Why long-lived species are more likely to be social: the role of local dominance

Recent studies have shown that individuals of species that livein groups tend to have high annual survival, but this link haslacked a theoretical explanation. We evaluate two hypothesesthat explain how longevity could have led to the evolution ofgroup living. The first is the territory inheritance hypothesis,and it proposes that longevity increases the probability ofnonbreeding subordinates surviving long enough to have the opportunityof inheriting their natal territory. Second, we propose a novelhypothesis, the reciprocal altruism hypothesis, which is thatlongevity increases local dominance by favoring nonaggressionpacts among neighboring residents because longevity increasesthe likelihood of reciprocal altruism. Birds thus accept subordinateresidency because the exclusion of nonlocal birds will meanthat, if they survive long enough, they will be likely to actuallyachieve territory inheritance. The reciprocal altruism hypothesisis supported by a wider array of evidence; becomes progressivelymore powerful as longevity increases, thus producing a positivefeedback; explains the evolution of local dominance (whereasthe territory inheritance hypothesis assumes its existence);and provides an explanation for why cooperative breeding shouldbe found more often in aseasonal environments.     

A surplus of positive trials: weighing biases and reconsidering equipoise

In this issue, Fries and Krishnan raise provocative new ideas to explain the surfeit of positive industry sponsored trials evaluating new drugs. They suggest that these trials were designed after so much preliminary work that they were bound to be positive (design bias) and that this violates clinical equipoise, which they characterize as an antiquated concept that should be replaced by a focus on subject autonomy in decision making and expected value for all treatments in a trial. We contend that publication bias, more than design bias, could account for the remarkably high prevalence of positive presented trials. Furthermore, even if all new drugs were efficacious, given the likelihood of type 2 errors, not all trials would be positive. We also suggest that clinical equipoise is a nuanced concept dependent on the existence of controversy about the relative value of two treatments being compared. If there were no controversy, then trials would be both unnecessary and unethical. The proposed idea of positive expected value is intriguing, but in the real world such clearly determinable values do not exist. Neither is it clear how investigators and sponsors, who are invested in the success of a proposed therapy, would (or whether they should) develop such a formula.     

Horn growth in male pronghornsAntilocapra americana: selection for precocialmaturation in stochastic environments

PronghornsAntilocapra americana (Ord, 1818), the sole member of a family unique to North America, grow rapidly and reproduce at an early age. Recent studies have found male pronghorns can grow large horns by 2 to 3 yrs of age. This pattern contrasts with many other ungulates, and it has profound implications for life history strategies. We examine 5 hypotheses that might explain precocial horn growth: (1) sampling bias, (2) nutrition, (3) phylogenetic inertia, (4) reproductive benefits conveyed by rapid horn growth alone, and (5) rapid horn growth as part of a suite of characteristics acquired due to precocial maturation. Hypotheses 1, 2 and 3 do not imply any natural selection, whereas hypotheses 4 and 5 do. We reject hypotheses 1, 2 and 4, and we cannot evaluate hypothesis 3. We conclude that hypothesis 5 most likely explains precocial maturation in male pronghorns, and mortality related to frequent, severe weather events may drive this pattern. We suggest several experiments to further examine relationships between age, size, and horn growth.     

How is a tissue built?

Tissues change in many ways in the period that they are part of a living organism. They are created in fairly repeatable structural patterns, and we know that the patterns are due to both the genes and the (mechanical) environment, but we do not know exactly what part or percentage of a particular pattern to consider the genes, or the environment, responsible for. We do not know much about the beginning of tissue construction (morphogenesis) and we do not know the methods of tissue construction. When the tissue structure is altered to accommodate a new loading, we do not know how the decision is made for the structural reconstruction. We do know that tissues grow or reconstruct themselves without ceasing to continue with their structural function, but we do not understand the processes that permit them to accomplish this. Tissues change their structures to altered mechanical environments, but we are not sure how. Tissues heal themselves and we understand little of the structural mechanics of the process. With the objective of describing the interesting unsolved mechanics problems associated with these biological processes, some aspects of the formation, growth, and adaptation of living tissues are reviewed. The emphasis is on ideas and models. Beyond the objective is the hope that the work will stimulate new ideas and new observations in the mechanical and chemical aspects of developmental biology.     

An energetics-based approach to understanding the menstrual cycle and menopause

To explain the menstrual cycle and menopause, human biologists during the past several decades have developed new models of the evolutionary origins and maintenance of female reproductive patterns that address both ultimate and proximate causation. Hypotheses proposed for these processes generally offer explanations for menstruation or for menopause, but not for both; ultimately, these explanations must be integrated. Reviewing current explanations, this paper offers an energetics-based evolutionary rationale compatible with past adaptations of Homo sapiens and with ecological patterns in small-scale, preindustrial social systems in which food resources vary and sometimes are scarce. This paper is an expansion of a poster paper presented at the 2002 Human Biology Association meetings in Buffalo, New York. Roberta L. Hall is professor of anthropology at Oregon State University. Her main interest is in evolutionary aspects of human biological variation. Current research involves body composition relationships with resting metabolic rate in males and females and climatic adaptions of nasal morphology. She also enjoys working with the Coquille Indian Tribe of southern Oregon on research concerning their prehistory and is studying ramifications of the coastal hypothesis of North American settlement.     

CLADISTIC TESTS OF ADAPTATIONAL HYPOTHESES

Abstract— A cladistic viewpoint provides an historical definition of adaptation and an operational ecological test for evolutionary adaptations. Adaptation is apomorphic function promoted by natural selection, as compared with plesiomorphic function. Adaptation is thus a conditional, hierarchical, comparative term, like homology. Hypotheses of adaptation that do not specify levels of apomorphy are weak; they should refer to and explain the function at the level at which it is apomorphic with respect to the plesiomorphic (outgroup) condition. The adaptational hypothesis serves as a prior prediction in the comparison of the apomorphic function of the derived trait with the plesiomorphic function of the plesiomorphic trait serving as the null hypothesis. It is useful to distinguish whether hypotheses about characters identify selection as facilitating: 1) the origin of a character; 2) its maintenance; 3) neither; or 4) both. The latter two are uniformitarian and testable in a strong sense. The former two possibilities use ancillary arguments to protect the hypothesis of the role of natural selection in one way or another, but might still be tested by the weak criterion of plausibility. Given an hypothesis of both origin and maintenance due to selection, the test of adaptation may still be thwarted because only certain kinds of cladistic structure allow feasible tests. Few of the really classic and common examples of supraspecific adaptation survive this kind of cladistic test.     

Climbing to reach females: Romeo should be small

The race for reaching mates by the time they are receptive, or sexual selection by scramble competition, has received little attention. We argue that smaller males are favored in species in which the male must climb to reach females located in high habitat patches. This new explanation we term the "gravity hypothesis" of sexual size dimorphism (SSD). We show that a simple biomechanical model of animal movement predicts that: (1) selection should favor a comparatively smaller size in the searching sex when searching involves climbing; and (2) this effect should be stronger in larger species than in smaller species. In reaching high habitats, smaller, faster searchers will be favored either through sexual selection by scramble competition and/or by escaping predation easier by running faster on vertical surfaces. Different spider species are found at a wide range of heights. We compiled a dataset of spider taxa and arranged their habitats according to four height categories, ranked from soil surface to trees. We show that, after controlling for phylogeny, both predictions of the gravity hypothesis of SSD are met. Thus, it appears that the constraint imposed by gravity on climbing males is a selective factor in determining male dwarfism.     

High male:female ratio of germ-line mutations: an alternative explanation for postulated gestational lethality in males in X-linked dominant disorders.

In this paper I suggest that a vastly higher rate of de novo mutations in males than in females would explain some, if not most, X-linked dominant disorders associated with a low incidence of affected males. It is the inclusion of the impact of a high ratio of male:female de novo germ-line mutations that makes this model new and unique. Specifically, it is concluded that, if an X-linked disorder results in a dominant phenotype with a significant reproductive disadvantage (genetic lethality), affected females will, in virtually all cases, arise from de novo germ-line mutations inherited from their fathers rather than from their mothers. Under this hypothesis, the absence of affected males is explained by the simple fact that sons do not inherit their X chromosome (normal or abnormal) from their fathers. Because females who are heterozygous for a dominant disorder will be clinically affected and will, in most cases, either be infertile or lack reproductive opportunities, the mutant gene will not be transmitted by them to the next generation (i.e., it will be a genetic lethal). This, not gestational lethality in males, may explain the absence of affected males in most, if not all, of the 13 known X-linked dominant diseases characterized by high ratios of affected female to male individuals. Evidence suggesting that this mechanism could explain the findings in the Rett syndrome is reviewed in detail.     

Inaccurate reconstruction of ancestral GC levels creates a "vanishing isochores" effect

It has recently been proposed, based on an analysis of orthologous gene sequences from closely related species, that GC-rich regions of primate and cetartiodactyl genomes are becoming GC-poorer, i.e., that GC-rich isochores are now vanishing in these lineages. We review an artefact of parsimony-based ancestor reconstruction in GC-rich DNA, and show that its magnitude explains the apparent vanishing of the GC-richest regions in cetartiodactyls, even if they are in fact at compositional equilibrium. The presently available data do not allow the disequilibrium hypothesis to be entirely ruled out in primates, yet, as we argue here, second-order artefacts can accumulate. They are therefore likely to explain many if not all of the observations, rendering unnecessary the general hypothesis of vanishing GC-rich isochores in mammals.     

Debates: Challenging a Recent Challenge to the Aggressive Spillover Hypothesis

Kralj‐Fiser et al. recently reviewed the lack of evidence in favor of the aggressive spillover hypothesis, an animal personality/behavioral syndrome explanation for pre‐copulatory sexual cannibalism. In doing so, they evaluated past tests of the hypothesis, set forth their ideas for criteria that need to be met to accept the spillover hypothesis, and conclude that the hypothesis is not generally supported. Here, I comment on several aspects of their position. In doing so, I identify areas in which we differ and point out several strengths of past tests of the spillover hypothesis. In particular, I suggest that researchers testing the spillover hypothesis have done an excellent job of studying sexual cannibalism in the broader context of a movement within behavioral ecology to understand where an animal's behavior falls along a continuum of plasticity.     

Community care and the fundholder.

According to the government, clearly agreed local arrangements should enable individual general practitioners to make their full contribution to the new system of community care without getting involved in extra bureaucracy. From 1 April the main part of that contribution will be to refer to social services those patients who seem to need social care. Many general practitioners are worried that such referrals will be complex and time consuming and will generate too much extra work. Moreover, general practitioners may also be asked to see patients specifically to help social workers'' assessment procedures, and many fear that such consultations will overwork and underpay them. General practitioner fundholders already use contracts to spell out what they expect from hospital services. From 1 April they will be able to set up contracts for community health services such as district nursing and chiropody, and possibly this might be extended to social aspects of community care. Over the past 14 months Dr Rhidian Morris and his partners in a fundholding practice in Devon have piloted contracts for all aspects of community care. In this article Dr Morris explains how the most radical part of the pilot project--the contract for social care--was set up. He argues that the lessons on communication that came from what was essentially a fundholding project could apply also to non-fundholding practices.     

Ornaments or offspring? Female sticklebacks (Gasterosteus aculeatus L.) trade off carotenoids between spines and eggs

Hypotheses and models to explain female ornaments often assume that the elaborated traits are condition dependent; nevertheless, few empirical studies have addressed this topic. We studied a population of three-spined sticklebacks (Gasterosteus aculeatus) in which the females have conspicuous, carotenoid-based red coloration to their pelvic spines. The red coloration seems not to be condition dependent, as coloration is negatively associated with age and body length and not associated with condition. Furthermore, redder females did not have a lower density of leucocytes. We found a negative association between the females' red carotenoid-based coloration in the spines and the amount of carotenoids in the female's gonads. Males choosing red-coloured females will fertilize eggs with small amounts of carotenoids and appear not to gain any benefit from their mates' phenotypic quality that could result in offspring of improved quality. These results do not support the 'direct selection hypothesis' to explain the existence of the female ornaments.     

Methodological Problems in Evolutionary Biology. XII. Against Evolutionary Ethics

Evolutionary ethics has recently become popular again. Some of its representatives elaborate new attempts to derive ethics from evolutionary biology. The attempts, like previous ones, fail because they commit the naturalistic fallacy. Premises from evolutionary biology together with normative premises also do not justify ethical principles. Other representatives argue that evolutionary considerations imply that ethics cannot be justified at all. Their arguments presuppose an unacceptable form of foundationalism. In principle, evolutionary biology might explain some aspects of morality, but in practice explanations are hard to come by. All this does not imply that evolutionary theory is irrelevant in normative settings. To the contrary, it may help us devise guidelines in environmental policy and health care policy. It is to be hoped that evolutionary ethicists will divert their research efforts to the elaboration of such guidelines.     

The social lifestyle of myxobacteria

Myxobacteria are social organisms that usually remain together even though they are not chemically attached to each other. They cooperatively feed and form aggregates and fruiting bodies. Their mode of movement, the forces and mechanisms that allow movement, the factors that keep them together, and the processes leading to the structures composed of many cells are only now beginning to be understood. Possibilities that may be key to their abilities are three models proposed elsewhere for different aspects of their biology. One hypothesis attempts to explain mound and fruiting body formation by assuming that the cells move in circular patterns around the major cell mass. The second explains gliding motility on the existence of shunts that periodically short out the proton gradient across the cell membrane, causing expansion and contraction of portions of the cell. The third model proposes that occasionally cells arise that move unidirectional instead of back and forth. These few cells may lead the majority of cells in new directions. BioEssays 20:1030–1038, 1998. © 1998 John Wiley & Sons, Inc.     

Infanticide by Male Lions Hypothesis: A Fallacy Influencing Research into Human Behavior

Recently, familial abuse and killing of children have been correlated with infanticidal behavior by nonhuman male animals which is postulated to be genetic. However, infanticide by males as an evolutionary mechanism is unlikely to occur in primates, and is equally unlikely in lions. To investigate the sexual selection hypothesis of infanticide for lions, four questions should be considered: (1) because they all mate freely with lionesses, are male pride lions closely related? (often they are not), (2) do males kill the young cubs when they join a pride? (few such cases have been observed), (3) do the females then mate with the new males to produce offspring? (yes), and (4) do the males remain with the pride for over two years to protect this new generation? (often not). Field data indicate that in NO instance do we know that male lions killed cubs in a new pride, mated with their mother, and then remained with the pride to protect their own young. Rather, female lions may kill more cubs than males and certainly cause many more cub deaths by allowing them to starve, [ infanticide by male lions, infanticide hypothesis, faulty science]     

New cases of inter-community infanticide by male chimpanzees at Ngogo,Kibale National Park,Uganda

Infanticide by males has been recorded in four chimpanzee populations, including that in Kibale National Park, Uganda. Some infanticidal attacks occur during inter-community aggression. The sexual selection hypothesis does not easily explain these attacks because they may not directly increase male mating opportunities. However, females in the attackers’ community may benefit by expanding their foraging ranges and thereby improving their reproductive success; thus infanticide may increase male reproductive success indirectly. We report two new cases of infanticide by male chimpanzees at Ngogo, Kibale National Park. Like two previous cases, these occurred during a boundary patrol and were almost certainly between-community infanticides. The patrolling males attacked despite the proximity of males from the victims’ presumed community. This probably explains why, unlike the earlier cases, they did not completely cannibalize their victims. Such attacks seem to be relatively common at Ngogo and infanticide may be an important source of infant mortality in neighboring communities. Our observations cannot resolve questions about the sexual selection hypothesis. However, they are consistent with the range expansion hypothesis: the infanticides occurred during a period of frequent encounters between communities associated with a mast fruiting event, and Ngogo community members greatly increased their use of areas near the attack site during another mast fruiting event one year later. Our observations contribute to growing evidence that lethal intergroup aggression is a common characteristic of wild chimpanzee populations.     

Colour polymorphism is likely to be disadvantageous to some populations and species due to genetic architecture and morph interactions

Polymorphism describes two or more distinct, genetically determined, phenotypes that co‐occur in the same population, where the rarest morph is maintained at a frequency above the mutation rate (Ford 1945; Huxley 1955). In a recent opinion piece, we explored a new idea regarding the role of genetic architectures and morph interactions in colour polymorphisms and how this can negatively affect population performance (Bolton et al. 2015). In this issue of Molecular Ecology, Forsman (2016) thoroughly discusses the current evidence for polymorphisms enhancing population performance and critiques the validity of the definitions of polymorphism we use in our original paper. We respond by clarifying that the negative consequences of polymorphisms that we discussed are likely to be most pertinent in species that have a particular set of characteristics, such as strong sexual or social interactions between morphs and discrete genetic architectures. Although it was not our intention to redefine polymorphism, we do believe that there should be further discussion about refining or characterizing balanced polymorphisms with respect to the degree of morph sympatry, discreteness of traits and their underlying genetic architecture, and the types of selection that drive and maintain the variation. The latter describes whether polymorphism is primarily maintained by external factors such as predation pressure or internal factors such as interactions with members of the same species. The contribution of Forsman (2016) is useful to this discussion, and we hope that our exchange of opinions will inspire new empirical and theoretical ideas on the origin and maintenance of colour polymorphisms.     

Design, Development and Decisions

Evolutionary ideas and modern biological knowledge have important roles to play in the understanding of human behaviour. Nevertheless, it is deeply misleading to regard humans as robots in the grip of their genes. A well designed brain should respond to the consequences of behaviour; if an understanding of the likely consequences can be achieved without actually performing the act, then a person who knows that they will be rewarded or punished for certain acts is bound to be influenced by that knowledge. A brain designed in that way facilitates the evolution of societies with explicit social approval of certain activities and explicit disapproval of others. The evolutionary approach to psychology does not imply that individuals do not make free choices. Individuals clearly do make a big difference to what happens in their lives through their decisions. They may be surprised by the consequences of their own actions. A well designed brain should be able to anticipate the consequences of various courses of action and choose between them on the basis of their likely costs and benefits. Planning before doing is clearly of great advantage. People do make well considered decisions and they benefit from doing so.     

HOMEOPATHY IS UNSCIENTIFIC AND UNETHICAL

In opposition to the premises of Against Homeopathy – a Utilitarian Perspective, all four respondents base their objections on the central claims that homeopathy is in fact scientifically plausible and is supported by empirical evidence. Despite ethical aspects forming the main thrust of Against Homeopathy, the respondents’ focus on scientific aspects represents sound strategy, since the ethical case against homeopathy would be weakened concomitant with the extent to which any plausibility for homeopathy could be demonstrated. The trouble here is that the respondents are attempting to perpetuate a sterile debate. The notion that homeopathic preparations could have any biological effects represents a fringe viewpoint, one not entertained by serious scientists nor supported by reason and evidence. In the present article, I shall endeavour to explain why the respondents do not have a valid case. I will deal firstly with their general approach to scientific plausibility and evidence, and then consider some of the specific claims they have made. Finally, I will answer the philosophical arguments some of the respondents have raised.     

The role of computation in modeling evolution

Artificial life uses computers and formal systems to model and explore the dynamics of evolution. A fundamental question for A-Life concerns the role of computation in these models, and how we are to interpret computer implementations that do not have actual contact with physical systems. In this paper I will discuss how models are seen to explain and predict in philosophy of science and how these ideas apply to A-Life. I will also explore how the notion of an epistemic cut, as defined by H. Pattee, can be realized in a computational model with an artificial physical world.