GEOLOGICAL HISTORY OF VERTEBRATE ANIMALS (INCLUDING MAN)
Vertebrates comprise the highest subkingdom of all animals with man
himself at the very top. They are characterized by the possession of
a vertebral column, which, in all but the very simple or primitive
forms, is an ossified backbone. Their main subdivisions are given
in the classification table near the beginning of the preceding
chapter. The oldest known Vertebrates, found in fossil form in middle
Ordovician strata, were represented by curious and bizarre creatures
called ostracoderms, or more popularly "armor fishes." They were not
true fishes because they were really somewhat lower in the scale of
organization than fishes. Some were distinctly fishlike in appearance,
and others notably resembled certain of the Arthropods, so that some
students consider them to have formed the connecting link between
the highest Invertebrates (Arthropods) and low order fishes of the
Vertebrates. The vertebral column always consisted of cartilage or
gristle and, in most forms, it extended through tail fin. None had true
side fins like fishes, but many were provided with a pair of jointed
flappers or paddles. The jawlike portions of the heads moved over each
other sidewise as, for example, in beetles and not up and down in true
Vertebrate fashion. Two eyes were always very close together. One of
the most striking features was the protection of the head and fore part
of the body by an armor of bony plates, while the rest of the body had
scales. They seldom grew to be more than six or seven inches long.
Beginning in the Devonian, they remained rare during the Silurian, and
then in the Devonian period they reached their climax of development
only to become extinct at its close. Many species were abundantly
represented in many parts of the world. By some the Ostracoderms are
thought to have been a primitive (sharklike) fish development in the
wrong direction, and hence they became extinct.
[Illustration: Fig. 57.--Two restored forms of very primitive and
ancient (Devonian) types of Vertebrates called "ostracoderms." They
were lower in organization than true fishes. (After Dean-Woodward and
British Museum, respectively.)]
Fishes, represented only by very primitive sharks, are known to
have existed as early as the Silurian period, but the remains are
scant. During the Devonian period, however, they showed a marvelous
development into many species and countless myriads of individuals.
The Devonian is, therefore, commonly called the "Age of Fishes."
These very ancient (Devonian) primitive (fish) types of Vertebrate
animal life are of profound significance in organic evolution because
they were the direct progenitors of the great groups of still higher
Vertebrates which since later Paleozoic time gradually increased in
diversity and complexity of structure through amphibians, reptiles,
birds, and mammals finally to man himself.
[Illustration: Fig. 58.--Restorations of characteristic Devonian
fishes, based upon actual fossils: a, a "lung fish" with leglike fins
(after Huasakof); b, a "ganoid." (After Nicholson.)]
In marked contrast to the most typical and highly organized fishes
so abundant to-day, all Devonian fishes were of simple types with
cartilaginous skeletons and vertebrated tails. Many of them were also
generalized types, that is, associated with their clearly defined fish
characters were others connecting them with certain higher Vertebrates,
as, for example, amphibians and reptiles. Thus all their tail fins
were vertebrated as in reptiles; their labyrinthine, internal tooth
structure was to be an amphibian feature when those creatures evolved;
many had protective armor or bony scales like most early amphibians and
many modern reptiles; and many had paired fins which were something
like jointed legs. Most abundant and highly organized of the Devonian
fishes were "ganoids," characterized by a covering of small plates or
bony scales set together but not overlapping like in typical modern
fishes. Their intricate tooth structure and limblike fins strongly
suggest the amphibians of later Paleozoic time. The skeleton of
cartilage gradually became somewhat ossified during succeeding geologic
periods. From their great profusion and diversity in the Devonian
period the ganoids have steadily fallen away until they now have very
few descendants like the gar pike.
Another important group of remarkable fishes, now totally extinct,
but common in Devonian and somewhat later time, had heavy, bony armor
plates over the fore part of the body. Those which grew to be fifteen
to twenty-five feet long were probably the rulers of the middle
Paleozoic seas. Another remarkable Devonian fish was able to breathe in
both water and air because, like their few modern descendants, they had
both gills and lungs. Because of their leglike fins and lung sac, it
is commonly believed that they were progenitors of the later Paleozoic
amphibians. The simplest of all fishes, the sharks, began in the
Silurian, underwent no important change through the millions of years
since, and are now of course well represented. During early Cenozoic
time the sharks seem to have reached culmination in size--sixty to
eighty feet long, with teeth five or six inches long.
Among modern fishes the most abundant by far, and the most highly
organized, are the true bony fishes, called the "teleosts," which
made their first appearance in the middle of the Mesozoic era. Those
earliest forms clearly show their descent from the ganoids. Apparently
they have not yet passed their prime.
We shall now consider the next higher group of Vertebrates, the
amphibians, which breathe by gills when young and later develop
lungs. Many live both on land and in water like the frogs. Unlike
fishes they have legs with toes and not fins. Beginning probably in
the Devonian as a branch of the fishes, amphibians showed a marvelous
development during later Paleozoic and very early Mesozoic times when
they reached their climax, after which they fell off remarkably, being
now relatively unimportant like the frogs and salamanders. They are of
special significance because they were the first of all the back-boned
animals (Vertebrates) to inhabit the land which they dominated only
until the great rise of reptiles of Mesozoic time. The reptiles in fact
evolved from the amphibians in the late Paleozoic when many transition
forms occurred. (Plate 15.) During those ancient days the numerous and
very diversified amphibians were like giant salamanders, commonly five
to eight feet long, with one Triassic form fifteen to twenty feet long,
and with heavily armored skulls two to four feet long.
Turning now to the reptiles we find that they are much more distinctly
land animals than the preceding types of Vertebrates. Reptilian life
of the earth began in late Paleozoic time as an evolutionary branch
of the amphibians. The earliest forms were in many ways much like the
amphibians, but gradually they diversified and progressed so that
before the close of the Mesozoic era, which has long been called the
"Age of Reptiles," they were the rulers of the world. "They covered
the land with gigantic herbivorous and carnivorous forms; they swarmed
in the sea, and, as literal dragons, they dominated the air." (Scott.)
Mesozoic reptiles are of special interest and significance not only in
themselves, but also because from one of their branches the birds were
evolved, and from another the mammals. "In advancing from the amphibian
to the reptile the evolution of the Vertebrates was far from finished.
The cold-blooded, clumsy and sluggish, small-brained and unintelligent
reptile is as far inferior to the higher mammals, whose day was still
to come, as it is superior to the amphibian and the fish." (Norton.)
Since the reptiles of the Mesozoic era constitute one of the few most
remarkable and diversified classes of animals which ever inhabited the
earth, we shall attempt to give the reader a fair idea of the most
typical groups which have been totally extinct since the close of the
Mesozoic era some millions of years ago. Of the swimming reptiles
which lived in the seas many types are known and only a few will be
described. Among these one important type was the ichthyosaur, a
fishlike form which not uncommonly grew to be twenty to even forty feet
long (Plate 18). The large head, sometimes four or five feet long,
contained as many as 200 big sharp teeth and enormous eyes up to a foot
in diameter. The body was heavy set, and the neck very short. There
were four short, stout swimming paddles, and the tail was vertebrated.
Some specimens of ichthyosaurs have been so perfectly preserved in
Mesozoic strata that even the unborn young are plainly seen in the
bodies! In some cases it is actually possible to tell what was the last
meal of a particular ichthyosaur those millions of years ago; in one
specimen, for example, remains of 200 creatures of the "cuttle-fish"
tribe having been found in the exact position of the stomach.
[Illustration: Fig. 59.--Chart showing the main branches in the history
of Vertebrate (back-boned) animal life reaching its culmination in man.
(By the author, in part after Cleland.)]
The mosasaurs of the late Mesozoic were the only real sea serpents of
the geologic ages. They were something like the ichthyosaurs, but with
smaller heads and much longer, more slender, serpentlike bodies. Some
grew to be thirty or forty feet long.
Plesiosaurs were perhaps the strangest of all the Mesozoic marine
reptiles. They grew to be forty to fifty feet long, with stout body,
very long, slender neck, small head, short tail, and four long,
powerful swimming paddles which were distinctly leglike. These and the
mosasaurs were both flesh eaters, as shown by the sharp teeth.
[Illustration: Plate 15.--(_a_) Restoration of a Late Paleozoic (Coal
Age) Landscape. Showing the main kinds of plants which have entered
into the making of most of our coal. Giant "club mosses" both with
and without branches, in the left background; giant "horsetail" (or
"scouring rush") plants on the right; and seed ferns in the left
foreground. A primitive reptile in the water; two large amphibians or
giant salamanders, called "stegocephalians," on the land; and a great
"dragon fly," two feet wide, in the air. (_From a drawing by Prof.
Williston. Courtesy of D. Van Nostrand Co._)]
[Illustration: Plate 15.--(_b_) Photograph of a Fossil Fern or Seed
Fern Frond on a Piece of Shale Millions of Years Old. The specimen
is of the Pennsylvanian Age and was taken from the coal fields of
Pennsylvania. (_After White, U. S. Geological Survey._)]
[Illustration: Plate 16.--Restoration Showing the General Appearance
of Some of the Largest Animals Which Ever Trod the Earth. A mounted
skeleton in the American Museum of Natural History is sixty-seven feet
long, and the skeleton of a similar creature in the Carnegie Museum,
Pittsburgh, is eighty-seven feet long. They lived millions of years ago
during the middle and late Mesozoic era. (_After C. R. Knight. Courtesy
of the American Museum of Natural History, New York._)]
The most remarkable walking reptiles of all time were the dinosaurs
or "terrible lizards." We shall describe enough types of these unique
creatures to give the reader a fair idea of their appearance and
habits. Most astonishing of all were the sauropods including the
largest animals which ever trod the earth. They grew to be as much
as sixty to ninety feet or more in length. Remarkably well preserved
skeletons have been found, one from Utah, eighty-seven feet long, being
mounted in the Carnegie Museum of Pittsburgh. The largest of these
brutes stood fifteen to twenty feet high and they must have weighed
thirty to fifty tons. The very long, serpentlike neck and tail, and
very small head were grotesque features. Considering the structure of
the dinosaurs, the kind of strata in which they are embedded, and the
associated fossil remains, it seems clear that they mostly lived in
and near fresh water and on near-by lowlands. The character of their
teeth shows that they fed entirely on soft plants which they must have
habitually bolted because their teeth were not well adapted to grinding
food. It is difficult to believe that a single huge beast could have
consumed less than a few hundred pounds of vegetable matter per day,
and, on account of the very small size of the head, he must have spent
most of his time eating. Also the comparatively very small size of
the brain, and its simplicity of structure, render it certain that
they were extremely stupid creatures. "To make up for this they had an
enormous enlargement of the spinal cord in the sacral region (i.e.,
over the hind legs). This sacral brain--if we may so call it--was ten
to twenty times bigger than the cranial brain. It was necessary in
order to work the powerful hind legs and tail." (Le Conte.)
[Illustration: Fig. 60.--Skeleton of a great four-legged (sauropod)
dinosaur. A mounted skeleton in the American Museum of Natural History,
New York, is sixty-seven feet long. This creature lived millions of
years ago during the Jurassic period. (After Marsh.)]
Another dinosaur, in some respects like the sauropod, was the stegosaur
which grew to be twenty to thirty feet long, and heavier than the
elephant. Unlike the sauropod, it had a short neck and was armored with
a double row of great plates over its back, and sharp spines (one to
three feet long) toward the end of the tail. The excessive stupidity of
the creature is proved by the fact that its very simple brain weighed
less than three ounces! Stegosaurs were plant eaters as indicated by
the tooth structure, and, though they looked ferocious, they were
probably not fighters, certainly at least nothing like the carnivorous
types of dinosaurs we shall soon describe.
[Illustration: Fig. 61.--Skeleton of the curious kind of dinosaur
(stegosaur) of Mesozoic Age with great bony plates over the back.
Length about thirty feet. (After Marsh.)]
The ferocious dinosaurs of Mesozoic time were carnivorous, or flesh
eaters, as shown by their numerous sharp teeth in relatively large
heads. The largest known type is the tyrannosaur, an almost perfect
skeleton of which, 40 feet long and 16 feet high, is mounted in the
American Museum of Natural History in New York (Plate 17). So far as
known, this was the largest carnivorous animal which ever walked on
the earth. It is evident from the structure that it walked on its
hind legs, the front ones having been much shorter and used something
like arms. There were also various other smaller forms of two-legged
flesh-eating dinosaurs, many of the wonderfully preserved tracks in
the Triassic sandstones of the Connecticut River Valley having been
made by such creatures when they walked around over soft, sandy mud
flats at least eight or ten million years ago. The sandy mud with its
tracks became somewhat hardened and then deeply buried under much more
sediment which, through the ages, has been eroded off, thus exposing to
view certain of the layers covered with tracks. Some bones of dinosaurs
have also been found in the Connecticut Valley.
[Illustration: Fig. 62.--Skeleton (restored) of a great two-legged
dinosaur of the Mesozoic era. This type of plant eater grew to be fully
twenty-five feet long. (After Marsh.)]
Another remarkable type of two-legged dinosaur was much like the flesh
eaters just described, but they were plant eaters. The largest of these
grew to be 30 feet long and 15 to 20 feet high, comparable, therefore,
to the tyrannosaur in size. A wonderful collection of almost perfect
skeletons may be seen in the museum in Brussels, Belgium. In mining
coal 1,000 feet below the surface in Belgium, twenty-two complete
skeletons and several partial skeletons were found in an ancient river
deposit of Cretaceous Age. A marvelously preserved specimen of one
of these two-legged plant eaters found in Wyoming, has been called a
"dinosaur mummy" because the skin and much of the flesh of the creature
had shriveled down upon its bones. The minutest details of the texture
of its skin are almost perfectly preserved.
[Illustration: Fig. 63.--Skeleton of a dinosaur (triceratops) with a
large remarkable head. This creature grew to be twenty-five feet long
during Cretaceous time. (After Marsh.)]
Another type of dinosaur, so different from the others, should be
briefly described. This was triceratops, or the "three-horned face"
beast, so named because of the three powerful horns which projected
forward from the top of the very large, flattened skull. It grew to be
twenty to twenty-five feet long. Skulls six to eight feet long have
been unearthed. Just where the brain might have developed, the skull
dished downward, and so one authority considers triceratops to have had
the largest head and smallest brain of all the great reptiles.
It is well known that dinosaurs of many types lived during the great
"Age of Reptiles," though by no means all types ranged through the
whole era. No dinosaurs are definitely known to have crossed the line
into the Cenozoic era. One of the most astonishing facts in the history
of animal life is the extinction of the mighty dinosaurs, but no very
satisfactory explanation has yet been offered. Probably their great
size was a contributing factor, for it is well known "that while very
large animals spend nearly all their time in eating, small animals
spend a small proportion of theirs, and most of it in other activities.
Now, as long as food is abundant, the larger animals of a race have the
better chances, but if a scarcity of food ensues, the larger animals
may all be suddenly swept out of existence." (Matthew.) Whatever may
have been the real reason for dinosaur extinction we can at least be
sure "that with the extensive changes in the elevation of land areas
(Rocky Mountain Revolution) which mark the close of the Mesozoic, came
the withdrawing of the great inland Cretaceous seas along the low-lying
shores of which the dinosaurs had their home, and with the consequent
restriction of old haunts, came the blotting out of a heroic race.
Their career was not a brief one, for the duration of their recorded
evolution was twice that of the subsequent mammalian (Cenozoic) age.
They do not represent a futile attempt on the part of nature to people
the world with creatures of insignificant moment, but are comparable
in majestic rise, slow culmination, and dramatic fall to the greatest
nations of antiquity." (Schuchert.)
Among the most extraordinary animals not only of the Mesozoic, but also
of all time, were the flying reptiles or literal dragons of the air.
Some were very small, while others were the largest creatures which
ever flew, with a spread of wing of twenty to twenty-five feet--twice
that of any modern bird. Unlike birds they had no feathers, but the
two wings consisted of large membranes (batlike) supported by one
enormously elongated finger of each front limb. The other fingers
were armed with sharp claws. The early Mesozoic flying reptiles had
sharp teeth, while the later ones were mostly entirely toothless, but
all were carnivorous. Their short bodies were supplied with tails of
varying lengths, one long-tailed species having a rudder at the end.
Their heads were fairly large, but of light build. The creature called
"pteranodon" was not only the largest of the flying reptiles, but
also probably the most highly specialized creature which ever lived,
everything possible apparently having been sacrificed to facilitate
flight (Plate 18). The hollow bones were so wonderfully light and
strong that it has been estimated that the living animal, with
twenty-five foot spread of wing, and head four feet long, could not
have weighed more than twenty-five pounds! The rear portions of the
body and hind limbs were very weak.
[Illustration: Fig. 64.--A small carnivorous flying reptile of Mesozoic
time. Spread of wings about two feet. (Restored by Marsh.)]
It should not be thought that the above-described groups of reptiles
were the only ones which existed during Mesozoic time. There were also
certain groups still living, like turtles, lizards, and crocodiles, but
they were doubtless mostly completely under the dominance of certain
of the now long-extinct types above described. The oldest-known fossil
snakes are from very late Mesozoic rocks, where they are small and
comparatively rare. More than likely they evolved from lizards by
deterioration of the legs. Poisonous snakes were not evolved until
early in the next (Cenozoic) era.
We shall now turn our attention to next to the highest class of
Vertebrate animals--the birds. They and the mammals are the only
warm-blooded animals. What is their ancestry? From what original stock
did they branch off? The oldest-known bird lived during the Jurassic
period, and it was so decidedly reptilian in character as to render it
practically certain that birds are specialized descendants of certain
Mesozoic reptiles, though not, as might be supposed, of the flying
reptiles. The few known specimens of the Jurassic birds were found
in the famous lithographic limestone quarries of Bavaria. At least
two of the specimens are in a marvelous state of preservation, with
practically the whole skeleton intact and almost perfect impressions of
the feathers on the rock. That the creature was really a bird is proved
not only by its feathers, but also its beak, brain, limb bones, and
feet. Among the reptilian characters are its long, vertebrated tail,
teeth set in sockets, and long claws on the wings. This reptilian bird
was about the size of a small crow.
By late Cretaceous time the birds made notable evolutionary progress
and they became diversified, more than thirty species being known from
Cretaceous rocks. These were distinctly more modern in structure
and appearance than the Jurassic bird. The only important reptilian
characteristic still retained was the possession of teeth. The tail
had become much shortened and the brain was still relatively smaller
than in modern birds. One type, about nine inches high, was a powerful
flier, as shown by the strong keel and wing bones. Another important
Cretaceous type was almost wholly a water dweller, with powerfully
developed legs used in swimming. Its teeth were set in grooves instead
of in sockets, thus indicating degeneration of tooth structure. This
type was notable for its size--five to six feet in length.
[Illustration: Fig. 65.--An early type of bird with teeth. This bird
grew to a height of about nine inches in Cretaceous time, millions of
years ago. (Restored by Marsh.)]
During the early part of the Cenozoic era birds became still more
advanced and numerous, with many modern groups represented. Some of
the more primitive types were, however, still left over during the
Tertiary, as, for example, a toothed bird, in which the teeth were
merely dentations of the bill, thus being the most degenerate of all
types of tooth structure.
Mammals comprise the highest class of all animals. They are, of course,
all warm blooded and characterized by suckling their young. So far
as known, mammal life began in the early Mesozoic era as a branch of
primitive reptiles, but they made little progress throughout the era
when they occupied a very subordinate position in the animal world.
They were few in number, small, and primitive in structure. There is
no evidence for the Mesozoic existence of any of the higher forms of
mammals, that is, those which give birth to well-formed young which
are prenatally attached to the mother by the so-called placentum.
"During the eons of the Mesozoic, from late Triassic time until its
close, the mammals (including the remote progenitors of humanity) were
in existence, but held in such effective check (by reptiles) that
their evolutionary progress was practically insignificant. This curb
is strikingly illustrated by the wonderful series of tiny jaws and
teeth of these diminutive creatures found in the Comanchian (early
Cretaceous) of Wyoming, in actual association with the single tooth of
a carnivorous dinosaur, many times the bulk of the largest mammalian
jaw. The removal of this check resulted (in the Tertiary period) in the
speedy evolution of the archaic mammals." (Schuchert.)
The phenomenal development of mammals during the Tertiary period forms
one of the most wonderful chapters in the whole evolution of organisms.
Even very early in the Tertiary, many important higher (placental)
types of mammals had evolved, and the simpler, more primitive Mesozoic
forms became very subordinate. By the close of the Tertiary the higher
types of mammals had become marvelously differentiated into most of
the present-day groups or types. A very significant feature of the
evolution was the steady increase in relative size of brain. The vast
numbers of fossil skeletons and bones of mammals found in Tertiary
strata is scarcely believable. In our brief discussion we can do no
more than describe a few representative examples of the Cenozoic
evolution of mammals.
The great diversity of modern placental animals may be suggested by
a few examples, as the tiger, dog, horse, camel, elephant, squirrel,
hedgehog, whale, monkey, and man. Forms like these, traced back
through their ancestors to the very early part of the Tertiary period,
gradually become less and less distinct until they cannot be at all
distinguished as separate groups, but rather there are ancestral
generalized forms which show combinations of features of the later
groups. Those early Tertiary generalized placental mammals had four
feet of primitive character, with five toes on each foot; the whole
foot, which from toe to heel touched the ground, was not adapted to
swift running; the teeth were simple (primitive) in type and of full
original number (forty-four); the toes were supplied with nails which
were about intermediate between real claws and hoofs in structure; and
the brain was relatively much smaller and simpler in structure than in
most modern mammals.
[Illustration: Fig. 66.--Chart showing the main features of interest
in the evolution of the horse family through several million years of
the present (Cenozoic) era of geologic time. (After Matthew, American
Museum of Natural History.)]
The history of the horse family furnishes an excellent illustration of
certain evolutionary changes among mammals. Skeletons of many species,
ranging from the early Tertiary to the present, have been found in
remarkable state of preservation representing every important change
in the history of the horse family. A study of the chart will make
clear some of the most striking changes which have taken place. The
oldest member of the horse family represented on the chart was about
the size of a small fox, with four toes and a degenerated fifth toe
(splint) on the front foot, and three toes and splint on the hind
foot. Since the chart was made a still more primitive form, even more
closely resembling the original five-toed ancestor, has been found.
Gradually the middle toe enlarged, while the others disappeared except
the two splints or very degenerate toes still left in the modern horse.
Increase in size of the animal and brain capacity accompanied these
changes. Also the teeth underwent notable change, and two originally
separate bones (radius and ulna) of the foreleg became consolidated
into a single stronger bone.
The even-toed hoofed mammals of to-day, like the deer, pig, and camel,
are also the product of evolution much like that of the horse, except
that two of the original five toes have been equally developed,
while the others have either greatly degenerated, as in the pig, or
disappeared entirely, as in the camel.
The elephants, or trunk-bearing animals, illustrate a very different
kind of evolution. They seem to have reached their climax of
development in the late Tertiary when they grew to be as much as 14
feet high, and were more abundant and widespread over the earth than at
any other time. The modern elephant, like the horse, has been traced
back through many intermediate forms to its primitive early Tertiary
ancestry. Some of the most important evolutionary changes took place
in the head portion. The trunk is a highly developed form of snout,
the earliest form of which was much like that of the modern tapir. The
tusks are highly specialized and elongated teeth. During the earlier
history the chin was very long and supported short tusks, so that there
were then four tusks.
Carnivorous mammals, like tigers and wolves, and gnawers, like rats and
squirrels, may also be traced back to generalized early Tertiary types.
Another kind of evolution is well illustrated by certain mammals which,
even in early Tertiary time, so thoroughly adapted themselves to a
water environment as to become whales, porpoises, etc.
[Illustration: Fig. 67.--Comparison of feet of monkeys and man.]
The primates include the highest group of all Vertebrates, and
therefore of all animals. Monkeys, apes, and man belong to the
primates. There is no evidence whatever for the appearance of even the
simplest and most primitive forms before the opening of the Cenozoic
era, but even very early in Tertiary time, lemurs and primitive types
of monkeys existed. Later in the Tertiary true monkeys and apes were
common, and by the close of the period some apes were highly enough
developed to strongly resemble certain of the oldest and most primitive
types of man. We have, however, no positive knowledge of the existence
of man in even the latest Tertiary. In the light of much evidence in
regard to the antiquity of man, it seems improbable that true human
fossils will ever be found in rocks older than the Quaternary, though
if we are willing to descend (far enough in the human scale toward
apes) it is not unlikely that man-apes may be discovered in very late
Tertiary rocks. The difficulty comes in the classification. Where
are we to draw the line between the higher apes and the lowest forms
of man? But this very difficulty is one of the strongest arguments
in favor of the organic evolution of man because practically all
intermediate forms between true man and certain other high-grade
primates are known from the strata. The following tabular summary of
the geological history of man is based upon the work of most of the
ablest students of the subject.
==========================+===============================+==============
3. Homo sapiens |Historic (bronze and iron) age.|Modern
(e.g., modern man) | |
|Neolithic ("recent stone") age |Postglacial
| (carefully shaped and |but
| polished stone implements) |prehistoric
--------------------------+-------------------------------+--------------
2. Homo primigenius |Upper Paleolithic ("ancient |Late Glacial
(e.g., Neanderthal | stone") age (rough bone |
man) | and stone implements, cave |
| frescoes, bone carvings, |
| etc.) |
|Lower Paleolithic ("ancient |Middle Glacial
| stone") age (rude stone |
| implements of so-called |
| "river man") |
--------------------------+-------------------------------+--------------
1. Early ancestral forms |Possibly some very crude |Early Glacial
(e.g., Pithecanthropus | stone implements |and possibly
erectus) | |late Tertiary
--------------------------+-------------------------------+--------------
Of the early ancestral forms, that is, those which were rather
distinctly man-apes, two will be very briefly referred to. One of
these, known as _Pithecanthropus erectus_, was a remarkable creature
whose partial skeleton, consisting of the upper part of a skull, lower
jaw, several teeth, and a thigh bone, was found in early Quaternary
deposits in Java in 1891. It was certainly a man-ape or possibly
ape-man of low order, about 5-1/2 feet high. The skull has a low crown,
very receding forehead, and prominent brow ridges, but the brain
capacity is 850 cubic centimeters, as compared to 500 cubic centimeters
in ordinary higher apes, and nearly 1,500 cubic centimeters in the
average modern man. The very recently extinct very low-type aborigines
of Tasmania had a skull capacity of 1,199 cubic centimeters.
In 1907 the lower jaw of an anthropoid or manlike ape set with rather
human teeth was found associated with very crude stone implements
seventy-five feet below the surface in river-deposited sand in Germany.
It is of either early or middle Glacial time and quite certainly
represents a lower order creature than the oldest Paleolithic man as
described below.
Many bones and implements of Paleolithic man (see above table) have
been found mainly in river gravels and caves. The relative ages
of Paleolithic human bones and implements are best determined by
the associated fossil animals. Thus the most ancient truly human
fossils are found directly associated with bones of very old types of
elephants, rhinoceroses, and hippopotamuses which are definitely known
to have lived during middle or early middle Glacial (Quaternary) time
corresponding to early Paleolithic time. A very conservative estimate
would make the age of such very old human remains at least 150,000 to
250,000 years because the Ice Age was at least 500,000 years long. In a
later human stage there are many associations with extinct animals like
an older type of mammoth, cave bear, cave hyena, and others of later
Glacial time estimated at 50,000 to 150,000 years ago. Last of all was
the latest Paleolithic stage corresponding to the close of the Ice Age,
the human remains of which are found associated with reindeer and the
latest mammoths which roamed in great numbers across Europe. This was
probably not more than 30,000 to 50,000 years ago.
Paleolithic man is so called because he fashioned stone weapons and
implements. The structure of skull and skeleton shows him to have
been a low-type savage, something over five feet high on the average,
with a forward stooping carriage. The average Paleolithic brain was
not greatly inferior in size to that of modern civilized man, but
it was not so highly organized and occupied a thick skull with much
lower forehead and heavy brow ridges. The bushmen of Australia and
the recently extinct Tasmanians are the nearest modern resemblances.
Many fine specimens of Paleolithic man have been found, especially in
cave deposits. That he was an expert hunter is proved by the great
accumulation of bones of now extinct animals found in and about his
haunts or camps, bones representing at least 100,000 horses having been
found around a single camp site!
[Illustration: Fig. 68.--Comparison of skulls: a, Paleolithic
(Neanderthal) man; b, modern man. (After Woodward, British Museum.)]
Only two among the many known Paleolithic man localities will be
briefly described. In the Perigord district of southwestern France a
number of caves contain human relics ranging in age from early to late
Paleolithic. Of special interest among these relics are fishhooks
made of bone, and crude sketches of animals such as the mammoth and
reindeer now extinct in that region. The Aurignac cave, also in France,
was no doubt a family or tribal burial place. Seventeen Paleolithic
human skeletons, associated with bones of extinct animals and crude
art works, were found in the cave. Near the entrance there were ashes
and charcoal mixed with burned and split bones of extinct animals.
Certain of the caves occupied by late Paleolithic man have their
walls decorated with sketches and even colored pictures. These are,
therefore, the oldest known art galleries. An excellent example is the
cave at Altamira in northern Spain. "As we glance at the pictures one
of the first things to impress us is the excellence of the drawing, the
proportions and postures being unusually good.... The next observation
may be that, in spite of this perfection of technique, there is no
perspective composition--that is, no attempt to combine or group the
figures.... It is also clear that the work of many different artists
is represented, covering a considerable period of time. The walls show
traces of many other paintings that were erased to make way for new
work." (Wissler.)
[Illustration: Fig. 69.--Sketch of a painting by Paleolithic man found
in a cave in west-central France. Various animals, including the
extinct mammoth elephant, are represented. (Courtesy of American Museum
of Natural History.)]
The Neolithic, or "recent stone" age was a gradual development from
the late Paleolithic, and man was then more highly developed and more
similar in structure to modern man. His stone implements were more
perfectly made, and often more or less polished and ground at the
edges. "The remains of Neolithic man are found, much as are those of
the North American Indians, upon or near the surface, in burial mounds,
in shell heaps (the refuse heaps of their settlements), in peat bogs,
caves, recent flood-plain deposits, and in beds of lakes near shore
where they sometimes built their dwellings upon piles.... Neolithic man
in Europe had learned to make pottery, to spin and weave linen, to hew
timber, and build boats, and to grow wheat and barley. The dog, horse,
ox, sheep, goat, and hog had been domesticated." (Norton.)
"Man is linked to the past through the system of life, of which he is
the last, the completing creation. But, unlike other species of that
closing system of the past, he, through his spiritual nature, is more
intimately connected with the opening future." (J. D. Dana.)