Chimpanzee (Pan troglodytes)
Picture: Copyright © 1997 Bill and Carol Lofton
What is evolution? Biological evolution is the change that species (kinds of living things) undergo over time. More precisely, it is the change in the gene pools of living populations of species which occurs over time. A gene is a hereditary unit that can be passed on unaltered for many generations. A gene pool is the set of all genes in a species or population.
What do you mean by "Evolution Happens"? Evolution has happened, evolution is happening and evolution will continue to happen!
Isn't it true that evolution is only a theory?
The popular use and scientific use of the term
theory are very different! A scientific theory, resulting from the
application of the scientific method, is an explanation for a phenomenon or set
of phenomena based
on extensive evidence and testing. The
scientific method is a well-recognized and well-defined series of steps used to acquire
an explanation for observed phenomena. A preliminary generalization, or
hypothesis, is formed on the basis of careful observation of the phenomenon
being studied. This hypothesis is then tested by further observations and
experiments. If the information gathered from observations and experiments over
time satisfies the conditions of the hypothesis, the hypothesis eventually
becomes accepted as a
scientific theory. For example, the atomic theory of matter states that matter
is composed of particles called atoms in various arrangements. The theory of
evolution is the only explanation for the origin of life that accounts for the
fossil, anatomical, molecular (including genetic), behavioral and geological
evidence. Although they continue to argue
over the details of exactly how the various mechanisms of evolution operate, biologists long ago concluded that evolution happens. This is because
evolution explains all of the evidence far better than all other proposed
explanations for the origin of life.
What exactly does the theory of evolution state?
The theory of evolution states that:
All life forms (species) have developed from other species.
All living things are related to one another to varying degrees through common descent (share common ancestors).
All life on Earth has a common origin. In other words, that in the distant past, there once existed an original life form and that this life form gave rise to all subsequent life forms.
The process by which one species evolves into another involves random heritable genetic mutations (changes), some of which are more likely to spread and persist in a gene pool than others. Mutations that result in a survival advantage for organisms that possess them, are more likely to spread and persist than mutations that do not result in a survival advantage and/or that result in a survival disadvantage.
Isn't it true that evolution as a theory cannot be observed or tested? No, this is not true. The very rapid evolution of viruses and bacteria can be easily observed. Example: Antibiotic resistant strains of many types of bacteria have evolved from strains that were very susceptible to these same antibiotics. Also, several speciation events (instances of one species evolving into another) involving multicellular organisms have been observed and documented! To learn about these, click here: Observed Instances of Speciation. In addition, molecular test results and findings, in both plants and animals, support evolution.
How does evolution occur? The three main mechanisms are mutation, natural selection and genetic drift. A mutation is any change in the DNA base sequence (genetic information) of a gene. However, only heritable mutations, those occurring in the gametes (reproductive cells) or the cell lineage contributing to the gametes, are involved in evolution. Such mutations, known as germinal mutations, can result from many factors, including natural background radiation, chemical mutagens and viral infection. Because only a small portion of the genetic sequence of the DNA molecule is used to code for proteins, most mutations do not result in new traits. Of the mutations which do result in new traits, most are harmful. That is, they interfere with an organisms physiology or in some other way reduce an organisms adaptability to its environment. However, sometimes just by chance, a mutation will occur which produces a trait that leaves an individual possessing it better adapted to its environment. In most cases, an individual that is better adapted to its environment, will tend to produce more offspring than an individual who is less well adapted.
Natural selection is the process by which traits that provide a reproductive advantage tend to increase in frequency in a given population over time, while traits that leave individuals at a reproductive disadvantage tend to decrease in frequency over time. A reproductive advantage may arise from differences in survival, in fertility, in rate of development, in mating success or by some other aspect of the life cycle. In fact, any trait that increases the chances that an individual will reproduce, is providing a reproductive advantage, even if this comes at the expense of the survival of the individual. For example, possessing a certain coloring pattern might increase an individuals chances of attracting a mate, but might also increase this individual's visibility to predators!
Genetic drift, is the process by which the frequencies of existing genes in a population change over time due to chance. One of two or more gene alternatives at a site on a chromosome (gene package) is known as an allele. Genetic drift occurs with all alleles, including those that result in either an increase or decrease in reproductive fitness. However, its effects are greatest with alleles that are neutral with regard to reproductive fitness. Although all such neutral alleles have an equal chance of being passed on to each subsequent generation, sampling error dictates that each allele will be passed on at a slightly different frequency than their alternatives. Over time this will lead to a change in the overall frequency of each allele. Eventually, all but one of the alleles will be eliminated from the gene pool. The impact genetic drift has on a population's genetic makeup, is inversely proportional to the size of the population. In other words, the smaller the population, the greater the impact.
What about missing links? Although they are present, transitional forms are rare in the fossil record. In fact, the fossil record demonstrates that some species have remained essentially unchanged for millions of years. This makes sense, because if a species is well adapted to its environment, its current traits will continue to be selected for. A species will only undergo major change, if its environment changes in a way which leaves it significantly less well adapted to survive. Such transitions tend to occur rapidly. A mammal species for example, might evolve into another distinct mammal species in less than a hundred thousand years. In the history of life, that is a short period of time. Speciation of plants and simpler animals, can occur much more rapidly. This evolutionary pattern of long periods of geologic time with little change, punctuated by short periods of rapid change, is referred to as punctuated equilibrium.
Can you list any examples of missing links? The most classic example of a transitional fossil is that of Archaeopteryx. This animal possessed both avian (bird) and reptilian characteristics.
Can you list some of the evidence supporting the theory of evolution?
The fossil record. The presence of shared
pseudogenes (damaged non-functional
copies of genes in the DNA base sequence) among various species. Click here: Plagiarized Errors and Molecular Genetics.
The fact that survival for all species is precarious (the prevalence
of extinctions in the fossil record is evidence of this). The fact that there are many instances of species
possessing crude adaptations to survival. The panda's thumb
is a good example of this. The fact that many species are
similar to one or more other species to varying degrees. The fact that some
pairs of very similar species, have the ability to interbreed producing sterile offspring. For example, a male
donkey (Equus asinus) and a female horse (Equus caballus) can interbreed to produce a mule. This suggests, that
the donkey and the horse are close evolutionary cousins. Another example involving two species even more closely related is the interbreeding of polar bears (Ursus maritimus) with grizzlies (Ursus arctos horribilis)
to produce fertile pizzly bears (Ursus × inopinatus).
Did humans evolve from chimps? Humans did not evolve from chimps! However, humans and chimps have a common ancestor. In other words, we're cousins. Evolution is not a ladder. It is a branching bush.
How is it possible for one species to be ancestral to more than one subsequent species? One process by which this can occur involves the division of a population into two or more smaller populations by a geographic barrier, so that interbreeding between the resulting populations is prevented. If the environments of the respective populations differ, different traits will be selected for in each and the evolution of these populations will follow different courses. This type of speciation is known as allopatric speciation. The splitting of one species into two or more species is known as divergence.
What is the difference between macroevolution and microevolution? From the perspective of evolutionary biology, macroevolution is nothing more than a lot of microevolution occurring over time, which leads to new species.
Isn't evolution inconsistent with the Second Law of Thermodynamics? Absolutely not! People who assert that the Second Law of Thermodynamics makes the evolution of life from simpler to more complex forms impossible, either do not understand the Second Law or are intentionally misleading their audience. The Second Law states that energy has a tendency to spread out and become less concentrated overall in a closed system over time. It also states that entropy, which can be defined as a measure of a system's energy that is unavailable for work, must increase overall in a closed system over time. Another common and potentially misleading definition for entropy, is the amount of disorder or uncertainty in such a system. However, this does not mean that complex chemical compounds cannot form from simpler chemical elements by natural processes. On his award winning Website, Frank L. Lambert Ph.D., makes the following emphatic statement:
Energetically, the second law of thermodynamics favors the formation of the majority of all known complex and ordered chemical compounds directly from their simpler elements. Thus, contrary to popular opinion, the second law does not dictate the decrease of ordered structure in its predictions, it only demands a "spreading out" of energy in all processes.
For more information, follow this link to the article in which the above statement appears: The Second Law of Thermodynamics and Evolution
Why do some insist that evolution resulting in new species of plants and animals does not occur? I believe that in most cases, people don't reject the concept of evolution because they disagree with the science. Rather, they refuse to consider it because it contradicts their religious beliefs. After all, to believe that the species living on Earth today evolved, is to believe that much of the Bible does not represent the literal truth. In the minds of religious fundamentalists, that cannot be considered. Even many religious people who are not fundamentalists, see evolutionism as incompatible with their religious faith.
In contrast, many religious organizations accept evolution. For example, the Roman Catholic Church recognizes evolution as an accepted scientific theory, supported by a great body of evidence. Faith & Reason Ministries is another Christian organization which accepts modern science, including evolution. In 1984 the Central Conference of American Rabbis adopted a resolution against the inclusion of creationism in school science textbooks. In 1987, the same organization adopted a resolution against the teaching of creationism or other religious dogma in public schools.
What about scientific creationism? Scientific creationism is not science, because special creation is not an explanation for life's origin, or a depiction of life's history, chosen because it best explains the evidence. Rather, it is an explanation and depiction chosen most frequently because it is consistent with Genesis. Nearly all creationists are religious fundamentalists and will continue to stand by their position regardless of whether or not the evidence supports it. If you think I am misrepresenting creationism, consider the following statements of two creationist organizations:
In their own words, "The Creation Research Society is a professional organization of trained scientists and interested laypersons who are firmly committed to scientific special creation." To be firmly committed to an explanation for something in the face of overwhelming contradictory evidence, is not the scientific way! In fact, if an explanation for the origin of life were to come along, that better explained the evidence than evolution, then it would eventually replace evolution. This is how science works.
The Institute for Creation Research suggests that you, "Do use the Word of God (The Bible indicates that most of the fossils must have been buried in one year - the year of the Flood)." to determine the age of fossils. If this is all one needs to do, then why bother doing research? Creationist organizations do not conduct research in order to find an explanation for the origin of life (they have the Bible for that). Instead, they simply attempt to find ways to disprove evolution.
Why did you create this Website? Many people think evolution is mere conjecture, or at best a hypothesis (educated guess). As mentioned above, many insist that it did not happen. In recent years, the teaching of evolution in public schools has been repeatedly challenged. This represents an attack on science itself. Trying to teach biology without including evolution is like trying to teach geology without talking about the formation, age and history of the earth. Anthropologist Eugenie C. Scott Ph.D. has said,
A biology or earth science course taught without the inclusion of evolution is an inferior course. Students who take these courses without being told that evolution unifies the data and concepts of the field are being cruelly short-changed. They will leave the course having been misled that science largely consists of the tedious memorization of lists of facts, rather than a tool we can use to help us understand the world of nature. This episodic, atomistic view of science is particularly regrettable: it turns students away from studying science, and perhaps worse yet, defeats our efforts to produce a scientifically literate society.
This Website is an attempt to counter antievolutionism, by helping to educate people about the overwhelming evidence that evolution is an inherent and universal characteristic of life.
Dr. Willie Smits greets Uce and her baby Bintang in Indonesian Borneo. Uce and Bintang are orangutans (Pongo pygmaeus).
Dr. Smits, founder of the Balikpapan Orangutan Survival Foundation rescued Uce from animal traders years earlier.
Intelligent Design: Scientifically and Religiously Bankrupt
The Nonscience Of The Scientific Arguments Against Evolution
Download the free Evolution Happens Gorilla Screen Saver from the gallery page today!
All in the Family Hominidae, an article written for Animal Diversity Web by Phil Meyers.
APPENDIX: Common Misconceptions Regarding Radiometric Dating Methods, by Dr. Roger C. Wiens.
Feathered SpiritsEssay by Merle Borg about the evolutionary origins of adolescent male recklessness.
The Scientific Study of Origins?An essay written by Loren A. King.
Why won't evolutionists enter into a strictly scientific, written debate on the creation-evolution issue?
An orphaned male bonobo named Bukavu.
© 2000 David Tannenbaum
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