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116-756: The book was reviewed many times, both positively and negatively, by biologists, anthropologists, psychoanalysts and others. Much criticism was directed at Lorenz's extension of his findings on non-human animals to humans. On Aggression was first published in German in 1963, and in English in 1966. It has been reprinted many times and translated into at least 12 languages. According to Lorenz, animals, particularly males, are biologically programmed to fight over resources. This behavior must be considered part of natural selection , as aggression leading to death or serious injury may eventually lead to extinction unless it has such

232-612: A predator on its prey rather than the kind of intraspecific aggression seen in nonhuman animals which is strictly limited. Driver concluded that ethology could contribute, alongside neurophysiology and psychology , to resolving the problem of conflict. The zoologists Richard D. Alexander and Donald W. Tinkle, comparing On Aggression with Ardrey's The Territorial Imperative in BioScience in 1968, noted that few books had been reviewed so often "or with as much vehemence in both defense and derogation" as these two. In their view, this

348-420: A synonymous substitution . However, many mutations in non-coding DNA have deleterious effects. Although both mutation rates and average fitness effects of mutations are dependent on the organism, a majority of mutations in humans are slightly deleterious. Some mutations occur in "toolkit" or regulatory genes . Changes in these often have large effects on the phenotype of the individual because they regulate

464-449: A " hydraulic " model of emotional or instinctive pressures and their release, shared by Freud 's psychoanalytic theory , and the abnormality of intraspecies violence and killing. Lorenz claimed that "present-day civilized man suffers from insufficient discharge of his aggressive drive" and suggested that low levels of aggressive behaviour prevented higher level responses resulting from "damming" them. His 'hydraulic' model, of aggression as

580-535: A "'good of the species' man". He criticises On Aggression for its "gem of a circular argument " that aggressive behaviour has a "species preserving" function, namely to ensure "that only the fittest individuals are allowed to breed". In Dawkins's view, the idea of group selection was "so deeply ingrained" in Lorenz's thinking that he "evidently did not realize that his statements contravened orthodox Darwinian theory ." Natural selection Natural selection

696-457: A "Nature" which would do the selection. At the time, other mechanisms of evolution such as evolution by genetic drift were not yet explicitly formulated, and Darwin believed that selection was likely only part of the story: "I am convinced that Natural Selection has been the main but not exclusive means of modification." In a letter to Charles Lyell in September 1860, Darwin regretted the use of

812-729: A 'recent' selective sweep near the centre of the block. Background selection is the opposite of a selective sweep. If a specific site experiences strong and persistent purifying selection, linked variation tends to be weeded out along with it, producing a region in the genome of low overall variability. Because background selection is a result of deleterious new mutations, which can occur randomly in any haplotype, it does not produce clear blocks of linkage disequilibrium, although with low recombination it can still lead to slightly negative linkage disequilibrium overall. Solly Zuckerman Solomon " Solly " Zuckerman, Baron Zuckerman OM KCB FRS (30 May 1904 – 1 April 1993)

928-400: A better explanation than Freud's opposed passions, the supposed drives for life (eros) and death or destruction (thanatos). However, Fromm noted that the ethologist Nico Tinbergen had rejected the hydraulic theory, and that Lorenz himself "modified it" in 1966, but without indicating that in the English translation of On Aggression . Fromm cites evidence from neuroscience that aggression

1044-519: A chromosome. During the formation of gametes, recombination reshuffles the alleles. The chance that such a reshuffle occurs between two alleles is inversely related to the distance between them. Selective sweeps occur when an allele becomes more common in a population as a result of positive selection. As the prevalence of one allele increases, closely linked alleles can also become more common by " genetic hitchhiking ", whether they are neutral or even slightly deleterious. A strong selective sweep results in

1160-554: A different, incompatible allele of the same gene. Selection against the heterozygote would then directly create reproductive isolation, leading to the Bateson–Dobzhansky–Muller model , further elaborated by H. Allen Orr and Sergey Gavrilets . With reinforcement , however, natural selection can favor an increase in pre-zygotic isolation, influencing the process of speciation directly. Natural selection acts on an organism's phenotype, or physical characteristics. Phenotype

1276-450: A force that builds relentlessly without cause unless released, remains less popular than a model in which aggression is a response to frustrated desires and aims. In the book, Lorenz describes the development of rituals among aggressive behaviors as beginning with a totally utilitarian action, but then evolving to more and more stylized actions, until finally, the action performed may be entirely symbolic and non-utilitarian, now fulfilling

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1392-462: A function of communication. In Lorenz's words: Thus while the message of inciting [a particular aggressive behavior performed by the female of cooperating mated pairs] in ruddy shelduck and Egyptian geese could be expressed in the words 'Drive him off, thrash him!', in diving ducks [a related species in which this trait has been further ritualized] it simply means, 'I love you.' In several groups, midway between these two extremes, as for example in

1508-474: A letter written to his wife Joan in 1993, shortly after Zuckerman died in London following a heart attack , aged 88: No doubt he was a strain as a husband, even as a father, but what a wonder he was in himself. The tirelessly inquiring mind, the energy for work, the variety of his thinking. As he grew old, his vanity was touching, as if he didn't really know his own unique value and he had to reassure himself with

1624-665: A member of a Royal Commission investigating environmental pollution from 26 February 1970. In 1951 Zuckerman published his paper summarizing the existing data both for and against the possibility of postnatal oogenesis . He taught at the University of East Anglia from 1969 to 1974, where he was involved in setting up a school of environmental sciences. He served as Secretary of the London Zoological Society from 1955 to 1977 and as its president from 1977 to 1984. Some of Zuckerman's achievements include being

1740-407: A number of other species." Fischer found Lorenz's account of nonhuman animals at the start of the book, written from Lorenz's own experience, "the most convincing and enlightening". Fischer noted that Lorenz acknowledges the role of culture in human life but that he perhaps underrated its effects on individual development. Fischer argued that Lorenz's view of the instinctive nature of human aggression

1856-575: A pioneer in the study of primate behaviour. His more notable publications include The Social Life of Monkeys and Apes published in 1931, and Scientists and War in 1966. Zuckerman wrote two volumes of autobiography: From Apes to Warlords and Monkeys Men and Missiles . He is also credited for making science a normal part of government policy in the Western world and wrote many articles on this topic, including some formal lectures, collected in Beyond

1972-479: A precursor to speciation . Alternatively, selection can be divided according to its effect on genetic diversity . Purifying or negative selection acts to remove genetic variation from the population (and is opposed by de novo mutation , which introduces new variation. In contrast, balancing selection acts to maintain genetic variation in a population, even in the absence of de novo mutation, by negative frequency-dependent selection . One mechanism for this

2088-429: A process by which animals and plants with traits considered desirable by human breeders are systematically favoured for reproduction. The concept of natural selection originally developed in the absence of a valid theory of heredity; at the time of Darwin's writing, science had yet to develop modern theories of genetics. The union of traditional Darwinian evolution with subsequent discoveries in classical genetics formed

2204-441: A region of the genome where the positively selected haplotype (the allele and its neighbours) are in essence the only ones that exist in the population. Selective sweeps can be detected by measuring linkage disequilibrium , or whether a given haplotype is overrepresented in the population. Since a selective sweep also results in selection of neighbouring alleles, the presence of a block of strong linkage disequilibrium might indicate

2320-430: A relatively high probability of surviving to adulthood. Natural selection can act on any heritable phenotypic trait , and selective pressure can be produced by any aspect of the environment, including sexual selection and competition with members of the same or other species. However, this does not imply that natural selection is always directional and results in adaptive evolution; natural selection often results in

2436-458: A reproductive advantage regardless of whether or not the trait is heritable. Following Darwin's primary usage, the term is used to refer both to the evolutionary consequence of blind selection and to its mechanisms. It is sometimes helpful to explicitly distinguish between selection's mechanisms and its effects; when this distinction is important, scientists define "(phenotypic) natural selection" specifically as "those mechanisms that contribute to

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2552-450: A role. However, Lorenz does not state that aggressive behaviors are in any way more powerful, prevalent, or intense than more peaceful behaviors such as mating rituals. Rather, he negates the categorization of aggression as "contrary" to "positive" instincts like love , depicting it as a founding basis of other instincts and its role in animal communication . Additionally, Lorenz addresses behavior in humans, including discussion of

2668-454: A species were uninteresting departures from their Platonic ideals (or typus ) of created kinds . However, the theory of uniformitarianism in geology promoted the idea that simple, weak forces could act continuously over long periods of time to produce radical changes in the Earth's landscape. The success of this theory raised awareness of the vast scale of geological time and made plausible

2784-490: A variety of aggression categories, each separately subject to natural selection , and states that aggressive behavior is, genetically, one of the most labile of all traits. He maintains that aggression is a technique used to gain control over necessary resources, and serves as a " density-dependent factor" in population control. He argues against the "drive-discharge" model created by Freud and Lorenz, where substitute aggressive activities (such as combative sports) should reduce

2900-483: A well-documented example involves the spread of a gene in the butterfly Hypolimnas bolina suppressing male-killing activity by Wolbachia bacteria parasites on the island of Samoa , where the spread of the gene is known to have occurred over a period of just five years. A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation is the presence of heritable genetic variation that results in fitness differences. Genetic variation

3016-532: Is heterozygote advantage , where individuals with two different alleles have a selective advantage over individuals with just one allele. The polymorphism at the human ABO blood group locus has been explained in this way. Another option is to classify selection by the life cycle stage at which it acts. Some biologists recognise just two types: viability (or survival) selection , which acts to increase an organism's probability of survival, and fecundity (or fertility or reproductive) selection, which acts to increase

3132-469: Is "essentially defensive", arising in "phylogenetically programed brain areas" for fight or flight when an animal or person feels threatened. Fromm points out that "self-propelling aggressiveness" is seen in people with brain disease, but not in "normal brain functioning". The biologist E. O. Wilson , in On Human Nature (1978), argues that both Lorenz and Fromm are essentially wrong. He lists

3248-405: Is all the parts of one whole) happened like as if they were made for the sake of something, these were preserved, having been appropriately constituted by an internal spontaneity, and whatsoever things were not thus constituted, perished, and still perish. But Aristotle rejected this possibility in the next paragraph, making clear that he is talking about the development of animals as embryos with

3364-500: Is central to natural selection. In broad terms, individuals that are more "fit" have better potential for survival, as in the well-known phrase " survival of the fittest ", but the precise meaning of the term is much more subtle. Modern evolutionary theory defines fitness not by how long an organism lives, but by how successful it is at reproducing. If an organism lives half as long as others of its species, but has twice as many offspring surviving to adulthood, its genes become more common in

3480-455: Is determined by an organism's genetic make-up (genotype) and the environment in which the organism lives. When different organisms in a population possess different versions of a gene for a certain trait, each of these versions is known as an allele . It is this genetic variation that underlies differences in phenotype. An example is the ABO blood type antigens in humans, where three alleles govern

3596-456: Is increased, which means that it leaves more offspring. If the traits that give these individuals a reproductive advantage are also heritable , that is, passed from parent to offspring, then there will be differential reproduction, that is, a slightly higher proportion of fast rabbits or efficient algae in the next generation. Even if the reproductive advantage is very slight, over many generations any advantageous heritable trait becomes dominant in

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3712-438: Is intrinsic to the concept of a species that hybrids are selected against, opposing the evolution of reproductive isolation, a problem that was recognised by Darwin. The problem does not occur in allopatric speciation with geographically separated populations, which can diverge with different sets of mutations. E. B. Poulton realized in 1903 that reproductive isolation could evolve through divergence, if each lineage acquired

3828-663: Is known as fecundity selection . Natural selection is a cornerstone of modern biology . The concept, published by Darwin and Alfred Russel Wallace in a joint presentation of papers in 1858 , was elaborated in Darwin's influential 1859 book On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life . He described natural selection as analogous to artificial selection,

3944-483: Is lowered by the presence of another. This may be because both rely on a limited supply of a resource such as food, water, or territory . Competition may be within or between species , and may be direct or indirect. Species less suited to compete should in theory either adapt or die out , since competition plays a powerful role in natural selection, but according to the "room to roam" theory it may be less important than expansion among larger clades . Competition

4060-555: Is modelled by r/K selection theory , which is based on Robert MacArthur and E. O. Wilson 's work on island biogeography . In this theory, selective pressures drive evolution in one of two stereotyped directions: r - or K -selection. These terms, r and K , can be illustrated in a logistic model of population dynamics : d N d t = r N ( 1 − N K ) {\displaystyle {\frac {dN}{dt}}=rN\left(1-{\frac {N}{K}}\right)\qquad \!} where r

4176-461: Is natural selection via any means other than sexual selection, such as kin selection, competition, and infanticide . Following Darwin, natural selection is sometimes defined as ecological selection, in which case sexual selection is considered a separate mechanism. Sexual selection as first articulated by Darwin (using the example of the peacock 's tail) refers specifically to competition for mates, which can be intrasexual , between individuals of

4292-568: Is only a 'so-called evil' and that its adaptive consequences are advantageous or at least neutral." Leach is however less sure that Lorenz is correct to equate animal and human aggression, the one taking standard ritualized forms, the other far more complex. The mental health researcher Peter M. Driver reviewed the book in Conflict Resolution in 1967 alongside two by Ardrey and one by Claire Russell and W. M. S. Russell, Human Behavior – A New Approach . He commented that those against

4408-410: Is selection favoring extreme trait values over intermediate trait values. Disruptive selection may cause sympatric speciation through niche partitioning . Some forms of balancing selection do not result in fixation, but maintain an allele at intermediate frequencies in a population. This can occur in diploid species (with pairs of chromosomes) when heterozygous individuals (with just one copy of

4524-412: Is slowed by the competition. The variant which is a candidate for a beneficial mutation in this limited carrying capacity environment must first out-compete the "less fit" variants in order to accumulate the requisite number of replications for there to be a reasonable probability of that beneficial mutation occurring. In biology, competition is an interaction between organisms in which the fitness of one

4640-461: Is still often used by non-biologists, modern biologists avoid it because it is tautological if "fittest" is read to mean "functionally superior" and is applied to individuals rather than considered as an averaged quantity over populations. Natural selection relies crucially on the idea of heredity, but developed before the basic concepts of genetics . Although the Moravian monk Gregor Mendel ,

4756-405: Is the growth rate of the population ( N ), and K is the carrying capacity of its local environmental setting. Typically, r -selected species exploit empty niches , and produce many offspring, each with a relatively low probability of surviving to adulthood. In contrast, K -selected species are strong competitors in crowded niches, and invest more heavily in much fewer offspring, each with

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4872-611: Is the differential survival and reproduction of individuals due to differences in phenotype . It is a key mechanism of evolution , the change in the heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with artificial selection , which is intentional, whereas natural selection is not. Variation of traits, both genotypic and phenotypic , exists within all populations of organisms . However, some traits are more likely to facilitate survival and reproductive success . Thus, these traits are passed onto

4988-435: Is the result of mutations, genetic recombinations and alterations in the karyotype (the number, shape, size and internal arrangement of the chromosomes ). Any of these changes might have an effect that is highly advantageous or highly disadvantageous, but large effects are rare. In the past, most changes in the genetic material were considered neutral or close to neutral because they occurred in noncoding DNA or resulted in

5104-474: The Industrial Revolution , many of the trees on which the moths rested became blackened by soot , giving the dark-coloured moths an advantage in hiding from predators. This gave dark-coloured moths a better chance of surviving to produce dark-coloured offspring, and in just fifty years from the first dark moth being caught, nearly all of the moths in industrial Manchester were dark. The balance

5220-441: The London Zoological Society in 1928, and worked as a research anatomist until 1932. In this period he founded the intellectual dining club, Tots and Quots . He denied, as early as 1928, that Australopithecus was a genealogical link between apes and humans and maintained this belief throughout his career. In 1932, Zuckerman published his most noteworthy pre-war work, Social Life of Monkeys and Apes . Zuckerman taught at

5336-551: The Roman poet Lucretius , expressed the idea that nature produces a huge variety of creatures, randomly, and that only those creatures that manage to provide for themselves and reproduce successfully persist. Empedocles' idea that organisms arose entirely by the incidental workings of causes such as heat and cold was criticised by Aristotle in Book II of Physics . He posited natural teleology in its place, and believed that form

5452-688: The Transportation Plan , but was privately referred to by its opponents as "Zuckerman's Folly". A focus of Zuckerman's plan, learned in Italy, was to target locomotives and the capacity to service them due to a shortage in France prior to the Normandy campaign. This had the effect of pushing railheads back from the front causing trucks to be diverted from a role of manoeuvre to one of logistics, which resulted in greater petrol consumption. After

5568-644: The University of Oxford from 1934 to 1945, during which time he was elected to a Fellowship of the Royal Society . During the Second World War, Zuckerman worked on several research projects for the British government, including the design of a civilian defence helmet (colloquially known as the Zuckerman helmet ) and measuring the effect of bombing on people and buildings and an assessment of

5684-524: The founder effect in initially small new populations. When genetic variation does not result in differences in fitness, selection cannot directly affect the frequency of such variation. As a result, the genetic variation at those sites is higher than at sites where variation does influence fitness. However, after a period with no new mutations, the genetic variation at these sites is eliminated due to genetic drift. Natural selection reduces genetic variation by eliminating maladapted individuals, and consequently

5800-518: The gadwall and wigeon , an intermediate meaning may be found, 'You are my hero. I rely on you.' J. L. Fischer, reviewing On Aggression in American Anthropologist in 1968, called it a "fascinating book by a distinguished animal ethologist" that would "annoy most social and cultural anthropologists" but nonetheless stated "an important thesis", namely that intraspecific aggression was "instinctive in man, as it can be shown to be in

5916-434: The genetic regulatory programs which control the development of the embryo at molecular level. Natural selection is here understood to act on embryonic development to change the morphology of the adult body. The term natural selection is most often defined to operate on heritable traits, because these directly participate in evolution. However, natural selection is "blind" in the sense that changes in phenotype can give

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6032-424: The modern synthesis of the mid-20th century. The addition of molecular genetics has led to evolutionary developmental biology , which explains evolution at the molecular level. While genotypes can slowly change by random genetic drift , natural selection remains the primary explanation for adaptive evolution . Several philosophers of the classical era , including Empedocles and his intellectual successor,

6148-468: The "principle by which each slight variation [of a trait], if useful, is preserved". The concept was simple but powerful: individuals best adapted to their environments are more likely to survive and reproduce. As long as there is some variation between them and that variation is heritable , there will be an inevitable selection of individuals with the most advantageous variations. If the variations are heritable, then differential reproductive success leads to

6264-496: The "upper power" but instead are generated in different forms naturally and then selected for reproduction by their compatibility with the environment. The more recent classical arguments were reintroduced in the 18th century by Pierre Louis Maupertuis and others, including Darwin's grandfather, Erasmus Darwin . Until the early 19th century, the prevailing view in Western societies was that differences between individuals of

6380-491: The Ivory Tower . There Zuckerman wrote about the role of science in policy, and how it developed in public (i.e. large funded collaborations) and in private (i.e. behind closed doors in laboratories). He was concerned that the public should understand the contested and serendipitous process of scientific discovery, in contrast to the discovery accounts which were popular, illustrating with hoax and eminent disagreements, at

6496-433: The Origin of Species (1942). W. D. Hamilton conceived of kin selection in 1964. This synthesis cemented natural selection as the foundation of evolutionary theory, where it remains today. A second synthesis was brought about at the end of the 20th century by advances in molecular genetics , creating the field of evolutionary developmental biology ("evo-devo"), which seeks to explain the evolution of form in terms of

6612-441: The adult population of the next generation. Though natural selection acts on individuals, the effects of chance mean that fitness can only really be defined "on average" for the individuals within a population. The fitness of a particular genotype corresponds to the average effect on all individuals with that genotype. A distinction must be made between the concept of "survival of the fittest" and "improvement in fitness". "Survival of

6728-551: The allele is fixed and the entire population shares the fitter phenotype. Far more common is stabilizing selection, which lowers the frequency of alleles that have a deleterious effect on the phenotype—that is, produce organisms of lower fitness. This process can continue until the allele is eliminated from the population. Stabilizing selection conserves functional genetic features, such as protein-coding genes or regulatory sequences , over time by selective pressure against deleterious variants. Disruptive (or diversifying) selection

6844-427: The allele) have a higher fitness than homozygous individuals (with two copies). This is called heterozygote advantage or over-dominance, of which the best-known example is the resistance to malaria in humans heterozygous for sickle-cell anaemia . Maintenance of allelic variation can also occur through disruptive or diversifying selection , which favours genotypes that depart from the average in either direction (that is,

6960-544: The antlers of stags , which are used in combat with other stags. More generally, intrasexual selection is often associated with sexual dimorphism , including differences in body size between males and females of a species. Natural selection is seen in action in the development of antibiotic resistance in microorganisms . Since the discovery of penicillin in 1928, antibiotics have been used to fight bacterial diseases. The widespread misuse of antibiotics has selected for microbial resistance to antibiotics in clinical use, to

7076-404: The apparently vestigial structure may retain a limited functionality, or may be co-opted for other advantageous traits in a phenomenon known as preadaptation . A famous example of a vestigial structure, the eye of the blind mole-rat , is believed to retain function in photoperiod perception. Speciation requires a degree of reproductive isolation —that is, a reduction in gene flow. However, it

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7192-442: The assumption that groups replicate and mutate in an analogous way to genes and individuals. There is an ongoing debate over the degree to which group selection occurs in nature. Finally, selection can be classified according to the resource being competed for. Sexual selection results from competition for mates. Sexual selection typically proceeds via fecundity selection, sometimes at the expense of viability. Ecological selection

7308-450: The best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will tend to produce offspring similarly characterised. This principle of preservation, I have called, for the sake of brevity, Natural Selection. Once he had his theory, Darwin was meticulous about gathering and refining evidence before making his idea public. He was in the process of writing his "big book" to present his research when

7424-595: The bombardment ( Operation Corkscrew ) of the Italian island of Pantelleria in 1943. He was thus one of the pioneers of the science of operational research . He was given an honorary commission as a wing commander in the Administrative and Special Duties Branch of the Royal Air Force on 13 May 1943, and promoted to honorary group captain on 20 September 1943. Zuckerman's suggestion, made when he

7540-423: The book, especially S. A. Barnett, T. C. Schneirla , and Solly Zuckerman , were specialists in animal behaviour, while most of the favourable reviews came from "experts in other fields". Driver stated that Lorenz had provided a "powerful thesis" to explain the "aggression gone wrong" in humans, mentioning the millions of deaths in world wars, aggression resembling (Driver argued) the unlimited interspecific attack of

7656-476: The concept of the "cost" of natural selection. Sewall Wright elucidated the nature of selection and adaptation. In his book Genetics and the Origin of Species (1937), Theodosius Dobzhansky established the idea that mutation, once seen as a rival to selection, actually supplied the raw material for natural selection by creating genetic diversity. Ernst Mayr recognised the key importance of reproductive isolation for speciation in his Systematics and

7772-434: The different alleles, or variants of the gene that produces the variants of the trait. Selection can be divided into three classes, on the basis of its effect on allele frequencies: directional , stabilizing , and disruptive selection . Directional selection occurs when an allele has a greater fitness than others, so that it increases in frequency, gaining an increasing share in the population. This process can continue until

7888-458: The dog-days, but only if we have it in winter. If then, it is agreed that things are either the result of coincidence or for an end, and these cannot be the result of coincidence or spontaneity, it follows that they must be for an end; and that such things are all due to nature even the champions of the theory which is before us would agree. Therefore action for an end is present in things which come to be and are by nature. The struggle for existence

8004-579: The evolution of particular populations of a species, and populations that evolve to be sufficiently different eventually become different species. Darwin's ideas were inspired by the observations that he had made on the second voyage of HMS Beagle (1831–1836), and by the work of a political economist, Thomas Robert Malthus , who, in An Essay on the Principle of Population (1798), noted that population (if unchecked) increases exponentially , whereas

8120-399: The extravagant plumage of some male birds such as the peacock. An alternate theory proposed by the same Ronald Fisher in 1930 is the sexy son hypothesis , that mothers want promiscuous sons to give them large numbers of grandchildren and so choose promiscuous fathers for their children. Aggression between members of the same sex is sometimes associated with very distinctive features, such as

8236-512: The father of modern genetics, was a contemporary of Darwin's, his work lay in obscurity, only being rediscovered in 1900. With the early 20th-century integration of evolution with Mendel's laws of inheritance, the so-called modern synthesis , scientists generally came to accept natural selection. The synthesis grew from advances in different fields. Ronald Fisher developed the required mathematical language and wrote The Genetical Theory of Natural Selection (1930). J. B. S. Haldane introduced

8352-473: The fittest" does not give an "improvement in fitness", it only represents the removal of the less fit variants from a population. A mathematical example of "survival of the fittest" is given by Haldane in his paper "The Cost of Natural Selection". Haldane called this process "substitution" or more commonly in biology, this is called "fixation". This is correctly described by the differential survival and reproduction of individuals due to differences in phenotype. On

8468-472: The food supply grows only arithmetically ; thus, inevitable limitations of resources would have demographic implications, leading to a "struggle for existence". When Darwin read Malthus in 1838 he was already primed by his work as a naturalist to appreciate the "struggle for existence" in nature. It struck him that as population outgrew resources, "favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be

8584-421: The formation of new species." Darwin wrote: If during the long course of ages and under varying conditions of life, organic beings vary at all in the several parts of their organisation, and I think this cannot be disputed; if there be, owing to the high geometrical powers of increase of each species, at some age, season, or year, a severe struggle for life, and this certainly cannot be disputed; then, considering

8700-494: The frontiers of science, because ultimately science ought to serve the public. This led to a concern about the policy for investing in science, or Foresight , which could not, in his view, expect to know what scientific discovery was likely to occur, and therefore how to choose projects for funding. He also advanced the case for engineers and other scientists to adopt an oath, similar to the Hippocratic Oath , to consider

8816-453: The function of many other genes. Most, but not all, mutations in regulatory genes result in non-viable embryos. Some nonlethal regulatory mutations occur in HOX genes in humans, which can result in a cervical rib or polydactyly , an increase in the number of fingers or toes. When such mutations result in a higher fitness, natural selection favours these phenotypes and the novel trait spreads in

8932-487: The idea that tiny, virtually imperceptible changes in successive generations could produce consequences on the scale of differences between species. The early 19th-century zoologist Jean-Baptiste Lamarck suggested the inheritance of acquired characteristics as a mechanism for evolutionary change; adaptive traits acquired by an organism during its lifetime could be inherited by that organism's progeny, eventually causing transmutation of species . This theory, Lamarckism ,

9048-722: The impacts of their work and avoid damaging the world, particularly the natural environment. Zuckerman was knighted in the 1956 New Year Honours , promoted Knight Commander of the Order of the Bath in the 1964 New Year Honours , elected to the American Philosophical Society in 1965, appointed to the Order of Merit on 23 April 1968, elected to the American Academy of Arts and Sciences in 1970, and

9164-502: The infinite complexity of the relations of all organic beings to each other and to their conditions of existence, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, I think it would be a most extraordinary fact if no variation ever had occurred useful to each being's own welfare, in the same way as so many variations have occurred useful to man. But if variations useful to any organic being do occur, assuredly individuals thus characterised will have

9280-444: The level or unit of selection . Individual selection acts on the individual, in the sense that adaptations are "for" the benefit of the individual, and result from selection among individuals. Gene selection acts directly at the level of the gene. In kin selection and intragenomic conflict , gene-level selection provides a more apt explanation of the underlying process. Group selection , if it occurs, acts on groups of organisms, on

9396-403: The maintenance of the status quo by eliminating less fit variants. Selection can be classified in several different ways, such as by its effect on a trait, on genetic diversity, by the life cycle stage where it acts, by the unit of selection, or by the resource being competed for. Selection has different effects on traits. Stabilizing selection acts to hold a trait at a stable optimum, and in

9512-406: The mutations that caused the maladaptation. At the same time, new mutations occur, resulting in a mutation–selection balance . The exact outcome of the two processes depends both on the rate at which new mutations occur and on the strength of the natural selection, which is a function of how unfavourable the mutation proves to be. Genetic linkage occurs when the loci of two alleles are close on

9628-546: The naturalist Alfred Russel Wallace independently conceived of the principle and described it in an essay he sent to Darwin to forward to Charles Lyell . Lyell and Joseph Dalton Hooker decided to present his essay together with unpublished writings that Darwin had sent to fellow naturalists, and On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection

9744-437: The next generation. These traits can also become more common within a population if the environment that favours these traits remains fixed. If new traits become more favored due to changes in a specific niche , microevolution occurs. If new traits become more favored due to changes in the broader environment, macroevolution occurs. Sometimes, new species can arise especially if these new traits are radically different from

9860-410: The opposite of over-dominance), and can result in a bimodal distribution of trait values. Finally, balancing selection can occur through frequency-dependent selection, where the fitness of one particular phenotype depends on the distribution of other phenotypes in the population. The principles of game theory have been applied to understand the fitness distributions in these situations, particularly in

9976-412: The other hand, "improvement in fitness" can occur in an environment where "survival of the fittest" is also acting. Richard Lenski 's classic E. coli long-term evolution experiment is an example of adaptation in a competitive environment, ("improvement in fitness" during "survival of the fittest"). The probability of a beneficial mutation occurring on some member of the lineage to give improved fitness

10092-405: The other hand, "improvement in fitness" is not dependent on the differential survival and reproduction of individuals due to differences in phenotype, it is dependent on the absolute survival of the particular variant. The probability of a beneficial mutation occurring on some member of a population depends on the total number of replications of that variant. The mathematics of "improvement in fitness

10208-404: The phenotype. Some traits are governed by only a single gene, but most traits are influenced by the interactions of many genes. A variation in one of the many genes that contributes to a trait may have only a small effect on the phenotype; together, these genes can produce a continuum of possible phenotypic values. When some component of a trait is heritable, selection alters the frequencies of

10324-511: The phrase survival of the fittest , which became a popular summary of the theory. The fifth edition of On the Origin of Species published in 1869 included Spencer's phrase as an alternative to natural selection, with credit given: "But the expression often used by Mr. Herbert Spencer of the Survival of the Fittest is more accurate, and is sometimes equally convenient." Although the phrase

10440-441: The phrase "either invariably or normally come about", not the origin of species: ... Yet it is impossible that this should be the true view. For teeth and all other natural things either invariably or normally come about in a given way; but of not one of the results of chance or spontaneity is this true. We do not ascribe to chance or mere coincidence the frequency of rain in winter, but frequent rain in summer we do; nor heat in

10556-688: The point that the methicillin-resistant Staphylococcus aureus (MRSA) has been described as a "superbug" because of the threat it poses to health and its relative invulnerability to existing drugs. Response strategies typically include the use of different, stronger antibiotics; however, new strains of MRSA have recently emerged that are resistant even to these drugs. This is an evolutionary arms race , in which bacteria develop strains less susceptible to antibiotics, while medical researchers attempt to develop new antibiotics that can kill them. A similar situation occurs with pesticide resistance in plants and insects. Arms races are not necessarily induced by man;

10672-406: The population. Established traits are not immutable; traits that have high fitness in one environmental context may be much less fit if environmental conditions change. In the absence of natural selection to preserve such a trait, it becomes more variable and deteriorate over time, possibly resulting in a vestigial manifestation of the trait, also called evolutionary baggage . In many circumstances,

10788-563: The population. In this way the natural environment of an organism "selects for" traits that confer a reproductive advantage, causing evolutionary change, as Darwin described. This gives the appearance of purpose, but in natural selection there is no intentional choice. Artificial selection is purposive where natural selection is not, though biologists often use teleological language to describe it. The peppered moth exists in both light and dark colours in Great Britain, but during

10904-729: The potential for war, and in support of Richard G. Sipes's "culture-pattern" model, where war and substitute activities will vary directly. Wilson compares aggression to "a preexisting mix of chemicals ready to be transformed by specific catalysts that are added," rather than "a fluid that continuously builds pressure against the walls of its containers." The anthropologist Donald Symons , in The Evolution of Human Sexuality (1979), accused Lorenz of inadequately documenting his major thesis. The evolutionary biologist Richard Dawkins described Lorenz in The Selfish Gene (1976) as

11020-527: The rate of reproduction, given survival. Others split the life cycle into further components of selection. Thus viability and survival selection may be defined separately and respectively as acting to improve the probability of survival before and after reproductive age is reached, while fecundity selection may be split into additional sub-components including sexual selection, gametic selection, acting on gamete survival, and compatibility selection, acting on zygote formation. Selection can also be classified by

11136-421: The same sex, that is male–male competition, or intersexual , where one gender chooses mates , most often with males displaying and females choosing. However, in some species, mate choice is primarily by males, as in some fishes of the family Syngnathidae . Phenotypic traits can be displayed in one sex and desired in the other sex, causing a positive feedback loop called a Fisherian runaway , for example,

11252-584: The second child and eldest son of Moses and Rebecca Zuckerman (née Glaser). Both his parents were the children of Jewish immigrants from the Russian Empire . He was educated at the South African College School . After studying medicine at the University of Cape Town and later attending Yale University , he went to London in 1926 to complete his studies at University College Hospital Medical School . He began his career at

11368-469: The selection of individuals that reproduce", without regard to whether the basis of the selection is heritable. Traits that cause greater reproductive success of an organism are said to be selected for , while those that reduce success are selected against . Natural variation occurs among the individuals of any population of organisms. Some differences may improve an individual's chances of surviving and reproducing such that its lifetime reproductive rate

11484-444: The simplest case all deviations from this optimum are selectively disadvantageous. Directional selection favours extreme values of a trait. The uncommon disruptive selection also acts during transition periods when the current mode is sub-optimal, but alters the trait in more than one direction. In particular, if the trait is quantitative and univariate then both higher and lower trait levels are favoured. Disruptive selection can be

11600-494: The study of kin selection and the evolution of reciprocal altruism . A portion of all genetic variation is functionally neutral, producing no phenotypic effect or significant difference in fitness. Motoo Kimura 's neutral theory of molecular evolution by genetic drift proposes that this variation accounts for a large fraction of observed genetic diversity. Neutral events can radically reduce genetic variation through population bottlenecks . which among other things can cause

11716-407: The term "Natural Selection", preferring the term "Natural Preservation". For Darwin and his contemporaries, natural selection was in essence synonymous with evolution by natural selection. After the publication of On the Origin of Species , educated people generally accepted that evolution had occurred in some form. However, natural selection remained controversial as a mechanism, partly because it

11832-446: The traits possessed by their predecessors. The likelihood of these traits being 'selected' and passed down are determined by many factors. Some are likely to be passed down because they adapt well to their environments. Others are passed down because these traits are actively preferred by mating partners, which is known as sexual selection . Female bodies also prefer traits that confer the lowest cost to their reproductive health, which

11948-518: The useful forms survived: So what hinders the different parts [of the body] from having this merely accidental relation in nature? as the teeth, for example, grow by necessity, the front ones sharp, adapted for dividing, and the grinders flat, and serviceable for masticating the food; since they were not made for the sake of this, but it was the result of accident. And in like manner as to the other parts in which there appears to exist an adaptation to an end. Wheresoever, therefore, all things together (that

12064-594: The war, Zuckerman was appointed a Companion of the Order of the Bath in the 1946 New Year Honours . He left the Royal Air Force on 1 September 1946, and was then Professor of Anatomy at the University of Birmingham until 1968, chief scientific adviser to the Ministry of Defence from 1960 to 1966, and the first chief scientific adviser to the British Government from 1964 to 1971. He was also

12180-568: Was "basically right", commenting that "Lorenz would probably cite the fury of his critics as further proof of the correctness of his thesis". Edmund R. Leach, comparing the book with Robert Ardrey 's The Territorial Imperative in The New York Review of Books in 1966, calls On Aggression "no landmark, but .. modest and wise, while Ardrey's version is only noisy and foolish." Leach writes that where Ardrey focuses on territoriality, Lorenz aims to demonstrate that "animal aggression

12296-674: Was Scientific Director of the British Bombing Survey Unit (BBSU), and accepted by Air Chief Marshal Arthur Tedder and Supreme Allied Commander U.S. General Dwight D. Eisenhower in the lead-up to the Normandy landings , that the Allies concentrate on disrupting the German-controlled French transportation system through heavy aerial bombing of rail lines and marshalling yards, was officially called

12412-629: Was a British public servant , zoologist and operational research pioneer. He is best remembered as a scientific advisor to the Allies on bombing strategy in the Second World War , for his work to advance the cause of nuclear non-proliferation, and for his role in bringing attention to global economic issues. Solomon Zuckerman was born in Cape Town in the British Cape Colony (modern-day South Africa) on 30 May 1904,

12528-421: Was achieved for a purpose, citing the regularity of heredity in species as proof. Nevertheless, he accepted in his biology that new types of animals, monstrosities (τερας), can occur in very rare instances ( Generation of Animals , Book IV). As quoted in Darwin's 1872 edition of The Origin of Species , Aristotle considered whether different forms (e.g., of teeth) might have appeared accidentally, but only

12644-611: Was an influence on the Soviet biologist Trofim Lysenko 's ill-fated antagonism to mainstream genetic theory as late as the mid-20th century. Between 1835 and 1837, the zoologist Edward Blyth worked on the area of variation, artificial selection, and how a similar process occurs in nature. Darwin acknowledged Blyth's ideas in the first chapter on variation of On the Origin of Species . In 1859, Charles Darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. He defined natural selection as

12760-684: Was awarded a life peerage on 5 April 1971, taking the title Baron Zuckerman of Burnham Thorpe in the County of Norfolk . He was elected a Fellow of the Royal Society (FRS) in 1943 . Zuckerman met his future wife, Lady Joan Isaacs , daughter of Gerald Isaacs, 2nd Marquess of Reading , in Oxford . They married in 1939 and had two children, a son, Paul, and a daughter, Stella. Stella Zuckerman died in 1992, predeceasing her parents. Joan, Lady Zuckerman entertained and did landscapes using pastels. She died in 2000. Martha Gellhorn described Zuckerman in

12876-898: Was because both men had tried to write about a sensitive and important question, human nature and to what extent it is determined by evolution. They call On Aggression a personal commentary from a professional zoologist where Ardrey's book is a well-documented book by a non-biologist. Both, in their view, tend "to rekindle old, pointless arguments of the instinct vs. learning variety" and both include "some peculiarly nonevolutionary or antievolutionary themes." The psychoanalyst Erich Fromm , writing in The New York Times in 1972, called Lorenz's theory "complicated and sometimes fuzzy". Fromm considered that in one way Lorenz had succeeded where Sigmund Freud had failed, Lorenz's hydraulic theory of aggression, innately programmed, being in Fromm's view

12992-482: Was described by Kleinman. An empirical example of "improvement in fitness" is given by the Kishony Mega-plate experiment. In this experiment, "improvement in fitness" depends on the number of replications of the particular variant for a new variant to appear that is capable of growing in the next higher drug concentration region. Fixation or substitution is not required for this "improvement in fitness". On

13108-493: Was later described by the Islamic writer Al-Jahiz in the 9th century, particularly in the context of top-down population regulation, but not in reference to individual variation or natural selection. At the turn of the 16th century Leonardo da Vinci collected a set of fossils of ammonites as well as other biological material. He extensively reasoned in his writings that the shapes of animals are not given once and forever by

13224-429: Was perceived to be too weak to explain the range of observed characteristics of living organisms, and partly because even supporters of evolution balked at its "unguided" and non- progressive nature, a response that has been characterised as the single most significant impediment to the idea's acceptance. However, some thinkers enthusiastically embraced natural selection; after reading Darwin, Herbert Spencer introduced

13340-797: Was read to the Linnean Society of London announcing co-discovery of the principle in July 1858. Darwin published a detailed account of his evidence and conclusions in On the Origin of Species in 1859. In the 3rd edition of 1861 Darwin acknowledged that others—like William Charles Wells in 1813, and Patrick Matthew in 1831—had proposed similar ideas, but had neither developed them nor presented them in notable scientific publications. Darwin thought of natural selection by analogy to how farmers select crops or livestock for breeding, which he called " artificial selection "; in his early manuscripts he referred to

13456-487: Was reversed by the effect of the Clean Air Act 1956 , and the dark moths became rare again, demonstrating the influence of natural selection on peppered moth evolution . A recent study, using image analysis and avian vision models, shows that pale individuals more closely match lichen backgrounds than dark morphs and for the first time quantifies the camouflage of moths to predation risk. The concept of fitness

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