M
Medjai
Guest
Some theories are good and have withstood the test of time well. The idea that all organisms, past and present, are interrelated by a process of ancestry and decent --- evolution --- is such a theory. On the other hand, some theories have stood the test of time poorly and are no longer credited with much explanatory power. Spontaneous generation --- the idea that organisms sprang from inorganic beginnings de novo, and are not all interelated --- has long been discarded as a useful scientific notion. It is taught in schools today, if at all, only as a historical curiosity.
The common expression "evolutionary theory" actually refers to two rather different sets of ideas: (1) the notion that absolutly all organisms living on the face of the Earth right now are descended from a single common ancestor, and (2) ideas of how the evolutionary process works --- how, for example, do new species arise from old ones, and what processes actually underlay the reduction from four toes to but a single digit on the front feet of horses during the course of their 50-million-year evolutionary history?
When scientist think about evolution in the first sence ---i.e., has it actually happened --- they strongly agree that it has, and many pronounce evolution in this sence to be fact. On the other hand, though biologist are in agreement on many of the basic mechanisms of the evolutionary process (the second sence of the expression "the theory of evolution"), many of the details are still being debated, as is healthy and normal in the unending human endeavor that is science.
All species on Earth are interrelated passes all tests to falsify it with flying colors --- and therefore that the theory of evolution in the first sence is as highly corroborated as any notion in science can be. Creationist are fond of pointing to the obvious fact that events that happened in the past are not subject to experimental verification or falsification, or to direct observation. After all, goes the creationist cry, no one was there at the beginning of the Cambrian Period to witness firsthand the supposed initial burst of evolutionary activity leading to the rapid evolution of complex animal life.
How can we study something scientifically that has already happened? Creationist also note that few reputable biologists seem willing to predict what will happen next in evolution. And after all, says the creationist, if evolution is truly a scientific theory it must be predictive --- in the narrow sence of "making statements about what the future will hold" (and, of course, inherently untestable to biologists living in the moment). According to this creationist interpretation of science, that biologists neither can nor will predict the evolutionary future is strong evidence that the very idea of evolution isn't really scientific at all.
All this fancy rhetoric beclouds the simple meaning of "predictivity" in science. All that "predictivity" really means is that if an idea is true, there should be certain consequences --- certain phenomena that we would expect --- predict ---to find if we looked. We should be able to go to nature --- to the physical, material world --- to see whether or not these predicted phenomena are really there. So, in this spirit, we simply ask, if the basic idea is correct that all organiams past and present are interrelated by a process of ancestry and descent that we call evolution, what should we expect to find in the real world as a consequence?
These observable consequences are the predictions we should be making --- not guesses about the future or "prophesy!"
Prediction 1: The very idea of evolution --- descent with modification --- implies that some species are more closely related to each other than they are to more distant relatives. Therefore, we predict that the living world is organized into groupings of closely similar species that are in turn parts of larger groups of more distant relatives that share fewer similarties, that are in turn parts of still larger groups with definate, if fewer, similarities. Eventually, the largest grouping of all --- all of life --- should be united by the shared possession of one or more characteristics.
In other words, if evolution is true, the living world should be organized in a hierarchical fashion of groups within groups --- a direct reflexion of how closely related to one another each organism is. In a very real sense, this prediction was discovered to hold true long before the idea of evolution was commonly accepted as the explanation for how the living world is organized. For at least a century before Charles Darwin (1809-1882) published On the Origen of Species by Means of Natural Selection, in 1859, biologists had recognized that life is organized into distinct groupings arranged in a natural, hierarchical fastion.
The common expression "evolutionary theory" actually refers to two rather different sets of ideas: (1) the notion that absolutly all organisms living on the face of the Earth right now are descended from a single common ancestor, and (2) ideas of how the evolutionary process works --- how, for example, do new species arise from old ones, and what processes actually underlay the reduction from four toes to but a single digit on the front feet of horses during the course of their 50-million-year evolutionary history?
When scientist think about evolution in the first sence ---i.e., has it actually happened --- they strongly agree that it has, and many pronounce evolution in this sence to be fact. On the other hand, though biologist are in agreement on many of the basic mechanisms of the evolutionary process (the second sence of the expression "the theory of evolution"), many of the details are still being debated, as is healthy and normal in the unending human endeavor that is science.
All species on Earth are interrelated passes all tests to falsify it with flying colors --- and therefore that the theory of evolution in the first sence is as highly corroborated as any notion in science can be. Creationist are fond of pointing to the obvious fact that events that happened in the past are not subject to experimental verification or falsification, or to direct observation. After all, goes the creationist cry, no one was there at the beginning of the Cambrian Period to witness firsthand the supposed initial burst of evolutionary activity leading to the rapid evolution of complex animal life.
How can we study something scientifically that has already happened? Creationist also note that few reputable biologists seem willing to predict what will happen next in evolution. And after all, says the creationist, if evolution is truly a scientific theory it must be predictive --- in the narrow sence of "making statements about what the future will hold" (and, of course, inherently untestable to biologists living in the moment). According to this creationist interpretation of science, that biologists neither can nor will predict the evolutionary future is strong evidence that the very idea of evolution isn't really scientific at all.
All this fancy rhetoric beclouds the simple meaning of "predictivity" in science. All that "predictivity" really means is that if an idea is true, there should be certain consequences --- certain phenomena that we would expect --- predict ---to find if we looked. We should be able to go to nature --- to the physical, material world --- to see whether or not these predicted phenomena are really there. So, in this spirit, we simply ask, if the basic idea is correct that all organiams past and present are interrelated by a process of ancestry and descent that we call evolution, what should we expect to find in the real world as a consequence?
These observable consequences are the predictions we should be making --- not guesses about the future or "prophesy!"
Prediction 1: The very idea of evolution --- descent with modification --- implies that some species are more closely related to each other than they are to more distant relatives. Therefore, we predict that the living world is organized into groupings of closely similar species that are in turn parts of larger groups of more distant relatives that share fewer similarties, that are in turn parts of still larger groups with definate, if fewer, similarities. Eventually, the largest grouping of all --- all of life --- should be united by the shared possession of one or more characteristics.
In other words, if evolution is true, the living world should be organized in a hierarchical fashion of groups within groups --- a direct reflexion of how closely related to one another each organism is. In a very real sense, this prediction was discovered to hold true long before the idea of evolution was commonly accepted as the explanation for how the living world is organized. For at least a century before Charles Darwin (1809-1882) published On the Origen of Species by Means of Natural Selection, in 1859, biologists had recognized that life is organized into distinct groupings arranged in a natural, hierarchical fastion.
