Chapter 23 Chapter 12 Modern Controversy-1

The debate over sociobiology was fueled by Darwinists confidently extending their theory into territory their opponents claimed to have occupied.However, in the vast majority of modern debates about evolution, evolutionists have been on the defensive, trying to fend off attacks from all sides.The level of contention varies.Some debates are carried out within the structure of the orthodox theory of evolution, and have not yet challenged the basic structure of the theory of evolution, but some people are trying to overthrow certain views in the past.This was presumably the case for the development of new ideas about human evolution, and Adrian Desmond's vehement opposition to the popularization of the idea that dinosaurs were warm-blooded animals (Desmond, 1976).If most biologists were to accept Desmond's view (which now seems unlikely), they would of course have to reinterpret the relationship between dinosaurs and birds and modern cold-blooded animals, but they would not need to. Consider Darwin's theory of how evolution occurs.Hypothesizing and testing new ideas like this is a sign of evolution's scientific vigor, and it goes a long way toward refuting the repeated charge that evolution is nothing more than blindly accepted dogma.More seriously, it has been claimed that modern Darwinism does not explain the evolutionary process correctly.Since Samuel Butler, there have always been many writers outside the scientific community willing to criticize the materialistic basis of choice theory.These attacks often end in calling for reconsideration of recourse to Lamarckism, or consideration of growth factors in determining the role of evolution (examples in recent years are Koestler, 1967, 1972; Koestler and Smithies, 1969; Taylor, 1983).Their intent was to suggest that evolution is not simply a process of trial and error, but must proceed along purposeful lines guided by some biological factor.Scientists often ignore such criticisms from non-scientists, perhaps unintentionally, and the general public feels that the idea of ​​natural selection is as flimsy as the explanation of biological complexity.Now Dawkins (1986) is making a bold attempt to make the public fully understand the mechanism of selection.Dawkins himself believed that Darwinism was the fundamental, yet perfectly accurate, explanation of the evolution of life.In recent years, however, a growing number of biologists have realized that evolution involves more than natural selection.In some cases, their proposals are merely additions to the synthetic theory of evolution and do not change the basic structure of Darwinism.Now, a handful of more radical biologists have turned to critics who believe selection theory is simply wrong.Those who wish to jettison the whole idea of ​​evolution pose a more fundamental challenge to modern Darwinism.It's easy to forget that creationism isn't the only movement claiming to accomplish this.In academia, there is also some debate about whether Darwinism is a true science.Some staunch proponents of a new technique in taxonomy, "revised cladology," insist that speculating about evolutionary relationships goes well beyond the bounds of science.Many non-scientists have expressed a keen interest in a number of strange, unconventional explanations of Earth's history, including Immanuel Velikovsky's new cataclysmic theory and Eric von Däniken's The extraterrestrial interference theory.These theoretical foundations are weak, and some scientists do not take them seriously.Francis Crick and Fred Hoyle also suggested that life might have come to Earth from outer space, both of whom have professed disbelief in the orthodox theory of chemical evolution.In addition to being more popular, special creationism also poses a greater threat to modern evolutionary theory because it is based on the claim that the origin of species must have been a supernatural process.Although called "scientific" creationism, this theory clearly seeks to keep the whole [evolution] problem out of the scope of scientific investigation.What's more, how many creationists still insist that the miraculous origin of life is exactly as described in the Bible, and that the origin of life happened thousands of years ago, and the whole process only took a few weeks.This view rejects not only evolution, but all scientific explanations of the past based on cosmology, geology, paleontology, and archaeology.While the creationist view can be defended, it can be argued that the methods of a movement motivated by a desire to support positions originally based on religion would never be scientific.Creationists attempt to use the [current] general criticism of modern evolution to back up their views and avoid detailed discussion of their own views, which would reveal that their theories, as comprehensive scientific theories of the past, were not There are big flaws.Begin the chapter with a discussion of new ideas that are at least largely compatible with past evolutionary theories, and move on to more radical theories (for a discussion of modern controversies, see Cherfas, ed., 1982; Maynard Smith , ed., 1982; Milkman, ed., 1982; Ruse, 1982; Ridlay, 1985).

debate in biology In recent decades, even some biologists have criticized the modern synthesis of evolution and genetics as too narrow a field.Evidence from all sides suggests that at least some aspects of the evolutionary process do not work in the orthodox Darwinian way.In some cases, such as the original "punctuated equilibrium" theory, new ideas were introduced that simply extended what was already in Darwinism but had not yet been recognized.Other theories have also been proposed to completely replace the very inaccurate theory of choice.Criticism at this level is still limited to the few biologists who can agree with one another on the precise nature of this new idea.What unites the various elements of criticism is the feeling that there must be something more purposeful and regular in the raw material of evolution than just a random flow of micromutations.In this respect, the old tradition of old-fashioned non-evolutionary thinking that prevailed in the nineteenth century still exists.There can be many paths to this new idea, and critics of choice theory argue that this variety shows the need for more flexible thinking.Unfortunately, since critics cannot agree, evolutionists can easily dismiss every criticism as unimportant.A lesser-known figure who has criticized modern Darwinism from a scientific point of view is Leon Kroizat (1958, 1964), whose work is currently attracting a number of biologists, their number Many, but good at publicizing (Nelson and Rosen, eds., 1981).Kruizart's "pan-paleobiogeography" is based on the idea that Darwinian explanations of dispersal and divergent evolution do not fit the facts of geographic distribution.Darwinism had envisioned "dominant" species being able to spread to occupy new areas, but Kruizart argued that the existing distribution of related species matched their ability to disperse.He proposed that, generally speaking, speciation takes place in the form of isolation and differentiation, that is, the separation of previously continuous widespread species by natural isolation.It has been argued that, by doing so, Kruizart revived problems in biogeography that had been neglected since the days of Darwin (Nelson, 1978).Kruizart was underappreciated throughout his life, probably because he did not hesitate to criticize Darwin and orthodox modern Darwinism.His theory also required a non-Darwinian component, somewhat similar to Orthogenesis, in that he believed that different populations tended to evolve in similar ways, even under different circumstances.Now, supporters of Kruizart argue that, thanks to a revolution in Earth science that has led to the acceptance of the theory of continental drift, Kluizart's argument has become even more compelling.Traditional geology has ignored the possibility of horizontal movement of the crust, but the new science of plate tectonics admits that drift is a natural result of the surface formation process (Hallam, 1973; Wood, 1985).The separation of once united continents is an integral part of Earth's history, and the theory of evolution must take this into account.Species distributions that were once explained in terms of dispersal can now be explained in terms of the process of continental drift.However, most biologists still don't think Kruizart's explanation of the distribution of species is plausible enough to pose a threat to Darwinian synthesis as a whole.The element of directed evolution in Kruizart's argument is a factor that leads people to link his views with those of other critics of Darwin.By far the most famous new evolutionary mechanism is the theory of punctuated equilibrium, which started out as a different emphasis within a Darwinian framework but gradually became a more comprehensive alternative to modern synthesis.The basic question is whether the evolutionary process is gradual or intermittent: is evolution a slow continuous process of change, as proponents of modern synthesis insist, or is it mainly long-term stability with occasional more rapid changes?There are some Darwinian mechanisms that could explain the relatively abrupt changes by geological standards, and initially, punctuated equilibrium models tried to emphasize the role of these events.In recent years, however, this model has evolved to attack the gradualism argument at its core, with the aim of establishing that discontinuity is a fundamental feature of evolution.In addition, the proponents of the punctuated equilibrium theory currently insist that in the process of evolution, different mechanisms are at work in different levels of evolution, and the gradual change emphasized by the modern synthesis theory is only the mechanism in the lowest level.The concept of sudden genetic shifts occurring at critical moments in evolution, though not part of the theory of punctuated equilibrium, reappears here.Opponents argue that none of these alternative theories are necessary.The seemingly sudden introduction of new species can still be explained in terms of the incompleteness of the fossil record, but to explain it in terms of promising monstrosities would be a throwback to the days of wild guesses that modern synthesis says are purely superfluous .Niels Eldredge and Stephen Jay Gould first proposed the model of punctuated equilibrium in their paper (El dredge and Gould, 1972; see also Gould and Eldredge, 1977; Eldredge, 1986).The reason for this model was that the two paleontologists felt that the modern synthesis theory put too much emphasis on the theory of gradual change.Population genetics explains microevolution as a gradual process, and it is widely believed that the same process over a long period of time leads to macroevolution (creation of new species, genera, etc.). G. G. Simpson, in Rhythms and Patterns of Evolution (Simpson, 1944), proposed the application of neo-Darwinism to paleontology, again citing the incompleteness of the fossil record to explain the seemingly sudden appearance of new species .Simpson and the other creators of synthetic evolution were initially prepared to acknowledge the role of rapid speciation, but the idea was shelved as gradualism grew louder.The theory of gradual change argues that the abundance of examples of gradual changes in the fossil record suggests that seemingly sudden changes give the illusion of a lack of examples of intermediate states.By the 1970s, however, more and more paleontologists were becoming dissatisfied with the idea of ​​gradualism, as many examples of gradual evolution had failed modern techniques.If there are no real instances of gradual evolution in the fossil record, the notion of attributing all sudden changes to poor records is shaken.It would be better to re-examine the evidence in light of new thinking, and to set aside the traditional Darwinian assumption of gradual change, while opting for an evolutionary model that takes into account the sudden appearance of new species in the fossil record. resulting phenomenon.

The basic argument of the punctuated equilibrium theory is based on the use of an orthodox Darwinian idea proposed by Ernst Mayer: the formation of species proceeds through the separation of "peripherally isolated" groups from the original species.This theory holds that new species form most readily when minority groups at the extreme margins of the original species' distribution are isolated.The extreme nature of this environment, together with the small population size, ensures that new traits evolve at a rapid rate.This kind of development may have gone through tens of thousands of years. The so-called "rapid" is from a geological point of view. If viewed according to the standards of experimental genetics, the time is long enough.Because of the rapidity with which such events occurred and were confined to the narrow areas where the changing populations resided, it is unlikely that any traces of evolutionary processes would be left in the fossil record.In some cases new species thus produced may re-enter areas formerly occupied by their parent species and become better adapted to the environment there.The new species quickly replaces the parent line and spreads over a wider area, leaving a fossil trail if the new species persists long enough.Thus new species appear suddenly in the fossil record, as if they were not related to the parent species.

Phrased in this way, the sudden "hiatus" exhibited by speciation events seems to fit the orthodox Darwinism of modern synthesis.However, this view reveals differences, largely due to paleontologists' belief that once a new species has occupied a wide area, its characteristics will stabilize and no more comparisons will occur until it is replaced by a new species. big change.This view suggests that "lineage" evolution -- that is, changes in a single lineage that has not differentiated -- is not the same.Thus, an evolutionary trend cannot involve continuous change in one direction from a single lineage, because natural selection acts on the individual organisms that make up the population.On the contrary, the evolutionary trend must include a series of speciation events, each of which produces a fixed species; the new species changing in the appropriate direction continuously replaces the old species, which constitutes the evolutionary trend.The mechanism leading to this tendency is called "species selection"—competition between species leads to the survival of those species best adapted to new environments and new biological ways, while others are eliminated (Stanlay, 1981).According to this view, the process of speciation is different from the general process of macroevolution, because speciation only involves selection acting on individuals, while large-scale evolutionary trends involve selection acting on species.The direction of change in speciation also has little to do with macroevolutionary trends.This is the case, in part, because small populations may not be representative of the original species due to random sampling.But even the changes that occur during speciation are adaptive, and, in fact, populations isolated under extreme environments do not necessarily have the same adaptive criteria for their traits as their parent species.Thus, in speciation, new forms arise essentially at random, only some of which may by chance become more dominant than their parents, allowing them to occupy entire areas.

More recently, Gould (1980, 1982) has posed a greater challenge to orthodox evolution.One way to understand the direction of this new thinking is to focus on the so-called stability of large populations, that is, on the balance between speciation hiatus.Darwinism can explain why large populations living in stable environments retain the same traits; "stabilizing selection" tends to eliminate individuals that vary greatly from their normal type.Darwinists would assume, however, that if the environment changed, even large groups would begin to evolve as a result of individual selection.Paleontologists believe that lineage evolution does not occur in large groups, that is to say, there must be something more stubborn than stabilizing selection to maintain fixed traits.One possibility is that "developmental constraints" are at play in the individual's growth.Genetic mutations cannot gradually alter a well-established pattern of embryonic growth that has become an intrinsic part of the organism.Only under exceptional conditions will this restriction be removed and a new developmental pathway leading to different adult traits established.If this is the case, then in speciation, the emergence of new traits is not random.In the existing growth pattern, only a small amount of change is possible, which limits the direction of evolution, so that evolution can only proceed along a fixed path.Because of the inherent constraints on embryonic growth, changes in speciation itself determine the overall evolutionary trend.This would produce directed evolution independent of the environment, perhaps along the same path as the old theory of mutational pressure and orthogenesis.

Figure 24. Patterns of evolution a) The orthodox Darwinian view of evolutionary tendencies, where there is some speciation, but all branching in the same direction, guided by selective pressure on individuals. b) Punctuated equilibrium model for species selection.Once each branch is formed, it is fixed. According to the evolutionary trends in different directions, the speciation is random, which leads to different survival conditions of the right branch on the basis of the reduction of the left branch. c) Affecting evolutionary trends due to "starting bias" in the punctuated equilibrium model: speciation is easier on the right than on the right due to intrinsic factors affecting variation.

The belief that existing growth patterns somehow control the emergence of new traits in species is known as "epistaltic" evolution.Proponents of this theory often cite the long-neglected Richard Goldschmidt (Goldschmidt, 1940, see Auen, 1974), who, when the genetic theory of selection emerged, based on similar Arguments against this theory of choice.The idea, also from Goldschmidt, was given a new lease on life, the idea that entirely new traits could suddenly arise through mutation.Goldschmidt's idea of ​​a promising deformity had been rejected because genetics seemed to indicate that large mutations were definitely lethal.However, it is conceivable that relatively small genetic changes affecting early stages of the growth process may cause development to proceed along new pathways, thus establishing a new functional target through the combined effects of later stages.Gould (1982) argued that such leaps in change are the turning points where evolution turns in entirely new directions, and that once new structures are formed along this path, selection will place adaptive uses on such structures.Some advocates of gradualist evolution believe that this view can be integrated into modern evolutionary theory (eg, Rachootin and Tonson, 1987), while others see this view as an alternative to Darwinism (L?vtvup , 1977; Pollard, ed., 1984; Ho and Saunders, ed., 1985).

An important side effect of this theory is that it is no longer necessary to assume that every trait in every organism has an adaptive purpose.Darwinists have been accused of being simple-minded 'adaptationists', that is, they blindly assume that because selection acts to produce only useful traits, every trait must have a purpose (Lewontin 1978; Gould and nd Lewontin, 1979).They often have to invent putative adaptations for various structures, and often justify the assumption without any good reason.In fact, of course, many seemingly unimportant traits have been shown to have been influenced by natural selection.Still, critics insist that Darwinists have gone too far with their emphasis on adaptation.Most likely, each organ was adapted for certain functions, but how did the basic mechanism of such an organ originate?Can a completely new structure be considered to have adaptive advantages at every stage of the generation process?For example, what is the use of half a 〖HTSS〗wing of 〖HTH〗?The traditional Darwinian answer to this question is that the structure may have developed for a different purpose in the first place, which is the concept of "pre-adaptation".The half-formed wings of the first birds may have been used to catch insects for food, only to be used for flight later.Instead, Gould and Lewandin point out that the basic form of a new structure, its prototype, may not be adaptable at all, but arise from accidental forces via the aforementioned jump-start of.Further development of such structures is again possible subject to mechanical constraints that limit the range of variation.Selection has only affected the superficial features of this organ, making it adaptive.

Some proponents of the preformed view of evolution are also skeptical of the view of hard inheritance derived from Weissmann's germplasm theory, and now the "central dogma" in molecular biology has established a historical reputation for hard inheritance. In 1953, Francis Crick and James Watson figured out the structure of DNA (Olby, 1974), and for the first time biologists understood how the information necessary to build a new organism is transmitted through the chemical structure of the coded gene go down.Their work establishes a fundamental picture of the flow of information in reproduction: DNA from parents makes RNA, which makes the proteins needed to build new organisms.There is no circuit from protein to DNA and, therefore, no pathway for the transmission of traits acquired by the body to genes.The work of Ted Steele (Steele, 1979) has sparked renewed interest in the possible existence of pathways for the reverse flow of information.As a result, it may lead to the reintroduction of Lamarckism.

Steele was doing experiments with the immune system of mice, and he claimed to have found that the [acquired] tolerance to some antigens in mice was heritable.Theoretically, he postulates that there is a trial-and-error process of adaptation in the immune system of the mice, resulting in a viral transfer into the DNA of germplasm cells.In fact, this mechanism does not violate the principles of molecular biology, but most biologists are skeptical of Steele's ideas, and all attempts to repeat his experiments have failed.Arthur Koestler was an active supporter of Steele's work, and Koestler in his early years (Koestler, 1971) had called for a reconsideration of Kamal's Lamarckian experiment with the midwife frog.Unfortunately, it is Koestler's position that the excitement that Steele's experiments in the early 1980s aroused now seems to have faded.

Koestler has long supported Lamarckism because he was dissatisfied with the materialist implications of choice theory (Koestler, 1967, 1972).He preferred to think of individual organisms as creative entities capable of influencing the evolution of a species through deliberate changes in their behaviour.Lamarckism holds that the biological effects of new habits are heritable and accumulate over many generations.According to Koestler, modern Darwinism has no intention of reintroducing purpose into evolution at all.Some of the founders of synthesis were of course skeptical of Darwinian intentions to "humanize" and actively opposed the idea that new patterns of behavior could impose a rigid evolutionary process (Simpson, 1953a).But conceiving of natural selection as a mechanical process of trial and error is not the only reasonable view, and some biologists have long favored a more flexible approach.When Alisdell Hardy (Hardy, 1965) argued that the act of innovation could affect the course of evolution, he was not invoking acquired inheritance, but a modified Darwinian version of the old "Baldwin effect" (Chapter 9) doctrine.Natural selection, in determining the adaptations of the structure of the body, has determined the direction of the habits. CH Waddington's "genetic assimilation" mechanism (Waddingtin, 1957) can also explain the problem clearly without invoking true Lamarckism. Philosophical and moral arguments against natural selection fuel support for non-Darwinian mechanisms such as Lamarckism and preformed views of evolution.However, this by no means means that Darwinism is as bad as its opponents claim.As we saw in our discussion of earlier theories with racist implications (Chapter 10), Lamarckism has a worse side.There may be genuine scientific reasons to think that synthetic evolution does not provide a comprehensive account of evolution, but most biologists feel that they will also value other theories if they can escape the moral one-sidedness of anti-Darwinism.Many people still feel that there is no need to give up natural selection at all. Is Darwin's theory of evolution unscientific? The accusation that Darwinists are eager to concoct entirely speculative ideas to explain the adaptation of various traits has led to a harsher criticism of Darwinism.Despite the abundance of research that modern synthesis has generated, writers outside the scientific community have insisted that Darwinism is unscientific.Some people think that natural selection is nothing more than a tautology, because natural selection refers to the survival of the fittest, and the fittest is defined as the survivors.Under the leadership of Karl Popper, some philosophers have decided that Darwinists attempt to explain anything in terms of adaptation, and that doing so is unverifiable, because in practice, to do so, it may always be Hypotheses are invented to explain each trait.In recent years, such serious accusations have even been made by some biologists, mainly staunch supporters of "cladology," a new school of taxonomy. The argument that Darwinism is mere idle tautology is common in philosophical critiques of the theory (Manser, 1965; Macbeth, 1971; Bethell, 1976).They came to this argument because natural selection has been described as "survival of the fittest," a phrase invented by Herbert Spencer and later adopted by Darwin.The question is: how can we know which organism is the best fit?According to critics, biologists' answer is simply that the fittest are those that actually live longer.Thus, "survival of the fittest" means "survival of the survivors".Natural selection is reduced to tautology, and a principle is true not only because it can be verified by facts, but also because the determination of its constituents must be logical.For example, the statement "all husbands are men" contains no useful information, and it must be, because only men can be "husbands."The whole concept of natural selection is nothing more than a play on words, so natural selection cannot be used as a mechanism of evolution. Darwinists would naturally object to this argument, which rests on a complete misunderstanding of how the theory of natural selection works (Ruse, 1982), and even biologists who do not share all of Darwinism's views express this particular objection against (eg, Gould, 1977c).The basis of natural selection is the belief that the fittest survive longer and reproduce more frequently, but fitness is not defined in terms of survival, but a measure of whether organisms can adapt to their living environment by obtaining food, escaping predators, etc. standard.In the long run, organisms that have this advantage in the struggle for survival generally live longer at the expense of others who do not have this advantage, and this is how natural selection can develop adaptive traits .If the fittest do survive, then you can't possibly imagine that's not true, and of course there are some theories of evolution based on random factors that don't recognize the superior reproductive capacity of the fittest.More recently, it has been suggested that "genetic drift" is more evolutionary, and Darwinists have launched a movement to argue that survival and reproduction are only associated with certain traits possessed by certain organisms.The study of the melanization of the birch moth (Chapter 11) became the paradigm for a whole series of studies which attempted to demonstrate this point of view.Predators appear to be unable to detect camouflaged organisms, so the melanized moths outlive the more prominently colored moths, apparently suggesting that survival is associated with certain traits that are thought to be 'adaptive' . Some Darwinists find it hard to believe that anyone would take this criticism seriously, but Dawkins (1982) argues that the problem arises due to the emergence of sociobiology, which tends to derive from reproductive success to define adaptability.The original Darwinists were well aware that fitness meant adaptive advantage, that is, advantage in the struggle for survival.In the modern study of reproductive behavior, however, a more refined approach has been necessary; how much genetic representation is present in the offspring becomes the measure of success.While doing so does not change the fact that success is achieved through some form of behavior that distinguishes an individual of that organism from other individuals, it is easy to confuse this modern notion of reproductive fitness with full survival.Brady (1979) admitted that in some cases, biologists cannot practically identify which traits are actually adaptive, so they have to define a gene as "adaptive", because this A gene occupies a high level in the population.Although adaptive advantages are masked in complex situations, no one denies the existence of adaptive advantages.In these cases Darwinists do fall into circular explanations, not of course because of the tautology of natural selection, but because of the fact that the theory is sometimes untestable in practice. This brings us to the attack from the second line, based on the claim that Darwinism is unfalsifiable and therefore unscientific.Philosopher Karl Popper is famous for his efforts to find a criterion for distinguishing science from pseudoscience.Recognizing that general laws cannot be drawn from the collection of definite and definite examples, Popper proposed that science is more based on finding fault than on finding the truth (Popper, 1959).A true science should subject all its hypotheses to experimental testing, and therefore should be constituted in such a way that any contradiction with nature is immediately revealed.Scientific hypotheses are "falsifiable," whereas pseudoscience deliberately obscures statements so that no counter-evidence can be found.According to Popper (Popper, 1974), according to this standard, Darwinism is untestable and therefore unscientific.At best, Darwinism can construct a "metaphysical framework", according to which a testable theory can probably be formed.This accusation stems in part from the fact that many Darwinists take a highly speculative view when explaining how particular structures evolved.According to Pope, there is always the possibility of an explanation for adaptation, but in the case of extinction-type explanations, there is no way to test that explanation as plausible.In addition, these assumptions are always based on individual circumstances rather than general laws, which means that Darwinism cannot predict the future course of events.The lack of predictive power again points to the inability to properly test Darwinism. Popper's views won more support, but Ruse (1977, 1982) challenged this application of philosophy to the field of evolution.A careful distinction must be made between the causal theory of evolution and the use of evolution to explain specific events in the past historical course of life.The mechanisms of modern Darwinism have been tested many times through the analysis of the genetic structure of populations.The same point is made by Wasserman (1978), who will explain how a Darwinian theory of how variation remains balanced in a stable population (which is testable) versus a Darwinian theory of explaining macroevolutionary change ( He claims this is untestable) distinction.Most Darwinists would probably feel that their theory had to account for change as well as stability, or the theory would not be of limited value.Dawkins pointed out (Dawkins, 1982) that Darwinists have attempted to develop different levels of selection theory, making different predictions about how some animals' behavior will be, and indeed by testing these predictions, social Biologists deny group selection in favor of individual selection.Ruth believes that the theory of Darwinism is embodied in its ability to incorporate a large number of phenomena into a comprehensive explanation system.In many fields, Darwinism has made verifiable predictions about general characteristics of nature.There may be specific areas where Darwinism doesn't seem to be the right explanation, but there are also many scientific theories that have superseded success despite a handful of facts that clearly falsify them.Although Newton's theory of universal gravitation was wrong in explaining Mercury's orbit, it was accepted because it had proven useful in guiding research in many other fields.我们不能期望有一种现行的理论可以对所有可以想到的问题作出正确的回答。 关于达尔文主义对生命历程中特定发展的解释，鲁斯承认并非总能提出可检验的假说。他指出，不过化石中的一般趋势符合达尔文主义的理论。可以想象能够证伪整个过去进化图景的发现，例如，假如在更古老的地层中发现出人类的化石。至于进化中的一般趋势，比如说明体型普遍增大的“科普律”，能否精炼成真正的具有预测能力的自然规律，还存在着争议。由于时间尺度的问题，这类规律不可能通过实验来检验，但是可以通过在化石中的进一步发现来检验它们。鲁斯指出，即使对于特定的适应解释，有时也是可以检验的，因为这种假说都是基于生活中类似的适应例子。面对这些异议，波普本人软化了对达尔文主义的看法(Pop per，1978)，但是在最近几年，生物学内部生发出十分相像的攻击。 最新的异议来自分类学当中一个叫做“分支系统学”的新学派。“分支”这个词是朱利安·赫胥黎1957年提出来的，用以表示进化树中上的一个分支。这项分类中的新技术是由威利·亨宁希发明的(Henning，英译本，1966），他坚持认为，要想尝试表示进化关系，就必须将注意力放在分支过程上，忽略那些与分支无关的变化。“分支系统学”这个词是由反对这场运动的一个人，恩斯特·迈尔引入的，亨宁希的追随者不太愿意接受这个词。虽然亨宁希对于传统的达尔文主义的分类与进化联系方式发出挑战，但是他并不认为他的技术是表示进化关系的一种方式。最近的几年，一些比较激进的支持这项新技术的人认为，即使不考虑进化，也可以表示类型之间的关系。这些“修正分支系统学家们”宣称，祖－裔联系是进化上至关重要的关系，但是从祖－裔所表现出来的关系中，无法得出它们之间的进化联系。这是对达尔文主义的一种直白的批评，他们试图将指责再扩大一些，认为对生命过去历史的重建是不科学的，而且他们非常热心地利用了已有的一些反自然选择论点。 亨宁希认为，生命类型组成了组合这种现象只能说明进化过程中的分支是规则的。正统的进化分类学显然也会考虑到这个问题，而且所有的进化论者都认识到他们可以利用分支系统学方法提供的更精确方式来表示他们所感兴趣的一些关系。然而，进化论者还要考虑到其他的因素，主要是变化在发展过程中的变化程度。如果一个分支和其祖先相比发生了很大的变化，就应该认定，现在位于该分支末端的类型，要比那些没有什么变化的分支末端类型，在分类排列上占据更高的位置。亨宁希认为知道变化的程度没有用，在考虑建立自然组合时，只能利用分支。他用“分支图解”了表述这些关系，在分支图解中，分支显示出真正的组合构成。对共同祖先的描绘是通过确定具有衍生性状组合来进行的，衍生性状指的是只在该组合中发展而来的性状，并不涉及到共同的原始性状(那些从更早的祖先衍生来的且其他组合也有的性状)。分支系统学通过使系统分类学家认识到一个组合中共同性状的重要性，从而提供了更加精确的方法来确定那些对于分类是最重要的特征。然而，分支系统学家坚持认为，将由一个共同祖先衍生而来所有分支归为一个组合，会破坏已经确定的动物界中的传统划分。例如，按照分支系统学，爬行动物并不构成一个单独的纲，因为爬行动物与鸟类和哺乳动物具有共同的性状。在传统的系统中，爬行动物纲的界定并不是根据爬行动物自己所具有的独特性状，而是根据后裔发展中所〖HTH〗缺少〖HTSS〗的性状界定的，按照分支系统学家的看法，这是一种毫无意义的抽象。 亨宁希想用分支图解来表示真正的进化关系。从分支中产生出现代类型分化的节点则对应于化石记录中祖先类型所处的可能位置。后来的分支系统学家，比如考林·帕特森(Patterson ，1980，1982)，则认为，所有已知的类型，无论是已经灭绝的还是仍然存活的，都要顺着分支图解的顶端来排列，那些较低等的节点只对应于理想化的组合，其中个体形态具有共同的性状。分支系统学家通过侧重于性状，而不是物种，因此不再关心进化过程的性质。按照这种方式绘制的分支图解与进化树无关；事实上，分支图解所显示出来的关系会与许多进化树上表现的关系相一致。涉及到这个问题，修正分支系统学家认为，进化与他们试图表达的自然规则无关。分支图解描述的是已知的关系，并不告诉我们产生出这些关系的进化途径。实际上，分支系统学的方法并不能告诉我们如何去识别祖－裔关联，分支系统学只能描述从未知共同祖先衍生而来的“姊妹”类型的组合。我们无法根据共同性状获悉一个物种是来自另一个物种，因为共同性状也许是衍生出来的，也许是两个物种都从共同祖先那里继承下来的。因此，修正分支系统学家认为整个重建过去进化历程的努力都建立在不正确的知识基础上，因此有些经过了一个世纪的研究而构建的进化树也没有得到过验证。这样，分支系统学家提供了宣告进化论不科学的新论点。 图25.分支系统学与进化分类学。 这个图形表示进化中的两个分支点，由此，产生了A、B、C三种类型。C支最后生成，但是在C支的进化过程中，C支的变化比比A和B都大得多。按照传统的进化分类学，A和B应该属于同一组合，而C则由于其变化的程度而应被分作一个单独的组合。相反，分支系统学却将B和C 联系在一起，尽管B和C之间有差别，因为它们的共同的祖先一样，而和A的共同祖先不同。以一个具体例子说，A代表现代爬行动物，B是恐龙，而C是鸟。进化学家将鸟分成一个单独的类，而将恐龙和现代爬行动物划分成一个类。分支系统学家则将鸟和恐龙当作更自然的组合，因为它们来自于一个共同的祖先。爬行动物并不形成一个自然的纲，因为对应它们的界定只能人为地将鸟类(和哺乳动物)排除在一个由于来自共同祖先而形成的自然组合中。〖ZK)〗 不过修正分支系统学家只占系统分类学家的少数。进化论者一直坚决地反对他们，进化论者人为，虽然修正分支系统学家的技术很高超，但是的思路是对科学的威胁。戴维·霍尔指出(Hull，1979），分支系统学家对进化论的攻击建立在方法论上的论据：因为他们的方法不允许分析进化关系，所以他们说进化是不科学的。这种攻击的价值值得怀疑，因为它的前提是他们的技术是唯一可用的技术。我们如何才能知道将来的改进不能使我们用同样严格的方法分析进化关系呢？分支系统学家的技术中有些方面是人为限定的，他们则解释那是自然事实，比如，对分支的处理总是二分法(一分为二)。进化理论并不限制多重的物种形成，而分支系统学家则认为不会发生多重的物种形成，因为他们的图解中无法表示这种现象。霍尔将整个这场争论与波普所宣称的进化论不可证伪的论断联系起来，他指出，波普的观点可以按照各种方式来使用。进化树是没有分支图解明确，但是进化树说明了许多自然的细节，因此〖HTH〗更〖HTSS〗可能被证伪。至于实际中的应用，进化论者也认为，在解释自然中形成的新性状时，达尔文主义的前提也是有用的（Ridley，1982b）。 1981年，在伦敦自然博物馆举行的一次关于人类起源的展览上，公开发生了一场有关分支系统学的激烈争论。这次展览所使用的文献遵循了分支系统学的观点，强调指出进化树是不确定的，甚至提到了类人猿化石的新发现。进化论者对这种争论作出了愤怒的反应，他们采用了很多方式，主要是给《自然》杂志的编辑写信。由于分支系统学强调分支化，所以有人将分支系统学与间断平衡理论联系在一起，指责二者都是到处蔓延的马克思主义的产物。还有人指出，由于分支系统学家正在动摇进化论，所以他们是在鼓励特创论，这样说也许并不过分。当然，修正分支系统学家们并没有声称物种的产生是奇迹的过程，但是他们声称进化不可能得到证实，这就意味着进化论和特创论都位于同样的科学水平。分支系统学家的唯一兴趣就是在抽象的自然关系图景中分来分去；他们并不关心各种类型是如何形成的。大多数生物学家依然感到科学有责任提出原因假说，来解释我们所观察到的物种是如何产生出来的。这些假说涉及到过去的事件，而且不像分支图解那样容易检验，但是〖HTH〗可以〖HTSS〗通过许多间接的方法来检验它们。放弃探索便意味着使整个地球过去生命的历史这个问题永远都成为不解之谜。 图26.分支图解与进化树 左边的分支图解代表由三个相关物种组成的一个组合，其中B和C具有共同的性状，而A则不具备。这个分支图解与右边两个进化树中的一个是一致的。A也许是B和C的祖先，或者A有可能独在一个旁支上。因此，分支图解从中不能得到祖－裔关系的信息，所以，分支系统学家否定进化树，认为进化树是不可证伪的。当然，这是一最简单的案例：一个连接着四中类型的分支图解将会和12中可能的进化树相一致（见Patterson，1982）。