Some notes and speculations about various topics. ||| Gegenwärtig - vorübergehend -
wohl eher eine Gedankensammlung als ein Naturwissenschaftsblog. Das Konzept eines "Naturwissenschaftsblogs" wird erst im kommenden Jahr (2018/2019) Umsetzung finden.
Character displacement of Cercopithecini primate visual signals
William L. Allen, Martin Stevens, and James P. Higham (June 2014) Nature Communications
Animal visual signals have the potential to act as an isolating barrier to prevent interbreeding of populations through a role in species recognition. Within communities of competing species, species recognition signals are predicted to undergo character displacement, becoming more visually distinctive from each other; however, this pattern has rarely been identified. Using computational face recognition algorithms to model primate face processing, we demonstrate that the face patterns of guenons (tribe: Cercopithecini) have evolved under selection to become more visually distinctive from those of other guenon species with whom they are sympatric. The relationship between the appearances of sympatric species suggests that distinguishing conspecifics from other guenon species has been a major driver of diversification in guenon face appearance. Visual signals that have undergone character displacement may have had an important role in the tribe’s radiation, keeping populations that became geographically separated reproductively isolated on secondary contact.
(I) ... a person has more or less power to observe what goes on in his own mind.
(II) ... when a person has in mind any two or more ideas (using this word to embrace any items of mental content, whether perceived or thought of), he has more or less power to bring to mind any relations that essentially hold between them.
(III) ... when a person has in mind any idea together with a relation, he has more or less power to bring up into mind the correlative idea.
Theoretical studies suggest that mating and pair formation is not likely to be random. Computer simulations suggested that sex among genetically complex organisms requires mate choice strategies for its evolutionary maintenance, to reduce excessive genetic variance produced by out-crossing. One strategy achieving this aim efficiently in computer simulations is assortative mating modeled as “self seeking like”. Another one is selection of “good genes”. Assortative mating increases the probability of finding a genetically similar mate, without fomenting inbreeding, achieving assortative mating without hindering the working of other mate selection strategies which aim to maximize the search for “good genes”, optimizing the working of sex in evolutionary terms. Here we present indirect evidence that in a significant proportion of human reproductive couples, the partners show much higher facial resemblances than can be expected by random pair formation, or as the outcome of “matching for attractiveness” or the outcome of competition for the most attractive partner accessible, as had been previously assumed. The data presented is compatible with the hypothesis derived from computer simulations, that human mate selection strategies achieve various aims: “self seeking like” (including matching for attractiveness) and mating with the best available genes.
We used an economic model based on evolutionary theory to guide an examination of relations among self-reported depressive symptoms and ratings of mate values of self, social, and sexual partners. This model treats assortative mating as a form of social exchange between partners of socially and sexually desirable traits.
Two studies used variants of the Mate Value Inventory (MVI), a multivariate assessment of attributes desired in social or sexual partners. For study 1, 115 male and 124 female undergraduates provided self reports on four forms of the MVI-11 and on the Beck Depression Inventory (BDI); for study 2, 208 male and 277 female undergraduates provided self reports on seven forms of the MVI-7 and on the BDI-II.
Both multisample structural equations models indicated that the parameters were statistically equivalent between female and male subsamples and provided an adequate fit to the data. The models revealed significant relations between the mate values ascribed to the self and those ascribed to short- and long-term partners as well as best friends. Furthermore, greater BDI scores significantly predicted lesser ratings of mate value for the self, and hence indirectly predicted lesser ratings of mate value for all types of partners evaluated. Limitations : Although the data obtained from the MVI demonstrated good psychometric validity, external validity has not yet been established.
The results are consistent with models predicting: (1) assortative mating by mate value, (2) differential exchange rates of mate value for different types of partners, (3) a negative relation between depressive symptoms and assessment of one’s own mate value, and (4) a possibly consequential mismatch of mate values when one partner exhibits or recovers from significant depressive symptoms. The results are inconsistent with models predicting (5) a generalized negativity bias due to depression.
Beginning in their late twenties, women face the unique adaptive problem of declining fertility eventually terminating at menopause. We hypothesize women have evolved a reproduction expediting psychological adaptation designed to capitalize on their remaining fertility. The present study tested predictions based on this hypothesis—these women will experience increased sexual motivations and sexual behaviors compared to women not facing a similar fertility decline. Results from college and community samples (N = 827) indicated women with declining fertility think more about sex, have more frequent and intense sexual fantasies, are more willing to engage in sexual intercourse, and report actually engaging in sexual intercourse more frequently than women of other age groups. These findings suggest women’s ‘‘biological clock” may function to shift psychological motivations and actual behaviors to facilitate utilizing remaining fertility.
According to signaling theory and a large body of supporting evidence, males across many taxa produce courtship signals that honestly advertise their quality. The cost of producing or performing these signals maintains signal honesty, such that females are typically able to choose the best males by selecting those that produce the loudest, brightest, longest, or otherwise highest-intensity signals, using signal strength as a measure of quality. Set against this background, human flirting behavior, characterized by its frequent subtlety or covertness, is mysterious. Here we propose that the explanation for subtle and ambiguous signals in human courtship lies in socially imposed costs that (a) vary with social context and (b) are amplified by the unusual ways in which language makes all interactions potentially public. Flirting is a class of courtship signaling that conveys the signaler’s intentions and desirability to the intended receiver while minimizing the costs that would accompany an overt courtship attempt. This proposal explains humans’ taxonomically unusual courtship displays and generates a number of novel predictions for both humans and non-human social animals. Individuals who are courting should vary the intensity of their signals to suit the level of risk attached to the particular social configuration, and receivers may assess this flexible matching of signal to context as an indicator of the signaler’s broader behavioral flexibility and social intelligence.
Risk-Taking: A Motivational Basis for Sex Differences
Elizabeth C. Arch (1993)
No current explanation about the bases for human action adequately accounts for the persistence of differences between the public achievement of women and men. An argument is presented here that underlying many of these differences are variations in the responses of males and females to situations perceived as risky. It is postulated that in such situations males are more likely to see a challenge that calls forth participation while females tend to respond as to a threat in ways that encourage avoidance of the risk. Application of this idea provides coherence to many disparate and sometimes anomalous findings and suggests lines of investigation that may prove to be fruitful.