There is a greater unity of all life than the many divisions and
sub-divisions of the analyst would seem to warrant. The dividing lines
between the different classes, orders, families and species are more
apparent than real, the barriers of separation not so impassable as
appear at first sight.
To begin at the bottom, there is no hard and fast line drawn between
living and non-living matter--or at least it is not always easy to say
where the line should be drawn. Tyndall says, “The tendency of modern
science is to break down the wall of partition between the organic and
the inorganic, and to reduce both to the operation of forces which are
the same in kind, but which are differently compounded.”
Passing on to the first grand division of life, it would seem that
nothing could be plainer than the line of cleavage between vegetable
and animal life. Yet there is a twilight zone between the two where
each shades off toward the other, and which is inhabited by several
living species of so doubtful a nature that scientists cannot agree
as to which of the two great kingdoms they belong. These doubtful
organisms are claimed by both the botanist and the geologist and are
described in the textbooks of both. Really they do not belong to either
division, but are simply organisms that have not risen in the scale of
life to the diverging point of the animal and vegetable kingdoms.
Ascending the animal scale we come to the line separating the
invertebrates from the vertebrates. Here, on the invertebrate side
are species that have the beginnings of a backbone--an elastic smooth
cord--and gill-slits, thus proving their relationship with the fishes,
the lowest of the vertebrates.
The connecting link between the fish and the reptile groups is
the amphibians--frogs, newts, salamanders, etc. The frog in its
tadpole stage is a fish, but acquiring legs and lungs it becomes an
air-breather, a land animal.
Between the reptile and the bird, and having certain characteristics of
both, there are at least three extinct species, known by their fossils.
One of these, archaeopteryx, had the skeleton and feathers of a bird
and a reptile tail composed of twenty vertebrae. Another was a flying
reptile with a bird-shaped head.
Reptiles (snakes, lizards, turtles, aligators, etc.) are cold-blooded,
egg-laying animals. Birds retain the egg-laying characteristic of
reptiles but are warm-blooded like the mammals. The latter differ from
both birds and reptiles in producing their young alive and suckling
them. Between the mammal and its ancestor, the reptile, but classed
with the former is the duck-mole of Australia. It is an egg-laying,
web-footed, duck-billed quadruped. After its young are hatched they
are suckled in a sort of mammary pouch which is without nipples. Above
the duck-mole, but so low in the mammal group that they are not really
mammals are the marsupials (kangaroos, opossums, etc.). Their young are
so immature at birth that they are for some time carried in a pouch by
the mother.
We have now come to the last great chasm--that between man and the
other mammals. As man belongs in the same group with them the chasm is
not so great in the sum of physical characters as is that between the
fish and the reptile groups, or between the reptiles and the mammals.
In regard to man and the higher apes the dividing line, viewed from the
stand-point of descent, is vertical rather than horizontal--like that
between mammals and birds.
There are no species, extinct or extant, between man and the ape. It
is not necessary for the proof of evolution that there should be.
“Missing links” are not more required here than they are between birds
and mammals which were evolved side by side from reptiles. If ten feet
below the topmost bough of a tree there is another branch it is not
necessary to show that there are, or have been, intermediate branches
to prove that both grew from the same trunk. Missing links are required
only _in the line of descent_.
Discoveries of the fossil remains of man are rare for many reasons.
(1) Land animals rarely leave their remains in the sediment of sea
and lake. (2) There is small chance of the sediment containing the
fossils of recently arrived animals--more especially of man, the
latest arrival--being lifted above the water level because of the slow
movements of the earth’s crust. (3) Only those animal remains that
are buried in localities where they will be impregnated with certain
mineral salts will be preserved. (4) They must be able to resist those
destructive agencies (especially erosion by water) that disintegrate
the rock in which they are embedded if they are to come down to us as
evidence. (5) Only a small part of the earth as yet has been searched,
and nearly all the fossil discoveries have been accidental. For these
reasons the geological record in respect to fossil evidences is far
from complete. Yet from time to time new discoveries are filling in the
gaps in the record.
Anthropologists present us with evidences of pre-historic races that
were far lower than the lowest savage of today. Some of the evidences
of man’s existence tens of thousands of years ago were known before
Darwin set the world astir with his revolutionary discovery, and the
old school geologists, like Hugh Miller, who had not been entirely
weaned from scriptural literalism were sadly puzzled in regard to the
evidences of these “pre-Adamites.”
Fossils have been found showing several gradations or stages
in development intermediate between man and his pre-human
ancestor--evidences which, if they do not completely bridge the chasm,
stand as ruined pillars, broken arches, isolated spans of the bridge
over which man was many hundreds of thousands of years in crossing.
The first skull discovered (sixty years ago) of the Neanderthal men
was so entirely different from other pre-historic skulls that one
scientist declared it was a mal-formation; but other fossils were found
later that proved the peculiarities to be racial characteristics.
These men, who lived in Europe down to thirty thousand years ago, were
squat, bent-kneed, thick-skulled, almost chinless, and with ridge-like
projections over deep-set eyes. In skull development they were lower
than any savage of today.
Older than the Neanderthal race, and lower in the human scale, were the
Heidelberg men, said to have been the first really human beings of whom
we have fossil evidences. Judging from the age of the fossil beds they
existed from 100,000 to 200,000 years ago.
Thirty years ago were found some of the fossil remains of a creature
in Java, some forty feet below the surface, that show characters
intermediate between the gorilla and the Neanderthal man; “the lowest
human cranium yet described, very nearly as much below the Neanderthal
as this is below the normal European.” This creature was named
Pithecanthropus Erectus (erect ape-man).
Lack of space prevents even a brief description of other and
intermediate types of man, such as the man of Spy, of Naulette, of
Predmost, etc.
As the more man develops (becomes specialized) the farther he is
removed from the lower animals, so, in tracing his descent toward
his origin we find him approaching them, apes included, in general
characteristics, for we approach the point of divergence.
Evolution is a fact. There is no doubt of that in the minds of those
who have investigated the subject without prejudice and with the
acquisition of truth as the sole aim. One may dispute a fact, but he
cannot deny it out of existence. Those who feel a sense of shame for
their close proximity to their cousin, the monkey, are advised to
increase that distance by carrying to higher development those traits
considered peculiarly human: Reason, a sense of justice, of broader
sympathy, and tolerance.
By his great discovery Darwin delivered the heaviest solar plexus blow
to human vanity it ever received. For this he deserves, and receives,
the eternal gratitude of every right-thinking man and woman.
How was evolution brought about? What are its laws, and how do they
work?