Darwin

Proc Natl Acad Sci U S A. 2009 Jun 16;106 Suppl 1:10033-9. Epub 2009 Jun 15.

Darwin and the scientific method.

Ayala FJ.

There is a contradiction between Darwin's methodology and how he described it for public consumption. Darwin claimed that he proceeded "on true Baconian [inductive] principles and without any theory collected facts on a wholesale scale." He also wrote, "How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service!" The scientific method includes 2 episodes. The first consists of formulating hypotheses; the second consists of experimentally testing them. What differentiates science from other knowledge is the second episode: subjecting hypotheses to empirical testing by observing whether or not predictions derived from a hypothesis are the case in relevant observations and experiments. A hypothesis is scientific only if it is consistent with some but not other possible states of affairs not yet observed, so that it is subject to the possibility of falsification by reference to experience. Darwin occupies an exalted place in the history of Western thought, deservedly receiving credit for the theory of evolution. In The Origin of Species, he laid out the evidence demonstrating the evolution of organisms. More important yet is that he discovered natural selection, the process that accounts for the adaptations of organisms and their complexity and diversification. Natural selection and other causal processes of evolution are investigated by formulating and testing hypotheses. Darwin advanced hypotheses in multiple fields, including geology, plant morphology and physiology, psychology, and evolution, and subjected them to severe empirical tests.

Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA. fjayala@uci.edu

Proc Natl Acad Sci U S A. 2007 May 15;104 Suppl 1:8567-73. Epub 2007 May 9.

Darwin's greatest discovery: design without designer.

Ayala FJ.

Darwin's greatest contribution to science is that he completed the Copernican Revolution by drawing out for biology the notion of nature as a system of matter in motion governed by natural laws. With Darwin's discovery of natural selection, the origin and adaptations of organisms were brought into the realm of science. The adaptive features of organisms could now be explained, like the phenomena of the inanimate world, as the result of natural processes, without recourse to an Intelligent Designer. The Copernican and the Darwinian Revolutions may be seen as the two stages of the one Scientific Revolution. They jointly ushered in the beginning of science in the modern sense of the word: explanation through natural laws. Darwin's theory of natural selection accounts for the "design" of organisms, and for their wondrous diversity, as the result of natural processes, the gradual accumulation of spontaneously arisen variations (mutations) sorted out by natural selection. Which characteristics will be selected depends on which variations happen to be present at a given time in a given place. This in turn depends on the random process of mutation as well as on the previous history of the organisms. Mutation and selection have jointly driven the marvelous process that, starting from microscopic organisms, has yielded orchids, birds, and humans. The theory of evolution conveys chance and necessity, randomness and determinism, jointly enmeshed in the stuff of life. This was Darwin's fundamental discovery, that there is a process that is creative, although not conscious.

Free Full Text PNAS

Group Selection

Endeavour. 2005 Mar;29(1):43-7.

The rise, fall and resurrection of group selection.

Borrello ME.

The changing fate of group selection theory illustrates nicely the importance of studying the history of science. It was Charles Darwin that first used something like group selection to explain how natural selection could give rise to altruistic behavior and moral instinct. These instincts could be accommodated by his theory of evolution, he argued, if they had evolved 'for the good of the community'. By the 1960s, group selection had a new and vocal advocate in V.C. Wynne-Edwards. But this gave critics of the theory that selection might act on groups, rather than at the level of individuals or genes, a definable target, and from the mid-1960s to the 1980s group selection was considered the archetypal example of flawed evolutionary thinking. However, at the end of the 20th century ideas of group selection re-emerged as an important component of a multilevel theory of evolution.

Department of Ecology, Evolution and Behavior, University of Minnesota, 100 Ecology Building, 1987 Upper Buford Circle, St Paul, MN 55108, USA. borrello@umn.edu


Ann Hum Biol. 2000 May-Jun;27(3):221-37.

Biological adaptation and social behaviour.

Crognier E.

In 1930, both Fisher and Wright identified Darwin's initial concept of adaptive evolution in the light of the genetical theory with intergenerational variation in allelic frequencies brought about by the action of natural selection through differential reproduction. They emphasized that selection only works at the level of the individual and that its only consequence is to increase fitness. One genetical evolution not easy to explain on these bases was that of social behaviour because any altruistic gene disadvantageous for its carriers in an antisocial environment would have been opposed by selection. In the 1950s, ethologists focusing on what appeared to be evolved collective behaviours, hypothesized that selection could operate at group level. Though the controversy between group selectionists and evolutionary geneticists ended by the rejection of the evolutionary role of group selection, it has remained a subject of investigation until now. Kin selection, proposed by Hamilton, offered a solution to the problem of the evolution of altruism and gave the impetus to the trend of adaptive explanations of basic behaviours, which was to become the core of human sociobiology. The intrusion of behaviour into the process of adaptive evolution was an invitation to investigate culture as an evolutive process. The first sociobiological interpretations of culture as a derivative of genetic processes were followed by other ideas in which culture, though channelled by evolved predispositions, was essentially free from biological determinism. It is concluded that as we have come to better understand human adaptation, its complexities have been further revealed, a development already implicit in Darwin's notion.

UMR 6578, CNRS and Université de la Méditerranée, Faculté de Médecine Secteur Centre, Marseille, France.


Nature. 1978 Aug 31;274(5674):849-55.

Selfish genes, evolutionary games, and the adaptiveness of behaviour.

Parker GA.

The science of sociobiology, which began in principle with the work of Fisher and Haldane and has more recently been developed by Hamilton, Maynard Smith, Trivers, Wilson and others, has been the centre of both scientific and political controversy. Dr Parker discusses the strengths and weaknesses of the approach, and illustrates that behaviour can be adapted in a complex way in conformity with sociobiological theory.

Moral Decisions

Proc Natl Acad Sci U S A. 2009 Jul 28;106(30):12506-11. Epub 2009 Jul 21.

Patterns of neural activity associated with honest and dishonest moral decisions.

Greene JD, Paxton JM.

What makes people behave honestly when confronted with opportunities for dishonest gain? Research on the interplay between controlled and automatic processes in decision making suggests 2 hypotheses: According to the "Will" hypothesis, honesty results from the active resistance of temptation, comparable to the controlled cognitive processes that enable the delay of reward. According to the "Grace" hypothesis, honesty results from the absence of temptation, consistent with research emphasizing the determination of behavior by the presence or absence of automatic processes. To test these hypotheses, we examined neural activity in individuals confronted with opportunities for dishonest gain. Subjects undergoing functional magnetic resonance imaging (fMRI) gained money by accurately predicting the outcomes of computerized coin-flips. In some trials, subjects recorded their predictions in advance. In other trials, subjects were rewarded based on self-reported accuracy, allowing them to gain money dishonestly by lying about the accuracy of their predictions. Many subjects behaved dishonestly, as indicated by improbable levels of "accuracy." Our findings support the Grace hypothesis. Individuals who behaved honestly exhibited no additional control-related activity (or other kind of activity) when choosing to behave honestly, as compared with a control condition in which there was no opportunity for dishonest gain. In contrast, individuals who behaved dishonestly exhibited increased activity in control-related regions of prefrontal cortex, both when choosing to behave dishonestly and on occasions when they refrained from dishonesty. Levels of activity in these regions correlated with the frequency of dishonesty in individuals.

Department of Psychology, Harvard University, 33 Kirkland Street, Cambridge, MA 02138, USA. jgreene@wjh.harvard.edu

Pushing moral buttons: the interaction between personal force and intention in moral judgment.
Greene JD, Cushman FA, Stewart LE, Lowenberg K, Nystrom LE, Cohen JD.
Cognition. 2009 Jun;111(3):364-71. Epub 2009 Apr 16.

The neural bases of cognitive conflict and control in moral judgment.
Greene JD, Nystrom LE, Engell AD, Darley JM, Cohen JD.
Neuron. 2004 Oct 14;44(2):389-400.

An fMRI investigation of emotional engagement in moral judgment.
Greene JD, Sommerville RB, Nystrom LE, Darley JM, Cohen JD.
Science. 2001 Sep 14;293(5537):2105-8.

Mutualism

J Evol Biol. 2006 Sep;19(5):1365-76.

The evolution of cooperation and altruism--a general framework and a classification of models.

Lehmann L, Keller L.

One of the enduring puzzles in biology and the social sciences is the origin and persistence of intraspecific cooperation and altruism in humans and other species. Hundreds of theoretical models have been proposed and there is much confusion about the relationship between these models. To clarify the situation, we developed a synthetic conceptual framework that delineates the conditions necessary for the evolution of altruism and cooperation. We show that at least one of the four following conditions needs to be fulfilled: direct benefits to the focal individual performing a cooperative act; direct or indirect information allowing a better than random guess about whether a given individual will behave cooperatively in repeated reciprocal interactions; preferential interactions between related individuals; and genetic correlation between genes coding for altruism and phenotypic traits that can be identified. When one or more of these conditions are met, altruism or cooperation can evolve if the cost-to-benefit ratio of altruistic and cooperative acts is greater than a threshold value. The cost-to-benefit ratio can be altered by coercion, punishment and policing which therefore act as mechanisms facilitating the evolution of altruism and cooperation. All the models proposed so far are explicitly or implicitly built on these general principles, allowing us to classify them into four general categories.



J Theor Biol. 2004 Feb 21;226(4):421-8.

Evolution of mutualism through spatial effects.

Yamamura N, Higashi M, Behera N, Yuichiro Wakano J.

Mutualism among species is ubiquitous in natural ecosystems but its evolution is not well understood. We provided a simple lattice model to clarify the importance of spatial structure for the evolution of mutualism. We assumed reproductive rates of two species are modified through interaction between species and examine conditions where mutualists of both species, that give some benefit to the other species with their own cost, invade non-mutualists populations. When dispersal of offspring is unlimited, we verified the evolution of mutualism is impossible under any condition. On the other hand, when the dispersal is limited to neighboring lattice sites, mutualists can invade if the ratio of cost to benefit is low and the intrinsic reproductive rate is low in case where the parameter values are symmetric between species. Under the same conditions, non-mutualists cannot invade mutualist populations, that is, the latter are evolutionarily stable. In case of asymmetric parameters, mutualists tend to invade if the average value of costs to two species is low or that of benefits is high, and if the intrinsic reproductive rate is low for one of the two species. A mechanistic explanation of why mutualists increase when the dispersal is limited is given by showing that mutualist pairs of the two species at the same lattice site rapidly increase at the initial phase of the invasion.


J Theor Biol. 1994 Oct 21;170(4):393-400.

Genetics of mutualism: the evolution of altruism between species.

Frank SA.

Conditions are analyzed under which natural selection favors an individual to help another species at a cost to its own reproduction. Traditional models for the evolution of altruism between species focus on the genetic relatedness between the original donor and the recipients of return benefits from the mutualistic partner species. A more general model is analyzed here that focuses on the synergistic effects between partner species caused by genetic variability. The model shows that the spread of altruism is enhanced by spatial correlations between species in the genetic tendency to give aid to partners. These spatial correlations between species are similar to the kin selection coefficients of relatedness that determine the course of social evolution within species. The model also shows that natural selection and ecological dynamics can create genetic correlations between neighbors of different species, even when the initial spatial distributions of the species are uncorrelated. Genetic correlations between species may play an important role in the origin and maintenance of altruism between species.

Department of Ecology and Evolutionary Biology, University of California, Irvine 92717.