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In the Light of Evolution: Volume V: Cooperation and Conflict (2011)

Chapter: Part III: REAL SELFISH (AND COOPERATIVE) GENES

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Suggested Citation:"Part III: REAL SELFISH (AND COOPERATIVE) GENES." National Academy of Sciences. 2011. In the Light of Evolution: Volume V: Cooperation and Conflict. Washington, DC: The National Academies Press. doi: 10.17226/13223.
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Part III

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REAL SELFISH (AND COOPERATIVE) GENES

It is remarkable that a field founded on the concept of selfish genes (Dawkins, 1976b) got so far for so long without paying much attention to specifiable genes. That is probably because we learned how phenotypic strategies of cooperation and conflict could be understood as the results of genes maximizing inclusive fitness. However, studies at the genic level are now becoming common and should shed light both on the mechanisms and the manner in which social selection operates.

In Chapter 8, Brielle Fischman and colleagues review and extend what is known about the molecular genetic mechanisms of eusociality. Some of the information comes from studies of particular genes and pathways but much is now coming from evolutionary analyses of genome-scale data. To the seven sequenced genomes of social insects, the authors add their own transcriptome-based protein-coding sequences for 10 social and nonsocial bee species, representing three origins of sociality. Some of the patterns are idiosyncratic. For example, early results from the honeybee genome pointed to the importance of odorant receptors and immunity genes, but these do not hold up in the broader analyses. New findings include increased rates of evolution of brain-related genes in the primitively eusocial bees, conceivably because of the increased cognitive demands of their competitive social environment. Juvenile hormone and insulin are often important in caste. This is not surprising if caste is nutritionally based, although the effects of juvenile hormone are quite different than in nonsocial insects. There is also a rapid evolutionary change in proteins involved in fundamental carbohydrate metabolism. Again, this

Suggested Citation:"Part III: REAL SELFISH (AND COOPERATIVE) GENES." National Academy of Sciences. 2011. In the Light of Evolution: Volume V: Cooperation and Conflict. Washington, DC: The National Academies Press. doi: 10.17226/13223.
×

fits with a nutritional basis for caste, but it seems surprising that changes are common in such basic pathways. These issues should be clarified with additional genome sequences and functional studies of individual species.

In Chapter 9, Joan Strassmann and David Queller explore a micro-bial social system where it is possible to manipulate genes. In the social amoeba Dictyostelium discoideum, starved cells come together in large groups in which 20% of the cells sacrifice themselves to make a stalk that aids in dispersal of the others as spores (Kessin, 2001). Besides this impressive altruism, this species has been shown to have cheating, kin recognition, and even primitive farming of their bacterial food. Numerous genes of many functional types can be mutated to cheaters. Some cheaters could destroy cooperation, yet cooperation is maintained for a variety of reasons, one being the rather high genetic relatedness in the field, part of which is due to kin recognition mediated by highly polymorphic adhesion genes. Other controls on cheating that have been demonstrated include the evolution of resistor genes, power asymmetries, and lottery-like mechanisms. Studies of the dimA and csaA genes have shown that cheating can also be controlled by idiosyncratic pleiotropies of particular genes. The cheating allele would be favored by selection but other deleterious effects of the same allele keep it from spreading, suggesting that cheat-proof cooperation often may be built using elements that are essential for other reasons. Consistent with ongoing social conflicts and arms races, social genes evolve rapidly.

Dawkins (1976b) argued that all genes are selfish, but the ones that show the trait most distinctively are selfish genetic elements. These are the renegades of the genome, chunks of DNA that replicate in part at least via different pathways than most genes and thus can be selected to conflict with other loci. Transposons, for example, increase their representation by jumping from one place to another, often at some cost to the organism. Other examples include meiotic drive elements, various modification-rescue systems, imprinted genes, B chromosomes, and organellar genes. In Chapter 10, John Werren tackles the issues of the function and adaptation of these elements. He surveys the evidence, sometimes strong and sometimes suggestive, that such elements have had important functional consequences for their genomes. For example, parts of transposons sometimes evolve into regulatory regions, and defenses against selfish elements may have led to the eukaryotic intron-splicing apparatus. But contrary to some recent suggestions, Werren argues that there is as yet little evidence that these are the adaptive reasons for the maintenance of these elements. Instead, selfish genetic elements are maintained by their selfish behavior, but the new chunks of DNA that they sprinkle throughout genomes sometimes get co-opted, domesticated, or otherwise modified to cause some beneficial effect to the organism.

Suggested Citation:"Part III: REAL SELFISH (AND COOPERATIVE) GENES." National Academy of Sciences. 2011. In the Light of Evolution: Volume V: Cooperation and Conflict. Washington, DC: The National Academies Press. doi: 10.17226/13223.
×
Page 165
Suggested Citation:"Part III: REAL SELFISH (AND COOPERATIVE) GENES." National Academy of Sciences. 2011. In the Light of Evolution: Volume V: Cooperation and Conflict. Washington, DC: The National Academies Press. doi: 10.17226/13223.
×
Page 166
Next: 8 Molecular Evolutionary Analyses of Insect Societies--BRIELLE J. FISCHMAN, S. HOLLIS WOODARD, and GENE E. ROBINSON »
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Biodiversity—the genetic variety of life—is an exuberant product of the evolutionary past, a vast human-supportive resource (aesthetic, intellectual, and material) of the present, and a rich legacy to cherish and preserve for the future. Two urgent challenges, and opportunities, for 21st-century science are to gain deeper insights into the evolutionary processes that foster biotic diversity, and to translate that understanding into workable solutions for the regional and global crises that biodiversity currently faces. A grasp of evolutionary principles and processes is important in other societal arenas as well, such as education, medicine, sociology, and other applied fields including agriculture, pharmacology, and biotechnology. The ramifications of evolutionary thought also extend into learned realms traditionally reserved for philosophy and religion.

The central goal of the In the Light of Evolution (ILE) series is to promote the evolutionary sciences through state-of-the-art colloquia—in the series of Arthur M. Sackler colloquia sponsored by the National Academy of Sciences—and their published proceedings. Each installment explores evolutionary perspectives on a particular biological topic that is scientifically intriguing but also has special relevance to contemporary societal issues or challenges. This book is the outgrowth of the Arthur M. Sackler Colloquium "Cooperation and Conflict," which was sponsored by the National Academy of Sciences on January 7-8, 2011, at the Academy's Arnold and Mabel Beckman Center in Irvine, California. It is the fifth in a series of colloquia under the general title "In the Light of Evolution." The current volume explores recent developments in the study of cooperation and conflict, ranging from the level of the gene to societies and symbioses.

Humans can be vicious, but paradoxically we are also among nature's great cooperators. Even our great conflicts-wars-are extremely cooperative endeavors on each side. Some of this cooperation is best understood culturally, but we are also products of evolution, with bodies, brains, and behaviors molded by natural selection. How cooperation evolves has been one of the big questions in evolutionary biology, and how it pays or does not pay is a great intellectual puzzle. The puzzle of cooperation was the dominant theme of research in the early years of Darwin's research, whereas recent work has emphasized its importance and ubiquity. Far from being a rare trait shown by social insects and a few others, cooperation is both widespread taxonomically and essential to life. The depth of research on cooperation and conflict has increased greatly, most notably in the direction of small organisms.

Although most of In the Light of Evolution V: Cooperation and Conflict is about the new topics that are being treated as part of social evolution, such as genes, microbes, and medicine, the old fundamental subjects still matter and remain the object of vigorous research. The first four chapters revisit some of these standard arenas, including social insects, cooperatively breeding birds, mutualisms, and how to model social evolution.

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