According to him the living substance in all organisms
consists of two quite distinct kinds of plasm, somatic and germinal.
The permanent germ-plasm, or the active substance of the two
germ-cells (egg-cell and sperm-cell), passes unchanged through a
series of generations, and is not affected by environmental
influences. The environment modifies only the soma-plasm, the organs
and tissues of the body. The modifications that these parts undergo
through the influence of the environment or their own activity (use
and habit), do not affect the germ-plasm, and cannot therefore be
transmitted.
This theory of the continuity of the germ-plasm has been expounded by
Weismann during the last twenty-four years in a number of able
volumes, and is regarded by many biologists, such as Mr. Francis
Galton, Sir E. Ray Lankester, and Professor J. Arthur Thomson (who has
recently made a thorough-going defence of it in his important work
_Heredity_),[129] as the most striking advance in evolutionary
science. On the other hand, the theory has been rejected by Herbert
Spencer, Sir W. Turner, Gegenbaur, Koelliker, Hertwig, and many others.
For my part I have, with all respect for the distinguished Darwinian,
contested the theory from the first, because its whole foundation
seems to me erroneous, and its deductions do not seem to be in accord
with the main facts of comparative morphology and physiology.
Weismann's theory in its entirety is a finely conceived molecular
hypothesis, but it is devoid of empirical basis. The notion of the
absolute and permanent independence of the germ-plasm, as
distinguished from the soma-plasm, is purely speculative; as is also
the theory of germinal selection. The determinants, ids, and idants,
are purely hypothetical elements. The experiments that have been
devised to demonstrate their existence really prove nothing.
It seems to me quite improper to describe this hypothetical structure
as "Neodarwinism." Darwin was just as convinced as Lamarck of the
transmission of acquired characters and its great importance in the
scheme of evolution. I had the good fortune to visit Darwin at Down
three times and discuss with him the main principles of his system,
and on each occasion we were fully agreed as to the incalculable
importance of what I may call transformative inheritance. It is only
proper to point out that Weismann's theory of the germ-plasm is in
express contradiction to the fundamental principles of Darwin and
Lamarck. Nor is it more acceptable in what one may call its
"ultradarwinism"--the idea that the theory of selection explains
everything in the evolution of the organic world. This belief in the
"omnipotence of natural selection" was not shared by Darwin himself.
Assuredly, I regard it as of the utmost value, as the process of
natural selection through the struggle for life affords an explanation
of the mechanical origin of the adapted organisation. It solves the
great problem: how could the finely adapted structure of the animal or
plant body be formed unless it was built on a preconceived plan? It
thus enables us to dispense with the teleology of the metaphysician
and the dualist, and to set aside the old mythological and poetic
legends of creation. The idea had occurred in vague form to the great
Empedocles 2000 years before the time of Darwin, but it was reserved
for modern research to give it ample expression. Nevertheless, natural
selection does not of itself give the solution of all our evolutionary
problems. It has to be taken in conjunction with the transformism of
Lamarck, with which it is in complete harmony.
The monumental greatness of Charles Darwin, who surpasses every other
student of science in the nineteenth century by the loftiness of his
monistic conception of nature and the progressive influence of his
ideas, is perhaps best seen in the fact that not one of his many
successors has succeeded in modifying his theory of descent in any
essential point or in discovering an entirely new standpoint in the
interpretation of the organic world. Neither Naegeli nor Weismann,
neither De Vries nor Roux, has done this. Naegeli, in his
_Mechanisch-Physiologische Theorie der Abstammungslehre_[130] which is
to a great extent in agreement with Weismann, constructed a theory of
the idioplasm, that represents it (like the germ-plasm) as developing
continuously in a definite direction from internal causes. But his
internal "principle of progress" is at the bottom just as teleological
as the vital force of the Vitalists, and the micella structure of the
idioplasm is just as hypothetical as the "dominant" structure of the
germ-plasm. In 1889 Moritz Wagner sought to explain the origin of
species by migration and isolation, and on that basis constructed a
special "migration-theory." This, however, is not out of harmony with
the theory of selection. It merely elevates one single factor in the
theory to a predominant position. Isolation is only a special case of
selection, as I had pointed out in the fifteenth chapter of my
_Natural history of creation_. The "mutation-theory" of De Vries,[131]
that would explain the origin of species by sudden and saltatory
variations rather than by gradual modification, is regarded by many
botanists as a great step in advance, but it is generally rejected by
zoologists. It affords no explanation of the facts of adaptation, and
has no causal value.
Much more important than these theories is that of Wilhelm Roux[132]
of "the struggle of parts within the organism, a supplementation of
the theory of mechanical adaptation." He explains the functional
autoformation of the purposive structure by a combination of Darwin's
principle of selection with Lamarck's idea of transformative heredity,
and applies the two in conjunction to the facts of histology. He lays
stress on the significance of functional adaptation, which I had
described in 1866, under the head of cumulative adaptation, as the
most important factor in evolution. Pointing out its influence in the
cell-life of the tissues, he puts "cellular selection" above "personal
selection," and shows how the finest conceivable adaptations in the
structure of the tissue may be brought about quite mechanically,
without preconceived plan. This "mechanical teleology" is a valuable
extension of Darwin's monistic principle of selection to the whole
field of cellular physiology and histology, and is wholly destructive
of dualistic vitalism.