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How did zootoxins evolve?

How did zootoxins evolve?


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I've always wondered how toxins in certain organisms have evolved. Particularly, organisms that produce toxins as a deterrent to predators as opposed to organisms that use it to paralyze their prey.

Where did this toxicity come from? How did it develop to what it is today?

There must've been a drawn out period where evolution 'tested' and 'fine-tuned' the toxin. Presumably until it was somewhat efficacious to the target. What are the current popular theories on this?


General overview.

Each toxin and poison probably have their own evolutionary "arms race". Generally, an organism contains a compound that is a bit harmful to other species. As a predator or prey species becomes tolerant to low doses of this compound through natural selection, the compound efficacy could be increased (again by natural selection) on a molecular level, or at a dosage or concentration level.

Below are a few examples of where this has become the case, and some more general examples of how venom evolved in the first place.

Examples.

California Newt.

These newts contain tetrodotoxin (you may be familiar with this from the fugu fish). It is preyed on by a species of garter snake. This is a textbook arms race as the garter snake is naturally selected to have beneficial alleles that are tolerant to the toxin.

Dart Frogs.

The golden dart frog Phyllobates terribilis contains enough batrachotoxin to kill 10 people. That is apparently overkilling for any predator it would surely have to face especially given that the only animal alive that is immune to the poison is the frog itself. However, the snake Liophis epinephelus can tolerate massive doses of batrachotoxin (although I've heard it gets pretty poorly after eating a frog, rather understandably). These two species are locked in an arms race that drives the frogs to produce an unbelievably fatal cocktail and the snakes to become ever more tolerant.

Snakes.

Modified sweat glands evolved to damage the prey as much as possible for immobilisation, partial digestion, or defence. There are textbooks about snake venom and toxins. Here is a neat article I found with a cursory search or if you want to sink your teeth into the topic (heh.) check out this article.

Long story short: venom sacks are modified saliva glands from non-venomous snake ancestors. The diagram shows generally just how modified these apparatus have become!

Platypus

Let's not forget the weird and wonderful monotremes. It's hard to pinpoint exactly what drove the platypus to develop venomous barbs on its elbow (last time I looked into it, it was still disputed if they were for defence or hunting).

But what we can learn from this is that venom can independently evolve. Although the venom producing proteins are different, they produce the same venom as some snakes.


Sortof. Just as every adaptation is the product of a small change in something the species already expressed, all toxins start out as something the organism just happens to produce as part of its life. Then there are two evolutionary paths for useful toxins:

  • Poisons - "If you eat me, you will be sorry." These typically begin as metabolites that happen to confer an advantage to an organism's siblings, work as an aid to escape, or are just mildly irritating to predators or parasites.
  • Venoms - "If I bite you, you will be sorry." These typically begin as digestive assistants - mucous or saliva.

Once there is some advantage to expressing a chemical in a certain way it can be considered to be "locked in" - organisms with that trait stand a better chance of surviving to reproduce and will therefore multiply. As the organisms that exhibit that toxin multiply, mutations in their descendants that improve the utility or effectiveness of the toxin allow those organisms to better survive, and so on. So, a saliva gland that once caused mild irritation in a certain species of prey becomes a descendant's vertebrate-paralyzing-venom gland.

References


Recapitulation theory

The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (ontogeny), goes through stages resembling or representing successive adult stages in the evolution of the animal's remote ancestors (phylogeny). It was formulated in the 1820s by Étienne Serres based on the work of Johann Friedrich Meckel, after whom it is also known as Meckel–Serres law.

Since embryos also evolve in different ways, the shortcomings of the theory had been recognized by the early 20th century, and it had been relegated to "biological mythology" [1] by the mid-20th century. [2]

Analogies to recapitulation theory have been formulated in other fields, including cognitive development [3] and music criticism. [4]


Evolution

The exact relationships between the different cnidarian groups are unknown. Among theories proposed on the evolution of the phylum Cnidaria, most treat the radial symmetry and tissue level of organization as evidence that the group is primitive (that is, it evolved before the evolution of bilateral symmetry) and hold that the medusa is the original body form, being the sexually reproductive phase of the life cycle. Another theory is that the original cnidarian was a planula-like organism that preceded both polyp and medusa. In either case, Hydrozoa is considered to be the most ancient of cnidarian classes, and Trachylina is thought to be the most primitive extant order of that group. An alternative view is that anthozoans are the stem of the phylum, which evolved from bilateral flatworms and is secondarily simplified. A corollary to this theory is that the polyp is the ancestral body form.

Speculations about the origin of the phylum are not easily resolved, for preservable skeletal structures developed relatively late in cnidarian evolution. The oldest fossilized cnidarians were soft-bodied. Representatives of all four modern classes have been identified in Ediacaran fauna of the Precambrian Period (that is, those appearing between about 635 million and 541 million years ago) known from more than 20 sites worldwide. As much as 70 percent of Ediacaran species have been considered to be cnidarians. Curiously, there are few fossil cnidarians of the Cambrian Period (541 million to 485.4 million years ago). The Conulariida, which existed from the Cambrian Period to the Triassic Period (251.9 million to 201.3 million years ago), are considered by some scientists to be skeletal remains of scyphopolyps, either ancestral to the coronates or without modern derivatives. Presumed fossil sea anemones are found in the lower Cambrian System. Colonies of Stromatoporoidea, considered to be an order of the class Hydrozoa that extended from the mid-Cambrian Period to the Cretaceous Period (about 145 million to 66 million years ago), produced massive skeletons. Although there were two groups of Paleozoic corals, neither of which has modern descendants, they were not great reef-builders during that era. Scleractinians arose in the mid-Triassic Period blue corals, gorgonians, millepores, and hydrocorals have records from the Jurassic Period (201.3 million to 145.0 million years ago) or the Cretaceous Period to the present. Most other cnidarians are known only from the Holocene Epoch (within the last 11,700 years).


Monogamy and Human Evolution

“Monogamy is a problem,” said Dieter Lukas of the University of Cambridge in a telephone news conference last week. As Dr. Lukas explained to reporters, he and other biologists consider monogamy an evolutionary puzzle.

In 9 percent of all mammal species, males and females will share a common territory for more than one breeding season, and in some cases bond for life. This is a problem — a scientific one — because male mammals could theoretically have more offspring by giving up on monogamy and mating with lots of females.

In a new study, Dr. Lukas and his colleague Tim Clutton-Brock suggest that monogamy evolves when females spread out, making it hard for a male to travel around and fend off competing males.

On the same day, Kit Opie of University College London and his colleagues published a similar study on primates, which are especially monogamous — males and females bond in over a quarter of primate species. The London scientists came to a different conclusion: that the threat of infanticide leads males to stick with only one female, protecting her from other males.

Image

Even with the scientific problem far from resolved, research like this inevitably turns us into narcissists. It’s all well and good to understand why the gray-handed night monkey became monogamous. But we want to know: What does this say about men and women?

As with all things concerning the human heart, it’s complicated.

“The human mating system is extremely flexible,” Bernard Chapais of the University of Montreal wrote in a recent review in Evolutionary Anthropology. Only 17 percent of human cultures are strictly monogamous. The vast majority of human societies embrace a mix of marriage types, with some people practicing monogamy and others polygamy. (Most people in these cultures are in monogamous marriages, though.)

There are even some societies where a woman may marry several men. And some men and women have secret relationships that last for years while they’re married to other people, a kind of dual monogamy. Same-sex marriages acknowledge commitments that in many cases existed long before they won legal recognition.

Each species faces its own special challenges — the climate where it lives, or the food it depends on, or the predators that stalk it — and certain conditions may favor monogamy despite its drawbacks. One source of clues to the origin of human mating lies in our closest relatives, chimpanzees and bonobos. They live in large groups where the females mate with lots of males when they’re ovulating. Male chimpanzees will fight with each other for the chance to mate, and they’ve evolved to produce extra sperm to increase their chances that they get to father a female’s young.

Our own ancestors split off from the ancestors of chimpanzees about seven million years ago. Fossils may offer us some clues to how our mating systems evolved after that parting of ways. The hormone levels that course through monogamous primates are different from those of other species, possibly because the males aren’t in constant battle for females.

That difference in hormones influences how primates grow in some remarkable ways. For example, the ratio of their finger lengths is different.

In 2011, Emma Nelson of the University of Liverpool and her colleagues looked at the finger bones of ancient hominid fossils. From what they found, they concluded that hominids 4.4 million years ago mated with many females. By about 3.5 million years ago, however, the finger-length ratio indicated that hominids had shifted more toward monogamy.

Our lineage never evolved to be strictly monogamous. But even in polygamous relationships, individual men and women formed long-term bonds — a far cry from the arrangement in chimpanzees.

While the two new studies published last week disagree about the force driving the evolution of monogamy, they do agree on something important. “Once monogamy has evolved, then male care is far more likely,” Dr. Opie said.

Once a monogamous primate father starts to stick around, he has the opportunity to raise the odds that his offspring will survive. He can carry them, groom their fur and protect them from attacks.

In our own lineage, however, fathers went further. They had evolved the ability to hunt and scavenge meat, and they were supplying some of that food to their children. “They may have gone beyond what is normal for monogamous primates,” said Dr. Opie.

The extra supply of protein and calories that human children started to receive is widely considered a watershed moment in our evolution. It could explain why we have brains far bigger than other mammals.

Brains are hungry organs, demanding 20 times more calories than a similar piece of muscle. Only with a steady supply of energy-rich meat, Dr. Opie suggests, were we able to evolve big brains — and all the mental capacities that come with it.

Because of monogamy, Dr. Opie said, “This could be how humans were able to push through a ceiling in terms of brain size.”


REACTION CENTERS

The RC complex is at the heart of photosynthesis so much attention has been paid to understand the evolution of RCs. A wealth of evidence, including structural, spectroscopic, thermodynamic, and molecular sequence analysis, clearly segregates all known RCs into two types of complexes, called type I and type II ( Blankenship, 2002). Anoxygenic phototrophs have just one type, either type I or II, while all oxygenic phototrophs have one of each type. The primary distinguishing feature of the two types of RCs are the early electron acceptor cofactors, which are FeS centers in type I RCs and pheophytin/quinone complexes in type II RCs. The distribution of RC types on the tree of life is shown in Figure 1 and a comparative electron transport diagram that compares the different RCs in different types of organisms is shown in Figure 2, with type I RCs color coded green and type II RCs color coded purple.

Electron transport diagram indicating the types or RCs and electron transport pathways found in different groups of photosynthetic organisms. The color coding is the same as for Figure 1 and highlights the electron acceptor portion of the RC. Figure courtesy of Martin Hohmann-Marriott.

Electron transport diagram indicating the types or RCs and electron transport pathways found in different groups of photosynthetic organisms. The color coding is the same as for Figure 1 and highlights the electron acceptor portion of the RC. Figure courtesy of Martin Hohmann-Marriott.

Further analysis strongly suggests that all RCs have evolved from a single common ancestor and have a similar protein and cofactor structure. This is clearly seen when structural overlays of both type I and II RCs are made, showing a remarkably conserved three-dimensional protein and cofactor structure, despite only minimal residual sequence identity ( Sadekar et al., 2006). These comparisons have been used to derive structure-based evolutionary trees that do not rely on sequence alignments. Figure 3 shows a schematic evolutionary tree of RCs that is derived from this sort of analysis. It proposes that the earliest RC was intermediate between type I and II (type 1.5) and that multiple gene duplications have given rise to the heterodimeric (two related yet distinct proteins that form the core of the RC) complexes that are found in most modern RCs.

Schematic evolutionary tree showing the development of the different types of RC complexes in different types of photosynthetic organisms. This tree is based on structural comparisons of RCs by Sadekar et al. (2006). Blue color coding indicates protein homodimer, while red indicates protein heterodimer complexes. Red stars indicate gene duplication events that led to heterodimeric RCs. Helio, Heliobacteria GSB, green sulfur bacteria FAP, filamentous anoxygenic phototroph.

Schematic evolutionary tree showing the development of the different types of RC complexes in different types of photosynthetic organisms. This tree is based on structural comparisons of RCs by Sadekar et al. (2006). Blue color coding indicates protein homodimer, while red indicates protein heterodimer complexes. Red stars indicate gene duplication events that led to heterodimeric RCs. Helio, Heliobacteria GSB, green sulfur bacteria FAP, filamentous anoxygenic phototroph.

A second important issue that relates to RC evolution is the question of how both type I and II RCs came to be in cyanobacteria, while all other photosynthetic prokaryotes have only a single RC. The various proposals that have been made to explain this fact can all be divided into either fusion or selective loss scenarios or variants thereof ( Blankenship et al., 2007). In the fusion hypothesis, the two types of RCs develop separately in anoxygenic photosynthetic bacteria and are then brought together by a fusion of two organisms, which subsequently developed the ability to oxidize water. In the selective loss hypothesis, the two types of RCs both evolved in an ancestral organism and then loss of one or the other RC gave rise to the organisms with just one RC, while the ability to oxidize water was added later. Both scenarios have proponents, and it is not yet possible to choose between them.


Analogy

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Analogy, in biology, similarity of function and superficial resemblance of structures that have different origins. For example, the wings of a fly, a moth, and a bird are analogous because they developed independently as adaptations to a common function—flying. The presence of the analogous structure, in this case the wing, does not reflect evolutionary closeness among the organisms that possess it. Analogy is one aspect of evolutionary biology and is distinct from homology (q.v.), the similarity of structures as a result of similar embryonic origin and development, considered strong evidence of common descent.

In many cases analogous structures, or analogues, tend to become similar in appearance by a process termed convergence. An example is the convergence of the streamlined form in the bodies of squid, shark, seal, porpoise, penguin, and ichthyosaur, animals of diverse ancestry. Physiological processes and behaviour patterns may also exhibit analogous convergence. Egg-guarding behaviour in the cobra, the stickleback, the octopus, and the spider is thought to have evolved independently among those animals, which are quite distant in their biological relationships.

Many New World cacti and African euphorbias are similar in appearance, being succulent, spiny, water-storing, and adapted to desert conditions generally. They are classified, however, in two separate and distinct families, sharing characteristics that have evolved independently in response to similar environmental challenges.


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Evolution of complex life cycles in helminth parasites

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Contents

Francesco Redi, the founder of biology, is recognized to be one of the greatest biologists of all time. [10] Robert Hooke, an English natural philosopher, coined the term cell, suggesting plant structure's resemblance to honeycomb cells. [11]

Charles Darwin and Alfred Wallace independently formulated the theory of evolution by natural selection, which was described in detail in Darwin's book The Origin of Species, which was published in 1859. In it, Darwin proposed that the features of all living things, including humans, were shaped by natural processes over long periods of time. The theory of evolution in its current form affects almost all areas of biology. [12] Separately, Gregor Mendel formulated in the principles of inheritance in 1866, which became the basis of modern genetics.

In 1953, James D. Watson and Francis Crick described the basic structure of DNA, the genetic material for expressing life in all its forms, [13] building on the work of Maurice Wilkins and Rosalind Franklin, suggested that the structure of DNA was a double helix.

Students who aspire to a research-oriented career usually pursue a graduate degree such as a master’s or a doctorate (e.g., PhD) whereby they would receive training from a research head based on an apprenticeship model that has been in existence since the 1800s. [7] Students in these graduate programs often receive specialized training in a particular subdiscipline of biology. [4]

Biologists who work in basic research formulate theories and devise experiments to advance human knowledge on life including topics such as evolution, biochemistry, molecular biology, neuroscience and cell biology.

Biologists typically conduct laboratory experiments involving animals, plants, microorganisms or biomolecules. However, a small part of biological research also occurs outside the laboratory and may involve natural observation rather than experimentation. For example, a botanist may investigate the plant species present in a particular environment, while an ecologist might study how a forest area recovers after a fire.

Biologists who work in applied research use instead the accomplishments gained by basic research to further knowledge in particular fields or applications. For example, this applied research may be used to develop new pharmaceutical drugs, treatments and medical diagnostic tests. Biological scientists conducting applied research and product development in private industry may be required to describe their research plans or results to non-scientists who are in a position to veto or approve their ideas. These scientists must consider the business effects of their work.

Swift advances in knowledge of genetics and organic molecules spurred growth in the field of biotechnology, transforming the industries in which biological scientists work. Biological scientists can now manipulate the genetic material of animals and plants, attempting to make organisms (including humans) more productive or resistant to disease. Basic and applied research on biotechnological processes, such as recombining DNA, has led to the production of important substances, including human insulin and growth hormone. Many other substances not previously available in large quantities are now produced by biotechnological means. Some of these substances are useful in treating diseases.

Those working on various genome (chromosomes with their associated genes) projects isolate genes and determine their function. This work continues to lead to the discovery of genes associated with specific diseases and inherited health risks, such as sickle cell anemia. Advances in biotechnology have created research opportunities in almost all areas of biology, with commercial applications in areas such as medicine, agriculture, and environmental remediation.

Specialists Edit

Most biological scientists specialize in the study of a certain type of organism or in a specific activity, although recent advances have blurred some traditional classifications. [ why? ]

    study genetics, the science of genes, heredity, and variation of organisms. study the nervous system. study the process of development and growth of organisms study the chemical composition of living things. They analyze the complex chemical combinations and reactions involved in metabolism, reproduction, and growth. study the biological activity between biomolecules. investigate the growth and characteristics of microscopic organisms such as bacteria, algae, or fungi. study life functions of plants and animals, in the whole organism and at the cellular or molecular level, under normal and abnormal conditions. Physiologists often specialize in functions such as growth, reproduction, photosynthesis, respiration, or movement, or in the physiology of a certain area or system of the organism. use experimental methods traditionally employed in physics to answer biological questions . apply the techniques of computer science, applied mathematics and statistics to address biological problems. The main focus lies on developing mathematical modeling and computational simulation techniques. By these means it addresses scientific research topics with their theoretical and experimental questions without a laboratory. and wildlife biologists study animals and wildlife—their origin, behavior, diseases, and life processes. Some experiment with live animals in controlled or natural surroundings, while others dissect dead animals to study their structure. Zoologists and wildlife biologists also may collect and analyze biological data to determine the environmental effects of current and potential uses of land and water areas. Zoologists usually are identified by the animal group they study. For example, ornithologists study birds, mammalogists study mammals, herpetologists study reptiles and amphibians, ichthyologists study fish, cnidariologists study jellyfishes and entomologists study insects. study plants and their environments. Some study all aspects of plant life, including algae, lichens, mosses, ferns, conifers, and flowering plants others specialize in areas such as identification and classification of plants, the structure and function of plant parts, the biochemistry of plant processes, the causes and cures of plant diseases, the interaction of plants with other organisms and the environment, the geological record of plants and their evolution. Mycologists study fungi, such as yeasts, mold and mushrooms, which are a separate kingdom from plants.
  • Aquatic biologists study micro-organisms, plants, and animals living in water. Marine biologists study salt water organisms, and limnologists study fresh water organisms. Much of the work of marine biology centers on molecular biology, the study of the biochemical processes that take place inside living cells. Marine biology is a branch of oceanography, which is the study of the biological, chemical, geological, and physical characteristics of oceans and the ocean floor. (See the Handbook statements on environmental scientists and hydrologists and on geoscientists.) investigate the relationships among organisms and between organisms and their environments, examining the effects of population size, pollutants, rainfall, temperature, and altitude. Using knowledge of various scientific disciplines, ecologists may collect, study, and report data on the quality of air, food, soil, and water. investigate the evolutionary processes that produced the diversity of life on Earth, starting from a single common ancestor. These processes include natural selection, common descent, and speciation.

Biologists typically work regular hours but longer hours are not uncommon. Researchers may be required to work odd hours in laboratories or other locations (especially while in the field), depending on the nature of their research.

Many biologists depend on grant money to fund their research. They may be under pressure to meet deadlines and to conform to rigid grant-writing specifications when preparing proposals to seek new or extended funding.

Marine biologists encounter a variety of working conditions. Some work in laboratories others work on research ships, and those who work underwater must practice safe diving while working around sharp coral reefs and hazardous marine life. Although some marine biologists obtain their specimens from the sea, many still spend a good deal of their time in laboratories and offices, conducting tests, running experiments, recording results, and compiling data.

Biologists are not usually exposed to unsafe or unhealthy conditions. Those who work with dangerous organisms or toxic substances in the laboratory must follow strict safety procedures to avoid contamination. Many biological scientists, such as botanists, ecologists, and zoologists, conduct field studies that involve strenuous physical activity and primitive living conditions. Biological scientists in the field may work in warm or cold climates, in all kinds of weather.

The highest honor awarded to biologists is the Nobel Prize in Physiology or Medicine, awarded since 1901, by the Royal Swedish Academy of Sciences. Another significant award is the Crafoord Prize in Biosciences established in 1980.


Contents

Until the late 19th century, creation was taught in nearly all schools in the United States, often from the position that the literal interpretation of the Bible is inerrant. With the widespread acceptance of the scientific theory of evolution in the 1860s after being first introduced in 1859, and developments in other fields such as geology and astronomy, public schools began to teach science that was reconciled with Christianity by most people, but considered by a number of early fundamentalists to be directly at odds with the Bible.

In the aftermath of World War I, the Fundamentalist–Modernist Controversy brought a surge of opposition to the idea of evolution, and following the campaigning of William Jennings Bryan several states introduced legislation prohibiting the teaching of evolution. Such legislation was considered and defeated in 1922 in Kentucky and South Carolina, in 1923 passed in Oklahoma, Florida, and notably in 1925 in Tennessee, as the Butler Act. [1] The American Civil Liberties Union (ACLU) offered to defend anyone who wanted to bring a test case against one of these laws. [1] John T. Scopes accepted, and he started teaching his class evolution, in defiance of the Tennessee law. The resulting trial was widely publicized by H. L. Mencken among others, and is commonly referred to as the Scopes Trial.

Scopes was convicted however, the widespread publicity galvanized proponents of evolution.

When the case was appealed to the Tennessee Supreme Court, the Court overturned the decision on a technicality (the judge had assessed the fine when the jury had been required to). Although it overturned the conviction, the Court decided that the law was not in violation of the First Amendment to the United States Constitution. The Court held:

We are not able to see how the prohibition of teaching the theory that man has descended from a lower order of animals gives preference to any religious establishment or mode of worship. So far as we know there is no religious establishment or organized body that has its creed or confession of faith any article denying or affirming such a theory. — John Thomas Scopes v. The State 154 Tenn. 105, 289 S.W. 363 (1927) [2]

The interpretation of the Establishment Clause of the First Amendment up to that time was that Congress could not establish a particular religion as the State religion. Consequently, the Court held that the ban on the teaching of evolution did not violate the Establishment Clause, because it did not establish one religion as the "State religion." As a result of the holding, the teaching of evolution remained illegal in Tennessee, and continued campaigning succeeded in removing evolution from school textbooks throughout the United States. [3] [4] [5]

In 1967, the Tennessee public schools were threatened with another lawsuit over the Butler Act's constitutionality, and, fearing public reprisal, Tennessee's legislature repealed the Butler Act. In the following year, the Supreme Court of the United States ruled in Epperson v. Arkansas (1968) that Arkansas's law prohibiting the teaching of evolution was in violation of the First Amendment. The Supreme Court held that the Establishment Clause prohibits the state from advancing any religion, and determined that the Arkansas law which allowed the teaching of creation while disallowing the teaching of evolution advanced a religion, and was therefore in violation of the Establishment Clause. This holding reflected a broader understanding of the Establishment Clause: instead of just prohibiting laws that established a state religion, the clause was interpreted to prohibit laws that furthered any particular religion over others. Opponents, pointing to the previous decision, argued that this amounted to judicial activism.

In reaction to the Epperson case, creationists in Louisiana passed a law requiring that public schools should give "equal time" to "alternative theories" of origin. The Supreme Court ruled in 1987 in Edwards v. Aguillard that the Louisiana statute, which required creation to be taught alongside evolution every time evolution was taught, was unconstitutional.

The Court laid out its rule in Edwards as follows:

The Establishment Clause forbids the enactment of any law 'respecting an establishment of religion.' The Court has applied a three-pronged test to determine whether legislation comports with the Establishment Clause. First, the legislature must have adopted the law with a secular purpose. Second, the statute's principal or primary effect must be one that neither advances nor inhibits religion. Third, the statute must not result in an excessive entanglement of government with religion. Lemon v. Kurtzman, 403 U.S. 602, 612-613, 91 S.Ct. 2105, 2111, 29 L.Ed.2d 745 (1971). State action violates the Establishment Clause if it fails to satisfy any of these prongs. — Edwards v. Aguillard [6]

The Court held that the law was not adopted with a secular purpose, because its purported purpose of "protecting academic freedom" was not furthered by limiting the freedom of teachers to teach what they thought appropriate ruled that the act was discriminatory because it provided certain resources and guarantees to "creation scientists" which were not provided to those who taught evolution and ruled that the law was intended to advance a particular religion because several state senators that had supported the bill stated that their support for the bill stemmed from their religious beliefs.

While the Court held that creationism is an inherently religious belief, it did not hold that every mention of creationism in a public school is unconstitutional:

We do not imply that a legislature could never require that scientific critiques of prevailing scientific theories be taught. Indeed, the Court acknowledged in Stone that its decision forbidding the posting of the Ten Commandments did not mean that no use could ever be made of the Ten Commandments, or that the Ten Commandments played an exclusively religious role in the history of Western Civilization. 449 U.S., at 42, 101 S.Ct., at 194. In a similar way, teaching a variety of scientific theories about the origins of humankind to schoolchildren might be validly done with the clear secular intent of enhancing the effectiveness of science instruction. But because the primary purpose of the Creationism Act is to endorse a particular religious doctrine, the Act furthers religion in violation of the Establishment Clause. — Edwards v. Aguillard [6]

The ruling was one in a series of developments addressing issues related to the American creationist movement and the separation of church and state. The scope of the ruling affected state schools and did not include independent schools, home schools, Sunday schools and Christian schools, all of whom remained free to teach creationism.

Within two years of the Edwards ruling a creationist textbook was produced: Of Pandas and People (1989), which attacked evolutionary biology without mentioning the identity of the supposed "intelligent designer." Drafts of the text used "creation" or "creator" before being changed to "intelligent design" or "designer" after the Edwards v. Aguillard ruling. [7] This form of creationism, known as intelligent design creationism, was developed in the early 1990s.

This would eventually lead to another court case, Kitzmiller v. Dover Area School District, which went to trial on September 26, 2005, and was decided in U.S. District Court on December 20, 2005, in favor of the plaintiffs, who charged that a mandate that intelligent design (ID) be taught was an unconstitutional establishment of religion. The opinion of Kitzmiller v. Dover was hailed as a landmark decision, firmly establishing that creationism and intelligent design were religious teachings and not areas of legitimate scientific research. Because the Dover Area School Board chose not to appeal, the case never reached a circuit court or the U.S. Supreme Court.

Just as it is permissible to discuss the crucial role of religion in medieval European history, creationism may be discussed in a civics, current affairs, philosophy, or comparative religions class where the intent is to factually educate students about the diverse range of human political and religious beliefs. The line is crossed only when creationism is taught as science.

There continue to be numerous efforts to introduce creationism in U.S. classrooms. One strategy is to declare that evolution is a religion, and therefore it should not be taught in the classroom either, or that if evolution is a religion, then surely creationism as well can be taught in the classroom. [8]

In the 1980s, UC Berkeley law professor Phillip E. Johnson began reading the scientific literature on evolution. This led him to author Darwin on Trial (1991), which examined the evidence for evolution from a religious point of view and challenged the assumption that the only reasonable explanation for the origin of species must be a naturalistic one. This book, and his subsequent efforts to encourage and coordinate creationists with more scientific credentials, was the start of the intelligent design movement. Intelligent design asserts that there is evidence that life was created by an "intelligent designer" (mainly that the physical properties of living organisms are so complex that they must have been "designed"). Proponents claim that intelligent design takes "all available facts" into account rather than just those available through naturalism. Opponents assert that intelligent design is a pseudoscience because its claims cannot be tested by experiment (see falsifiability) and do not propose any new hypotheses.

Many proponents of the intelligent design movement support requiring that it be taught in the public schools. For example, the Discovery Institute (DI), a conservative think tank, [9] and Phillip E. Johnson support the policy of "Teach the Controversy," which entails presenting to students evidence for and against evolution, and then encouraging students to evaluate that evidence themselves.

While many proponents of intelligent design believe that it should be taught in schools, others believe that legislation is not appropriate. Answers in Genesis (AiG) has said:

"AiG is not a lobby group, and we oppose legislation for compulsion of creation teaching. . why would we want an atheist forced to teach creation and give a distorted view? But we would like legal protection for teachers who present scientific arguments against the sacred cow of evolution such as staged pictures of peppered moths and forged embryo diagrams." [10]

The National Science Teachers Association is opposed to teaching creationism as a science, [11] as is the Association for Science Teacher Education, [12] the National Association of Biology Teachers, [13] the American Anthropological Association, [14] the American Geosciences Institute, [15] the Geological Society of America, [16] the American Geophysical Union, [17] and numerous other professional teaching and scientific societies.

Developments by state Edit

Alabama Edit

In 1996, the Alabama State Board of Education adopted a textbook sticker that was a disclaimer about evolution. It has since been revised and moderated. [18] In September 2015, the Alabama State Board of Education unanimously approved that evolution and climate change should be required material for the state educational curriculum, these changes to be implemented by 2016. At the same time, a referendum was set for potentially removing the textbook disclaimers. [19]

Arizona Edit

In January 2013, it was approved the Arizona's Senate Bill 1213 which enabled teachers of public state schools to discuss "the scientific strengths and scientific weaknesses" of the "teaching of some scientific subjects, including biological evolution, the chemical origins of life, global warming, and human cloning can cause controversy." [20]

Arkansas Edit

In March 2021, the Arkansas House passed House Bill 1701 by a vote of 72–21, which would have allowed public schools to teach intelligent design. [21] The next month, however, the Arkansas Senate Education Committee rejected it by a vote of 3–3. [22] [23]

California Edit

In August 2008 Judge S. James Otero ruled in favor of University of California in Association of Christian Schools International v. Roman Stearns agreeing with the university's position that various religious books on U.S. history and science, from A Beka Books and Bob Jones University Press, should not be used for college-preparatory classes. [24] The case was filed in spring 2006 by Association of Christian Schools International (ACSI) against the University of California claiming religious discrimination over the rejection of five courses as college preparatory instruction. [25] On August 8, 2008, Judge Otero entered summary judgment against plaintiff ACSI, upholding the University of California's standards. [24] The university found the books "didn't encourage critical thinking skills and failed to cover 'major topics, themes and components' of U.S. history" and were thus ill-suited to prepare students for college. [24]

Florida Edit

On February 19, 2008, the Florida State Board of Education adopted new science standards in a 4-3 vote. The new science curriculum standards explicitly require the teaching of the "scientific theory of evolution," [26] whereas the previous standards only referenced evolution using the words "change over time." [27]

Georgia Edit

In 2002, six parents in Cobb County, Georgia, in the case Selman v. Cobb County School District (2006) sued to have the following sticker removed from public school textbooks:

This textbook contains material on evolution. Evolution is a theory, not a fact, regarding the origin of living things. This material should be approached with an open mind, studied carefully, and critically considered.

Approved by
Cobb County Board of Education

Thursday, March 28, 2002 [28]

Defense attorney E. Linwood Gunn IV said, "The only thing the school board did is acknowledge there is a potential conflict [between the science of evolution and creationism] and there is a potential infringement on people's beliefs if you present it in a dogmatic way. We're going to do it in a respectful way." [29] Gerald R. Weber, legal director of the ACLU of Georgia, said, "The progress of church-state cases has been that the [U.S.] Supreme Court sets a line, then government entities do what they can to skirt that line. . Here the Supreme Court has said you can't teach creationism in the public schools. You can't have an equal-time provision for evolution and creationism. These disclaimers are a new effort to skirt the line." [29] Jefferey Selman, who brought the lawsuit, claims, "It singles out evolution from all the scientific theories out there. Why single out evolution? It has to be coming from a religious basis, and that violates the separation of church and state." [30] The Cobb County Board of Education said it adopted the sticker "to foster critical thinking among students, to allow academic freedom consistent with legal requirements, to promote tolerance and acceptance of diversity of opinion, and to ensure a posture of neutrality toward religion." [31]

On January 13, 2005, a federal judge in Atlanta ruled that the stickers should be removed as they violated the Establishment Clause of the First Amendment. [28] The Board subsequently decided to appeal the decision. [32] In comments on December 15, 2005, in advance of releasing its decision, the appeal court panel appeared critical of the lower court ruling and a judge indicated that he did not understand the difference between evolution and abiogenesis. [33]

On December 19, 2006, the Board abandoned all of its legal activities and will no longer mandate that biology texts contain a sticker stating "evolution is a theory, not a fact." Their decision was a result of compromise negotiated with a group of parents, represented by the ACLU, that were opposed to the sticker. The parents agreed, as their part of the compromise, to withdraw their legal actions against the Board. [34]

Kansas Edit

On August 11, 1999, by a 6-4 vote the Kansas State Board of Education changed their science education standards to remove any mention of "biological macroevolution, the age of the Earth, or the origin and early development of the universe," so that evolutionary theory no longer appeared in statewide standardized tests and "it was left to the 305 local school districts in Kansas whether or not to teach it." [35] This decision was hailed by creationists, and sparked a statewide and nationwide controversy with scientists condemning the change. [36] Challengers in the state's Republican primary who made opposition to the anti-evolution standards their focus were voted in on August 1, 2000, so on February 14, 2001, the Board voted 7-3 to reinstate the teaching of biological evolution and the origin of the earth into the state's science education standards. [35]

In 2004, the Board elections gave religious conservatives a majority and, influenced by the Discovery Institute, they arranged the Kansas evolution hearings. On August 9, 2005, the Board drafted new "science standards that require critical analysis of evolution – including scientific evidence refuting the theory," [37] which opponents analyzed as effectively stating that intelligent design should be taught. [38] The new standards also provide a definition of science that does not preclude supernatural explanations, and were approved by a 6-4 vote on November 8, 2005—incidentally the day of the Dover Area School Board election which failed to re-elect incumbent creationists (see #Pennsylvania). [39]

In Kansas' state Republican primary elections on August 1, 2006, moderate Republicans took control away from the anti-evolution conservatives, [40] leading to an expectation that science standards which effectively embraced intelligent design and cast doubt on Darwinian evolution would now be changed. [41]

On February 13, 2007, the Board approved a new curriculum which removed any reference to intelligent design as part of science. In the words of Bill Wagnon, the Board chairman, "Today the Kansas Board of Education returned its curriculum standards to mainstream science." [42] The new curriculum, as well as a document outlining the differences with the previous curriculum, has been posted on the Kansas State Department of Education's website. [43]

In June 2013, Kansas adopted the national Next Generation Science Standards, which teaches evolution as a fundamental principle of life sciences. [44]

Kentucky Edit

In October 1999, the Kentucky Department of Education replaced the word "evolution" with "change over time" in state school standards. [45]

Louisiana Edit

On June 12, 2008, a bill (SB561) named the "Louisiana Academic Freedom Act" passed into law.

Ohio Edit

In 2002, proponents of intelligent design asked the Ohio State Board of Education to adopt intelligent design as part of its standard biology curriculum, in line with the guidelines of the Edwards v. Aguillard holding. In December 2002, the Board adopted a proposal that required critical analysis of evolution, but did not specifically mention intelligent design. This decision was reversed in February 2006 following both the conclusion of the Dover lawsuit and repeated threats of lawsuit against the Board. [46] [47]

Pennsylvania Edit

In 2004, the Dover Area School Board voted that a statement must be read to students of 9th grade biology mentioning intelligent design. This resulted in a firestorm of criticism from scientists and science teachers and caused a group of parents to begin legal proceedings (sometimes referred to as the Dover Panda Trial) to challenge the decision, based on their interpretation of the Aguillard precedent. Supporters of the school board's position noted that the Aguillard holding explicitly allowed for a variety of what they consider "scientific theories" of origins for the secular purpose of improving scientific education. Others have argued that intelligent design should not be allowed to use this "loophole." [48] On November 8, 2005, the members of the Board in Dover were voted out and replaced by evolutionary theory supporters. This had no bearing on the case. [49] On December 20, 2005, federal judge John E. Jones III ruled that the Dover Area School Board had violated the Constitution when they set their policy on teaching intelligent design, and stated that "In making this determination, we have addressed the seminal question of whether ID is science. We have concluded that it is not, and moreover that ID cannot uncouple itself from its creationist, and thus religious, antecedents." [50]

Tennessee Edit

On April 10, 2012, a bill (HB 368/SB 893) passed in protecting "teachers who explore the 'scientific strengths and scientific weaknesses' of evolution and climate change." Science education advocates said the law could make it easier for creationism and global warming denial to enter U.S. classrooms. Brenda Ekwurzel of the Union of Concerned Scientists saw it as a risk to education, quoting "We need to keep kids' curiosity about science alive and not limit their ability to understand the world around them by exposing them to misinformation." [51] The passing of the law was praised by proponents of intelligent design. [51]

Texas Edit

On November 7, 2007, the Texas Education Agency (TEA) director of science curriculum Christine Comer was forced to resign over an e-mail she had sent announcing a talk given by an anti-intelligent design author. In a memo obtained under the Texas Public Information Act, TEA officials wrote "Ms. Comer's e-mail implies endorsement of the speaker and implies that TEA endorses the speaker's position on a subject on which the agency must remain neutral." [52] In response over 100 biology professors from Texas universities signed a letter to the state education commissioner denouncing the requirement to be neutral on the subject of intelligent design. [53] The 2017 science curriculum eliminated language that openly questioned evolution, but still leaves room for teaching creationism. [54]

In July 2011, the Texas State Board of Education (SBOE), which oversees the Texas Education Agency, did not approve anti-evolution instructional materials submitted by International Databases, LLC, while continuing to approve materials from mainstream publishers. [55]

Virginia Edit

Despite proponents' urging that intelligent design be included in the school system's science curriculum, the school board of Chesterfield County Public Schools in Virginia decided on May 23, 2007, to approve science textbooks for middle and high schools which do not include the idea of intelligent design. However, during the board meeting a statement was made that their aim was self-directed learning which "occurs only when alternative views are explored and discussed," and directed that professionals supporting curriculum development and implementation are to be required "to investigate and develop processes that encompass a comprehensive approach to the teaching and learning" of the theory of evolution, "along with all other topics that raise differences of thought and opinion." During the week before the meeting, one of the intelligent design proponents claimed that "Students are being excluded from scientific debate. It's time to bring this debate into the classroom," and presented A Scientific Dissent From Darwinism. [56] [57]

In 2017, Bertha Vazquez, a middle school science teacher and director of the Teacher Institute for Evolutionary Science at the Richard Dawkins Foundation for Reason and Science, published a comparison of the nation's middle school science standards. [58] [59]

In 2000, a poll commissioned by People for the American Way found that among Americans:

  • 29% believe public schools should teach evolution in science class but can discuss creationism there as a belief
  • 20% believe public schools should teach evolution only
  • 17% believe public schools should teach evolution in science class and religious theories elsewhere
  • 16% believe public schools should teach creation only
  • 13% believe public schools should teach both evolution and creationism in science class
  • 4% believe public schools should teach both but are not sure how. [60]

In 2006, a poll conducted by Zogby International commissioned by the Discovery Institute found that more than three to one of voters surveyed chose the option that biology teachers should teach Darwin's theory of evolution, but also "the scientific evidence against it." Approximately seven in ten (69%) sided with this view. In contrast, one in five (21%) chose the other option given, that biology teachers should teach only Darwin's theory of evolution and the scientific evidence that supports it. One in ten was not sure. [61]

Teachers have also been polled. In 2019, following up on a 2007 survey, teachers reported increasing numbers of hours spent teaching evolution, and more teachers were likely to emphasize broad scientific consensus on evolution and not give credence to creationism. The results also suggested that personally creationist teachers were less likely to be represented among public high school biology teachers. Part, but not all, of the explanation involves adoption in at least twenty states of the Next Generation Science Standards. [62]

. the First Amendment does not permit the state to require that teaching and learning must be tailored to the principles or prohibitions of any religious sect or dogma. the state has no legitimate interest in protecting any or all religions from views distasteful to them. [63]

McLean v. Arkansas (1982), the judge wrote that creation scientists:

. cannot properly describe the methodology used as scientific, if they start with a conclusion and refuse to change it regardless of the evidence developed during the course of the investigation. [63]

. Because the primary purpose of the Creationism Act is to advance a particular religious belief, the Act endorses religion in violation of the First Amendment. [63]

If a teacher in a public school uses religion and teaches religious beliefs or espouses theories clearly based on religious underpinnings, the principles of the separation of church and state are violated as clearly as if a statute ordered the teacher to teach religious theories such as the statutes in Edwards did. [63]

The Supreme Court has held unequivocally that while belief in a Divine Creator of the universe is a religious belief, the scientific theory that higher forms of life evolved from lower ones is not. [63]

The proper application of both the endorsement and Lemon tests to the facts of this case makes it abundantly clear that the Board's ID Policy violates the Establishment Clause. In making this determination, we have addressed the seminal question of whether ID is science. We have concluded that it is not, and moreover that ID cannot uncouple itself from its creationist, and thus religious, antecedents. [50]


Evolution in Medicine

A recent series of article in the Proceedings of the National Academy of Sciences (PNAS) discusses the role of evolutionary biology in modern medicine. The authors collectively make a forceful point – medicine is an applied science. It is based upon a number of basic sciences, and one of those basic sciences is evolution.

The most obvious example is bacterial antibiotic resistance. Antibiotics place a selective pressure on a bacterial population, often resulting in the emergence of resistant strains. Understanding this “evolutionary arms race” between bacteria and antibiotics allows us to develop strategies for minimizing resistance.

But there are less obvious ways in which evolutionary principles apply to infectious diseases. It has been known for a long time that sickle-cell trait provides resistance to malaria (the blood cells are less hospitable to the P. falciparum protozoan parasite that is one cause of malaria). This explains the persistence of sickle cell disease in populations where malaria is endemic.

Evolutionary principles may also improve our vaccine strategy. Vaccines are another way to create selective pressures on infectious organisms. We may inadvertently target vaccines against proteins that select out less virulent strains, selecting for the more virulent or infectious strains. Understanding of this allows us to instead target vaccines against virulence without targeting less deadly strains.

An example given is the following:

The diphtheria toxoid vaccine selects against toxin production, which is what causes disease, rather than other features of Corynebacterium. Thus, diphtheria infections and clinical isolations still occur, but the extant strains lack toxin production.

The authors also provide examples of how evolutionary principles can direct future research. They reference new research looking into the role of intestinal parasites and autoimmune diseases. The research is based upon the premise that humans co-evolved not only with our intestinal flora, but with certain parasites, such as intestinal worms. Now we live in a largely hygienic environment, and have even taken steps to eliminate parasites. This may have unintentionally deprived our immune systems of needed stimulation, resulting in poor immune regulation, and subsequent increase in auto-immune diseases like asthma and multiple sclerosis.

The authors also point out that the incidence of lactose intolerance inversely correlates with the duration of dairy farming in various populations. Populations that have consumed dairy products for thousands of years have evolved the ability to produce lactase even into adulthood, while populations without dairy farming have not.

Knowledge of common descent and cladistic patterns (evolutionary relationships) also allows for the targeting of drugs at genes and gene products that are present in certain pests and parasites but not in the crops or animals they infect.

There are more examples, and collective they provide a compelling case that evolutionary principles are important to understanding populations, genetics, infectious diseasease, diet, and other issues of public health – in diagnosis, treatment, and research. Therefore, the authors argue, evolution is an important topic for medical professionals to understand, and I completely agree.

In the press release for this special issue of PNAS, they report:

Their ideas may be gaining ground. This past summer, the American Association of Medical Colleges (AAMC) and the Howard Hughes Medical Institute (HHMI) published a joint report, titled Scientific Foundations for Future Physicians. The report calls for ambitious changes in the science content in the premedical curriculum and on the Medical College Admission Test (MCAT), including increased emphasis on evolution. “For the first time, the AAMC and HHMI are recommending that evolution be one of the basic sciences students learn before they come to medical school,” Nesse explained.

(Randolph Nesse is an author on the final paper in the series.)

Increasing the basic science standards for medical students can only help the goals of science-based medicine, and I am glad to see that evolutionary biology is being recognized as the core basic science that it is.

This recognition is also not new. There is already a journal of evolution in medicine, available online as the Evolution and Medicine Review. Some of the current PNAS authors have also written about the topic previously, including this 2006 editorial in Science titled Medicine Needs Evolution.

The PNAS series is an indicator that their views are indeed taken seriously.


Watch the video: Which are the most poisonous animals? #sciencefacts #mostpoisonousanimals (September 2022).