pass now from inorganic to organic existence; from the testimony of
physicists, to that of zoölogists. This transition in itself starts a
scientific problem, beyond which we are carried onward to a distinct and
very complicated area of existence, higher in order, and pressing upon
attention an incalculable variety of details, exceedingly difficult to
harmonize. In the earlier stage of physical research, all observation
and experiment lead forward to general results, which gain ready
acceptance because they may be said to be involved in scientific
procedure itself. In this more advanced stage it is otherwise. In the
former, unorganized matter is the same everywhere; and the laws of
energy can be studied with equal facility in Europe or in America, in
northern latitudes or in southern. But when we begin to direct attention
upon life in its manifold forms, as these are scattered all over the
world, multitudes of distinct observations have to be prosecuted, and
their results slowly accumulated, before even the most competent workers
can occupy a position from which it is possible to make a beginning with
our forecast of general conclusions. Even in the most favorable
circumstances, a great deal must be left to problematic inference, and
even to imagination. Gatherings of facts may be recorded in a manner
which places them beyond reach of doubt, while theories founded upon
them hang long in suspense, waiting confirmation on condition of being
able to endure protracted criticism, and manifold applications. This
accounts for the difficulty experienced in finding ready to hand general
conclusions which have secured universal acceptance, when we begin to
move somewhat freely over the wide regions presenting the manifold
problems of organized existence. And as it is solely with general
conclusions, that religious thought is concerned, some share of
perplexity must attach to the attempt to discuss the question of
harmony. We must here therefore be considerably involved in questions
affecting theories which have gained wide favor in scientific circles,
as well as with clearly recorded and certain results. Some general
questions, such as that affecting the classification of animals, must be
regarded as peculiarly scientific. Whether the classification of
Linnæus, or of Cuvier, or some other more recently suggested, is to be
preferred, is a matter which does not here concern us. But a theory of
the origin of species must be considered, because it is not purely
scientific, but brings science into direct relation with common thought
as to the order of the universe, and may therefore stand related to
religious thought.
Immediately on directing attention to organized existence,--to LIFE in
any form,--we encounter a new problem, namely the relation of the
organized to the unorganized. How is the appearance of this higher order
of existence to be accounted for? Can we find in the nature of matter,
and in the mechanical and chemical laws influencing its position and
combination, any explanation of the appearance of life in the world? Or
must we regard life as a new and higher fact, unexplained by reference
to the lower form of existence, and incapable of explanation in this
way? Whether there is a clear line of demarcation between vegetable and
animal life is a comparatively subordinate question. It is the wider and
more perplexing question which most fundamentally affects our general
conceptions as to the history and government of the world? And when this
question is pressed singly,--how can we account for the appearance of
life in the world?--science has no answer to present. Life still remains
a mystery in scientific times, as it had been in past ages. Much has
been written as to the origin of species; nothing to any purpose has yet
been said as to the origin of life itself. The secrets of the universe
in this respect have eluded discovery, and a constrained silence is the
consequence.
But if science itself has nothing to say as to this fundamental problem,
scientific men have much to say as to the probability of a true solution
of the mystery being forthcoming. There is in many quarters an
expectation that we may yet understand the physical principles, that is,
the mechanical and chemical combinations, which go to explain life as a
working organism.[AO] The suggestions of Rumford and Joule may yet bear
results in this direction, for it is matter of general agreement that
living organism may be regarded as an engine doing a given amount of
work, on condition of being supplied with a given amount of fuel in the
form of nourishment. When therefore Rumford suggests that the animal is
a more economical engine than any of the mechanical contrivances which
man constructs, and when Joule advances considerably beyond this to
suggest that the animal more resembles an electro-magnetic engine, than
a heat engine, it seems quite within the range of possibility that in
some such direction discovery may yet be made of the physical principles
involved in life.
This, however, leaves untouched the deeper question as to the _origin of
life_. We are entirely ignorant of any beginning of life which is not
traced directly to a preceding living organism. Either, as in the case
of plants, there is increase of life by fission, or separation from an
earlier growth, or by means of seed grown upon the parent plant; or, as
in the case of animals, by germ or ovum. But the question of the origin
of life is remote from us historically, and perplexing to us
experimentally. If we seek guidance historically, we turn to geology,
and learn that the structure of the earth has involved successive
formations. The materials of the earth's crust are not thrown together
confusedly, but "exhibit a certain order of arrangement";[AP] the
mineral masses are partly aqueous, partly igneous, in formation;
according as they are one or other, they contain organic remains, or are
marked by their absence. All that can be inferred from the data thus
afforded is that at a certain period in the world's history, when
temperature and other conditions affecting the possibility of organic
existence were favorable, life appeared. As to the cause of its
appearance, geology can give no testimony. If next, we refer to
palæontology, we learn of the existence of colossal animals which have
long since become extinct; but such researches only widen our
acquaintance with different orders of animals, contributing nothing
towards the solution of the problem concerning the origin of life. The
experimental science of the present day, with all the advantages
arising from microscopical observation, is altogether unable to offer
any explanation. Experiments for the purpose of testing the probability
of "spontaneous generation" have been already described, and their
failure leaves experimental science without any direct testimony; while
their history yields powerful indirect evidence in support of the
position that origin of life apart from germ is unknown.
It is, however, desirable here, in order to give completeness to our
view of the present situation, to remark that among scientific men there
are some who have no expectation of a scientific explanation of the
origin of life; while others are exceedingly hopeful that such
explanation may be reached, in the latter class appearing naturally all
those who openly proclaim against what they name an "incomprehensible
act of creation," and voluntarily place themselves in antagonism to
religious thought. It is, therefore, of some consequence to indicate the
grounds on which such opposite views rest. On the one side, Professor
Tait, while suggesting the possibility of yet discovering the physical
principles which determine life, nevertheless adds, "Let no one imagine
that, should we ever penetrate this mystery, we shall thereby be enabled
to produce, except from life, even the lowest form of life."[AQ] On the
other hand Professor Schmidt of Strasburg maintains the opposite view,
affirming that "the investigation of nature does not shrink from
enrolling _life_, and the processes of life in the world of the
comprehensible."[AR] This latter assertion is not to be accounted for on
the ground that Schmidt is the ardent admirer and defender of the theory
of origin of species by natural selection, for it is clear, as he
maintains in replying to Max Müller, that "the origin of life has in
fact nothing to do with actual Darwinism, or natural selection, unless
the principle of selection be extended to the inorganic world of
matter."[AS] Mr. Darwin himself does not suggest any such extension, and
his theory of species is not chargeable with it. It should, indeed, be
clearly recognized on all hands that the naturalist confines himself to
a narrower range of inquiry, taking existing phases of life as the
subject of his study. Accordingly, whoever claims that the origin of
life comes within the compass of science, does so on the ground that
there is no demarcation between the organic and the inorganic,--that the
former may arise directly from the latter,--and so he commits himself to
a doctrine of descent world-wide in its application, involving
development in the world of all its varied phases of existence from a
mass of unorganized matter.
This explains the difference of opinion among scientific men as to the
possibility of accounting for the origin of life. A certain number deny
the possibility, as they do the possibility of explaining scientifically
the origin of matter on the explicit ground indicated by
Laplace,--"Present events are connected with the events of the past by a
link resting on the obvious principle, that a thing can not begin to
exist without a cause which produces it."[AT] They do not find in
inorganic matter sufficient cause to account for life, and their
expectations are restricted accordingly. Those who cherish a contrary
expectation, do not vindicate it by contradiction of the obvious
principle enunciated by Laplace, or even by maintaining that inorganic
matter is adequate to produce living organism. They cling to the more
general and doubtful position that no limits are to be assigned to
science, or as it is often stated, all nature belongs to the
comprehensible. The failure of past experiments is no proof that
inevitable failure awaits other experiments which may yet be made. To
abandon expectation seems to them to be unfaithful to science. In this
fashion, Professor Schmidt declares that "to any one who holds open the
possibility that, even now, animate may be evolved from inanimate,
without the mediation of progenitors, _the first origin of life in this
natural method is at once self-evident_."[AU] To this view the other
side may legitimately reply, that if the origin of life be as easily
accounted for, as provision is here made for the "self-evident," science
will soon be at a discount. To those regarding the matter from without,
and waiting for testimony as to what is scientifically established, it
is clear that there is no explanation of the origin of life; and I think
it will be most commonly held that the weight of reason as to
expectations for the future lies with those who abandon the anticipation
of any scientific explanation. There is, however, in actual conclusions
on scientific evidence nothing involving conflict with religious
conviction; and allowance will be made for continued and extended
experiments, provided only that the "holding open the possibility," does
not make the probability "self-evident."
Passing thus from the unsolved problem of the origin of life,--with the
attendant acknowledgment that there is no scientific theory of the
world's descent from primordial atoms, we advance to the testimony of
science concerning different orders of life, and their relations to each
other. Here there is no restriction as to the use of scientific methods;
there is wide range for free action by the hosts of observers required
for the work. A sense of the relief which this implies, in contrast with
the hampering restraints surrounding the earlier question, imparts to
the words of Schmidt a more jubilant tone, as he says, "Between
beginning and end, we naturalists may do as we please."[AV]
In this region it will be universally admitted that the development of
species by selection is the conception which has gained greatest hold
upon the scientific mind within recent times. Accordingly it seems
better to begin with an outline of this theory, and of its history as
developed by Mr. Darwin, keeping, however, steadily in view the range of
problem with which the theory has to deal.
As already remarked the origin of life is a problem quite distinct, and
the theory of selection does not entangle itself by maintaining origin
of life by development from unorganized matter. Mr. Darwin clearly
guarded himself against responsibility for such a conception of its
origin.[AW] Restricting thus far, we have to keep in view the vast range
of the problem demanding scientific explanation.
Animal life manifests itself by spontaneous movement,--movement from
within the living organism, in contrast with movement caused by energy
applied from without. This holds true of every living germ, from which a
mature animal form may be developed. This is the test of the presence of
life under the microscope in minute germinal structures otherwise
incapable of observation. In its lowest known form life appears in a
minute vessel containing so much nourishment, which is within a nucleus
or vital centre from which movement originates.[AX] This depends for
its development on external conditions such as heat and moisture.[AY]
Advance in the scale is connected with greater complexity in the
organism. As we ascend, separate organs appear, fulfilling distinct
functions, and controlled by means of a nerve system whose ramifications
are according to the intricacy of the organism. The appearance of such a
nerve system implies sensibility and motor activity, provision for an
_experience_ more or less varied, and _movement_ in some measure
according with it, or adapted to it. From a nerve system consisting of a
centre and a few fibres, we gradually ascend, until in the higher
vertebrate orders, we find a vast system of nerves harmonized and
governed from a grand centre or terminus constituting the brain.[AZ]
With the steadily advancing complexity of nerve system, there is great
diversity in the orders of animals, in the variety of actions of which
they are capable, in adaptation to different conditions of life, and in
the modes in which they obtain subsistence. The scientific problem
is--How far can we account for all this complex system of things by the
action of natural causes?
As we are here specially concerned with ruling conceptions, and only
indirectly with details, the relations of the animal and vegetable
kingdoms may be passed, with the acknowledgment that the two are
obviously distinct, and yet that the vegetable very nearly merges into
the animal at certain points, as illustrated by sensibility, if not by
locomotion. So may we waive discussion of the classification of animals,
which involves important points closely connected with the main
question. Allowing that the wonderful diversity in animal organization,
may admit of different modes of classification; and yet granting that
the structure of the animal economy in all its forms proceeds on common
principles, which must lead to practical agreement as to modes of
classification; we deal with the single question as to the natural
causes serving to explain different orders.
Mr. Darwin's suggestion, largely supported by evidence from many
quarters, and now commanding a very general support is, that all this
diversity may be regarded as the product of a long process of
development. This theory takes the whole orders of existence into one
sweep. The lowest type of animal life presents to view the beginning of
a protracted history; the highest order of animate existence indicates
the stage of advance at which we observe things at the present period.
For such a theory the history of individual development belonging to
whatever order, and the history of distinct orders as indicating
improvement and deviation of whatever aspect, present evidence of
special value. The most important causes relied upon as contributing to
the formation of a scientific theory may be presented under these four
heads--(1) The action of external causes as provided for by environment;
(2) power of adaptability within each organism, providing for changes
according to requirement from without, which may be described as
"adaptive changes of structure;" (3) "the struggle for existence," in
accordance with which the strongest gain the mastery and consequent
advantage in obtaining the means of subsistence; and (4) "natural
selection" among the sexes, giving to the offspring all advantages
according to the laws of hereditary descent.
The essential feature in this theory is the _power of adaptability
inherent in the organism_. This is postulated as characteristic of all
organized existence; and it is implied, that this power of adaptability
multiplies in a degree approximating to the measure of complexity
belonging to the organism. The inherent capacity for deviation is thus
much less in the mollusk than in the bird; and in the bird much less
than in the quadruped. Thus the development process which must,
according to this view, have been exceedingly slow in the earlier
stages, must have been greatly accelerated when more complex organisms
had come into existence, and all the advantages accrued from greater
diversity of materials. Such is a brief outline of the theory; and
looked at simply as a theory, there is a manifest attraction in the
boldness of the conception, and the wide sweep of the generalization
which it includes. Taken merely as an intellectual representation
setting forth a conceivable order of things in the universe, it has a
great deal to command attention and awaken interest. It is, indeed, a
novelty in the history of scientific thought, and as such at variance
with previous conceptions, both scientific and non-scientific. But it is
no more at variance with religious thought, than with ordinary notions
of preceding times; while to the author whose name is now associated
with it all over the scientific world, it is a more striking testimony
of the marvels of creative power,[BA] than notions previously current,
which regarded it as historically true that every existing variety of
animal was launched into being by a distinct creative act. Whatever may
be the ultimate view of the history of life on the earth, based on
purely scientific data,--and we are still a far way removed from what
may be regarded as scientific evidence for such a view,--the fewer the
primordial forms to which the multiplicity of existing species can be
traced, the greater is the marvel which science presents, and the more
convincing becomes the intellectual necessity by which we travel back to
a Supernatural Intelligence as the source of all. On the other hand, the
slow process by which scientific research tends to make out the natural
history of living organisms far removed from each other in the scale of
being, tracing many groups to a common parentage, and assigning their
appearance in the world to distinct periods in its history, will be
seen to be so far anticipated and favored by the graphic description of
the introduction of animal life given in the opening page of revelation,
where different orders are assigned to successive epochs.
While, however, these things are said at the outset, as affording
commencement for the study of an evolution theory, and delivering us
from the supposition that there is an inevitable antagonism between
science and recognition of the supernatural, we revert to the ruling
principle for this whole inquiry, that science must prosecute its own
researches, unfettered by forecast of consequences; and that the Bible
is not to be handled as if it were a book of science, for it neither
lays restraints upon human inquiry, nor delivers us from the need for
it.
The best method for entering upon a study of the theory of evolution by
natural selection is to take Mr. Darwin's own account of the manner in
which it began to take shape before his mind. In his "historical sketch
of the recent progress of opinion on the origin of species,"[BB] he
traces to Lamark the first suggestions on the subject, directing public
attention to the question in 1801; thereafter a succession of
naturalists including St. Hilaire, Wells, and Patrick Matthew, from
separate and incidental observations, dwelt upon the difficulty of
distinguishing species, and on the evidence of an archetypal idea, or
common plan of structure, being applicable in the history of whole
orders. Mr. Darwin then gives the following biographical references at
the outset,--"When on board H. M. S. 'Beagle,' as naturalist, I was much
struck with certain facts in the distribution of the organic beings
inhabiting South America, and in the geological relations of the present
to the past inhabitants of that continent. These facts seemed to throw
some light on the origin of species--that mystery of mysteries, as it
has been called by one of our greatest philosophers. On my return home,
it occurred to me in 1837, that something might perhaps be made out on
this question by patiently accumulating and reflecting on all sorts of
facts which could possibly have any bearing on it. After five years'
work I allowed myself to speculate on the subject, and drew up some
short notes; these I enlarged in 1844 into a sketch of the conclusions
which then seemed to me probable: from that period to the present day I
have steadily pursued the same object."[BC] Such is Mr. Darwin's opening
paragraph in the now celebrated _Origin of Species_. No one interested
in such investigations will hesitate to approve and trust the "patiently
accumulating and reflecting on all sorts of facts;" nor can there be any
hesitation in granting the warrantableness of his beginning to speculate
as to the probable results. On the other hand, even the most ardent
admirers of the evolution theory can not refuse to allow that only its
principles are certain, while its ultimate form is still matter of
conjecture and speculation. Quite divergent lines of speculation have
found a start within the compass of the phenomena brought under review,
and it is already apparent that opposite tendencies of thought have
effected a lodgment under the common name of evolution. In these
circumstances there is no direct call, as there are no proper materials,
for attempting a reconciliation between the principles of religion, and
definite scientific conclusions as to the origin of species. We are
still occupying that position which makes historical treatment of the
subject the most appropriate, leaving to speculation the probable lines
of adjustment which may render possible a wider induction bearing on a
general theory of the universe.
The observations of Alfred Russell Wallace in the Malay Archipelago led
towards the same conclusions as those indicated by Darwin, to whom Mr.
Wallace dedicated his book,[BD] giving the results of research extending
from 1854 to 1862, and in confirmation of Darwin's theory, though
differing on important points, Wallace published in 1870 his
_Contribution to the Theory of Natural Selection_. Mr. Darwin's views
when first promulgated received decided though somewhat guarded support
from Sir Charles Lyell, whose geological studies marked him out as a
highly qualified witness on the subject, and were strongly favored by
Dr. Hooker, author of _Introduction to the Australian Flora_, while they
encountered not a little criticism, and were met with announcements of
formal reservations, on the part of distinguished naturalists.