To a scientist, fact can describe a repeatable observation that all can agree on; it can refer to something that is so well established that nobody in a community disagrees with it; and it can also refer to the truth or falsity of a proposition. To the public, theory can mean an opinion or conjecture e. Individual organisms do not evolve in their lifetimes, but variations in the genes they inherit can become more or less common in the population of organisms. That should make it quite clear that having a theory is more than having mere facts, not less. Evolutionary biology provides a scientific framework for understanding the changes that have occurred since the first life forms arose on Earth several billion years ago.
Worse still, words with relatively clear meanings in the vernacular are employed with very different definitions in science, a phenomenon that greatly confuses discussions of science when they are conducted in nonscientific contexts. This can be taken in as pretentious to be sure. Selection: The Mechanism of Evolution 2nd ed. Scientists have discovered fossil birds with feathers and legs like modern birds, but which also have teeth, clawed digits on their forelimbs, and a tailbone like their reptilian ancestors. For Kirtley had gone to Tennessee with Clarence Darrow to testify for evolution at the Scopes trial of 1925.
What follows is an amended description of what one might say to communicate doubts about neo-Darwinism while avoiding semantic mistakes and communicating more than mere sound-byte arguments: When evolution is defined as mere change over time within species, no one disputes that such evolution is a fact. Futuyma, Evolutionary Biology, 2nd ed. No, I don't think it's possible, which is why it isn't a Law, although I suspect that some individual aspects, like selection and drift, could be formulated as Laws. It is a scientific theory only, and it has in recent years been challenged in the world of sciencethat is, not believed in the scientific community to be as infallible as it once was. They are part of evolutionary theory because, in many cases, we don't know for sure which one predominates in a particular case—or even if there might be another mechanism such as Lamarckian inheritance, molecular drive, or mutationism. That satisfies the requirements for a scientific theory. Within this tree of life, there are also occasional reticulations where two branches fuse, rather than separate.
In most theories, small isolated populations are the source of new species, and the process of speciation takes thousands or tens of thousands of years. Evolution and the Genetics of Populations. Actually, Newton's Theory of Gravity did a pretty good job, but Einstein's Theory of Relativity does a better job of explaining it. The best that we can hope for is that they understand the argument that they oppose. Gould would argue that creationists should take off their blinders to see reality, whereas Carson would go one step further, to warn them of the dire consequences of ignoring the evolutionary principles of adaption and natural selection. Sue Barnes, Biology 5th ed. Since 'change of gene frequencies in populations' is the 'official' definition of evolution, randomness has transgressed Darwin's border and asserted itself as an agent of evolutionary change.
In other cases, the available evidence is less strong. If evolution is less than a fact, and scientists can't even make up their minds about the theory, then what confidence can we have in it? There is some confusion about evolution as a fact and evolution as a theory. These terms describe three distinct aspects of science. Neither this failure to distinguish between fact or path and theory by scientists, nor that perpetuated by antievolutionists, is compatible with a proper understanding of the scientific definitions of these terms. It is also a fact. When we say a thing is a fact, then, we only mean that the probability of it being true is high—so high that we are not bothered by doubt about it and are ready to act accordingly. In some frightening cases, bacteria have evolved resistance to every available antibiotic, so there is no longer any effective treatment.
With its vocabulary of hundreds of thousands of words, one might expect English to boast a surplus of ways to express different concepts. Virtuosity in invention replaces testability as the criterion for acceptance. These methods include the collection, measurement, observation, and mapping of traits onto evolutionary trees. There are no alternatives to evolution as history that can withstand critical examination. Any changes during the lifetime of organisms which are not inherited by their offspring are not part of biological evolution. I have at least, as I hope, done good service in aiding to overthrow the dogma of separate creations. For example, in some of the best such textbooks we find: Today, nearly all biologists acknowledge that evolution is a fact.
Mammalian evolution has been fundamentally driven by viruses. Natural selection is only one of several mechanisms in the theory of evolutionary change that explains how organisms historically adapt to changing environments. According to idealized principles of scientific discourse, the arousal of dormant issues should reflect fresh data that give renewed life to abandoned notions. There isn't, and we've got to stop helping the anti-science people with their agenda. Now in this use of the term fact, the only proper one, evolution is a fact. In it refers to observed changes in organisms, to their descent from a common ancestor, and at a technical level to a change in over time; it can also refer to explanatory theories such as 's theory of which explain the mechanisms of evolution.
However, when it comes to some of the most fundamental concepts in science, there is a dearth of unambiguous terminology. On the other hand, there are questions about the mechanism of the observed changes. The Bible is an important historical document. Evolution genetic change over generations happens, just like gravity does. It is a fact, as fully as the fact of the earth's revolution about the sun. Evolutionists have been very clear about this distinction of fact and theory from the very beginning, if only because we have always acknowledged how far we are from completely understanding the mechanisms theory by which evolution fact occurred.
A common misconception is that evolution cannot be reliably observed because it all happened millions of years ago and the science therefore is not dependent on facts in the initial sense above. When scientists use the word theory, it has a different meaning to normal everyday use. Theories are concepts stating cause—effect relations. Arguments that seemed kooky just a decade ago have reentered the mainstream. There are several theories about the mechanisms of evolution, and there are still active debates about specific mechanisms. The second argumentthat the imperfection of nature reveals evolutionstrikes many people as ironic, for they feel that evolution should be most elegantly displayed in the nearly perfect adaptation expressed by some organismsthe camber of a gull's wing, or butterflies that cannot be seen in ground litter because they mimic leaves so precisely. We must infer them from results that still surround us: living and fossil organisms for evolution, documents and artifacts for human history, strata and topography for geology.