There are many kinds of mutation. For example a point mutation involves the substitution of one nucleotide base in the DNA sequence by a different nucleotide, and in some cases this leads to a change in a single amino-acid in the encoded protein. In other cases a stop signal can be introduced by the mutation so that only part of the gene is read into a protein sequence, and the protein that results is truncated, rather like a sentence which is chopped in half.
Most mutations are neutral with regard to reproductive fitness. Other sections of our DNA are involved in the regulation of gene expression the actual making of the protein that the gene encodes , while the function of the rest of our DNA is not yet well understood. Even when mutations appear in the DNA which encodes genes, most are lost from the gene pool since they make no difference to reproductive success.
Most mutations that have any phenotypic effect, that is, that make any difference to the organism, are deleterious. Only a very small percentage of mutations is beneficial, that is, increase the reproductive fitness of the organism: Yet it is this tiny proportion of beneficial alleles which provides novelty and scope for change as part of the process of generating biological diversity.
One example of a beneficial mutant allele comes from the mosquito. In this organism a mutant gene arose by chance which conferred the ability to break down the type of organophosphates commonly used in insecticides. Not surprisingly this mutant gene rapidly swept through the world-wide mosquito population, thereby providing resistance to such insecticides, a good example of evolution in progress. Clearly this particular mutation has been of greater benefit to mosquitoes than it has to humans. So far we have considered only evolution within a biological lineage, that is, within a single species.
A species refers to a population of organisms which interbreed with each other but not with other organisms. Speciation is thought to occur either by allopatric mechanisms, which happen when a population is split into two or more geographically divided sub-divisions that organisms cannot bridge such as the formation of a new ocean separating two landmasses as a result of continental drift [Figure 13], or by sympatric mechanisms which occur when two sub-populations become reproductively isolated without first becoming geographically isolated.
Some biologists think that special mechanisms, different from those that we have considered so far, may be involved in speciation, whereas others believe that in many cases the molecular mechanisms that have been described so far are adequate to account for reproductive isolation. The issue awaits a clear resolution. Genetically, the reasons for reproductive isolation may in some cases be quite trivial in comparison with the much greater degree of genetic diversity which exists within a species.
For example, in a sympatric form of speciation a mutation might occur in a key developmental gene which regulates some aspect of reproduction so that successful mating can only occur within the population which shares the mutant allele. Speciation may result from something as trivial as a change in plumage colour, or the inability of a bird to learn the correct mating song from its parents — no song, no sex — or the formation of a new mountain range between a population of snails which used to interbreed.
When the two populations finally get back together again after a few millions of years in isolation, it may often happen that their accumulation of mutant alleles now means that they can no longer interbreed. Until recently it was difficult to identify genes that might be specifically involved in speciation. However, the use of organisms that multiply quickly, like fruit-flies, coupled with rapid sequencing techniques and the power of computer programs to compare gene sequences, is changing the situation.
For example if attempts are made to breed the fruitfly Drosophila simulans with another species of fruit-fly called Drosophila melanogaster , then the male hybrid offspring die. Recently this has been shown to be due to a gene called Nup96 on chromosome 3 of Drosophila simulans which interacts with one or more unknown genes on the Drosophila melanogaster male X chromosome to cause the death of the offspring [5].
So it is likely to be this particular gene that contributes to the reproductive barrier between these two species. In fact sequencing of the Nup96 gene from many individuals from both species has revealed important inter-species differences in the sequence between the two species. Since differences in gene sequence translate into differences in protein structure and properties, this most likely explains the incompatibility of the simulans version of the gene when in the presence of the melanogaster X chromosome.
So in this case it is quite likely that accumulating mutations in a single gene were sufficient to precipitate the branching of two separate lineages. Mass extinctions like these are followed by periods of radiation when new species evolve to fill the empty ecological niches left behind. It has been estimated that there are about 20 million species alive today, but in contrast about 2 billion species have come into being and then gone extinct during the history of our planet. Speciation is easiest to study in lakes and on islands where the environment is highly restricted [6].
However, more recently genetic and geological studies have revealed a more complex picture [7]. Irrespective of the precise sequence of events, the large number of Cichlid species found until recently in Lake Victoria provides a striking example of rapid speciation in action. The different species show differences in morphology body structure and appearance which are linked to their feeding habits. For example, virtually every major food source in the lake is exploited by one species or another.
Some cichlids eat insects, others crustaceans, others eat plants, and yet others mollusks. Each new species has found their particular ecological niche. In fact one species, H. Just years ago a small new lake called Lake Nabugabo became isolated from Lake Victoria by a narrow sand-bar and this lake already has 7 different Cichlid species, 5 of which are not found in Lake Victoria and which therefore most likely evolved during these past years. The Lake Nabugabo species vary most from the Lake Victoria species in male colour.
So the cichlid species of these two lakes provides a vivid example of the way in which speciation can be rapid in terms of geological time and abundant, given the right environment. It is sometimes thought that speciation events must involve the evolution of completely new genes. This is also a mistaken idea. We are all living fossils in the sense that our genes have extremely ancient roots.
In most cases those proteins carry out in the mouse the same set of tasks as they perform in humans. In recent evolution, that is evolution which has occurred during the past million years, it is not the generation of completely new genes which has been the key mechanism driving evolutionary change, but the reorganisation and refining of genes already in existence. To use an analogy from architecture, the myriad forms of building which characterise the city of Cambridge come mainly not from the use of different types of stone and brick, but from different configurations of similar bricks and stones.
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A lot of the novelty generated during evolution appears to come from gene duplication. Occasionally a gene is duplicated as a cell divides so that two copies of that gene are integrated into the genome of the daughter cells instead of the original one. If this occurs in the germ-line cells sperm or eggs then the gene-duplication event will be passed on to the progeny. Sometimes the new gene ends up in a different part of the genome so that its regulation is different, or it may not even be expressed as a protein at all [8]. For example, our own chromosome 7 encodes 1, genes, but also pseudogenes, which lie there like molecular fossils of our evolutionary past [10].
The second copy of the gene may be under different selection constraints from the original copy. This means that its gene sequence can start drifting faster due to accumulating mutations, endowing the protein with similar but not identical properties to those it had before. But increases in gene number alone do not account for increases in morphological complexity [11].
The simple nematode worm possesses nearly 20, genes but lacks the full range of cell types seen in the fruit-fly which contains fewer than 14, genes. Vertebrates have only about twice as many genes as invertebrates, despite their greater range of tissue-types and increased complexity of structure. It has also been calculated that perhaps twice as much human non-coding DNA is facing selection pressure during genetic change as compared to the coding regions those DNA sequences that actually encode proteins.
So it seems likely that in many cases speciation will be found to involve changes in a whole panoply of regulatory DNA sequences in addition to genes that encode proteins. In science theories tend to get discarded unless they continue to fit the data. Most biologists do not work on evolutionary theory per se , rather they carry out their research within the evolutionary paradigm.
And what they find in practice is that the theory is like a work-horse which continues to make sense of the data and so they go on believing in it.
Argument from Design
For example, the sequencing of human DNA, a consequence of the Human Genome project, has provided data which makes perfect sense within evolutionary theory. Now what you expect if all living organisms have a shared evolutionary history is that many genes will be found in common between organisms, but that the differences in the sequences of genes, and indeed in the actual genes utilised, will increase in proportion to evolutionary time. In other words, the longer it was since one organism shared a common ancestor with another, the more time there will be for genes to change or to be used in novel ways.
But if the genes are really essential to life as they are, then there'll be a strong selection pressure to keep them the same way. Remember that natural selection is a very conservative force, preventing change. One of the remarkable findings from a comparison between the genomes of humans, worms, flies and yeast is just how similar we all are, and yet there are some significant differences as well.
Kinases are enzyme proteins that regulate almost every aspect of your body's functions. Now you can divide all the family of kinases up into subfamilies, based on similarities between the gene sequences. There are 93 families that are shared between humans, flies and worms and a further 51 families that are shared between humans, flies, worms and yeast. So we actually contain thousands of genes that are present also in yeast and that haven't changed that much since our evolutionary path split off from yeast about 1 billion years ago.
And we share even more genes with the lowly worm and the fly from which we split off in the so-called Cambrian explosion about million years ago. So genes are like molecular fossils, telling us much about our evolutionary histories [13]. Having spent some time outlining the key elements in biological evolution, we can now consider how it relates to the biblical doctrine of creation. We have already noted in chapter 5 that Christians are robust theists: Just as the existence of the TV drama depends upon the continual targeting of electrons on to the TV screen to generate the necessary images, and there would be no drama if the flow of electrons ceased, so there would no scientists and nothing for scientists to describe were God to cease his on-going creative and sustaining activity.
The word create is clearly used to refer to processes in many biblical texts, such as the creation of the people of Israel, or the creation of the New Jerusalem, or the creation of new animals which takes place during the normal process of animal birth [14] , or the creation of light and darkness which God does every day in the normal passage from day to night [15].
The modern tendency to look for God at the boundaries of our present knowledge is quite alien to biblical thought. Evolution can simply be viewed as the mechanism that God has chosen to bring biological diversity into being. As with any other scientific theory, evolution is our current best guess as to how God has brought about that process. Therefore insofar as Dawkins is contrasting evolutionary theory with creationist beliefs, he is correct to suggest that these are rival theories about the origins of biological diversity: One could argue that as long as there are creationists around, so will there be clones of Richard Dawkins around, because as long as different groups of people invest scientific theories with rival ideologies, then so long will those disputes feed on each other and indeed benefit from each other in a synergistic way.
The adoption of a robust biblically based theism, however, evacuates evolutionary theory of any kind of philosophical pretensions, least of all of any claim to be an argument for a materialistic philosophy. Occasionally popular writers, even Christian writers, suggest that evolutionary theory is under some kind of crisis within the scientific community. This is not true.
In recent years the theory has been enormously strengthened by the advent of molecular genetics. The theory is so powerful because it links together disparate data from a wide range of scientific disciplines, including zoology, anatomy, biochemistry, molecular biology, geology, palaeontology, anthropology and ecology. There is no alternative rival theory on offer at the present time. Christians should therefore be truth-tellers when it comes to accurately describing the convictions of the current generation of biological scientists. It should be noted that such a stance undermines the use of scientific theories as arenas for ideological conflict.
Instead it places the emphasis of the conflict, such as that between atheists and Christians, on the competing metaphysical convictions adopted by these protagonists. Curtis described work prior to Darwin that helped set the stage for the rapid acceptance of evolution by the scientific community.
Creation–evolution controversy
The concept of evolution was accepted immediately; however, the mechanisms, including natural selection, were still being discussed. Evidence for human evolution also continued to accumulate, demonstrating kinship with other animals. Curtis closed with a quote from a letter from President Woodrow Wilson: It surprises me that at this late date such questions should be raised.
Raulston, urged the prohibition of the teaching of evolution in schools to prevent the corruption of society and the downfall of civilization Anonymous If science was not consistent with Christ's religion, he concluded, the choice was obvious. Evolution was an incentive to larceny and murder.
If people lost faith in Genesis, they were likely to lose faith in the rest of the Bible. Raulston argued that there was no justification for accusing Tennesseans of being yokels or ignoramuses, but that if learning would cause loss of faith, they would be better left in a state of ignorance. The address of the retiring vice president of the AAAS zoology section, and self-proclaimed evolutionist and Christian, Edwin Linton, was reprinted in two parts Linton a , b.
Unlike dogmatic religionists, Linton argued, scientists do not suggest that their views are infallible, but rather that they are the best explanation available, to be changed if new evidence is presented. Modernist theologians show no hostility toward the theory of evolution; only the fundamentalists have objections. Linton described a wave of antiscience sentiment sweeping the country. Linton characterized the leading opponents of science as antisocial eccentrics, citing as an example the antivaccinationists, who opposed smallpox vaccinations.
In the face of clear evidence of a reduction in the illness, they remained unconvinced because they were in-convincible. A recent attempt to measure how the teaching of evolution damaged religious beliefs showed 66 respondents reporting that their faith was strengthened, 20 reporting no effect, and 2 reporting a weakening of faith. Linton closed by quoting the biblical Philip's suggested method of scientific inquiry to Nathanael: In late , the American Association of University Professors agreed to develop more efficient means of cooperation in opposing the spread of antievolution legislation Anonymous a.
An antievolution bill had been defeated in Louisiana, and a new one was pending in Arkansas.
One week later, the decision of the Tennessee Supreme Court was announced. A three-to-one vote upheld the antievolution law Anonymous b. The specific Scopes decision was sent back to the court for retrial on a technicality. Not all biologists accepted evolution. A letter to the journal Ecology was reprinted in Science Moore Barrington Moore, the first editor of Ecology and a past president of the Ecological Society of America, discontinued his subscription because papers on evolution had been published in Ecology.
A posthumous publication from W. Davis, Harvard emeritus professor of physical geography, called science and religion the greatest products of the human mind Davis Davis recognized that his definition would cause dissent, since many believed in the supernatural origin of modern religion. However, many of these same people could easily accept the human origin of primitive religions. When theology and science conflicted, theologians generally formed the attack.
However, without exception, reconciliation of religious and scientific beliefs resulted from a modification of the theological perspective, not from a change in science. Acceptance of evolution was an example of the process.
The Birth of the Battle
Davis credited theologians with a desire to improve the human condition, a direct goal of few professors. Nearly two decades later, an article by K. Mather addressed the problem of antiscientific thinking. Although critics of science and scientific methods had been around for centuries, Mather argued, the conflict between evolution and religion in the 19th century gave rise to an antiscience attitude among much of the population that continued into the s Mather Mechanistic and materialistic methods of science appeared to reduce the status of man and could be blamed for a lapse in moral principles and ethical standards.
Mather saw the solution as more, not less, science. The potential for nuclear war and the dangers of overpopulation were issues that engendered antiscience attitudes. Scientists needed the courage to publicly counter the antiscience arguments, although to do so could result in branding as anti-American by some of the active an-tiscience organizations. Like Smith and other scientists before him, Mather argued that education was essential for life in a free society.
Schaar described some of the professional duties and responsibilities of chemists. Schaar quoted a editorial from the Chemical Bulletin in which wider distribution of knowledge was seen as a counter to an illiberal spirit including censorship, the Eighteenth Amendment, the Ku Klux Klan, and the antievolution movement Schaar Schaar took encouragement from the waning of dispute between science and religion over evolution.
Science transcended international borders, and in nations that allowed science to progress, there was also social progress. Schaar concluded that scientists and engineers have a responsibility to share knowledge and to educate the public. A review by C. John Thomas Scopes suggested that, from the per-spective of a third of a century, everyone involved with the trial behaved badly Reed The spectacle was a made-up affair that reflected the feelings of the time.
Many states enacted restrictive laws, and in Tennessee, several legislators voted for the antievolution law, expecting a veto from the governor; however, the governor refused. The effect on those teaching biology was chilling. Reed urged scientists to read the book as a reminder not to let antievolutionism creep back into the classroom. Promising potential scientists had avoided a career in science because of the atmosphere created by the trial. Science and The Scientific Monthly merged operations in Editorial policy changes produced more news articles and comments.
Evolution and creation remained important issues. In the next four decades, references to the controversy appeared, addressing three major legal challenges to the teaching of evolution, and the introduction of the concept of intelligent design. Rather than attempting to prevent teaching of evolution, creationists started to demand equal time. At least 11 states had laws proposed with variations on that theme. Creationists urged the adoption of texts that included creationist materials, and requested that, if evolution was presented, creationism be given equal time Wade The dispute began 10 years earlier when two housewives, concerned that their children would be confused by the evolutionary perspective at school and the biblical teaching at home, began a movement to have the California State Board of Education change the textbooks.
The Creation Research Society, with members who included scientists with doubts about evolution, got involved, and a private citizen offered new science guidelines that included creationism as an alternative to the science guidelines used by the board. The board accepted the revisions, over the objection of scientific advisors. The first high school text written by a practicing biologist was by Alfred C. Kinsey, of Indiana University, in Grabiner and Miller The first edition had explicit definitions of evolution and Darwin; later editions removed or reduced such references.
In the early s, several texts included descriptions of evolution, but most of them included little direct coverage of evolutionary theory. Russian scientific advances of the late s prompted a new look at teaching science. The development of the Biological Sciences Curriculum Study texts, with explicit descriptions of evolution and its implications, brought the issue before the public.
Significant resistance to teaching evolution remained, and Grabiner and Miller blamed the community of professional scientists for failing to pay attention to what was happening to high school science. The California creationist suit was expected to be a replay of the Scopes trial, but the focus was drastically narrowed by the creationist lawyers Broad a.
The creationists felt this was enough of a victory and stopped the case. Louisiana passed a law requiring creation science be presented when Darwin's theory was described Broad b. Treen signed the bill, saying he had some reservations but felt that academic freedom could not be harmed by inclusion, only by exclusion, of different points of view. Governor Treen reported getting letters from both sides of the issue from the biology department of his own university, Tulane. Arkansas passed a new law in March, with little discussion. Louisiana's bill had been vigorously debated by scientists, creationists, and the press.
In California, evolution was attacked as a religion; in Louisiana, creationism was considered science Broad b. In each case, the creationists' effort was to put creation and evolution on the same footing. The NAS group agreed to put together a booklet explaining evolution in layman's terms. The NABT agreed on a booklet specifically responding to creationists' arguments. Both groups recognized that they were facing a political, not a scientific problem.
Eugenie Scott, then of the University of Kentucky, described a local effort to change the policy of a school board near Lexington. Both the creationists and the evolutionists used a localaction approach to convince the school board. The evolutionists won by a vote of three to two. Such local actions would be required to counteract the creationist activities Lewin a. First, creationism was not science, but religion.
Undeniable: evolution and the science of creation | Review | Chemistry World
Second, academic freedom was infringed by the law. Finally, the statute was unconstitutionally vague, not giving fair notice of what could and could not be taught. Other creationists believe in an older Earth, with species still created separately by God. Finally, believers in Intelligent Design hold that evolution might occur, but that a deity started or guides the process.
Creationism vs. Evolution: 6 Big Battles
Advances in geology in the s and s shook the foundations of young-Earth creationism spread by preachers who interpreted the Bible literally. Charles Darwin's "The Origin of Species," published in , complicated matters further. Now, science was not only shooting holes in the Biblical tale of a young Earth created in mere days, it was suggesting that God didn't even create all animals and plants.
The trial was intended to generate publicity, and it worked like a charm. The cast was star-studded: Famous attorney Clarence Darrow defended Scopes, while the three-time populist Presidential candidate Williams Jennings Bryan prosecuted. Americans listened to the court proceedings over the radio.
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The Tennessee Supreme Court later overturned the verdict on a technicality, but upheld the law preventing evolution from being taught. After the trial, other states enacted their own anti-evolution laws. But gradually, the anti-evolution movement lost steam, and evolution snuck back into textbooks.
The teaching of evolution versus creationism was spotty until The Soviet Union had just launched the Sputnik satellite, and the United States was facing a shortage of mathematicians. Eisenhower and Congress passed the National Defense Education Act, a funding bill designed to improve science education.