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Next generation of preventive interventions.
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Current evolutionary perspectives on adolescent romantic relations and sexuality.
This article describes current evolutionary research on adolescent sexual and romantic behavior. It first reviews functional explanations for basic sex differences in behavior. As in other pair-bonding mammals, women seek dominant males, and men seek and guard young, fertile females. Recent work is then described on adolescent competitiveness, mate selection, and pair bonding. The outcomes of even childhood social competition can be profound, with healthy, early-maturing, attractive children deriving lifelong benefits. Adolescent competition is intense among girls as well as boys. Depression is more common for boys with few sex partners, and for girls with many. Based on cross-cultural data and on analysis of pubertal changes in girls and boys, it can be concluded that adolescents have an evolved propensity for early sexual experimentation, followed by more judicious mate choice. Yet the bond with a girl's first sex partner is often profound. Amorous infatuations are intense in both sexes and usually mitigate within 3 years, for plausible adaptive reasons. Early menarche and unmarried motherhood impose developmental disadvantages on children but may be an evolved adaptation for stressful family conditions and a shortage of marriageable men. Gaining an understanding of normal adolescence can help in diagnosing, preventing, and treating problematic behaviors.
Genetic and psychosocial evolution and the future of psychiatry.
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A conceptual model for studying parenting behaviors in immigrant populations.
Transition is a concept common to migration and parenthood. Immigrants leave their homeland, experience the chaos of moving, then begin life in a new country. A new parent relinquishes an identity, waits for the birth of an infant, then develops an altered identity with reconfigured relationships. Belsky's theoretical framework is modified to illustrate the determinants of parenting in immigrants who make the transition to parenthood and cultural transition simultaneously. The primary focus is on the contextual determinants of premigration, postmigration, ethnicity, and the sociopolitical environment. Possible directions for nursing practice and research are proposed.
A theory of modern cultural shifts and meltdowns.
Many cultural attributes such as adornment, language slang, mannerisms and rituals are thought to have little or no influence on individual survival and reproduction, functioning rather as markers of cultural identity that promote group cohesion. Here, I show that if cultural markers are under weak selection and subject to loss or substitution, then the breakdown of cultural cohesiveness may proceed without stabilizing reactions until many or most of a culture's identifiers are forever lost. This may culminate in a 'cultural meltdown', whereby the culture is caught in a vortex of ever-decreasing membership and insufficient selection against the accumulation of unfamiliar markers. In progressively altering the topology of communication from diffusion to broadcasting, globalization may be both accelerating the erosion of cultural identities and amplifying dominance behaviours above their normal adaptive levels.
Random drift and large shifts in popularity of dog breeds.
A simple model of random copying among individuals, similar to the population genetic model of random drift, can predict the variability in the popularity of cultural variants. Here, we show that random drift also explains a biologically relevant cultural phenomenon--changes in the distributions of popularity of dog breeds in the United States in each of the past 50 years. There are, however, interesting deviations from the model that involve large changes in the popularity of certain breeds. By identifying meaningful departures from our null model, we show how it can serve as a foundation for studying culture change quantitatively, using the tools of population genetics.
Vocal clans in sperm whales (Physeter macrocephalus).
Cultural transmission may be a significant source of variation in the behaviour of whales and dolphins, especially as regards their vocal signals. We studied variation in the vocal output of 'codas' by sperm whale social groups. Codas are patterns of clicks used by female sperm whales in social circumstances. The coda repertoires of all known social units (n = 18, each consisting of about 11 females and immatures with long-term relationships) and 61 out of 64 groups (about two social units moving together for periods of days) that were recorded in the South Pacific and Caribbean between 1985 and 2000 can be reliably allocated into six acoustic 'clans', five in the Pacific and one in the Caribbean. Clans have ranges that span thousands of kilometres, are sympatric, contain many thousands of whales and most probably result from cultural transmission of vocal patterns. Units seem to form groups preferentially with other units of their own clan. We suggest that this is a rare example of sympatric cultural variation on an oceanic scale. Culture may thus be a more important determinant of sperm whale population structure than genes or geography, a finding that has major implications for our understanding of the species' behavioural and population biology.
Random drift and culture change.
We show that the frequency distributions of cultural variants, in three different real-world examples--first names, archaeological pottery and applications for technology patents--follow power laws that can be explained by a simple model of random drift. We conclude that cultural and economic choices often reflect a decision process that is value-neutral; this result has far-reaching testable implications for social-science research.
Neighbour-nets portray the Chinese dialect continuum and the linguistic legacy of China's demic history.
As with species studied by evolutionary biologists, languages are evolving entities. They can evolve in tree-like patterns, possibly blurred by borrowing, but they can also develop in non-tree-like schemes. For instance, diglossia, as in the case of Chinese, can counterbalance the hierarchical pattern expected from differentiation by internal change associated with isolation by distance of speech communities. Using two lexical datasets, either the basic lexicon supposedly more immune to borrowing or a representative sample of the whole lexicon, we investigate the development pattern of Chinese dialects using a neighbour-net approach, which is an unprejudiced technique for representing object relationships. The resulting graphs are consistent with a dialect continuum shaped by counterbalanced effects of homogenizing diglossia and borrowing versus differentiating spread of speech communities. Historical events and linguistic claims can be mapped on these graphs.
Why is stress so deadly? An evolutionary perspective.
The reaction of the body to prolonged stress has many harmful effects. Classical theory assumes that stress responses have evolved due to their short-term selective advantages ('flight or fight'), and despite their adverse long-term effects. In contrast, we demonstrate that the adverse effects of stress responses may have a selective advantage. Using an analytical model we show that a gene that causes the early death of a relatively unfit individual can increase in frequency in a structured population even if it has no positive effect on that individual. This result offers a new perspective on the relations between stress factors, stress responses and stress-related diseases.
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.
Isolation and characterization of a novel alkalitolerant thermophile, Anaerobranca horikoshii gen. nov., sp. nov.
Nine moderately alkalitolerant thermophilic bacteria with similar properties were isolated from water and soil samples obtained from Yellowstone National Park. These Gram-type-positive, rod-shaped bacteria produce cells with primary branches. The cells are peritrichous and exhibit only slight tumbling motility. At 60 degrees C the pH range for growth is 6.9 to 10.3, and the optimum pH is 8.5. At pH 8.5 the temperature range for growth is 34 to 66 degrees C, with an optimum temperature of 57 degrees C. The strains are mainly proteolytic. The fermentation products from yeast extract are acetate, CO2, and H2. Fumarate added to minimal medium containing yeast extract is stoichiometrically converted to succinate, indicating that it is used as an alternative electron acceptor. The DNA G + C content is 33 to 34 mol%. On the basis of its unique properties, such as branch formation, growth at alkaline pH values at elevated temperatures, and the relative distance of its 16S rRNA sequence from those of other known bacteria, we propose that strain JW/YL-138T (T = type strain) and eight similar strains represent a new genus and species, Anaerobranca horikoshii. Strain JW/YL-138 is designated the type strain of the type species, A. horikoshii, which was named in honor of Koki Horikoshi, a pioneer in the field of alkaliphilic bacteria.
Sequence divergence of measles virus haemagglutinin during natural evolution and adaptation to cell culture.
Phylogenetic analysis of the sequence of the H gene of 75 measles virus (MV) strains (32 published and 43 new sequences) was carried out. The lineage groups described from comparison of the nucleotide sequences encoding the C-terminal regions of the N protein of MV were the same as those derived from the H gene sequences in almost all cases. The databases document a number of distinct genotype switches that have occurred in Madrid (Spain). Well-documented is the complete replacement of lineage group C2, the common European genotype at that time, with that of group D3 around the autumn of 1993. No further isolations of group C2 took place in Madrid after this time. The rate of mutation of the H gene sequences of MV genotype D3 circulating in Madrid from 1993 to 1996 was very low (5 x 10(-4) per annum for a given nucleotide position). This is an order of magnitude lower than the rates of mutation observed in the HN genes of human influenza A viruses. The ratio of expressed over silent mutations indicated that the divergence was not driven by immune selection in this gene. Variations in amino acid 117 of the H protein (F or L) may be related to the ability of some strains to haemagglutinate only in the presence of salt. Adaptation of MV to different primate cell types was associated with very small numbers of mutations in the H gene. The changes could not be predicted when virus previously grown in human B cell lines was adapted to monkey Vero cells. In contrast, rodent brain-adapted viruses displayed a lot of amino acid sequence variation from normal MV strains. There was no convincing evidence for recombination between MV genotypes.
Evolution of developmental stages in cultures of Bacillus cereus.
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Hydrogen peroxide yields during the incompatible interaction of tobacco suspension cells inoculated with Phytophthora nicotianae.
Rates of H(2)O(2) production by tobacco suspension cells inoculated with zoospores from compatible or incompatible races of the pathogen Phytophthora nicotianae were followed by direct measurement of oxygen evolution from culture supernatants following catalase addition. Rates of HO(2)(*)/O(2)(-) production were compared by following the formation of the formazan of sodium, 3'-[1-[phenylamino-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro) benzene-sulfonic acid hydrate. In the incompatible interaction only, both reactive oxygen species (ROS) were produced by the cultured host cells in a minor burst between 0 and 2 h and then in a major burst between 8 and 12 h after inoculation. Absolute levels of H(2)O(2) could not be accurately measured due to its metabolism by host cells, but results are consistent with the majority of H(2)O(2) being formed via dismutation of HO(2)(*)/O(2)(-). The effects of inhibitors of endogenous Cu/Zn superoxide dismutase (diethyldithiocarbamate) and catalase (3-amino-1,2,4-triazole and salicylic acid) were also examined. Yields of ROS in the presence of the inhibitors diphenylene iodonium, allopurinol, and salicylhydroxamic acid suggest that ROS were generated in incompatible host responses by more than one mechanism.
Time course of oxygen evolution during photosynthesis in synchronized cultures of algae.
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Of colic and rumbling in the guts.
Infant colic is a common disorder of doubtful aetiology. The known facts have been interpreted in a historical and geographical context. The apparent increase in incidence of the condition in the Westernized world during the twentieth century may reflect the technological advances and social changes that have occurred in recent years.