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"Variability is not actually caused by
man; he only unintentionally exposes
organic beings to new conditions of
life, and then nature acts on the
organization and causes it to vary.
Man can and does select the variations
given to him by nature, and thus accumulates
them in any desired manner.
Man thus adapts
animals and plants for
his own benefit or pleasure. Man may
do this methodically, or he may do it unconsciously by preserving the
individuals most useful or
pleasing to him without any intention of altering the breed.
It is
certain that he can largely influence the character of a breed
by selecting, in each successive generation,
individual differences so slight
as to be inappreciable except by an educated eye. This unconscious process of selection has been
the great agency in the formation of the most distinct and useful domestic
breeds. That many breeds produced by man have to a large extent the character
of natural
species, is shown by the inextricable doubts
whether many of them are varieties or aboriginally distinct
species.
There is no
reason why the
principles which have acted so
efficiently under domestication should not have acted under
nature. In the
survival of favored individuals and
races, during the constantly recurrent struggle for
existence, we see a powerful and ever acting
form of selection.
The
struggle for existence inevitably follows
from the high geometrical ratio of increase which is
common to all
organic beings. This high rate of increase is proved by
calculation, by the rapid increase
of many animals and plants during a succession of peculiar seasons, and
when naturalized in new countries.
More individuals are born than can
possibly survive. A grain in the
balance may determine which
individuals shall
live, and which shall
die, which variety or
species shall increase in number, and which
shall decrease, or finally become extinct.
As the individuals of
the same species come in all regards into
the closest competition with
each other, the struggle will
generally be most severe between them; it will be almost
equally severe between the varieties of
the same species, and next in severity
between the species of the same genus.
On the other
hand the struggle will often be severe between
beings remote in the scale of
nature. The slightest advantage in certain
individuals, at any age or
during any season, over those with which they come into
competition, or
better adaptation in however slight a
degree to the surrounding physical
conditions, will, in the long run, turn the
balance.
With
animals having separated sexes, there
will be in most cases a struggle between the males for the possession of the females. The most vigorous
males, or those which have most
successfully struggled with their conditions of life, will generally leave most progeny.
Success will often depend on the
males having special weapons, or means of defense, or charms;
and a slight advantage will lead to victory.
As geology plainly proclaims that each land has undergone great
physical changes,
we might have expected to find that
organic beings have varied under
nature, in the same
way as they have varied under
domestication.
If there has been any variability under
nature, it would be an unaccountable
fact if natural selection had not come into
play. It has often been asserted, but the
assertion is incapable of proof, that the amount of variation under
nature is a strictly limited quantity.
Man, though acting on external
characters alone and often capriciously, can produce
within a short period a great
result by adding up mere individual
differences in his domestic productions; and everyone admits that
species present
individual differences. But,
besides such differences, all naturalists
admit that natural varieties
exist, which are considered sufficiently
distinct to be worthy of record in systematic works.
No one has drawn
any clear distinction between
individual differences and
slight varieties; or between more plainly marked varieties and
sub-species and species. On separate
continents, and on different parts of the same continent when divided by
barriers of any category, and
on outlying islands, what a multitude of
forms exist, which some
experienced naturalists rank as varieties,
others as geographical races or
sub-species, and
others as distinct, though closely
allied species!
If then,
animals and plants do
vary, let it be ever so slightly or slowly, why should not variations or
individual differences, which
are in any way beneficial, be
preserved and accumulated through natural selection, or the
survival of the fittest?
If man can by patience select
variations useful to him, why, under changing and
complex conditions of
life, should not variations useful to
nature's
living
products often arise, and be preserved or
selected? What limit can be put to this power,
acting during long ages and rigidly
scrutinizing the whole
structure, and habits of each
creature, - favoring the
good and rejecting the
bad?
I
can see no limit to this power, in slowly and
beautifully adapting each
form to the most
complex relations of
life. The theory of natural selection, even if
we look no farther than this, appears to be
in the highest degree probable."
As each species tends by its geometrical rate of
reproduction to increase inordinately in
number; and as the modified
descendants of each species will be
enabled to increase by as much as they become more diversified in habits and
structure, so as to be able to
seize on many and widely different places in the economy of nature, there will be a constant tendency in
natural selection to preserve the most
divergent offspring of any one species.
Hence, during a long continued course of modification, the
slight differences characteristic of
varieties of the same species, tend to
be augmented into the greater differences characteristic of the
species of the same genus. New and improved
varieties will inevitably supplant and exterminate the older, less improved,
and intermediate varieties; and thus species
are rendered to a large extent defined and distinct
objects.
Dominant
species belonging to the larger groups
within each class tend to give
birth to new and dominant forms; so that each
large group tends to become still larger, and at the same time more divergent
in character. But as all groups cannot thus go on increasing in size, for the
Earth would not hold them, the more dominant
groups beat the less dominant.
This tendency in the large groups to go
on increasing in size and diverging in
character, together with the inevitable contingency of much extinction,
explains the arrangement of all the
forms of life in groups subordinate to groups,
all within a few great classes,
which has prevailed throughout all time."
"We can to a certain extent
understand how it is that
there is so much beauty throughout
nature; for this may be largely attributed to
the agency of selection.
That
beauty, according to
our sense
of it, is not universal, must be admitted by everyone who will look at some
venomous snakes, at some fishes, and at certain hideous
bats with a distorted resemblance to the
human face.
Sexual selection has given the most brilliant
colors, elegant
patterns, and other ornaments
to the males, and sometimes to
both sexes, of many birds, butterflies, and
other animals. With birds it
has often rendered the voice of the male
musical to the
female, as well as to
our ears.
Flowers and
fruit have been rendered
conspicuous by brilliant colors in contrast with the green foliage, in order
that the flowers may be easily
seen, visited, and fertilized by
insects, and the seeds
disseminated by birds.
How it comes that
certain colors, sounds, and forms should give pleasure to
man and the lower
animals, - that is, how the sense of
beauty in its simplest
form was first acquired, -
we do not know any more than how certain
odors and flavors were first rendered agreeable."
"It can hardly be supposed that a false
theory would
explain, in so satisfactory a manner
as does the theory of
natural selection, the
reason all
living
things have much in
common, in their
chemical composition, their cellular
structure, their
laws of growth, and their liability to injurious
influences.
It has
recently been objected that this is an unsafe method of arguing; but it is a
method used in judging of the
common events of
life, and has often been used by the greatest
natural
philosophers. The undulatory
theory of light has thus been arrived at; and the
belief in the revolution of the
Earth on its own axis was until lately
supported by hardly any direct evidence.
It is no valid objection that
science as yet throws no
light on to the far higher
problem of the
essence or origin of life."
"When
we no longer look at an organic being
as a savage looks at a ship, as
something wholly beyond his comprehension; when
we regard every
production of
nature as one which has had a long
history; when
we contemplate every
complex
structure and
instinct as the summing up of many
contrivances, each useful to the possessor, in
the same way as any great
mechanical invention is the summing up
of the labor, the experience, the reason, and even the blunders of numerous
workmen; when we thus view each
organic being, how far more interesting does the study of
natural
history become!"
"It is
interesting to contemplate a tangled bank, clothed with many
plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with
worms crawling through the damp
earth, and to
reflect that these
elaborately constructed forms, so different from each
other, and
dependent upon each
other in so
complex a manner, have all been produced
by laws acting around
us. "
"There is grandeur in this
view of life
with its several powers, having been
originally breathed by the
Creator into a few forms or into one; and that,
whilst this Earth has gone cycling on
according to the fixed law of gravity,
from so simple a beginning endless forms
most beautiful and most wonderful have been,
and are being, evolved."
"False facts are
highly injurious to the progress of science, for they often endure long; but
false views, if
supported by some evidence, do little harm, for everyone takes a salutary
pleasure in proving their falseness; and when this
is done, one path towards
error is closed and the
way to truth is often at the same
time opened."
"I see no good
reason why the views given in this volume should
shock the
religious
feelings of anyone. It is so easy to
hide our
ignorance under such
expressions as the "plan of
creation," "unity of design," etc., and to think that we give an explanation when
we only restate a
fact."
Charles Darwin, naturalist, excerpts from Origin of the
Species
"What is wrong with the
idea that God
created evolution as an extremely long process in which life forms change over time and positive changes, relative to the
environment, increase the chances that a life form
will pass on its genes to the next generations. Something tells me
God is not in a hurry." - Steve Paskay
"There are eminent
scientists and theologians who, while accepting the established
findings of science, from the
big bang to the evolution of
our species, also
perceive
creative spirit and palpable
love within themselves to the extent that they
cannot rule out an ultimate
divine
energy and
presence within every
thing that
exists." - Bill McAuliffe
DNA
analysis suggests that there was an
Eve,
the
mother of all homo
sapiens.
the primate
handVersatility is the hallmark of the
primate hand. With minor variations between species, thirty-five joints
accommodate the palm and fingers to branches and objects of all sizes, shapes,
and orientations. Six layers of muscles produce movements that propel the
animals and effect gripping patterns
used in maintaining feeding and resting positions, securing an infant's hold on
its mother, removing parasites from
the fur, catching insects, plucking fruits, extracting foods from their
source, and positioning objects for tactile,
olfactory, and visual scrutiny.
Multiple structural constraints on
mobility stabilize joints in regions that are habitually exposed to stresses
during these positional and manipulatory
activities. The locations and configurations of these constraints vary
considerably among species, as do the relative proportions of hand segments,
reflecting the diversity of their locomotor and feeding
patterns.
The key to the
versatility of primate hands is
to be found in the nature of the thumb and the fingertips. The thumb is
structurally and functionally differentiated from the rest of the fingers. The
tips of all five digits are relatively broad, with moist, ridged, sensitive
palmar pads that are supported by nails. The advantages of a grasping hand are
most apparent in the levels of the forest where vines, bushes, and the
slender upper and outer branches of the canopy offer the least purchase to a
paw with claws on the fingertips.
Differentiation of the thumb provides
the ability for prehension of objects by one hand. The variety and skill of
prehensile activities depend upon the details
of joint structure, the
relative length of the thumb and fingers, the sensory nerve supply to the
distal digital pads, and the motor control of
hand movements by the brain.
the human
handPounding with hand-held hammer stones has possibly been the
tool-using and tool-making activity with the greatest
frequency and antiquity in hominid
evolution. It is an activity which directs large, repetitive
forces toward the central region
of the palm.
Production of
forceful and accurate blows by a hand-held stone requires
control of the hammer stone by firm
precision grips which assure both retention of the stone in the hand and fine
adjustments in its orientation by the thumb and fingers.
Stabilization
of objects that are held in the other hand and pounded by hammer
stones in the production of tools also
requires firm precision grips and the ability to vary the orientation of the
stone.
The central region of the modern human palm is stabilized,
buttressed, and protected against intrinsic and extrinsic
forces associated with the grasp
and manipulation of stones in pounding by
robust bones and a fat-pad.
A secure grasp and controlled maneuvering
of stones by the thumb, fingers, and palm are facilitated by a unique
pattern of hand proportions and
joint-and-muscle configurations that permit cupping of the hand and the
formation of a wide variety of grips.
The proportionately long thumb
and short fingers with broad fingertip pads are able to maneuver the stones and
to hold them firmly, exploiting the leverage of the fingers, or bracing the
stones against the palm.
The unique arrangement of intrinsic
musculature and orientation of joints along the second, third, and fifth rays,
favoring rotation of the
fingers, allow optimal positioning of the thumb and fingers for grasping and
orienting the stones.
Grips that were found through
experimentation to accommodate
and control the stones most comfortably and
effectively involved primarily the thumb, index, and third fingers. These
included the pad-to-side and three-jaw-chuck thumb/finger grips and extensions
of these grips that incorporate the palm as a passive buttress. The
three-jaw-chuck thumb/finger grip is most effective both for wielding hammer
stones and for throwing stones.
Stones of about 500 grams, comparable
in size to tennis balls, are held by the thumb, index, and third fingers,
frequently against the side of the flexed fourth finger which in turn is
buttressed by the flexed fifth finger as a support. The tip of the thumb and
index and third fingertips control the
orientation of the stone and keep it away from the palm, so that the leverage
of these rays is exploited in propelling the stone. The pressure and leverage
of these rays are important factors in controlling the rotation and speed of an object
thrown by the hand.
The modern human hand
structure of the joints along
the fifth ray probably contributes to the effectiveness of the
finger/active-palm squeeze grip, which employs all the fingers and active
convergence of the palm around a cylindrical tool, such as an antler hammer, to
secure it, so that the tool functions as an extension of the hand and/or arm.
The use of small modern tools such as needles and pencils involves the
rotation and translation of objects by the pads of the fingertips opposed to
the tip of the thumb pad, exploiting a unique human compartmentalization of
these pads.
a mutant
primate with a strange DNAWhen one looks at the
chromosomes of humans and the living great apes (orangutan,
gorilla, and chimpanzee), it is immediately apparent that there is a great deal
of similarity between the number and overall appearance of the chromosomes
across the four different species.
There are differences but the overall similarity is striking.
The following observations can be made about similarities and
differences among the four species.
The great apes have 24 pairs of chromosomes while
humans have only 23 pairs.
Except for differences in non genetic heterochromatin, chromosomes 6,
13, 19, 21, 22, and X have identical banding patterns in all four
species.
Chromosomes 3, 11, 14, 15,
18, 20, and Y look the same in three of the four species (those three being gorilla, chimps, and
humans), and chromosomes 1, 2p, 2q, 5, 7 - 10, 12, and 16 are alike in two
species.
Chromosomes 4 and 17 are
different among all 4 species.
Most
of the chromosomal differences among the four species involve inversions - localities on the
chromosome that have been inverted, or swapped end for end. This is a
relatively common occurrence among many species, and has been documented in humans. An
inversion usually does not reduce fertility.
Other types of
rearrangements include a few translocations (parts swapped among the
chromosomes), and the presence or absence of nucleolar organizers. All of these
differences can be observed to be occurring in modern populations.
The
largest single chromosomal rearrangement among the four
species is the unique number of chromosomes
(23 pairs) found in humans as opposed to the great apes (24 pairs).
There are two potential
naturalistic explanations for the difference
in chromosome numbers - either a fusion of two separate chromosomes occurred in
the human line, or a fission of a chromosome occurred among the apes.
The evidence favors a
fusion event in the human line.
The chromosomes were apparently joined
end to end, and the ends of chromosomes (called the telomere ) have a
distinctive structure from the rest of the chromosome. Evidence suggests that
the vicinity of chromosome 2 where the fusion is expected to occur, we see
first sequences that are characteristic of the pre-telomeric region, then a
section of telomeric sequences, and then another section of pre-telomeric
sequences. In the telomeric section, it is observed that there is a point where
instead of being arranged head to tail, the telomeric repeats suddenly reverse
direction - evidence of fusion.
In chromosomes that have been fused we
should see evidence of two centromeres, the distinctive central part of the
chromosome. Evidence of fusion exists as remnants of the 2p and 2q centromeres
appear.
Some may raise the objection that if the fusion was a
naturalistic event, how could the first human ancestor with the fusion have
successfully
reproduced?
We have all heard that
the horse and the donkey produce an infertile mule in crossing because of a
different number of chromosomes in the two species.
Variations in chromosome
number are known to occur in many different animal
species, and although they sometimes seem to
lead to reduced fertility, this is often not the case.
The last
remaining species of wild horse,
Przewalski's (sha-val-skis) Wild Horse has 66 chromosomes while the
domesticated horse has 64 chromosomes. Despite this difference in chromosome
number, Przewalski's Wild Horse and the domesticated horse can be crossed and
do produce fertile offspring which possess 65 chromosomes.
Another
chromosomal rearrangement has recently been discovered, this one shared both by
humans and chimpanzees, but not found in any of the other monkeys or apes that
were tested.
This rearrangement was the movement of about 100,000
DNA pairs from human chromosome 1
to the Y chromosome10.
See
The Tree of
Life
See Ian Player
See
John Muir
See Edward
Abbey
See Rachel Carson
See
Henry David Thoreau
See John Wesley Powell
See Marcus Aurelius V
See Thomas Aquinas
See Rene
Descartes
See David Hume
See
John Stuart Mills
See Ralph Waldo Emerson
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