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Current scientific theory places the origin of life at around 3.5 billion years ago. It holds that succeeding life forms have been the result of a process of gradual, slow, and progressive change that began with organisms consisting of one cell developing over time into a great variety of increasingly complex organisms consisting of many cells. Scientists have named this process evolution. I. The Principle of Natural Selection
Thomas Malthus (1766-34)
was an English clergyman trained in
Charles Darwin (1809-82) was an English naturalist who shared
this In the Galápagos Islands, however, Darwin observed species of finches that were similar to, as well as different from, finches he had observed in South America. The similarities among these birds from these two The Galápagos Islands separate and distant locations implied that they had a common ancestor; the differences suggested that the new features had been acquired after they arrived there. Based on this observation, he concluded that the struggle for existence under diverse environmental conditions selects the features that are favorable for survival; those that are unfavorable are eliminated. He came to believe that new traits are acquired at random, i.e. by accident, and retained by a process of natural selection, that is by unintelligent natural causes. (The term natural selection was first used in 1831 by the Scottish agriculturalist Patrick Matthew in a book he had written and Darwin had read.) In The Origin of Species, he later wrote:
Based on the evidence, Darwin came to believe that species evolve by transmitting from generation to generation those characteristics that prove, by trial and error, to be advantageous in the struggle to survive to reproductive age the pressures of population increase, environmental conditions, and limited food supply. This principle applies not only to species, he believed, but also to individuals within a species. Even though some inferior individuals may survive to reproductive age and pass on their traits, in the long run the struggle selects the superior and weeds out the inferior. In time, the superior traits spread throughout the population. As a rule, the strongest, smartest, and fastest animals, i.e., the fittest, get the first pick and biggest share of food, territory and mates, live longer, and reproduce more of their kind.
Wild pigs fighting for dominance.
The study of the geology of areas he had visited during his voyage suggested to Darwin that evolution had to have taken place slowly and gradually over a very long period of time, in many ways comparable to the slow and gradual effect wind and water had in shaping the mountains and river valleys he had observed. Even though he did not have direct evidence - no one had ever seen evolution actually take place - he speculated that the existence of the all species existing in Nature arose in the same manner. He thought that the accumulation of small changes would produce fully functional intermediate forms which, in time, would evolve into completely new and unrelated species. He held this belief despite the fact that the fossil record did not provide evidence of the existence of any transitional forms of life, asserting that they would eventually be found. His view was in accordance with the prevailing scientific opinion held at the time that Nature does not make jumps. ('Natura non facit saltum'.) Later, he applied his theory to the evolution of Man, pointing out the similarities between human beings and apes, and positing the existence of a missing link between them.
Beginning in the 1950s, several studies
have been carried out of natural selection in operation which show
that new species can slowly and gradually evolve from earlier species
to whom they are related through a sequence of subspecies. (This
process is called micro-evolution.) Nevertheless,
scientists have not been able to
prove that this slow, step-by-step process has ever produced new
forms of life above the level of species, such as the genus and
family, or that it has given rise to species that are fundamentally
different. For example, new species of cats such as the lynx, tiger,
and lion, or birds such as the eagle, ostrich, and penguin could
have evolved slowly and gradually from an ancestral form of cat
and bird respectively because they are related, but could not, and
thus did not, evolve the same way from an earlier species common
to both because each has features that are unique and unrelated.
By the same principle, fishes could not and did not evolve into
amphibians, then reptiles, then birds, and finally mammals, and
no itermediary fossils have ever been found that validate this presently
held belief. Therefore, contrary to the Darwin recognized the above as being a potential key weakness in his theory. In The Origin of Species he wrote: "The number of intermediate varieties which have formerly existed on earth must be truly enormous. Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and gravest objection which can be urged against my theory."
Although opposed by some scientists during his lifetime,
most notably by the renowned American goeologist Luis Agazzis, Darwin's
theory was accepted by the majority of them and has become the prevailing
view today. From a philosophical standpoint, by explaining evolution
strictly as the result of natural causes, his theory obviated the
need for a Creator and provided the justification for a materialistic
interpretation of reality which is so widespread today, especially
among scientists.
Not long after Darwin presented his theory of the slow and gradual process that produces biological changes, big and small, visible from the outside, two investigators discovered the nature of changes, both slow and sudden, that take place on the inside. |
mathematics
who administered to the needs of the poor. Like others in his country,
he had been shocked by the brutality of the revolution that had
taken place in France where masses of the poor had risen with unrestrained
violence against the rich. Wishing to know the underlying causes
of poverty, he applied his mathematical knowledge to their search
and discovered that population, both animal and human, increases
much faster than the supply of food available. This discovery led
him to conclude that in the struggle to fulfill their needs with
insufficient food supply only the stronger individuals survive.
view. When young, he embarked on an eventful five-year journey to
South America, the Galápagos Islands, Australia, and many Pacific
islands where he studied plants, animals, geology, geography, climate,
and native people. At the time, the scientific opinion prevailed
that the Earth's geologic features, as well as the characteristics
of species, were fixed, i.e., that everything had been created as
unchanging. This view was supported by
the description of creation in Genesis, which implied that species
had been created "after their kind" and bred "true
to type."
(A species is a naturally existing
population of similar organisms that breed among themselves.)
belief that Nature does not make jumps, there is ample evidence
which indicates that it does.
(This process is called macro- evolution.)
Likewise, although evidence has been found that
apes (gorillas, chimpanzees, gibbons and orangutans) and humans
are similar in several ways, to date no fossil evidence has been
uncovered of the existence of a fully functional intermediate life
form, a missing link, between humans and apes that would indicate
a slow and gradual evolution from the former to the latter.
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