Scientifically speaking evolution is a theory, but only because there are no absolute facts in science... just testable theories that have yet to prove false.
Let us examine some other biological scientific theories...
1) Germ theory. This is the theory that micro-organisms can cause disease.
2) Cancer theory. (e.g. the theory that cancer occurs when cells escape normal cellular regulation).
3) Antibiotic theory (e.g. the theory that penicillin or other similar molecules will kill bacteria).
4) The theory that neurons transmit electrical impulses.
How about some non-biological scientific theories...
1) Atoms are made up of electrons, protons and neutrons (which themselves are made up of smaller particles).
2) Electricity is due to the movement (conductance) of electrons.
The list is nearly endless. All of these are, scientifically speaking, theories but are espoused as fact in common usage because experimentally they have stood the test of time. The case for evolution is as strong, if not stronger, than germ theory. The exact biological details of how a specific germ infects a cell, causes the disease symptoms, or is purged by our immune system might be hotly debated, but germ theory as a whole is not.
Similarly, scientists debate about the mode and tempo of evolution, about the exact mechanism(s) of speciation for a given speciation event, and about the exact contributions of different mutational forces & mechanisms, fitness levels required for survivability, and the underlying biochemical processes. The existence of evolution is not under debate because in experiment after experiment... scientific observation after scientific observation... time and time again, for the two centuries that scientists investigating this concept, evolution has held true, testable, and verifiable. Many of the experiments reach back in time, even to the prokaryotic/eukaryotic split.
If you are worried about the scientific debate part, I should inform you that there is a also debate about the exact nature of protons, electrons, and neutrons (e.g. string theory) or what gravity is (gravitons?, how does gravity exert force). That electrons or the force of gravity exists is not really in contention. Neither is the existence of evolution.
Evolution provides a framework for all of biology. It is sort of the "unified field" theory of biology. The theory is that good. Evolutionary theory has greatly increased our understanding of biology and medicine and continues to have tremendous predictive capacity.
Here is an evolution based prediction that is in the news lately. Bird flu. The H5N1 strain of bird flu, by random mutation and repeated exposure to humans acquired (evolved) the ability to infect humans. Scientists are now worried that the H5N1 strain might evolve the ability to spread from human to human. "Beneficial" for the survival of that viral strain, "bad" for humans individually. I can not say what H5N1 transmissibility means for the long term fitness of the human species.
What has become clear to me is that:
1) Most people do not understand evolution in general, if polls are any indication. Even fewer people understand molecular evolution which is what many of the findings being recognized are. A failing of our education system to stand up to the political pressure of the Fundies?. Perhaps.
2) The basic religious objection to evolution is that the religious folk do not wish to be related to apes because man is divine (made in gods image). Being related to every other organism in the natural world would somehow sully the notion of Man's divinity.
3) Religion = belief based on faith
4) Science = testable hypothesis
Religion = belief & faith
I believe the car is red. (Or if you prefer "I believe that man and apes did share a common ancestor )." You will still believe the car is red even if science proves beyond a reasonable doubt that the car is white and that the owner only drives it during brilliant red sunsets. It is a matter of faith, the car is red. Objective & verifiable observation-based reality has little bearing on the matter.
Science = testable hypothesis
I postulate that the car is red. In order test this red color hypothesis I will scrape off some of the paint and test the the paints light absorption and reflective properties. Further, I will dissolve the paint and subject it to a mass-spectrophotometer in oder to determine the chemical make up of the paint. I will compare the properties of the experimental sample to the properties of known paints and pigments. As my knowledge increases about cars, paint pigments, and light over time, I will revisit my old results too see if they agree with my new results. And if not, why.
As for evolution, thousands of scientists world wide test, expand, and retest evolutionary theory everyday. Evolution has yet to prove false. Humans and the chimpanzee are evolutionary cousins, a blink of an eye away on the evolutionary tree. If you doubt it, go to http://www.ncbi.nlm.nih.gov/. Look up the scientific papers reporting the chimp and human genomes in pubmed. Do a little bit of background reading on homology searches. Prove to yourself the relationships between organisms by doing a your own homology searches using blast & clustal. Build a evolutionary tree. You do not have to be a scientist to do this, although you will have to do more background reading than a scientist would. The tools and information are all there in the public data bases. The power of comparative genomics is awesome.
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Let us examine some other biological scientific theories ...
How about some non-biological scientific theories...
The list is nearly endless. All of these are, scientifically speaking, theories but are espoused as fact in common usage because experimentally they have stood the test of time. The case for evolution is as strong, if not stronger, than germ theory. The exact biological details of how a specific germ infects a cell, causes the disease symptoms, or is purged by our immune system might be hotly debated, but germ theory as a whole is not.
Similarly, scientists debate about the mode and tempo of evolution, about the exact mechanism(s) of speciation for a given speciation event, and about the exact contributions of different mutational forces & mechanisms, fitness levels required for survivability, and the underlying biochemical processes. The existence of evolution is not under debate because in experiment after experiment ... scientific observation after scientific observation ... time and time again, for the two centuries that scientists investigating this concept, evolution has held true, testable, and verifiable. Many of the experiments reach back in time, even to the prokaryotic/eukaryotic split.
If you are worried about the scientific debate part, I should inform you that there is a also debate about the exact nature of protons, electrons, and neutrons (e.g. string theory) or what gravity is (gravitons?, how does gravity exert force). That electrons or the force of gravity exists is not really in contention. Neither is the existence of evolution.
Evolution provides a framework for all of biology. It is sort of the "unified field" theory of biology. The theory is that good. Evolutionary theory has greatly increased our understanding of biology and medicine and continues to have tremendous predictive capacity.
Here is an evolution based prediction that is in the news lately. Bird flu. The H5N1 strain of bird flu, by random mutation and repeated exposure to humans acquired (evolved) the ability to infect humans. Scientists are now worried that the H5N1 strain might evolve the ability to spread from human to human. "Beneficial" for the survival of that viral strain, "bad" for humans individually. I can not say what H5N1 transmissibility means for the long term fitness of the human species.
What has become clear to me is that: 1) Most people do not understand evolution in general, if polls are any indication. Even fewer people understand molecular evolution which is what many of the findings being recognized are. A failing of our education system to stand up to the political pressure of the Fundies?. Perhaps. 2) The basic religious objection to evolution is that the religious folk do not wish to be related to apes because man is divine (made in gods image). Being related to every other organism in the natural world would somehow sully the notion of Man's divinity. 3) Religion = belief based on faith 4) Science = testable hypothesis Religion = belief & faith I believe the car is red. (Or if you prefer "I believe that man and apes did share a common ancestor )." You will still believe the car is red even if science proves beyond a reasonable doubt that the car is white and that the owner only drives it during brilliant red sunsets. It is a matter of faith, the car is red. Objective & verifiable observation-based reality has little bearing on the matter. Science = testable hypothesis I postulate that the car is red. In order test this red color hypothesis I will scrape off some of the paint and test the the paints light absorption and reflective properties. Further, I will dissolve the paint and subject it to a mass-spectrophotometer in oder to determine the chemical make up of the paint. I will compare the properties of the experimental sample to the properties of known paints and pigments. As my knowledge increases about cars, paint pigments, and light over time, I will revisit my old results too see if they agree with my new results. And if not, why. As for evolution, thousands of scientists world wide test, expand, and retest evolutionary theory everyday. Evolution has yet to prove false. Humans and the chimpanzee are evolutionary cousins, a blink of an eye away on the evolutionary tree. If you doubt it, go to http://www.ncbi.nlm.nih.gov/. Look up the scientific papers reporting the chimp and human genomes in pubmed. Do a little bit of background reading on homology searches. Prove to yourself the relationships between organisms by doing a your own homology searches using blast & clustal. Build a evolutionary tree. You do not have to be a scientist to do this, although you will have to do more background reading than a scientist would. The tools and information are all there in the public data bases. The power of comparative genomics is awesome.