Part 1
November 21, 2011
The website Understanding Evolution, hosted by The University of California Museum of Paleontology, Berkeley, offers its readers numerous helpful resources regarding the science and history of evolutionary biology. The site’s stated goal is to “help you understand what evolution is, how it works, how it factors into your life, how research in evolutionary biology is performed, and how ideas in this area have changed over time.” Among its resources is a list of popular misconceptions about evolutionary theory. In this two part series, we’d like to highlight some of the site’s most helpful responses to these misconceptions. The full list, and many other wonderful resources, can be found at Understanding Evolution.
Misconceptions about Evolutionary Theory and Process
"Evolution is a theory about the origin of life."
Evolutionary theory does encompass ideas and evidence regarding life's origins (e.g., whether or not it happened near a deep-sea vent, which organic molecules came first, etc.), but this is not the central focus of evolutionary theory. Most of evolutionary biology deals with how life changed after its origin. Regardless of how life started, afterwards it branched and diversified, and most studies of evolution are focused on those processes.
For more, see our questions on "What is Evolution?" and "Isn't the Origin of Life Highly Improbable?".
"Evolution is like a climb up a ladder of progress; organisms are always getting better."
One important mechanism of evolution, natural selection, does result in the evolution of improved abilities to survive and reproduce; however, this does not mean that evolution is progressive — for several reasons. First, natural selection does not produce organisms perfectly suited to their environments. It often allows the survival of individuals with a range of traits — individuals that are "good enough" to survive. Hence, evolutionary change is not always necessary for species to persist. Many taxa (like some mosses, fungi, sharks, opossums, and crayfish) have changed little physically over great expanses of time.
Second, there are other mechanisms of evolution that don't cause adaptive change. Mutation, migration and genetic drift may cause populations to evolve in ways that are actually harmful overall or make them less suitable for their environments. For example, the Afrikaner population of South Africa has an unusually high frequency of the gene responsible for Huntington's disease because the gene version drifted to high frequency as the population grew from a small starting population.
Finally, the whole idea of "progress" doesn't make sense when it comes to evolution. Climates change, rivers shift course, new competitors invade — and an organism with traits that are beneficial in one situation may be poorly equipped for survival when the environment changes. And even if we focus on a single environment and habitat, the idea of how to measure "progress" is skewed by the perspective of the observer. From a plant's perspective, the best measure of progress might be photosynthetic ability; from a spider's it might be the efficiency of a venom delivery system; from a human's, [his] cognitive ability. It is tempting to see evolution as a grand progressive ladder with Homo sapiens emerging at the top. But evolution produces a tree, not a ladder — and we are just one of many twigs on the tree.
Second, there are other mechanisms of evolution that don't cause adaptive change. Mutation, migration and genetic drift may cause populations to evolve in ways that are actually harmful overall or make them less suitable for their environments. For example, the Afrikaner population of South Africa has an unusually high frequency of the gene responsible for Huntington's disease because the gene version drifted to high frequency as the population grew from a small starting population.
Finally, the whole idea of "progress" doesn't make sense when it comes to evolution. Climates change, rivers shift course, new competitors invade — and an organism with traits that are beneficial in one situation may be poorly equipped for survival when the environment changes. And even if we focus on a single environment and habitat, the idea of how to measure "progress" is skewed by the perspective of the observer. From a plant's perspective, the best measure of progress might be photosynthetic ability; from a spider's it might be the efficiency of a venom delivery system; from a human's, [his] cognitive ability. It is tempting to see evolution as a grand progressive ladder with Homo sapiens emerging at the top. But evolution produces a tree, not a ladder — and we are just one of many twigs on the tree.
For more, see our questions "What is Evolution?" and "Did Evolution Have to Result in Human Beings?".
"Evolution means that life changed 'by chance.'"
Chance and randomness do factor into evolution and the history of life in many different ways; however, some important mechanisms of evolution are non-random and these make the overall process non-random. For example, consider the process of natural selection, which results in adaptations — features of organisms that appear to suit the environment in which the organisms live (e.g., the fit between a flower and its pollinator, the coordinated response of the immune system to pathogens, and the ability of bats to echolocate). Such amazing adaptations clearly did not come about "by chance." They evolved via a combination of random and non-random processes. The process of mutation, which generates genetic variation, is random, but selection is non-random. Selection favored variants that were better able to survive and reproduce (e.g., to be pollinated, to fend off pathogens, or to navigate in the dark). Over many generations of random mutation and non-random selection, complex adaptations evolved. To say that evolution happens "by chance" ignores half of the picture.
For more see our questions on "What is Evolution?" and "How do randomness and chance align with belief in God’s sovereignty and purpose?".
For more see our questions on "What is Evolution?" and "How do randomness and chance align with belief in God’s sovereignty and purpose?".
“Humans are not currently evolving”
Humans are now able to modify our environments with technology. We have invented medical treatments, agricultural practices, and economic structures that significantly alter the challenges to reproduction and survival faced by modern humans. So, for example, because we can now treat diabetes with insulin, the gene versions that contribute to juvenile diabetes are no longer strongly selected against in developed countries.
Some have argued that such technological advances mean that we've opted out of the evolutionary game and set ourselves beyond the reach of natural selection — essentially, that we've stopped evolving. However, this is not the case. Humans still face challenges to survival and reproduction, just not the same ones that we did 20,000 years ago. The direction, but not the fact of our evolution has changed. For example, modern humans living in densely populated areas face greater risks of epidemic diseases than did our hunter-gatherer ancestors (who did not come into close contact with so many people on a daily basis) — and this situation favors the spread of gene versions that protect against these diseases.
For more see our question "Did evolution have to result in human beings?".
"Species are distinct natural entities, with a clear definition, that can be easily recognized by anyone."
Many of us are familiar with the biological species concept, which defines a species as a group of individuals that actually or potentially interbreed in nature. That definition of a species might seem cut and dried — and for many organisms (e.g., mammals), it works well — but in many other cases, this definition is difficult to apply. For example, many bacteria reproduce mainly asexually. How can the biological species concept be applied to them? Many plants and some animals form hybrids in nature, even if they largely mate within their own groups. Should groups that occasionally hybridize in selected areas be considered the same species or separate species? The concept of a species is a fuzzy one because humans invented the concept to help get a grasp on the diversity of the natural world. It is difficult to apply because the term species reflects our attempts to give discrete names to different parts of the tree of life — which is not discrete at all, but a continuous web of life, connected from its roots to its leaves.
Some have argued that such technological advances mean that we've opted out of the evolutionary game and set ourselves beyond the reach of natural selection — essentially, that we've stopped evolving. However, this is not the case. Humans still face challenges to survival and reproduction, just not the same ones that we did 20,000 years ago. The direction, but not the fact of our evolution has changed. For example, modern humans living in densely populated areas face greater risks of epidemic diseases than did our hunter-gatherer ancestors (who did not come into close contact with so many people on a daily basis) — and this situation favors the spread of gene versions that protect against these diseases.
For more see our question "Did evolution have to result in human beings?".
"Species are distinct natural entities, with a clear definition, that can be easily recognized by anyone."
Many of us are familiar with the biological species concept, which defines a species as a group of individuals that actually or potentially interbreed in nature. That definition of a species might seem cut and dried — and for many organisms (e.g., mammals), it works well — but in many other cases, this definition is difficult to apply. For example, many bacteria reproduce mainly asexually. How can the biological species concept be applied to them? Many plants and some animals form hybrids in nature, even if they largely mate within their own groups. Should groups that occasionally hybridize in selected areas be considered the same species or separate species? The concept of a species is a fuzzy one because humans invented the concept to help get a grasp on the diversity of the natural world. It is difficult to apply because the term species reflects our attempts to give discrete names to different parts of the tree of life — which is not discrete at all, but a continuous web of life, connected from its roots to its leaves.
Misconceptions about Natural Selection and Adaptation
“Natural selection involves organisms trying to adapt”.
Natural selection leads to the adaptation of species over time, but the process does not involve effort, trying, or wanting. Natural selection naturally results from genetic variation in a population and the fact that some of those variants may be able to leave more offspring in the next generation than other variants. That genetic variation is generated by random mutation — a process that is unaffected by what organisms in the population want or what they are "trying" to do. Either an individual has genes that are good enough to survive and reproduce, or it does not; it can't get the right genes by "trying." For example bacteria do not evolve resistance to our antibiotics because they "try" so hard. Instead, resistance evolves because random mutation happens to generate some individuals that are better able to survive the antibiotic, and these individuals can reproduce more than other, leaving behind more resistant bacteria.
“The fittest organisms in a population are those that are strongest, healthiest, fastest, and/or largest.”
In evolutionary terms, fitness has a very different meaning than the everyday meaning of the word. An organism's evolutionary fitness does not indicate its health, but rather its ability to get its genes into the next generation. The more fertile offspring an organism leaves in the next generation, the fitter it is. This doesn't always correlate with strength, speed, or size. For example, a puny male bird with bright tail feathers might leave behind more offspring than a stronger, duller male, and a spindly plant with big seed pods may leave behind more offspring than a larger specimen — meaning that the puny bird and the spindly plant have higher evolutionary fitness than their stronger, larger counterparts.
“Natural selection produces organisms perfectly suited to their environments.”
Natural selection is not all-powerful. There are many reasons that natural selection cannot produce "perfectly-engineered" traits. For example, living things are made up of traits resulting from a complicated set of trade-offs — changing one feature for the better may mean changing another for the worse (e.g., a bird with the "perfect" tail plumage to attract mates maybe be particularly vulnerable to predators because of its long tail). And of course, because organisms have arisen through complex evolutionary histories (not a design process), their future evolution is often constrained by traits they have already evolved. For example, even if it were advantageous for an insect to grow in some way other than molting, this switch simply could not happen because molting is embedded in the genetic makeup of insects at many levels.
Part 2
November 22, 2011
The website Understanding Evolution, hosted by The University of California Museum of Paleontology, Berkeley, offers its readers numerous helpful resources regarding the science and history of evolutionary biology. The site’s stated goal is to “help you understand what evolution is, how it works, how it factors into your life, how research in evolutionary biology is performed, and how ideas in this area have changed over time.” Among its resources is a list of popular misconceptions about evolutionary theory. In this two part series, we’d like to highlight some of the site’s most helpful responses to these misconceptions. The full list, and many other wonderful resources, can be found at Understanding Evolution.
Misconceptions about Evolution and the Nature of Science
“Evolution is not science because it is not observable or testable.”
This misconception encompasses two incorrect ideas: (1) that all science depends on controlled laboratory experiments, and (2) that evolution cannot be studied with such experiments. First, many scientific investigations do not involve experiments or direct observation. Astronomers cannot hold stars in their hands and geologists cannot go back in time, but both scientists can learn a great deal about the universe through observation and comparison. In the same way, evolutionary biologists can test their ideas about the history of life on Earth by making observations in the real world. Second, though we can't run an experiment that will tell us how the dinosaur lineage radiated, we can study many aspects of evolution with controlled experiments in a laboratory setting. In organisms with short generation times (e.g., bacteria or fruit flies), we can actually observe evolution in action over the course of an experiment. And in some cases, biologists have observed evolution occurring in the wild.
"Evolution is 'just' a theory."
This misconception stems from a mix-up between casual and scientific use of the word theory. In everyday language, theory is often used to mean a hunch with little evidential support. Scientific theories, on the other hand, are broad explanations for a wide range of phenomena. In order to be accepted by the scientific community, a theory must be strongly supported by many different lines of evidence. Evolution is a well-supported and broadly accepted scientific theory; it is not ‘just' a hunch.
For more, see the question "What is evolution?"
"Evolutionary theory is invalid because it is incomplete and cannot give a total explanation for the biodiversity we see around us."
This misconception stems from a misunderstanding of the nature of scientific theories. All scientific theories (from evolutionary theory to atomic theory) are works in progress. As new evidence is discovered and new ideas are developed, our understanding of how the world works changes and so too do scientific theories. While we don't know everything there is to know about evolution (or any other scientific discipline, for that matter), we do know a great deal about the history of life, the pattern of lineage-splitting through time, and the mechanisms that have caused these changes. And more will be learned in the future. Evolutionary theory, like any scientific theory, does not yet explain everything we observe in the natural world. However, evolutionary theory does help us understand a wide range of observations (from the rise of antibiotic-resistant bacteria to the physical match between pollinators and their preferred flowers), does make accurate predictions in new situations (e.g., that treating AIDS patients with a cocktail of medications should slow the evolution of the virus), and has proven itself time and time again in thousands of experiments and observational studies.
For more, see the questions "How can evolution account for the complexity of life on earth today?" and "How can evolution account for the complexity of life on earth today?"
"Gaps in the fossil record disprove evolution."
While it's true that there are gaps in the fossil record, this does not constitute evidence against evolutionary theory. Scientists evaluate hypotheses and theories by figuring out what we would expect to observe if a particular idea were true and then seeing if those expectations are borne out. If evolutionary theory were true, then we'd expect there to have been transitional forms connecting ancient species with their ancestors and descendents. This expectation has been borne out. Paleontologists have found many fossils with transitional features, and new fossils are discovered all the time. However, if evolutionary theory were true, we would not expect all of these forms to be preserved in the fossil record. Many organisms don't have any body parts that fossilize well, the environmental conditions for forming good fossils are rare, and of course, we've only discovered a small percentage of the fossils that might be preserved somewhere on Earth. So scientists expect that for many evolutionary transitions, there will be gaps in the fossil record.
For more see out question "What does the fossil record show?"
Misconceptions about the Acceptance and Implications of Evolution
“Evolution is a theory in crisis and is collapsing as scientists lose confidence in it.”
Evolutionary theory is not in crisis; scientists accept evolution as the best explanation for life's diversity because of the multiple lines of evidence supporting it, its broad power to explain biological phenomena, and its ability to make accurate predictions in a wide variety of situations. The vast majority of scientists do not debate whether evolution took place, but they do debate many details of how evolution occurred and occurs in different circumstances. Antievolutionists may hear the debates about how evolution occurs and misinterpret them as debates about whether evolution occurs. Evolution is sound science and is treated accordingly by scientists and scholars worldwide.
For more see the questions "Does thermodynamics disprove evolution?", "How can evolution account for the complexity of life on earth today?" and "How can evolution account for the complexity of life on earth today?"
"Evolution supports the idea that 'might makes right' and rationalizes the oppression of some people by others."
In the nineteenth and early twentieth centuries, a philosophy called Social Darwinism arose from a misguided effort to apply lessons from biological evolution to society. Social Darwinism suggests that society should allow the weak and less fit to fail and die and that this is good policy and morally right. Supposedly, evolution by natural selection provided support for these ideas. Pre-existing prejudices were rationalized by the notion that colonized nations, poor people, or disadvantaged minorities must have deserved their situations because they were "less fit" than those who were better off. In this case, science was misapplied to promote a social and political agenda. While Social Darwinism as a political and social orientation has been broadly rejected, the scientific idea of biological evolution has stood the test of time.
"Evolution and religion are incompatible."
Because of some individuals and groups stridently declaring their beliefs, it's easy to get the impression that science (which includes evolution) and religion are at war; however, the idea that one always has to choose between science and religion is incorrect. People of many different faiths and levels of scientific expertise see no contradiction at all between science and religion.
In fact, science and religion can have a constructive relationship. The majority of scientists during the emergence of modern science in medieval Europe, for example, were devout or conventionally religious. Religious belief, then, can function as a framework within which scientific progress flourishes. Religious belief can also be influenced by science. In the Galileo Affair, scientific evidence of a heliocentric universe caused the church to revisit its interpretation of a part of Scripture.
Oddly enough, some people argue that God’s existence is actually a scientific claim and should be tested like any other. However, God’s existence is not something that can be tested by the scientific method in the same way the existence of postulated new elementary particles are tested in supercolliders. Because science provides knowledge about the natural world, no amount of testing or theorizing could prove or disprove the existence of a supernatural creator. Rather than an empirical claim about nature or its laws, the claim that God exists is a metaphysical one, a statement about what there is, whether it be natural or supernatural.
For more see the questions "What is the proper relationship between science and religion?", "Can scientific and scriptural truth be reconciled?", "What were the initial Christian responses to Darwin?", and "What role could God have in evolution?"
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