denote movement in the direction which we have sketched in outline,
and shall shortly proceed to define more accurately. In so doing, I
perhaps beg the question, to be proved I hope later, as to whether the
observed direction is progressive: but I no longer beg the question of
whether evolution is a directional process. However we may argue on
the facts, the facts remain: and the facts are that there has been an
increase in certain qualities of organisms, both physical and mental,
during geological time.
Meanwhile, let it be remembered, the simplest forms have survived side
by side with the more complex, the less specialized with the more
specialized. Even when we can trace a causal relation between the rise
of one group and the decay of another, as with the mammals and birds on
the one hand, and the reptiles on the other, even then numbers of the
defeated group continue to exist. Thus, in broad terms, evolution is
not a transformation, be it progressive or no, of the whole of living
matter, but of a part of it.
I will endeavour to sum up, in brief, what seem to me the salient
points of that process, a sketch of which, inevitably hasty and
inadequate, I have just tried to give.
During the time of life’s existence on this planet, there has been
an increase, both in the average and far more in the upper level, of
certain attributes of living things.
In the first place there has been an increase in their size, brought
about by two methods, first by the increase of size of the units of
life themselves (cells, metazoan individuals, communities), secondly
by their aggregation; and this has been accompanied by a (very roughly)
parallel increase in the duration of life.
Next, there has been an increase in their complexity; and this in its
turn depends upon the fact that a division of labour has been brought
about between the parts of organisms, each part becoming specialized
for greater efficiency in the performance of some particular function.
In the fewest words, the separate bits of machinery of which organisms
are composed have become more efficient.
In the third place, there has been an increase in the harmony of these
parts, and consequently in the unity of the whole. Delicate mechanisms
for co-ordination have been developed, and arrangements whereby one
portion becomes dominant over the rest, and so a material basis for
unification is given.
In the fourth place, there has been an increase of self-regulation.
The outer environment changes from month to month, from hour to hour.
The more complex products of evolution are in high degree exempt from
the consequences of these changes, through being the possessors of a
constant internal environment which, beyond the narrowest limits, it is
most difficult to alter.
Fifthly, there has been an increase in the possibility of bringing
past experience to bear on present problems. At the base is the power
of modifying normal reactions with repetition; then come some simple
degrees of memory; then associative memory, as in birds and mammals,
for whom most reactions are not given in the inherited constitution,
but must be learnt; then rational memory, in which the power of
generalization liberates life from blind dependence upon the local and
the accidental; and finally tradition, whereby the amount of experience
available to the developing race is not constituted merely by the
isolated and limited experiences of its members, but by their sum. More
and more of the past becomes directly operative in the present; further
and further into the future can the aim of the present extend.
Finally we can conclude with a high degree of certainty that the
psychical faculties--of knowing, feeling, and willing--have increased
in intensity, and also in their relative importance for the life of the
individual organism.
We have condensed our summary into these six general statements; if
we wish to reach a still more general form, the most general form
possible, we can redistil it thus: During the course of evolution in
time, there has been an increase in the control exerted by organisms
over their environment, and in their independence with regard to it;
there has been an increase in the harmony of the parts of organisms;
and there has been an increase in the psychical powers of organisms, an
increase of willing, of feeling, and of knowing.
This increase has not been universal; many organisms have remained
stationary or have even regressed; many have shown increase in
one particular but not in others. But the _upper level_ of these
properties of living matter has been continually raised, their average
has continually increased. It is to this increase, continuous during
evolutionary time, in the average and especially in the upper level of
these properties that, I venture to think, the term biological progress
can be properly applied.
Used thus it is no more an a priori or an undefined concept. It is a
name for a complicated set of actual phenomena, and if, with progress
thus defined, we were to speak of a law of progress in evolution, we
should be using the term law in a perfectly legitimate way, as denoting
a generalization based on observed facts, and not as pre-supposing any
vitalistic principle of perfectibility, any necessary and mysterious
tendency of organisms to advance independently of circumstances.
The gas laws state that the pressure of a gas kept at constant volume
increases in a particular way with increase of temperature. Now the
pressure of a confined gas depends on the rate at which its particles
bombard the walls in which they are contained, and the speed at which
they are travelling. In a gas whose temperature is raised, many
particles will, at any given moment, be travelling more slowly than the
average rate when it was cooler, many even which had been travelling
fast may now be travelling slowly. None the less, the average speed of
all the particles is greater; and this and nothing else is what with
perfect justification we sum up as our _law_.
In biological evolution, some organisms degenerate, some remain
stationary, but the average of certain properties, and more especially
their upper level, increases; and this tendency for certain properties
to become more marked, this and nothing else, is what we sum up and
generalize, again with perfect justification, as the law of biological
progress.
The mechanism of biological progress demands a word: for it is
noticeable that a mere fact, however well attested, makes a very
different kind of impression from a fact explained and brought into
relation with the rest of our knowledge. The impression is either less
powerful; or else, an explanation being sought for, an erroneous one is
found. It was Darwin’s great merit that, not content with the piling up
of evidence in favour of the reality of Evolution, he at the same time
advanced a theory which made it at least possible to understand how
Evolution could have come to pass as a natural process. The effect was
multiplicative on men’s minds, not merely additive, for facts are too
bulky to be lugged about conveniently except on wheels of theory.
The fact of biological progress has struck many observers. Some have
been content to believe that the single magic formula of “Natural
Selection” would explain it adequately and without further trouble,
forgetting that there must be at least some points of difference
between a natural selection producing a degenerate type and natural
selection leading to progress. Some biologists have lumped it,
together with all other evolutionary processes which seem to show
us a development along predetermined lines, under the head of
_orthogenesis_--the (hypothetical!) tendency of organisms to unfold
just one type of hidden potentiality. Bergson has been particularly
struck with it: refuses to allow that it can have anything to do with
Natural Selection or any determinist process, and ascribes it to his
_élan vital_.
Here, as so often elsewhere, Bergson reveals himself as a good poet but
a bad scientist. His intellectual vision of evolution as a fact, as
something happening, something whole, to be apprehended in a unitary
way--that is unsurpassed. He seems to see it as vividly as you or I
might see a hundred yards race, holding its different incidents and
movements all in his mind together to form one picture. But he then
goes on to give a symbolic description of what he sees--and then
thinks that his symbols will serve in place of analytic explanations.
There _is_ an “urge of life”; and it is, as a matter of fact, urging
life up the steps of progress. But to say that biological progress is
explained by the _élan vital_ is to say that the movement of a train
is “explained” by an _élan locomotif_ of the engine: it is to fall
into the error, so often condemned in scientists by philosophers, and
ridiculed in both by satirists, of hanging or at least disposing of a
difficulty by giving it a long name.
Let us think of the condition of life on earth at any given moment of
her evolution. Certain possibilities have been realized by her--others
have not. To take a trenchant example, before the Carboniferous or
thereabouts, the vertebrates had not realized their possibilities of
terrestrial existence--nearly half the globe’s surface lay waiting to
be colonized by backboned animals. The earth’s surface was conquered
then--but the air remained unsubdued before the mid-Secondary. In every
period, there must be not only actual gaps unfilled in the economy of
nature--such and such an animal is without parasites, such and such
a hot spring or salt lake is without tenants; but also improvements
can be made in existing types of organization--a tapeworm could be
more firmly attached, a salt-lake shrimp could tolerate an even higher
concentration of brine.
These two sorts of possibilities really overlap. For instance, an
increased efficiency of vision must be an improvement in pre-existing
structures and creatures; it also involves the conquest of new regions
of environment, and so in a real sense the occupation of a new
biological niche.
In any case, the changes which would confer advantage in the struggle
for existence may take place in any direction--with, or against, or at
right angles to the stream of progress. By means of those which march
with that stream, the upper level of life’s attainment is raised.
But the struggle still goes on: and again, starting from this new
condition, there will be variations in every direction which will have
survival value, and some of these will be progressive; and so the
upper level will be once more raised.
The process will take time, for, whatever theory of variation we may
hold[8]--the old idea of small continuous variations; or that of large
mutations big enough to produce new species at one jump; or the most
probable theory of numerous small mutations--they one and all must
grant that the largest variation occurring at one time in a living
species is infinitesimal in comparison with the secular changes of
evolution.
There will further be a premium upon progressive changes, since a
progressive change will generally land its possessor in virgin soil,
so to speak; if not in an actually new physical environment, then in a
biologically new situation. The placental mammal occupies the same dry
land as did the wonderful reptilian types of the Secondary epoch. But
constant temperature and embryonic nutrition within its mother provide
delicately adjusted conditions in the early phases of development which
in their turn enabled a more elaborate and more delicately responding
brain machinery to be constructed in development, and so advanced their
possessors on to new shores of control and independence.
There will thus be a constant biological pressure (to use a term
which, though still symbolic, a mere analogy, is less misleading and
question-begging than _élan vital_) tending to push some of life on
to new levels of attainment, new steps in progress, _because_ any
variations in that direction will have selection value, a selection
value above the ordinary. And the process will be a gradual one,
because variations are not very large; so that life no more realizes
all potentialities of progress at once than did the United States or
any other new country receive a uniform population over all its extent
as soon as it was discovered, but had its people move in from the
coasts in a regular and orderly advance.
There are plenty of parallels from human affairs. Indeed, the
evolutionist can often gain valuable light on his subject, on what
one may call the economics of the process, by turning to study the
development of human inventions and machines. There, although the
ways in which variations arise, and the way they are transmitted, are
different from those of organic evolution, yet the type of “pressure,”
the perpetual struggle, and the advantage of certain kinds of variation
therein--these are in essence really similar.
What could be more striking than the parallel between the rise of the
mammals to dominance over the reptiles, and the rise of the motor
vehicle to dominance over that drawn by horses?
In both cases, a comparatively long period in which the new type is in
a precarious and experimental stage, only just managing to exist, of
small size and rare occurrence, and in no real sense a serious rival to
its old-established competitors. Then, suddenly, a change. It reaches
a level at which it can effectively compete with them. What happens?
In the case both of man-made machine and evolving vertebrate group,
there is first a sudden increase in numbers of the new, a corresponding
decrease in numbers of the old type. The upper level of size of the
new type also begins to increase, and it begins to split up into a
great number of differentiated sub-types. Some of these sub-types
become extinct, others, on the other hand, are gradually improved,
while still others undergo such rapid change as to merit the style of
new sub-types. The upper level of size, complexity, and efficiency
increase, both in animal and machine.
It is as well to remember that survival-value means only what it says.
A variation with survival-value helps its possessors to survive: it
is not the best possible variation of the kind. In the developing
motor-car, the substitution of four for one or two cylinders was a
great improvement. It had “survival-value”; and not until the majority
of cars came to be four-cylindered was the additional advantage of
six or eight cylinders large enough to bring them into existence as
dominant types.
To the interrelated evolution of carnivore and herbivore, again,
leading to increase of size and speed in both, of wariness in one, of
tooth and claw in the other, we have again a close parallel in the
interrelated evolution of armour-plating and of projectiles. Here
again the process is gradual. We can further see that the sudden
“development” of full modern armour on the first iron-clad would
have been actually disadvantageous, since it would have reduced
its speed relatively to other less heavily protected ships, without
conferring any corresponding benefit in the way of defence against the
comparatively inefficient projectiles of the day. Only when the range
and piercing power of the projectiles increased did increase of armour
become imperative.
To resume our pressure analogy, the natural increase of all organisms
leads to a “biological pressure.” So long as a species remains
unchanged, so long must it stay subjected to the full force of this
pressure. But if it changes in such a way that it can occupy a new
niche in environment, it is expanding into a vacuum or a region of
lower pressure. Natural increase soon fills this up to the same level
of pressure, and conditions thus become favourable for expansion into
new low-pressure areas previously out of reach of the normal range
of variation. Variation towards such “low-pressure” regions may be
progressive, retrogressive, or neutral: but it is obvious that at
each stage of evolution there will always be a low-pressure fringe,
representing a considerable fraction of the “low-pressure” area within
the range of variability, the occupation of which would be biologically
progressive.
Thus from the well-established biological premisses of (1) the tendency
to geometrical increase with consequent struggle for existence,
(2) some form of inherited variability, we can deduce as necessary
consequence, not only the familiar but none the less fundamental
fact of Natural Selection, but also the almost neglected fact that
a _certain fraction_ of the guiding force of Natural Selection will
inevitably be pushing organisms into changes that are progressive.
This will of course be true only so far as the general conditions of
the environment remain within certain limits: it is probable that too
great reductions of temperature or moisture on the surface of the
earth would lead to a gradual reversal of progress before the final
extinction of life. Up to the present, however, it is clear that such
conditions have not occurred, or, possibly, have occurred only for
short periods. The general state has been one in which steady, slow
progress has been achieved. Progress, like adaptation, is in pre-human
evolution almost entirely the resultant of blind chance and blind
necessity.
What corollaries and conclusions may be drawn from the establishment
of the fact of biological progress? In the first place, it permits us
to treat human progress as a special case of a more general process.
Biologically speaking, the human species is young--not perhaps still
in infancy, but certainly not yet attained to any stable maturity.
The conception, common enough in much traditional thought, that man
as a species is old, far removed from all pristine vigour and power,
is demonstrably untrue. The genus Homo has not yet adapted itself
to the new conditions and the new possibilities arising out of the
acquisition of reason and tradition. Its history so far is a record of
experiment after experiment. From a period so short and so empirical
it is impossible to deduce any general law of progress. In certain
respects, as we shall see more in detail later, there has been advance;
in others, the species has been stationary. But whether humanity in
this or that particular has progressed is for the moment comparatively
immaterial. Humanity is part of life, a product of life’s movement; and
in life as a whole there is progress.[9]
What is more, there was progress before man ever appeared on the earth,
and its reality would have been in no way impaired even if he had never
come into being. His rise only continued, modified, and accelerated a
process that had been in operation since the dawn of life.
Here we find, in the intellectual sphere at least, that assurance which
men have been seeking from the first. We see revealed, in the fact of
evolutionary progress, that the forces of nature conspire together to
produce results which have value in our eyes, that man has no right
to feel helpless or without support in a cold and meaningless cosmos,
to believe that he must face and fight forces which are definitively
hostile. Although he must attack the problems of existence in a new
way, yet his face is set in the same direction as the main tide of
evolving life, and his highest destiny, the end towards which he has so
long perceived that he must strive, is to extend to new possibilities
the process with which, for all these millions of years, nature has
already been busy, to introduce less and less wasteful methods, to
accelerate by means of his consciousness what in the past has been the
work of blind unconscious forces. “In la sua volontade è nostra pace.”
For this is one of the most remarkable facts of evolution--that
consciousness, until a very late period, has played in it a negligible
part. Indeed the rise of consciousness to become a factor of importance
in evolution has been one of the most notable single items of progress.
Darwin gave the deathblow to teleology by showing that apparently
purposive structures could arise by means of a non-purposive mechanism.
“Purpose” is a term invented to denote a particular operation of the
human mind, and should only be used where a psychological basis may
reasonably be postulated. On the other hand, a result can be attained
by conscious purpose without the waste of time and of living material
needed by the indirect method of natural selection; and thus the
substitution of purposed for unpurposed progress is itself a step in
progress.
As another corollary of our concept of progress, it follows that we
can and should consider, not only the direction of any evolutionary
process, but also its rate.
An evolutionary process, if it is to be considered progressive, must
have a component in one particular direction--a direction which we have
already defined. But this is not all; for even if it be moving in the
right direction, and yet be moving extremely slowly, it may, if it have
any interaction with a much more rapid progressive movement, actually
exert a drag on this; its relative motion--relative to the main current
of progress--will be backwards, and we may have to class it as the
reverse of progressive. For example, the interaction of carnivore and
herbivore, pursuer and pursued, led during the development of the
vertebrates to the evolution of much that was good--speed, strength,
alertness, and acuity of sense--and of many noble types of living
things. But with the advent of man, different methods have been
introduced, new modes of competition and advance; and the tiger and
the wolf not only cease to be agents of progress in its new form,
but definitely stand in its way and must be stamped out, or at least
reduced to a condition in which they can no longer interfere as active
agents in evolution.
Some such considerations as these will help perhaps to resolve various
difficulties of ethics--how, for instance, that which seems good to me
may seem evil to another. Even the good, if it be a drag on the better,
is evil. Expressed thus, the proposition is a paradox; but expressed in
terms of direction and relative speed, it is at once intelligible.
But the test of any such general biological theory as I have outlined
will be its application to human problems. And here too, I venture to
say, the value of biological method is apparent. What we ask, and
rightly ask, is whether in the laws of biological progress we can find
any principle which we can apply directly to guide us in devising
methods for human progress.
I do not propose to follow the example of many rather hasty
philosophers and biologists, who have thought that, whenever the
study of lower organisms permitted the promulgation of a biological
law, such law can be lifted bodily from its context and be applied
without modification to human affairs. Man is an organism--but a very
exceptional and peculiar organism. Any biological law which epitomizes
only facts about the lower creatures is not a general biological law,
for general biological laws must take account not only of plants and
animals, but of man as well. In practice, however, the simplest method
is to frame our biological laws without considering man, and then to
see in what way they must be modified if they are to be applied to him.