Journal or Scientific and Industrial Research Vol 39, June 1980, pp. 298-301 Seminar.on Evolution of Social Behaviour RAG HA VENDRA R. GADAGKAR . Centre for Theoretical Studies, Indian Institute oC Science, Bangalore S60012 The Mahabaleshwar seminars on modem biology numbers of offspring. pays less, while developing sponsored by Tata Institute of Fundamental Research, vegetative tissue to be able to compete better is Ahmednagar College, Indian Institute of Science and advantageous. In such a situation, for example, plants University Grants Commission represent a fresh would grow taller to get more sunlight, although they approach to the organization of scientific meetings in produce less seeds. This phenomenon is called K as much as they are intensive study courses in selected selection. (K is a standard symbol for carrying areas of current interest for a multidisciplinary capacity). In the lectures on population genetics and gathering of active research workers. The fact that the natural selection, Sulochana Gadgil introduced basic seminars are held in the romantic hill resort of geneti~, considered the factors responsible for Mahabaleshwar right in the heart of the Western producing gene-frequency changes and discussed Ghats, adds another dimension to their attractiveness. Hardy-Weinberg equilibrium which obtains in a · Madhav Gadgil of the Centre for Theoretical sexually reproducing population in the absence of Studies, Indian Institute of Science, Bangalore these factors. She then considerc!d the simplest conducted the last seminar during 15-27October1979 ·mathematical model for evolution under natural with the assistance of J.H. Crook of Bristol University, selection and stressed conditions necessary to ensure W.G. Eberhard and M.J. West-Eberhard of the the validity of evolutionary arguments for the presence University of Costa Rica, J.F. Ei~nberg of the of a trait. The limits of applicability of Fisher's Smithsonian Institution, Raghavendra Gadagkar, and fundamental theorem of natural selection were also Sulochana Gadgil of the Indian Institute of Science, discussed. K.C. Malhotra of the Indian Statistical Institute, J. Maynard Smith of the University of Sussex and R.L. Principles of Social Evolution Trivers of the University of California, Santa Cruz. Two lectures on kin selection by Mary Jane West­ The meeting was inaugurated by John Maynard Eberhard marked the beginning of a series of eleven· Smith who gave a brief historical introduction to the lectures on the principles of social evolution. The concept of evolution in biology. concept of kin selection argues that because kin are likely to share a number of genes in common, Principles of Population Biology interaction between kin that might actually lower one's This section consisted of two lectures each by own individual fitness (number of offspring left behind) Madhav Gadgil (on population dynamics and rand K can still be selected by nature, because they enhance selection) and Sulochana Gadgil (on population inclusive fitness (the number of copies of common genetics and natural selection). Madhav Gadgil genes left behind, irrespective of who is carrying the introduced the participants to the basic concepts of . genes). Although kin selection is an inevitable population dynamics such as birth rates, death rates, consequence of natural selection and a number of survivorship and fertility curves, age composition and people including Darwin, Fisher and Haldane had models for the study of population growth. Essentially grasped this concept, the credit for the modern theory this lecture dealt with the basic algebra necessary to goes to W.D. Hamilton. In 1964, Hamilton explicitly understand the subsequent lectures. In the lecture ori r defined kin selection and inclusive fitness and showed and K selection, he showed how organisms living in how these ideas form a framework to explain many rich and relatively unsaturated habitats devote much forms of social behaviour that seem contradictory to more of their resources to seed production or natural selection at first sight. Hamilton's ideas have reproduction in general. These are said to be r selected become very popular, because he immediately applied species (r standing for population growth rate). On the them to the social Hymenoptera, a group of insects that other hand, in a crowded habitat, where there is much provides a suitable test of these ideas. Among the competition from conspecifics, investing in larger Hymenoptera there is a peculiar mode of reproduction 298 c GADAGKAR: SEMINAR ON EVOLUTION OF SOCIAL BEHAVIOUR such that sisters are more closely related to.each other work on the functions of beetle horns. By studying a than mothers are to daughters. The fact that in a variety of horned beetles in the sugarcane fields of number of Hymenopteran species, females forego Columbia, ·be has shown that the beetles use their reproduction to help raise more sisters, provides a horns to fight other beetles in the course ofcompetition dramatic demonstration of the importance of kin for mates and mating sites. This was followed by a selection. Apart from the social Hymenoptera· it is lecture on social heirarchy by Mary Jane West­ believed today that kin selection is the moulding force Eberhard. She described a number of situations of of many a social organization, because cooperation social heirarchy from insects to primates and discussed among relatives is less risky in that there is some the consequences of such heirarchical organization. In inclusive fitness.in helping a relative even if the help is summary, group life leads to social competition which not proportionately reciprocated. inevitably sets up a heirarchical organization. In such The next lecture was by John Maynard Smith on an organization the losers in the social competition do group selection, another concept that attempts to not lose everything because the act of losing is in itself a explain altruistic acts and similar social behaviour. signal to adopt alternative strategies. This lecture led Group selection as originally developed by Wyne logically to the next one by John Maynard Smith who Edwards argues that in small isolated populations with emphasiz.ed the concept of game theory in analyzing very low intermigrations altruistic acts that enhance animal conflicts. Maynard Smith was actually the first the survival of the group as a whole will be selected one to introduce this idea in the study ofevolution. The even if they lower the fitness of the individual altruist. most important outcome of his studies is that during Maynard Smith used an example at hand to drive the situations of conflict the result depends on the point home. Mahabaleshwar and especially the area strategies adopted by players in the game, so to speak, where the participants lived is populated by very large and that living organisms are programmed to adopt numbers of a particular insect called cicada, the males different strategies depending on the circumstances. of which sing a loud song all in synchrony every 30-40 Thus, in the light of this, evolution can be looked upon min or so. While the cause or function of this cicada as progress towards the adoption of evolutionarily song is not known, Maynard Smith used this stable strategies. It is in this context that game theory communal singing as an argument that he thought offers a unique mode of treatment of evolutionary Wyne Edwards would have used to explain group problems. A more technical seminar was delivered by selection. Thus, a group selectionist would argue that Sulochana Gadgil on the work she and her colleagues the cicadas were singing periodically to assess their are carrying out at the Indian Institute of Science. This population density and. they would then adjust the rate involved the dynamical formulation of problems of their reproduction so as not to overexploit the related to game theory and evolutionarily stable habitat. The prevailing consensus as expressed by strategies in classjcal population genetics equations. Maynard Smith was that although group selection can John Hurrell Crook followed with a lecture on social operate under very special conditions,·it is not at all spacing and territoriality. Drawing upon the work of a clear that such conditions in fact occur in nature. large number of people, he described the various However, he suggested that the evolution of sex is an possible advantages and disadvantages of territoriality interesting case to explore the possibility of group associated with feeding efficiency and predator selection. avoidance, with particular reference to the birds. He There were two lectures related to sexual selection also gave an introductory lecture on ethology which set and mate competition by William G. Eberhard. In the the background for subsequent lectures on different first lecture be developed the general concept of sexual social systems. Lastly, Robert L. Trivers discussed selection. Sexual selection, a concept recogniz.ed since various aspects of the problem of sex ratios. Starting the time of Charles Darwin, pertains to selection which from Fisher's theory of a 1: 1 sex ratio and Hamilton's enhances reproductive success as opposed to mere theories of extraordinary sex ratios, he drew upon his survival. Although the net fitness depends on both own work with the ants and the whales to review the survival and reproductive success, it is known that causes and consequences of deviations from the sometimes sexual selection leads to the development of normal sex ratio. exaggerated secondary sexual characters that might actually lower survival. For example, the escalated Evolution of Social Systems antlers of some deer and the train of peacock might In this section, various social groups of animals such actually prevent escape from predators but are selected as insects, birds and mammals were surveyed. William through female choice because these characters come Eberhard began the series with a lecture on the origin to be associated with reproductive success of the males. of group living in insects and spiders.