Physical strength, fighting ability, and aggressiveness in adolescents.

OBJECTIVES: Recent research suggests that evolutionary selection pressures have shaped mental mechanisms to be able to assess one's own and other's physical strength, fighting ability, and aggressiveness. According to the recalibrational theory, anger may be linked to fighting ability and serve as a bargaining mechanism to improve welfare obtained in social conflict. We hypothesized that late adolescent men (but not mid-adolescent men or women) use this mechanism, as it would be particularly adaptive for them to avoid potential costs from direct conflict in male competition. METHODS: The present study investigated the relationship between fighting ability (estimated from handgrip strength [HGS], a measure of upper body strength, and self-reported fighting ability) and aggressiveness (physical and nonphysical) in 288 Spanish adolescents aged 14-18 years. RESULTS: Our results indicated a positive relationship between self-perceived fighting ability and HGS in both sexes during adolescence. There was no association between fighting ability and aggressiveness in late adolescent women (17-18 years). For men, there was a positive relationship between fighting ability and physical aggression, but the strength of this relationship decreased with age. Additionally, for men, there was a positive relationship between fighting ability and anger but only in late adolescence, and thus arguing that for adolescent men aggression strategies shift from physical to nonphysical as they age. CONCLUSIONS: With reference to the recalibrational theory of anger, our results suggest that the sex- and age-dependent associations between fighting ability and physical and nonphysical aggression indicate divergent adaptive skills between sexes, which are driven by intrasexual competition.

Effect of the enclosure on carriers' body weight loss in the cotton-top tamarin (Saguinus oedipus).

Infant carrying in cotton-top tamarins is a costly activity that results in weight loss by the fathers and helpers. However, to date, measures of carrying costs have been obtained in small indoor enclosures. We studied body weight changes in adult and subadult individuals from eight large groups (n > 5) for 9 weeks after the birth of infants. Four groups were housed in large indoor/outdoor enclosures (42 m(2) x 3.3 m high), and four were housed in small indoor enclosures (12 m(2) x 2.4 m high). All of the individuals were weighed regularly at least three times a week. Reproductive males lost more weight in the big indoor/outdoor enclosures (mean=6.51%) than in the small indoor ones, as did male adult helpers (mean=5.59%) and female adult helpers (mean=4.4%). Still-growing subadult individuals also lost weight in the big indoor/outdoor enclosures (mean=3.17%), although the differences did not reach significance (P=0.07). These results support the hypothesis that cotton-top tamarins living in more natural settings experience higher weight loss than those housed under less-natural conditions.

Elección de pareja estable a través de anuncios de periódico / Evolutionary predictions about mate choice: a study based on personal advertisements

El estudio transcultural de elección de pareja de Buss (1989) indica que la muestra de la población española difiere en las preferencias de algunos rasgos de las predicciones evolutivas. A partir de 7.415 anuncios de la sección de 'relaciones estables/matrimonio' de periódicos españoles analizamos los rasgos ofrecidos y buscados por varones y mujeres de distintas clases de edad. Algunos resultados apoyan las predicciones evolutivas: los varones buscan mujeres más jóvenes y con atractivo físico y ofrecen estatus socioeconómico. Las mujeres buscan varones más mayores con estatus y recursos y ofrecer. atractivo físico. Otros resultados son contrarios a las predicciones evolutivas y parecen ser específicos de la muestra de la población española estudiada: las mujeres buscan más que los varones el atractivo físico y la fidelidad. Los rasgos ofrecidos y buscados difieren en las distintas clases de edad, por lo que deben estar influidos por factores socioculturales (AU)

The cross-cultural study of mate preferences by Buss (1989) suggests that the Spanish sample, with regard to some trait preferences, does not follow evolutionary predictions. We used 7415 advertisements published in Spanish newspapers to analyse traits sought and offered by men and women of different age groups. Some results supported evolutionary predictions: men sought younger, physically attractive women, and offered their socioeconomic status; women sought older men with status/resources, and in turn offered physical attractiveness. However, other results are contrary to evolutionary predictions, and appear to be specific for the studied Spanish population: women seek physical attractiveness and fidelity more than men. Traits offered and sought varied according to different age groups, and would therefore seem to be influenced by sociocultural factors (AU)

Why do cotton-top tamarin female helpers carry infants? A preliminary study.

Shortly after giving birth, cotton-top tamarin mothers frequently attack the eldest female helpers [Snowdon et al., American Journal of Primatology 31:11-21, 1993]. Sometimes this aggression leads to the eviction of the eldest daughters from their natal groups 3-4 months after the birth of infants [Price & McGrew, Folia Primatologica 57:16-27, 1991]. We propose that daughters, during the act of carrying infants, may receive less aggression from mothers than when they are not carrying. On the other hand, given that mothers benefit from having others carry their infants, overall aggression received by female helpers from their mothers might be lower in those female helpers with a larger relative contribution to this activity. Four groups were observed during the first 9 weeks following the birth of infants, and aggression received was recorded for symmetrical as well as nonsymmetrical interactions. We found a positive correlation between contribution to infant carrying of female helpers and the overall aggression received from their mothers. Furthermore, the two eldest daughters with highest values of carrying contribution were evicted from their natal groups 3-4 months after the birth of infants. Although mothers do not appear to be more tolerant of female helpers that contribute the most to infant carrying, daughters do benefit from reduced aggression during the act of carrying, and remain in their natal group during the time period when infants must be carried.

Mate choice differences according to sex and age : An analysis of personal advertisements in Spanish newspapers.

We used 7,415 advertisements published in Spain to analyze traits sought/offered by men and women from different age groups. Findings regarding age, socioeconomic status, and physical attractiveness requirements support evolutionary predictions about mate preferences. However, changes in trait preferences among women under 40 appear to be contingent on Spain's socioeconomic transformation. Women under 40 seek mainly physical attractiveness in men, whereas those over 40 seek mainly socioeconomic status. The trait most sought by men in all age groups is physical attractiveness. Traits sought and offered by advertisers may be conditioned by the personal situation of the advertiser. Mean age of advertisers (around their forties) and Spain's social indicators suggest that the majority of advertisers have been unsuccessful in the mating arena at the conventional age.