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PubMed2001

A model for the emergence of cooperation, interdependence, and structure in evolving networks.

Evolution produces complex and structured networks of interacting components in chemical, biological, and social systems. We describe a simple mathematical model for the evolution of an idealized chemical system to study how a network of cooperative molecular species arises and evolves to become more complex and structured. The network is modeled by a directed weighted graph whose positive and negative links represent "catalytic" and "inhibitory" interactions among the molecular species, and which evolves as the least populated species (typically those that go extinct) are replaced by new ones. A small autocatalytic set, appearing by chance, provides the seed for the spontaneous growth of connectivity and cooperation in the graph. A highly structured chemical organization arises inevitably as the autocatalytic set enlarges and percolates through the network in a short analytically determined timescale. This self organization does not require the presence of self-replicating species. The network also exhibits catastrophes over long timescales triggered by the chance elimination of "keystone" species, followed by recoveries.

Animals↗
PubMed1977

Dual origin of highly social behavior among bees.

A study of behavior and structure indicates that highly eusocial behavior arose twice in the bees--i.e., in the stingless bees (Meliponinae) and in the honeybees (Apinae). Morphological features demonstrate the distinctiveness of these two groups and the relationship of the latter to bumblebees (Bombini) and orchid bees (Euglossin). The social behaviors of the stingless bees and honeybees, while more or less equally elaborate, are so different as to support their independent origins. The primitive apids, along with the related Xylocopinae (in the Anthophoridae), appear to have had the potential for parasocial, subsocial, and primitively eusocial behavior and from such forms the two highly eusocial groups arose.

Animals↗
PubMed1984

[Effect of social factors on the long-term course of schizophrenia].

On the basis of the literature and of his own research concerning the long-term-evolution and the vocational rehabilitation of schizophrenics, the author shows that social factors play an important role in the long-term-evolution of schizophrenia. Of particular importance is the influence of the therapeutic setting, of overtaxing "life-events", of the family atmosphere, of the institutional infrastructure, of the expectations of the social environment, and of several socio-economic and cultural factors. Biological and psychosocial influences can be combined into a multiconditional model of schizophrenia in three phases, in which the vulnerability- und information-processing-hypothesis are central. This model leads to interesting consequences for the prevention and the therapy of schizophrenia.

Antipsychotic Agents↗
PubMed2006

The animal cultures debate.

Recent interest in animal cultures has been fuelled by high-profile reports of intra- and interpopulation differences in the behavioural repertoires of primates and cetaceans, consistent with the existence of socially learned traditions. Several studies have mapped spatial differences in behaviour, revealing a mosaic of behavioural phenotypes within species. The dominant current approach attempts to determine whether this is cultural variation by excluding asocial learning, ecological or genetic factors. However, claims of animal cultures remain controversial because such comparisons are subject to weaknesses; thus, new approaches to isolating the influence of culture on behaviour are required. Here we suggest that, rather than attributing behaviour to explanatory categories, researchers would often be better advised to partition variance in behaviour to alternative sources.

Animal Communication↗
PubMed1982

Community mental-health programs and social history: an inter-American comparison.

This theoretical paper argues that the evolution of community mental health, as both a concept and a movement, is a function of social history. Furthermore cross-cultural differences in social history are seen as best explaining differences between the Americas in the relative speed and nature of the development of community mental health. Pertinent social history factors in the United states, Ontario (Canada), and Colombia (South America) are presented as providing some evidence for the validity of the paper's thesis. Finally, a universal developmental sequence model is discussed and depicted in figure form. The implications for future developments in community mental health are briefly discussed in the context of the model.

Colombia↗
PubMed2004

Local co-adaptation leading to a geographical mosaic of coevolution in a social parasite system.

The geographical mosaic theory of coevolution predicts differences in the advance or trajectory of the coevolutionary process between local communities due to their composition and the strength of ecological selection pressures through competition and resource availability. In this study, we investigate local co-adaptation in different populations of a social parasite. We conducted cross-fostering experiments to test for interpopulational differences in raiding efficiency between various populations of a slave-making ant and the defence abilities of local hosts. Here, we demonstrate that the success of raids strongly depends on the combination of populations of the parasite Harpagoxenus sublaevis and its host Leptothorax acervorum, indicating very localized coevolution. We found no absolute differences between slave-maker populations; the outcome of an encounter depended more on whether the two opponents occur in sympatry or allopatry. Furthermore, this study supports the results of our earlier work, that the unparasitized English L. acervorum population is most aggressive against the parasite.

Adaptation, Biological↗
PubMed1993

Reconstructing the evolution of mind.

Since Darwin, the idea of intellectual continuity has gripped comparative psychology. Psychological evolution has been viewed as the accumulation of gradual changes over time, resulting in an unbroken chain of mental capacities throughout the diversity of life. Some researchers have even maintained that no fundamental psychological differences exist among species. An alternative model argues that a rather profound new psychology related to mental state attribution may have evolved recently in the primate order. The author explores recent experimental research from chimpanzees, rhesus monkeys, and children that is consistent with this second model of psychological evolution. Drawing on the fields of developmental, comparative, and social psychology, as well as evolutionary and developmental biology, the author outlines a research agenda aimed at reconstructing the evolution of metacognition.

Animals↗
PubMed2007

Spread of arbitrary conventions among chimpanzees: a controlled experiment.

Wild chimpanzees (Pan troglodytes) have a rich cultural repertoire--traditions common in some communities are not present in others. The majority of reports describe functional, material traditions, such as tool use. Arbitrary conventions have received far less attention. In the same way that observations of material culture in wild apes led to experiments to confirm social transmission and identify underlying learning mechanisms, experiments investigating how arbitrary habits or conventions arise and spread within a group are also required. The few relevant experimental studies reported thus far have relied on cross-species (i.e. human-ape) interaction offering limited ecological validity, and no study has successfully generated a tradition not involving tool use in an established group. We seeded one of two rewarded alternative endpoints to a complex sequence of behaviour in each of two chimpanzee groups. Each sequence spread in the group in which it was seeded, with many individuals unambiguously adopting the sequence demonstrated by a group member. In one group, the alternative sequence was discovered by a low ranking female, but was not learned by others. Since the action-sequences lacked meaning before the experiment and had no logical connection with reward, chimpanzees must have extracted both the form and benefits of these sequences through observation of others.

Animals↗
PubMed2026

Pattern Formation in a Spatial Public Goods Dilemma due to Diffusive or Directed Motion.

The costly provision of public goods serves as a model problem for the evolution of cooperative behavior, presenting a social dilemma between the collective benefits of shared resources and the individual incentive to free-ride in resource production. The spatial structure of populations can also impact cooperation over public goods, as diffusion of public goods and intentional motion of individuals towards regions with greater resources can interact with population and public goods dynamics to produce heterogeneous patterns in the spatial distribution of strategies and resources. In this paper, we build off a model introduced by Young and Belmonte for the reaction dynamics of interacting individuals and an explicit public good, deriving a system of PDEs that describes the spatial profiles of strategies and the public good in the presence of both diffusive motion of individuals and resources and chemotaxis-like directed motion of individuals in response to gradients in the concentration of public goods. Through linear stability analysis, we show that spatial patterns in strategic and public goods profiles can emerge due to either Turing instability with high defector diffusivity or a directed-motion instability through strong sensitivity of cooperators towards increasing resource concentration. We further explore the emergent spatial patterns with a mix of weakly nonlinear stability analysis and numerical simulation, showing that, for a wide range of reaction parameters, diffusion-driven instability appears to increase cooperation and public goods across the spatial domain, while directed motion of cooperators towards public goods tends to decrease cooperation and environmental quality across the environment.

Models, Biological↗
PubMed2004

Does she smell like a queen? Chemoreception of a cuticular hydrocarbon signal in the ant Pachycondyla inversa.

Primitive ant societies, with their relatively simple social structure, provide an opportunity to explore the evolution of chemical communication, in particular of mechanisms underlying within-colony discrimination. In the same colony, slight differences in individual odours can be the basis for discrimination between different castes, classes of age and social status. There is some evidence from correlative studies that such inter-individual variation is associated with differences in reproductive status, but direct proof that certain chemical compounds are detected and recognized by ants is still lacking. In the ponerine ant Pachycondyla inversa, fertile queens and, in orphaned colonies, dominant egg-laying workers are characterized by the predominance of a branched hydrocarbon, 3,11-dimethylheptacosane (3,11-diMeC(27)) on the cuticle. Using electroanntennography and gas chromatography with electroantennographic detection, we show that the antennae of P. inversa workers react to this key compound. 3,11-diMeC(27) is correlated with ovarian activity and, because it is detected, is likely to assume the role of a fertility signal reflecting the quality of the sender.

Alkanes↗
PubMed1988

The oldest fossil bee: Apoid history, evolutionary stasis, and antiquity of social behavior.

Trigona prisca, a stingless honey bee (Apidae; Meliponinae), is reported from Cretaceous New Jersey amber (96-74 million years before present). This is about twice the age of the oldest previously known fossil bee, although Trigona is one of the most derived bee genera. T. prisca is closely similar to modern neotropical species. Most of bee evolution probably occurred during the approximately 50 million years between the beginning of the Cretaceous when flowering plants (on which bees depend) appeared and the time of T. prisca. Since then, in this phyletic line of Meliponinae, there has been almost no morphological evolution. Since the fossil is a worker, social organization had arisen by its time.

Journal Article↗
PubMed2000

A preliminary study of spatial distribution and mating system of pygmy mouse lemurs (Microcebus cf. myoxinus).

According to current hypotheses on the evolution of life history traits and social systems of Malagasy lemurs, nocturnality is associated with a solitary lifestyle and a polygynous or promiscuous mating system. Recent studies, however, have indicated that this may not be true of all lemurs. The goal of this study was to investigate the sociality and the mating system of pygmy mouse lemurs (Microcebus cf myoxinus), which are the smallest known primates, and which retain characteristics of the most primitive primates. I compared my findings with data on the sympatric Microcebus murinus and Cheirogaleus medius. Observational, morphometric and spatial distribution data were obtained by a radiotracking study in 1994, and from a capture-recapture study conducted during 1995/96. Pygmy mouse lemurs usually slept alone in a tangle of vegetation. During the mating season, sleeping sites of males were distributed over a much broader area than were female sites, indicating that male home ranges are larger than those of females. The home ranges of males overlapped during the mating season, and males occasionally roamed over long distances during a single night. Pygmy mouse lemurs forage primarily alone. Analysis of estrus stages indicate that female cycles are unsynchronized during the mating season. There was a lack of sexual dimorphism in body size but not in body mass. Males were heavier than females during the reproductive season but lighter than females the rest of the year. Testes of males varied in size seasonally and enlarged significantly during the mating season. The presence of a vaginal sperm plug in a female indicated the importance of preventing additional matings in this species. Thus pygmy mouse lemurs follow the predictions derived from sexual selection theory for multi-male mating systems with promiscuous matings and male sperm competition.

Animals↗
PubMed1991

The International Clinical Epidemiology Network (INCLEN): a progress report.

The International Clinical Epidemiology Network (INCLEN) was established in 1982 to strengthen the research capacity of medical schools in the developing world through the development of Clinical Epidemiology Units (CEUs). The role of these units is to promote a rational approach to clinical and health care decision making, drawing on the methods of clinical epidemiology, biostatistics, health economics and health social science. This paper summarizes the evolution of the INCLEN model and the experience to date. Progress with Phase 1, the designation of sites for CEU development and the provision of advanced research training by developed country training centres has been substantial. The network now consists of 27 units: 26 in developing country medical schools in Asia, Latin America, India and Africa and 1 in France. More than 60% of the target of 270 fellows have completed training and returned to take up faculty positions in their unit. The remainder will be trained and on site by 1995. The non-return rate of fellows (2%) is very low. Research productivity is significant given only 60 fellows have been working in their CEUs for more than 3 years following the completion of training. An appropriate balance between hospital and community-based research is evident and changes in clinical and health care policy have been made based on the research conducted. The educational responsibilities of all units include courses and workshops in critical appraisal and clinical epidemiology for medical trainees and colleagues. Graduate training programs have emerged in 3 units so far. Major challenges lie ahead as we move into Phase 2 of the project--self sustainability and the transfer of training responsibility to the CEUs. The problems encountered during Phase 1 will need to be addressed. These include time protection for research, the limited availability of research funds, the low priority given to research careers and the poor linkage between health researchers and government policy makers. Our experience echos the recommendations of the recent report of the Commission on Health Research for Development, namely that donors and national governments should give increased priority to the role of health research in less developed countries. We conclude that with continuing support and special attention to the problems encountered, the INCLEN approach can contribute to ensuring that the medical establishment is part of the solution rather than the problem faced by health systems in less developed countries.

Developing Countries↗
PubMed2001

On the difficulty of defining disease: a Darwinian perspective.

Most attempts to craft a definition of disease seem to have tackled two tasks simultaneously: 1) trying to create a series of inclusion and exclusion criteria that correspond to medical usage of the word disease and 2) using this definition to understand the essence of what disease is. The first task has been somewhat accomplished, but cannot reach closure because the concept of "disease" is based on a prototype, not a logical category. The second task cannot be accomplished by deduction, but only by understanding how the body works and what each component is for, in evolutionary detail. An evolutionary view of the origins of the body and its vulnerabilities that result in disease provides an objective foundation for recognizing pathology. Our social definition of disease will remain contentious, however, because values vary, and because the label "disease" changes judgments about the moral status of people with various conditions, and their rights to medical and social resources.

Biological Evolution↗