Evolution 101
For a belief system called Evolutionary Philosophy, it is helpful to have a grounding in the principles of evolution. This topic is well covered in many other places, so here is just a reminder of a few of the basic concepts that are vital to know. Definitions are generally taken from Wikipedia, where proper sources are cited, or from some of my favorite books. If you wish to discuss your belief that evolution does not exist, please do so elsewhere. I am moving beyond that battle.
Evolution - the gradual process of change across successive generations in the heritable characteristics of biological populations.
Basic Divisions of Biology - according to the magnitude of time and space adopted for analysis, the scientific study of life is divided from bottom to top as follows: Biochemistry - the chemical processes in all living organisms; Molecular Biology - the study of biological functions at the molecular level; Cellular Biology - the study of cells at the molecular level; Organismal Biology - the study of biology at the level of a discrete individual; Sociobiology - the study of biological origins of social behavior; Ecology - the scientific study of the relationships between plants, animals, and their environment; and Evolutionary Biology - the field concerned with the origin and descent of species, as well as their change over time.
Scientific Method - a method or procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, experimentation, and the formulation, testing, and modification of hypotheses. The chief characteristic which distinguishes a scientific method of inquiry from other methods of acquiring knowledge is that scientists seek to let reality speak for itself, and contradict their theories about it when those theories are incorrect, i.e., the theories are falsifiable. Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses via predictions that can be derived from them. These steps must be repeatable, to guard against mistake or confusion in any particular experimenter. Scientific inquiry is generally intended to be as objective as possible, to reduce biased interpretations of results. Another basic expectation is to document, archive, and share all data and methodology so they are available for careful scrutiny by other scientists, giving them the opportunity to verify results by attempting to reproduce them. This practice, called full disclosure, also allows statistical measures of the reliability of these data to be established.
Trial and Error - is an experimental method of problem solving, repair, tuning, or obtaining knowledge. Learning doesn't happen from failure itself but rather from analyzing the failure, making a change, and then trying again. This approach can be seen as one of the two basic approaches to problem solving and is contrasted with an approach using insight and theory. However, there are intermediate methods that, for example, use theory to guide the method, an approach known as guided empiricism. Powerful insights may be obtained through iterative trials over several “generations” of testing. The path of evolution has been described as following blind trials where errors are discarded using the process of natural selection — a path that has lead to complex designs for life over billions of years of iterations.
On the Origin of Species - book by Charles Darwin published in November 1859 considered to be the foundation of evolutionary biology. Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection.
Experiments on Plant Hybridization - paper by Gregor Mendel published in 1866 demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance. Although the significance of Mendel's work was not recognized until the turn of the 20th century, the independent rediscovery of these laws formed the foundation of the modern science of genetics.
Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid - paper by James Watson and Francis Crick published in 1953 described the double helix structure of DNA. This article is often termed a "pearl" of science because it is brief and contains the answer to a fundamental mystery about living organisms. This mystery was the question of how it was possible that genetic instructions were held inside organisms and how they were passed from generation to generation.
Natural Selection - is the process by which biological traits become either more or less common in a population due to differences in the reproductive success of the bearers of those traits. It is a key mechanism of evolution. Variation exists within all populations of organisms. This occurs partly because random mutations cause changes in the genome of an individual organism, and these mutations can be passed to offspring. Throughout the individuals’ lives, their genomes interact with their environments to cause variations in traits. Individuals with certain variants of the trait may survive and reproduce more than individuals with other variants. Therefore the population evolves. Natural selection is one of the cornerstones of modern biology. The term was introduced by Darwin in his influential 1859 book On the Origin of Species, in which natural selection was described as analogous to artificial selection, a process by which animals and plants with traits considered desirable by human breeders are systematically favored for reproduction. Natural selection is the only known cause of adaptation, but not the only known cause of evolution. Other, non-adaptive causes of evolution include mutation and genetic drift.
Sexual Selection - is a significant element of Charles Darwin’s theory of natural selection. In his 1859 book On the Origin of Species, Darwin stated that the sexual form of selection “...depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring.” His sexual selection examples include ornate peacock feathers, birds of paradise, the antlers of stag, and the manes of lions.
Group Selection / Multilevel Selection - Group selection refers to the idea that genetic differences can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the effect on the fitness of individuals within that group. For several decades, critiques cast serious doubt on group selection as a major mechanism of evolution. Experimental results starting in the late 1970s though, demonstrated that group selection was far more effective than the then-current theoretical models had predicted. A review of this experimental work has shown that the early group selection models were flawed because they assumed that genes acted independently, whereas in the experimental work it was apparent that gene interaction, and more importantly, genetically based interactions among individuals, were an important source of the response to group selection. These newer models suggest that selection may sometimes act above the gene level. The argument rests on whether groups can have a functional organization in the same way individuals do and, consequently, whether groups can also be "vehicles" for selection. For example, groups that cooperate better may have out-reproduced those that did not. Also, individuals who do not cooperate may be punished by the group. Resurrected in this way, group selection is usually called multilevel selection theory (MLS). MLS compares the many layers of competition and evolution. The lowest level is the genes, next come the cells, and then the organism level, and finally the groups. The different levels function cohesively to maximize fitness, or reproductive success. After establishing these levels, MLS goes further by saying that selection for the group level, which is competition between groups, must outweigh the individual level, which is individuals competing within a group, for a group-beneficial trait to spread. Gene-culture coevolution is another modern hypothesis that indicates group selection. It treats culture as a separate evolutionary system that acts in parallel to the usual genetic evolution to transform human traits. It is believed that this approach of combining genetic influence with cultural influence over several generations is not present in the other hypotheses such as reciprocal altruism and kin selection, making gene-culture coevolution one of the strongest realistic hypotheses for group selection.
Mutation / Genetic Drift / Genetic Draft - Mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic chemicals, as well as errors that occur during meiosis or DNA replication. Mutation can result in several different types of change in sequences; these can either have no effect, alter the product of a gene, or prevent the gene from functioning properly or completely. Genetic drift is the change in allele frequency from one generation to the next that occurs because alleles are subject to sampling error. As a result, when selective forces are absent or relatively weak, allele frequencies tend to "drift" upward or downward randomly. This drift halts when an allele eventually becomes fixed, either by disappearing from the population, or replacing the other alleles entirely. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations that began with the same genetic structure to drift apart into two divergent populations with different sets of alleles. The time for a neutral allele to become fixed by genetic drift depends on population size, with fixation occurring more rapidly in smaller populations. Genetic draft is the process by which an allele may increase in frequency by virtue of being linked to a gene that is positively selected. Proximity on a chromosome may allow genes to be dragged along with a selective sweep experienced by an advantageous gene nearby. Whether a neutral allele becomes fixed is a matter of chance.
Gene-Environment Interaction (GxE) - GxE is the phenotypic effect of interactions between genes and the environment. Naive nature versus nurture debates assume that variation in a given trait is primarily due to either genetic variability or exposure to environmental experiences. The current scientific view is that neither genetics nor environment are solely responsible for producing individual variation, and that virtually all traits show gene–environment interaction.
Competition vs. Cooperation - Competition between members of a species is the driving force behind evolution and natural selection; the competition for resources such as food, water, territory, and sunlight results in the ultimate survival and dominance of the variant of the species best suited for survival. Competition arises whenever at least two parties strive for a goal which cannot be shared or which is desired individually but not in sharing and cooperation. It is the opposite of cooperation. Cooperation is the process of working or acting together. In its simplest form it involves things working in harmony, side by side, while in its more complicated forms, it can involve something as complex as the inner workings of a human being or even the social patterns of a nation. It is the alternative to working separately in competition. These two strategies, to compete or to cooperate, are the basic choices all living things must decide between when faced with a question of how to act.
Evolutionarily Stable Strategy (ESS) - ESS was first developed in 1973 to define a class of solutions to game theory problems, equivalent to the Nash equilibrium, which could be applied to the evolution of social behavior in animals. ESS describes a strategy that, if most members of a population adopt it, cannot be bettered by an alternative strategy. It is a strategy that does well against copies of itself. An ESS is stable, not because it is particularly good for the individuals participating in it, but simply because it is immune to treachery from within. Systems remain evolutionarily stable when cheaters do not continually win.
Tit For Tat Strategy - A very simple strategy submitted by Anatol Rapoport to a computer programming contest that evaluated competing theories in a game of Iterated Prisoner’s Dilemma (IPD). Tit For Tat cooperates on the first move, and subsequently echoes (reciprocates) what the other player did on the previous move. In his 1984 book Evolution of Cooperation, Robert Axelrod described how Tit For Tat easily won two IPD tournaments. He then went on to summarize that success in an evolutionary game correlated with the following characteristics: be nice - cooperate, never be the first to defect; be provokable - return defection for defection, cooperation for cooperation; don't be envious - be fair with your partner; don't be too clever or, don't try to be tricky.
Role of Gossip - In terms of its evolutionary psychology origins, gossip has been found to be an important means by which people can monitor cooperative reputations and so maintain widespread indirect reciprocity. Indirect reciprocity is defined here as "I help you and somebody else helps me." With the advent of the Internet, gossip is now widespread on an instant basis, from one place in the world to another. What used to take a long time to filter through is now instant. This transmission of gossip plays a large role in stopping “free riders” from spending lifetimes exploiting new relationships with unsuspecting members of society. With gossip, their reputations may precede them and their non-cooperation may be punished accordingly. Gossip also creates a bond between the teller and the hearer, as they share information of mutual interest and spend time together.
Robustness vs. Fragility - These two opposing characteristics of systems were discussed in the 2010 update to The Black Swan by Nassim Taleb. Robustness of a biological system is the persistence of a certain characteristic or trait in a system under perturbations or conditions of uncertainty. Survival in the long term requires robustness. This is why nature favors redundancies. One type is simple defensive redundancy, the insurance that allows species to survive under adversity thanks to the availability of spare parts. Nature does not do anything too big; it limits the size of its units such that the failure of any one individual does not threaten the entire species. Nature does not like too much connectivity and globalization so as to limit the effect of epidemics. Naive optimization is fragile. Overspecialization is fragile. Too big to fail is fragile. Debt is fragile. Monocultures are fragile. Another type of robust redundancy is functional, where the same functions can be performed by two different structures. The final biological redundancy is the case where an organ can be employed to perform a certain function that is not its current central one. Under epistemic limitations — some opacity concerning the future — progress and survival cannot take place without one of these types of redundancies.
Evolution - the gradual process of change across successive generations in the heritable characteristics of biological populations.
Basic Divisions of Biology - according to the magnitude of time and space adopted for analysis, the scientific study of life is divided from bottom to top as follows: Biochemistry - the chemical processes in all living organisms; Molecular Biology - the study of biological functions at the molecular level; Cellular Biology - the study of cells at the molecular level; Organismal Biology - the study of biology at the level of a discrete individual; Sociobiology - the study of biological origins of social behavior; Ecology - the scientific study of the relationships between plants, animals, and their environment; and Evolutionary Biology - the field concerned with the origin and descent of species, as well as their change over time.
Scientific Method - a method or procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, experimentation, and the formulation, testing, and modification of hypotheses. The chief characteristic which distinguishes a scientific method of inquiry from other methods of acquiring knowledge is that scientists seek to let reality speak for itself, and contradict their theories about it when those theories are incorrect, i.e., the theories are falsifiable. Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses via predictions that can be derived from them. These steps must be repeatable, to guard against mistake or confusion in any particular experimenter. Scientific inquiry is generally intended to be as objective as possible, to reduce biased interpretations of results. Another basic expectation is to document, archive, and share all data and methodology so they are available for careful scrutiny by other scientists, giving them the opportunity to verify results by attempting to reproduce them. This practice, called full disclosure, also allows statistical measures of the reliability of these data to be established.
Trial and Error - is an experimental method of problem solving, repair, tuning, or obtaining knowledge. Learning doesn't happen from failure itself but rather from analyzing the failure, making a change, and then trying again. This approach can be seen as one of the two basic approaches to problem solving and is contrasted with an approach using insight and theory. However, there are intermediate methods that, for example, use theory to guide the method, an approach known as guided empiricism. Powerful insights may be obtained through iterative trials over several “generations” of testing. The path of evolution has been described as following blind trials where errors are discarded using the process of natural selection — a path that has lead to complex designs for life over billions of years of iterations.
On the Origin of Species - book by Charles Darwin published in November 1859 considered to be the foundation of evolutionary biology. Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection.
Experiments on Plant Hybridization - paper by Gregor Mendel published in 1866 demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance. Although the significance of Mendel's work was not recognized until the turn of the 20th century, the independent rediscovery of these laws formed the foundation of the modern science of genetics.
Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid - paper by James Watson and Francis Crick published in 1953 described the double helix structure of DNA. This article is often termed a "pearl" of science because it is brief and contains the answer to a fundamental mystery about living organisms. This mystery was the question of how it was possible that genetic instructions were held inside organisms and how they were passed from generation to generation.
Natural Selection - is the process by which biological traits become either more or less common in a population due to differences in the reproductive success of the bearers of those traits. It is a key mechanism of evolution. Variation exists within all populations of organisms. This occurs partly because random mutations cause changes in the genome of an individual organism, and these mutations can be passed to offspring. Throughout the individuals’ lives, their genomes interact with their environments to cause variations in traits. Individuals with certain variants of the trait may survive and reproduce more than individuals with other variants. Therefore the population evolves. Natural selection is one of the cornerstones of modern biology. The term was introduced by Darwin in his influential 1859 book On the Origin of Species, in which natural selection was described as analogous to artificial selection, a process by which animals and plants with traits considered desirable by human breeders are systematically favored for reproduction. Natural selection is the only known cause of adaptation, but not the only known cause of evolution. Other, non-adaptive causes of evolution include mutation and genetic drift.
Sexual Selection - is a significant element of Charles Darwin’s theory of natural selection. In his 1859 book On the Origin of Species, Darwin stated that the sexual form of selection “...depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring.” His sexual selection examples include ornate peacock feathers, birds of paradise, the antlers of stag, and the manes of lions.
Group Selection / Multilevel Selection - Group selection refers to the idea that genetic differences can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the effect on the fitness of individuals within that group. For several decades, critiques cast serious doubt on group selection as a major mechanism of evolution. Experimental results starting in the late 1970s though, demonstrated that group selection was far more effective than the then-current theoretical models had predicted. A review of this experimental work has shown that the early group selection models were flawed because they assumed that genes acted independently, whereas in the experimental work it was apparent that gene interaction, and more importantly, genetically based interactions among individuals, were an important source of the response to group selection. These newer models suggest that selection may sometimes act above the gene level. The argument rests on whether groups can have a functional organization in the same way individuals do and, consequently, whether groups can also be "vehicles" for selection. For example, groups that cooperate better may have out-reproduced those that did not. Also, individuals who do not cooperate may be punished by the group. Resurrected in this way, group selection is usually called multilevel selection theory (MLS). MLS compares the many layers of competition and evolution. The lowest level is the genes, next come the cells, and then the organism level, and finally the groups. The different levels function cohesively to maximize fitness, or reproductive success. After establishing these levels, MLS goes further by saying that selection for the group level, which is competition between groups, must outweigh the individual level, which is individuals competing within a group, for a group-beneficial trait to spread. Gene-culture coevolution is another modern hypothesis that indicates group selection. It treats culture as a separate evolutionary system that acts in parallel to the usual genetic evolution to transform human traits. It is believed that this approach of combining genetic influence with cultural influence over several generations is not present in the other hypotheses such as reciprocal altruism and kin selection, making gene-culture coevolution one of the strongest realistic hypotheses for group selection.
Mutation / Genetic Drift / Genetic Draft - Mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic chemicals, as well as errors that occur during meiosis or DNA replication. Mutation can result in several different types of change in sequences; these can either have no effect, alter the product of a gene, or prevent the gene from functioning properly or completely. Genetic drift is the change in allele frequency from one generation to the next that occurs because alleles are subject to sampling error. As a result, when selective forces are absent or relatively weak, allele frequencies tend to "drift" upward or downward randomly. This drift halts when an allele eventually becomes fixed, either by disappearing from the population, or replacing the other alleles entirely. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations that began with the same genetic structure to drift apart into two divergent populations with different sets of alleles. The time for a neutral allele to become fixed by genetic drift depends on population size, with fixation occurring more rapidly in smaller populations. Genetic draft is the process by which an allele may increase in frequency by virtue of being linked to a gene that is positively selected. Proximity on a chromosome may allow genes to be dragged along with a selective sweep experienced by an advantageous gene nearby. Whether a neutral allele becomes fixed is a matter of chance.
Gene-Environment Interaction (GxE) - GxE is the phenotypic effect of interactions between genes and the environment. Naive nature versus nurture debates assume that variation in a given trait is primarily due to either genetic variability or exposure to environmental experiences. The current scientific view is that neither genetics nor environment are solely responsible for producing individual variation, and that virtually all traits show gene–environment interaction.
Competition vs. Cooperation - Competition between members of a species is the driving force behind evolution and natural selection; the competition for resources such as food, water, territory, and sunlight results in the ultimate survival and dominance of the variant of the species best suited for survival. Competition arises whenever at least two parties strive for a goal which cannot be shared or which is desired individually but not in sharing and cooperation. It is the opposite of cooperation. Cooperation is the process of working or acting together. In its simplest form it involves things working in harmony, side by side, while in its more complicated forms, it can involve something as complex as the inner workings of a human being or even the social patterns of a nation. It is the alternative to working separately in competition. These two strategies, to compete or to cooperate, are the basic choices all living things must decide between when faced with a question of how to act.
Evolutionarily Stable Strategy (ESS) - ESS was first developed in 1973 to define a class of solutions to game theory problems, equivalent to the Nash equilibrium, which could be applied to the evolution of social behavior in animals. ESS describes a strategy that, if most members of a population adopt it, cannot be bettered by an alternative strategy. It is a strategy that does well against copies of itself. An ESS is stable, not because it is particularly good for the individuals participating in it, but simply because it is immune to treachery from within. Systems remain evolutionarily stable when cheaters do not continually win.
Tit For Tat Strategy - A very simple strategy submitted by Anatol Rapoport to a computer programming contest that evaluated competing theories in a game of Iterated Prisoner’s Dilemma (IPD). Tit For Tat cooperates on the first move, and subsequently echoes (reciprocates) what the other player did on the previous move. In his 1984 book Evolution of Cooperation, Robert Axelrod described how Tit For Tat easily won two IPD tournaments. He then went on to summarize that success in an evolutionary game correlated with the following characteristics: be nice - cooperate, never be the first to defect; be provokable - return defection for defection, cooperation for cooperation; don't be envious - be fair with your partner; don't be too clever or, don't try to be tricky.
Role of Gossip - In terms of its evolutionary psychology origins, gossip has been found to be an important means by which people can monitor cooperative reputations and so maintain widespread indirect reciprocity. Indirect reciprocity is defined here as "I help you and somebody else helps me." With the advent of the Internet, gossip is now widespread on an instant basis, from one place in the world to another. What used to take a long time to filter through is now instant. This transmission of gossip plays a large role in stopping “free riders” from spending lifetimes exploiting new relationships with unsuspecting members of society. With gossip, their reputations may precede them and their non-cooperation may be punished accordingly. Gossip also creates a bond between the teller and the hearer, as they share information of mutual interest and spend time together.
Robustness vs. Fragility - These two opposing characteristics of systems were discussed in the 2010 update to The Black Swan by Nassim Taleb. Robustness of a biological system is the persistence of a certain characteristic or trait in a system under perturbations or conditions of uncertainty. Survival in the long term requires robustness. This is why nature favors redundancies. One type is simple defensive redundancy, the insurance that allows species to survive under adversity thanks to the availability of spare parts. Nature does not do anything too big; it limits the size of its units such that the failure of any one individual does not threaten the entire species. Nature does not like too much connectivity and globalization so as to limit the effect of epidemics. Naive optimization is fragile. Overspecialization is fragile. Too big to fail is fragile. Debt is fragile. Monocultures are fragile. Another type of robust redundancy is functional, where the same functions can be performed by two different structures. The final biological redundancy is the case where an organ can be employed to perform a certain function that is not its current central one. Under epistemic limitations — some opacity concerning the future — progress and survival cannot take place without one of these types of redundancies.
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© 2012 Ed Gibney
