ON LONGEVITY AND SHORTNESS OF LIFE
WRITTEN 350 B. C. E
TRANSLATED BY G. R. T. ROSS
ARISTOTLE
384 BC - 322 BC
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PART 1
The reasons for some animals being long-lived
and others short-lived, and, in a word, causes
of the length and brevity of life call for
investigation.
The necessary beginning to our inquiry is
a statement of the difficulties about these
points. For it is not clear whether in animals
and plants universally it is a single or
diverse cause that makes some to be long-lived,
others short-lived. Plants too have in some
cases a long life, while in others it lasts
but for a year.
Further, in a natural structure are longevity
and a sound constitution coincident, or is
shortness of life independent of unhealthiness?
Perhaps in the case of certain maladies a
diseased state of the body and shortness
of life are interchangeable, while in the
case of others ill-health is perfectly compatible
with long life.
Of sleep and waking we have already treated;
about life and death we shall speak later
on, and likewise about health and disease,
in so far as it belongs to the science of
nature to do so. But at present we have to
investigate the causes of some creatures
being long-lived, and others short-lived.
We find this distinction affecting not only
entire genera opposed as wholes to one another,
but applying also to contrasted sets of individuals
within the same species. As an instance of
the difference applying to the genus I give
man and horse (for mankind has a longer life
than the horse), while within the species
there is the difference between man and man;
for of men also some are long-lived, others
short-lived, differing from each other in
respect of the different regions in which
they dwell. Races inhabiting warm countries
have longer life, those living in a cold
climate live a shorter time. Likewise there
are similar differences among individuals
occupying the same locality.
Part 2
In order to find premisses for our argument,
we must answer the question, What is that
which, in natural objects, makes them easily
destroyed, or the reverse? Since fire and
water, and whatsoever is akin thereto, do
not possess identical powers they are reciprocal
causes of generation and decay. Hence it
is natural to infer that everything else
arising from them and composed of them should
share in the same nature, in all cases where
things are not, like a house, a composite
unity formed by the synthesis of many things.
In other matters a different account must
be given; for in many things their mode of
dissolution is something peculiar to themselves,
e. g. in knowledge and health and disease.
These pass away even though the medium in
which they are found is not destroyed but
continues to exist; for example, take the
termination of ignorance, which is recollection
or learning, while knowledge passes away
into forgetfulness, or error. But accidentally
the disintegration of a natural object is
accompanied by the destruction of the non-physical
reality; for, when the animal dies, the health
or knowledge resident in it passes away too.
Hence from these considerations we may draw
a conclusion about the soul too; for, if
the inherence of soul in body is not a matter
of nature but like that of knowledge in the
soul, there would be another mode of dissolution
pertaining to it besides that which occurs
when the body is destroyed. But since evidently
it does not admit of this dual dissolution,
the soul must stand in a different case in
respect of its union with the body.
Part 3
Perhaps one might reasonably raise the question
whether there is any place where what is
corruptible becomes incorruptible, as fire
does in the upper regions where it meets
with no opposite. Opposites destroy each
other, and hence accidentally, by their destruction,
whatsoever is attributed to them is destroyed.
But no opposite in a real substance is accidentally
destroyed, because real substance is not
predicated of any subject. Hence a thing
which has no opposite, or which is situated
where it has no opposite, cannot be destroyed.
For what will that be which can destroy it,
if destruction comes only through contraries,
but no contrary to it exists either absolutely
or in the particular place where it is? But
perhaps this is in one sense true, in another
sense not true, for it is impossible that
anything containing matter should not have
in any sense an opposite. Heat and straightness
can be present in every part of a thing,
but it is impossible that the thing should
be nothing but hot or white or straight;
for, if that were so, attributes would have
an independent existence. Hence if, in all
cases, whenever the active and the passive
exist together, the one acts and the other
is acted on, it is impossible that no change
should occur. Further, this is so if a waste
product is an opposite, and waste must always
be produced; for opposition is always the
source of change, and refuse is what remains
of the previous opposite. But, after expelling
everything of a nature actually opposed,
would an object in this case also be imperishable?
No, it would be destroyed by the environment.
If then that is so, what we have said sufficiently
accounts for the change; but, if not, we
must assume that something of actually opposite
character is in the changing object, and
refuse is produced.
Hence accidentally a lesser flame is consumed
by a greater one, for the nutriment, to wit
the smoke, which the former takes a long
period to expend, is used up by the big flame
quickly.
Hence [too] all things are at all times in
a state of transition and are coming into
being and passing away. The environment acts
on them either favourably or antagonistically,
and, owing to this, things that change their
situation become more or less enduring than
their nature warrants, but never are they
eternal when they contain contrary qualities;
for their matter is an immediate source of
contrariety, so that if it involves locality
they show change of situation, if quantity,
increase and diminution, while if it involves
qualitative affection we find alteration
of character.
Part 4
We find that a superior immunity from decay
attaches neither to the largest animals (the
horse has shorter life than man) nor to those
that are small (for most insects live but
for a year). Nor are plants as a whole less
liable to perish than animals (many plants
are annuals), nor have sanguineous animals
the pre-eminence (for the bee is longer-lived
than certain sanguineous animals). Neither
is it the bloodless animals that live longest
(for molluscs live only a year, though bloodless),
nor terrestrial organisms (there are both
plants and terrestrial animals of which a
single year is the period), nor the occupants
of the sea (for there we find the crustaceans
and the molluscs, which are short-lived).
Speaking generally, the longest-lived things
occur among the plants, e. g. the date-palm.
Next in order we find them among the sanguineous
animals rather than among the bloodless,
and among those with feet rather than among
the denizens of the water. Hence, taking
these two characters together, the longest-lived
animals fall among sanguineous animals which
have feet, e. g. man and elephant. As a matter
of fact also it is a general rule that the
larger live longer than the smaller, for
the other long-lived animals too happen to
be of a large size, as are also those I have
mentioned.
Part 5
The following considerations may enable us
to understand the reasons for all these facts.
We must remember that an animal is by nature
humid and warm, and to live is to be of such
a constitution, while old age is dry and
cold, and so is a corpse. This is plain to
observation. But the material constituting
the bodies of all things consists of the
following-the hot and the cold, the dry and
the moist. Hence when they age they must
become dry, and therefore the fluid in them
requires to be not easily dried up. Thus
we explain why fat things are not liable
to decay. The reason is that they contain
air; now air relatively to the other elements
is fire, and fire never becomes corrupted.
Again the humid element in animals must not
be small in quantity, for a small quantity
is easily dried up. This is why both plants
and animals that are large are, as a general
rule, longer-lived than the rest, as was
said before; it is to be expected that the
larger should contain more moisture. But
it is not merely this that makes them longer
lived; for the cause is twofold, to wit,
the quality as well as the quantity of the
fluid. Hence the moisture must be not only
great in amount but also warm, in order to
be neither easily congealed nor easily dried
up.
It is for this reason also that man lives
longer than some animals which are larger;
for animals live longer though there is a
deficiency in the amount of their moisture,
if the ratio of its qualitative superiority
exceeds that of its quantitative deficiency.
In some creatures the warm element is their
fatty substance, which prevents at once desiccation
and congelation; but in others it assumes
a different flavour. Further, that which
is designed to be not easily destroyed should
not yield waste products. Anything of such
a nature causes death either by disease or
naturally, for the potency of the waste product
works adversely and destroys now the entire
constitution, now a particular member.
This is why salacious animals and those abounding
in seed age quickly; the seed is a residue,
and further, by being lost, it produces dryness.
Hence the mule lives longer than either the
horse or the ass from which it sprang, and
females live longer than males if the males
are salacious. Accordingly cock-sparrows
have a shorter life than the females. Again
males subject to great toil are short-lived
and age more quickly owing to the labour;
toil produces dryness and old age is dry.
But by natural constitution and as a general
rule males live longer than females, and
the reason is that the male is an animal
with more warmth than the female.
The same kind of animals are longer-lived
in warm than in cold climates for the same
reason, on account of which they are of larger
size. The size of animals of cold constitution
illustrates this particularly well, and hence
snakes and lizards and scaly reptiles are
of great size in warm localities, as also
are testacea in the Red Sea: the warm humidity
there is the cause equally of their augmented
size and of their life. But in cold countries
the humidity in animals is more of a watery
nature, and hence is readily congealed. Consequently
it happens that animals with little or no
blood are in northerly regions either entirely
absent (both the land animals with feet and
the water creatures whose home is the sea)
or, when they do occur, they are smaller
and have shorter life; for the frost prevents
growth.
Both plants and animals perish if not fed,
for in that case they consume themselves;
just as a large flame consumes and burns
up a small one by using up its nutriment,
so the natural warmth which is the primary
cause of digestion consumes the material
in which it is located.
Water animals have a shorter life than terrestrial
creatures, not strictly because they are
humid, but because they are watery, and watery
moisture is easily destroyed, since it is
cold and readily congealed. For the same
reason bloodless animals perish readily unless
protected by great size, for there is neither
fatness nor sweetness about them. In animals
fat is sweet, and hence bees are longer-lived
than other animals of larger size.
Part 6
It is amongst the plants that we find the
longest life-more than among the animals,
for, in the first place, they are less watery
and hence less easily frozen. Further they
have an oiliness and a viscosity which makes
them retain their moisture in a form not
easily dried up, even though they are dry
and earthy.
But we must discover the reason why trees
are of an enduring constitution, for it is
peculiar to them and is not found in any
animals except the insects.
Plants continually renew themselves and hence
last for a long time. New shoots continually
come and the others grow old, and with the
roots the same thing happens. But both processes
do not occur together. Rather it happens
that at one time the trunk and the branches
alone die and new ones grow up beside them,
and it is only when this has taken place
that the fresh roots spring from the surviving
part. Thus it continues, one part dying and
the other growing, and hence also it lives
a long time.
There is a similarity, as has been already
said, between plants and insects, for they
live, though divided, and two or more may
be derived from a single one. Insects, however,
though managing to live, are not able to
do so long, for they do not possess organs;
nor can the principle resident in each of
the separated parts create organs. In the
case of a plant, however, it can do so; every
part of a plant contains potentially both
root and stem. Hence it is from this source
that issues that continued growth when one
part is renewed and the other grows old;
it is practically a case of longevity. The
taking of slips furnishes a similar instance,
for we might say that, in a way, when we
take a slip the same thing happens; the shoot
cut off is part of the plant. Thus in taking
slips this perpetuation of life occurs though
their connexion with the plant is severed,
but in the former case it is the continuity
that is operative. The reason is that the
life principle potentially belonging to them
is present in every part.
Identical phenomena are found both in plants
and in animals. For in animals the males
are, in general, the longer-lived. They have
their upper parts larger than the lower
(the male is more of the dwarf type of build
than the female), and it is in the upper
part that warmth resides, in the lower cold.
In plants also those with great heads are
longer-lived, and such are those that are
not annual but of the tree-type, for the
roots are the head and upper part of a plant,
and among the annuals growth occurs in the
direction of their lower parts and the fruit.
These matters however will be specially investigated
in the work On Plants. But this is our account
of the reasons for the duration of life and
for short life in animals. It remains for
us to discuss youth and age, and life and
death. To come to a definite understanding
about these matters would complete our course
of study on animals.
THE END
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