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PubMed2005

Mate fidelity and intra-lineage polygyny in greater horseshoe bats.

Mating strategies that lead to increased kinship within socially cooperative groups may offer inclusive fitness benefits to individuals, but can also result in higher levels of inbreeding. Here we show in a sexually segregated bat species that females avoid this conflict through two mating behaviours. First, most females revisit and breed with specific, individual males across years, so that their single offspring born in different years are full siblings. Second, relatives in the maternal line, including mothers and daughters, share breeding partners (intra-lineage polygyny) more often than expected by chance. Although these behaviours increased levels of co-ancestry among colony members, there was no concomitant rise in inbreeding. We suggest that when females engage in mate fidelity and intra-lineage polygyny, kin ties among female roost mates will be strengthened, thereby potentially contributing to social group cohesiveness. Our findings reveal the hidden complexity that can underlie polygynous breeding, and highlight a new potential route by which female mate choice could influence social evolution.

Animals↗
PubMed2005

Evolution of indirect reciprocity.

Natural selection is conventionally assumed to favour the strong and selfish who maximize their own resources at the expense of others. But many biological systems, and especially human societies, are organized around altruistic, cooperative interactions. How can natural selection promote unselfish behaviour? Various mechanisms have been proposed, and a rich analysis of indirect reciprocity has recently emerged: I help you and somebody else helps me. The evolution of cooperation by indirect reciprocity leads to reputation building, morality judgement and complex social interactions with ever-increasing cognitive demands.

Altruism↗
PubMed2006

Fine-scale genetic structure and dispersal in cooperatively breeding apostlebirds.

In cooperatively breeding species, restricted dispersal of offspring leads to clustering of closely related individuals, increasing the potential both for indirect genetic benefits and inbreeding costs. In apostlebirds (Struthidea cinerea), philopatry by both sexes results in the formation of large (up to 17 birds), predominantly sedentary breeding groups that remain stable throughout the year. We examined patterns of relatedness and fine-scale genetic structure within a population of apostlebirds using six polymorphic microsatellite loci. We found evidence of fine-scale genetic structure within the study population that is consistent with behavioural observations of short-distance dispersal, natal philopatry by both sexes and restricted movement of breeding groups between seasons. Global F(ST) values among breeding groups were significantly positive, and the average level of pairwise relatedness was significantly higher for individuals within groups than between groups. For individuals from different breeding groups, geographical distance was negatively correlated with pairwise relatedness and positively correlated with pairwise F(ST). However, when each sex was examined separately, this pattern was significant only among males, suggesting that females may disperse over longer distances. We discuss the potential for kin selection to influence the evolution and maintenance of cooperative breeding in apostlebirds. Our results demonstrate that spatial genetic structural analysis offers a useful alternative to field observations in examining dispersal patterns of cooperative breeders.

Animal Migration↗
PubMed2003

Genetic diversity, asymmetrical aggression, and recognition in a widespread invasive species.

The evolution and persistence of cooperative social units depends on the ability to distinguish group members from nonmembers. The precision of discrimination, in turn, relies on variation in the labels that individuals use to recognize group members. However, this same variation can be selected against if individuals that are rejected as nonmembers incur a high cost. Here we provide evidence that selection against individuals from genetically diverse groups has contributed to the formation of the unicolonial colony structure that characterizes introduced populations of the invasive Argentine ant (Linepithema humile). Studies in both the laboratory and the field showed that individuals from less genetically diverse colonies attack individuals from more diverse colonies and that attackers survived agonistic encounters more than six times as often as recipients of aggression. This selection, in concert with reductions in genetic diversity after a founder event, likely creates a barrier to the establishment of new, genetically diverse introductions from the native range and may reduce genetic diversity within established populations in the introduced range.

Aggression↗
PubMed2006

Broca's arrow: evolution, prediction, and language in the brain.

Brodmann's areas 44 and 45 in the human brain, also known as Broca's area, have long been associated with language functions, especially in the left hemisphere. However, the precise role Broca's area plays in human language has not been established with certainty. Broca's area has homologs in the great apes and in area F5 in monkeys, which suggests that its original function was not linguistic at all. In fact, great ape and hominid brains show very similar left-over-right asymmetries in Broca's area homologs as well as in other areas, such as homologs to Wernicke's area, that are normally associated with language in modern humans. Moreover, the so-called mirror neurons are located in Broca's area in great apes and area F5 in monkeys, which seem to provide a representation of cause and effect in a primate's environment, particularly its social environment. Humans appear to have these mirror neurons in Broca's area as well. Similarly, genetic evidence related to the FOXP2 gene implicates Broca's area in linguistic function and dysfunction, but the gene itself is a highly conserved developmental gene in vertebrates and is shared with only two or three differences between humans and great apes, five between humans and mice, and eight between humans and songbirds. Taking neurons and portions of the brain as discrete computational segments in the sense of constituting specific Turing machines, this evidence points to a predictive motor and conceptual function for Broca's area in primates, especially for social concepts. In human language, this is consistent with evidence from typological and cognitive linguistics.

Biological Evolution↗
PubMed2005

Understanding and sharing intentions: the origins of cultural cognition.

We propose that the crucial difference between human cognition and that of other species is the ability to participate with others in collaborative activities with shared goals and intentions: shared intentionality. Participation in such activities requires not only especially powerful forms of intention reading and cultural learning, but also a unique motivation to share psychological states with others and unique forms of cognitive representation for doing so. The result of participating in these activities is species-unique forms of cultural cognition and evolution, enabling everything from the creation and use of linguistic symbols to the construction of social norms and individual beliefs to the establishment of social institutions. In support of this proposal we argue and present evidence that great apes (and some children with autism) understand the basics of intentional action, but they still do not participate in activities involving joint intentions and attention (shared intentionality). Human children's skills of shared intentionality develop gradually during the first 14 months of life as two ontogenetic pathways intertwine: (1) the general ape line of understanding others as animate, goal-directed, and intentional agents; and (2) a species-unique motivation to share emotions, experience, and activities with other persons. The developmental outcome is children's ability to construct dialogic cognitive representations, which enable them to participate in earnest in the collectivity that is human cognition.

Aging↗
PubMed1995

Gating of thrombin in platelet aggregates by pO2-linked lowering of extracellular Ca2+ concentration.

Platelet accretion at sites of vascular injury yields a neo-tissue comprising packed platelets and having an interstitial space not supplied with blood. Within growing thrombi platelet masses become anoxic and depolarize to yield interstitial cation concentrations characteristic of the more voluminous platelet cytosol, with extracellular [Ca2+] falling below that adequate to support the plasma clotting system. The platelet-associated clotting system reactivates during disaggregation of the thrombi in vitro, which proceeds with high yield of apparently basal, functional platelets when specific anticoagulants are included in the disaggregating media. The capacity of regulatory demand to lower extracellular [Ca2+] in the microenvironment of platelet aggregates provides a physiological basis for evolution of the highly cooperative calcium interactions of the hemostasis system.

Adenosine Triphosphate↗
PubMed2006

Touch communicates distinct emotions.

The study of emotional signaling has focused almost exclusively on the face and voice. In 2 studies, the authors investigated whether people can identify emotions from the experience of being touched by a stranger on the arm (without seeing the touch). In the 3rd study, they investigated whether observers can identify emotions from watching someone being touched on the arm. Two kinds of evidence suggest that humans can communicate numerous emotions with touch. First, participants in the United States (Study 1) and Spain (Study 2) could decode anger, fear, disgust, love, gratitude, and sympathy via touch at much-better-than-chance levels. Second, fine-grained coding documented specific touch behaviors associated with different emotions. In Study 3, the authors provide evidence that participants can accurately decode distinct emotions by merely watching others communicate via touch. The findings are discussed in terms of their contributions to affective science and the evolution of altruism and cooperation.

Adolescent↗
PubMed2000

Morphological castes in a vertebrate.

Morphological specialization for a specific role has, until now, been assumed to be restricted to social invertebrates. Herein we show that complete physical dimorphism has evolved between reproductives and helpers in the eusocial naked mole-rat. Dimorphism is a consequence of the lumbar vertebrae lengthening after the onset of reproduction in females. This is the only known example of morphological castes in a vertebrate and is distinct from continuous size variation between breeders and helpers in other species of cooperatively breeding vertebrates. The evolution of castes in a mammal and insects represents a striking example of convergent evolution for enhanced fecundity in societies characterized by high reproductive skew. Similarities in the selective environment between naked mole-rats and eusocial insect species highlight the selective conditions under which queen/worker castes are predicted to evolve in animal societies.

Analysis of Variance↗
PubMed2002

Donors to charity gain in both indirect reciprocity and political reputation.

Darwinian evolution can explain human cooperative behaviour among non-kin by either direct or indirect reciprocity. In the latter case one does not expect a return for an altruistic act from the recipient as with direct reciprocity, but from another member of the social group. However, the widespread human behaviour of donating to poor people outside the social group, for example, to charity organizations, that are unlikely to reciprocate indirectly and thus are equivalent to defectors in the game is still an evolutionary puzzle. Here we show experimentally that donations made in public to a well-known relief organization resulted both in increased income (that the donors received from the members of their group) and in enhanced political reputation (they were elected to represent the interests of their group). Donations may thus function as an honest signal for one's social reliability.

Cooperative Behavior↗
PubMed2003

Are reproductive skew models evolutionarily stable?

Reproductive skew theory has become a popular way to phrase problems and test hypotheses of social evolution. The diversity of reproductive skew models probably stems from the ease of generating new variations. However, I show that the logical basis of skew models, that is, the way in which group formation is modelled, makes use of hidden assumptions that may be problematical as they are unlikely to be fulfilled in all social systems. I illustrate these problems by re-analysing the basic concessive skew model with staying incentives. First, the model assumes that dispersal is an all-or-nothing response: all subordinates disperse as soon as concessions drop below a certain value. This leads to a discontinuous 'cliff-edge' shape of dominant fitness, and it is not clear that selection will balance a population at such an edge. Second, it is assumed that subordinates have perfect knowledge of their benefits if they stay in the group. I examine the effects of relaxing these two assumptions. Relaxing the first one strengthens reproductive skew theory, but relaxing the latter makes evolutionary stability disappear. In cases where subordinates cannot accurately measure benefits provided by the individual dominant with which they live, so that their behaviour instead evolves as a response to population-wide average benefits, the logic of reproductive skew models does not apply. This warns against too indiscriminate an application of reproductive skew theory to problems in social evolution: for example, transactional models of extra-pair paternity assume perfect knowledge of paternity, which is unlikely to hold true in nature. It is recommended that models specify the mechanisms by which individuals can adjust their behaviour to that of others, and pay attention to changes that occur in evolutionary versus behavioural time.

Animals↗
PubMed2005

Ancient DNA.

In the past two decades, ancient DNA research has progressed from the retrieval of small fragments of mitochondrial DNA from a few late Holocene specimens, to large-scale studies of ancient populations, phenotypically important nuclear loci, and even whole mitochondrial genome sequences of extinct species. However, the field is still regularly marred by erroneous reports, which underestimate the extent of contamination within laboratories and samples themselves. An improved understanding of these processes and the effects of damage on ancient DNA templates has started to provide a more robust basis for research. Recent methodological advances have included the characterization of Pleistocene mammal populations and discoveries of DNA preserved in ancient sediments. Increasingly, ancient genetic information is providing a unique means to test assumptions used in evolutionary and population genetics studies to reconstruct the past. Initial results have revealed surprisingly complex population histories, and indicate that modern phylogeographic studies may give misleading impressions about even the recent evolutionary past. With the advent and uptake of appropriate methodologies, ancient DNA is now positioned to become a powerful tool in biological research and is also evolving new and unexpected uses, such as in the search for extinct or extant life in the deep biosphere and on other planets.

DNA↗
PubMed2005

Mutations in the Pneumocystis jirovecii DHPS gene confer cross-resistance to sulfa drugs.

Pneumocystis jirovecii is a major opportunistic pathogen that causes Pneumocystis pneumonia (PCP) and results in a high degree of mortality in immunocompromised individuals. The drug of choice for PCP is typically sulfamethoxazole (SMX) or dapsone in conjunction with trimethoprim. Drug treatment failure and sulfa drug resistance have been implicated epidemiologically with point mutations in dihydropteroate synthase (DHPS) of P. jirovecii. P. jirovecii cannot be cultured in vitro; however, heterologous complementation of the P. jirovecii trifunctional folic acid synthesis (PjFAS) genes with an E. coli DHPS-disrupted strain was recently achieved. This enabled the evaluation of SMX resistance conferred by DHPS mutations. In this study, we sought to determine whether DHPS mutations conferred sulfa drug cross-resistance to 15 commonly available sulfa drugs. It was established that the presence of amino acid substitutions (T(517)A or P(519)S) in the DHPS domain of PjFAS led to cross-resistance against most sulfa drugs evaluated. The presence of both mutations led to increased sulfa drug resistance, suggesting cooperativity and the incremental evolution of sulfa drug resistance. Two sulfa drugs (sulfachloropyridazine [SCP] and sulfamethoxypyridazine [SMP]) that had a higher inhibitory potential than SMX were identified. In addition, SCP, SMP, and sulfadiazine (SDZ) were found to be capable of inhibiting the clinically observed drug-resistant mutants. We propose that SCP, SMP, and SDZ should be considered for clinical evaluation against PCP or for future development of novel sulfa drug compounds.

Amino Acid Substitution↗