Physical Attractiveness as a Signal of Biological Quality

It has been commonly thought that standards of beauty are arbitrary cultural conventions that vary between cultures and time. In my thesis I found that it is not so. Instead, I show that attractiveness and preferred traits serve as cues to phenotypic qualities that provide selective benefits for those who choose their mates based on these criteria. In the first study I show that attractive men have a stronger antibody response to the hepatitis b vaccine and higher levels of testosterone than their less attractive peers. Men with low levels of testosterone also tend to have high levels of the stress hormone cortisol, suggesting that their immune responses may have been inhibited by stress hormones. Thus, facial attractiveness may serve as an honest cue of the strength of immune defence in men. In the second study, I show that the attractiveness of the male body is also a cue of better immunity. In addition, I show that adiposity, both in men’s faces and bodies, is a better cue of the strength of immunity and attractiveness than of masculinity. In the third study, I test the preferences of women from 13 countries for facial cues of testosterone and cortisol. I show that there is cross-cultural variation in women’s preference for cues of testosterone and cortisol in male faces. I found a relationship between the health of a nation and women’s preferences for cues of testosterone in the male face and the interaction between preferences for cues of testosterone and cortisol. I show also a relationship between preferences for cues of testosterone and a societal-level measure of parasite stress. Thus, it seems that societal-level ecological factors influence the relative value of traits as revealed by combinations of testosterone and stress hormones. In the fourth study, I show that women’s immune responsiveness (amount of antibodies produced) does not predict facial attractiveness. Instead, plasma cortisol level is negatively associated with attractiveness, indicating that stressed women look less attractive. Fat percentage is curvilinearly associated with facial attractiveness, indicating that being too thin or too fat reduces attractiveness. This study suggests that in contrast to men, facial attractiveness in women does not indicate the strength of immune defence, but is associated with other aspects of long-term health and fertility: circulating levels of the stress hormone cortisol and the percentage of body fat. In the last study I show that the attractiveness of men’s body odor is positively correlated with stress hormone levels, suggesting also that the attractiveness of body odors may signal the phenotypic quality of males to females. However, the attractiveness of men’s body odor was not associated with testosterone levels. My thesis suggests that the standard of beauty is not in the eye of the beholder. Instead, our standard of beauty is hardwired in our brains by genes that are selected by natural selection and also influenced by current environmental conditions.Lukuisat viimeaikaiset tutkimukset evoluutiopsykologian alalla ovat osoittaneet että kasvojen ja vartalon puoleensavetävyydellä on huomattava vaikutus ihmisen parinvalinnassa. Evoluutiopsykologit olettavat, että fyysinen puoleensavetävyys kertoo henkilön fenotyyppisestä- tai geneettisestä laadusta pariutumiskumppanina, mutta mitä tämä laatu on ja miksi puoleensavetävyys olisi rehellinen signaali laadusta, on jäänyt epäselväksi ja kiistanalaiseksi. Väitöskirjani ensimmäisessä osatutkimuksessa selvitin miesten immuunijärjestelmän tehokkuuden yhteyttä miesten kasvojen puoleensavetävyyteen tutkimalla kuinka voimakkaasti miesten immuunijärjestelmä reagoi hepatiitti B -rokotteeseen tuottamalla vasta-aineita virusta vastaan. Kokeessa havaitsin että naiset arvioivat komeimmiksi miehiä, joilla oli voimakkain immuunivaste ja korkein testosteronitaso. Toisessa osatutkimuksessa havaitsin, että myös miesten vartalon puoleensavetävyys on yhteydessä immuunipuolustusjärjestelmän tehokkuuteen. Lisäksi havaitsin, että vartalon rasvaprosentti on voimakkaammin yhteydessä vartalon puoleensavetävyyteen ja immuunijärjestelmän tehokkuuteen kuin vartalon maskuliinisuus. Kolmannessa osakokeessa tutkin eroaako naisten mieltymys testosteronitasosta ja stressihormonitasosta kertoviin miesten kasvonpiirteisiin maantieteellisesti. Tutkimuksessa esitin 13 eri maassa naisille kuvia miesten kasvoista, joita oli manipuloitu testosteronista ja stressihormonista kertovien piirteiden suhteen. Kokeessa havaitsin että köyhissä maissa, joissa terveydenhuolto on huono naiset suosivat voimakkaammin testosteronista kertovia piirteitä kuin paremman terveydenhuollon omaavissa maissa. Tutkimus viittaa siihen, että ympäristöolosuhteet vaikuttavat siihen, millaisista miestenkasvoista naiset pitävät. Neljännessä osakokeessa tutkin kuvastaako naisen kasvojen puoleensavetävyys hänen immuunijärjestelmänsä toiminnan tehokkuutta. Havaitsin, että toisin kuin miehillä, naisilla kasvojen puoleensavetävyydellä ei ole yhteyttä hänen kykyyn tuottaa vasta-aineita hepatiitti B -rokotetta vastaan. Sen sijaan huomasin, että miehet suosivat naisia jolla on alhainen stressihormonitaso. Myös naisen rasvaprosentilla oli vaikutusta puoleensavetävyyteen. Sekä liian alhainen että liian korkea rasvaprosentti heikensi puoleensavetävyyttä. Aikaisempien tutkimusten perusteella tiedetään sekä liian alhaisen, että liian korkean rasvaprosentin heikentävän naisen hedelmällisyyttä. Korkean stressihormonitason tiedetään myös heikentävän naisen hedelmällisyyttä, joten tutkimusten valossa näyttäisi siltä, että miehet ovat sopeutuneet suosimaan naisten kasvoissa piirteitä jotka kuvastavat hedelmällisyyttä, mutta ei hyvää immuniteettikykyä. Viimeisessä osatutkimuksessani havaitsin, että miesten hajun puoleensavetävyys ei ole yhteydessä heidän testosteroni- ja estradiolitasoihinsa. Sen sijaan naiset suosivat sellaisten miesten ominaishajua joilla oli korkea stressihormonitaso koetilanteessa. Väitöskirjatutkimukseni viittaavat siihen, että fyysisellä puoleensavetävyydellä on vankka biologinen pohja, eikä kauneuskäsitys ole vain sosiaalisesti rakentunut mielivaltainen konstruktion, kuten monet humanistit väittävätSiirretty Doriast

Evidence for the stress-linked immunocompetence handicap hypothesis in humans

Secondary sexual traits that develop under the action of testosterone, such as masculine human male facial characteristics, have been proposed to signal the strength of the immune system due to the sex hormone's immunosuppressive action. Recent work has suggested that glucocorticoid stress hormones may also influence expression of such sexual signals due to their effects on immune function. Precise roles, however, remain unclear. Here we show positive relationships between testosterone, facial attractiveness and immune function (antibody response to a hepatitis B vaccine) in human males, and present some preliminary evidence that these relationships are moderated by naturally co-occurring cortisol (a glucocorticoid stress hormone involved in the fight-or-flight response). We conclude that our results provide support for a role of glucocorticoids in hormonally mediated sexual selection

Todellisuuden tutkimiseen tarvitaan vain yhtä tiedettä

Vuosisatojen ajan akateeminen yhteis&ouml; on jakautunut jyrk&auml;sti luonnontieteisiin ja humanistisiin tieteisiin. Keinotekoisesti yll&auml;pidetty jako on hidastanut tieteen kehityst&auml; ja saanut usein avoimen vihamielisi&auml; ja poliittisia ulottuvuuksia. Erilaisista n&auml;k&ouml;kulmistaan, selitystavoistaan ja menetelmist&auml;&auml;n huolimatta luonnontieteet ja ihmistieteet tutkivat samaa todellisuutta. Siksi tieteenaloja ei pit&auml;isi n&auml;hd&auml; kesken&auml;&auml;n kilpailevina vaan toisiaan t&auml;ydent&auml;vin&auml;. Ristiriidat johtuvat aina tutkijoista, eiv&auml;t koskaan tieteist&auml;. Onneksi tiede korjaa itse&auml;&auml;n, ja muutosten tuuli puhaltaa akateemisessa maailmassa.</p

Exposure to copper during larval development has intra- and trans-generational influence on fitness in later life

Anthropogenic pollution has a disadvantageous influence on various life-history traits. Although direct effects are well known, potential fitness-related trans-generational costs are less studied. Previously, empirical findings have demonstrated that environmental conditions faced by the parental generation have an effect on the traits expressed by their offspring. Here, to study this conjecture larvae of the common fruit fly (Drosophila mela-nogaster) were either exposed to a sub-lethal concentration of copper or reared on uncontaminated larval medium. Adult flies were kept under uncontaminated conditions. For the next generation, individuals were mated with their own group and their offspring were either exposed to copper or fed with uncontaminated larval medium. We found that in the parental generation copper exposure reduced fecundity compared with uncontaminated controls. In the progeny, females suffered impaired fecundity only if their larval condition differed from the conditions experienced by their parents. If the progeny was raised under similar conditions than the parental generation, no effect on fecundity was discovered, suggesting acclimatization to the prevailing conditions after short-time copper exposure (two generations). Our results demonstrate that exposure to an environmental stressor like heavy metals causes intra-and trans-generational fitness costs. Further, individuals may be able to acclimatize in prevailing contaminated conditions, but this might in turn debase fitness under uncontaminated conditions. Our findings are consistent with the prediction of the adaptive parental effects hypothesis which states that parents may produce offspring that are more successful under conditions faced by their parents

Evoluutiopsykologia ja ihmisen vaistot tieteenä

Tieteessä tapahtuu -lehdessä käytiin ansiokas keskustelu psykoanalyysin asemasta tieteenä vuonna 2001. Nyt on käyty vastaava keskustelu ihmisen vaistoista ja evoluutiopsykologiasta. Petter Portin (2003) ei usko, että ihmisellä on vaistoja. Monet evoluutiopsykologit puolestaan väittävät, että ihmisellä on pikemminkin enemmän ja monimutkaisempia vaistoja kuin muilla eläimillä

Does the Dark Triad predict self-perceived attractiveness, mate value, and number of sexual partners both in men and women?

Previous literature has shown associations between the Dark Triad (i.e., narcissism, Machiavellianism, psychopathy), other-perceived attractiveness, and personality. Nevertheless, the study of the Dark Triad as predictor of traits related to sociosexual dynamics (i.e., self-perceived attractiveness, mate value, and number of sexual partners) still remain unknown. Hence, we aimed to fill this gap by assessing the relationship between these variables in a mixed-sex sample of young-adults. The results showed that: 1) narcissism and psychopathy, but not Machiavellianism, were positively correlated to number of sexual partners for the group of men and the group of women separately. 2) only narcissism was positively correlated to self-perceived attractiveness and mate value in both sexes. 3) narcissism successfully predicted higher self-perceived attractiveness and mate value both in men and women; whereas narcissism, psychopathy, and sex significantly contributed to the prediction of number of sexual partners. We discuss our results in the light of the interaction between evolutionary thinking and socioenvironmental factors

Macroinvertebrate species occupancy frequency distribution patterns in eutrophic lakes

Metacommunity models describe species occupancy frequency distribution (hereinafter 'SOFD'). Our goal is to present how the differences in eight macroinvertebrate orders dispersal ability affect SOFD patterns. A total of 293 species from eight macroinvertebrate orders were observed in 14 eutrophic lakes in southern Finland. Species occupancy ranged from 1 to 14. About 30% (89 out of 293) of the species were found in only one lake, yielding a surprisingly high number of rare species. So, there were few widely distributed common species and numerous rare species with a restricted distribution. Combined data from eight macroinvertebrate orders supported the bimodal truncated SOFD pattern. Similarly, the low dispersal ability orders, watermites and mayflies, fitted the bimodal truncated SOFD pattern. However, bimodal symmetric SOFD pattern also fitted relatively well to the dragonflies and damselflies with high dispersal ability. It seems that differences in dispersal ability among different macroinvertebrate orders may partly explain observed differences. Moreover, our results supported slightly more a niche-based model rather than a metapopulation dynamics model in eutrophic lakes littoral macroinvertebrate metacommunities. Our results highlight that the dispersal ability is important trait for species conservation in patchily distributed habitat.</p

Schizophrenia: The new etiological synthesis

Schizophrenia has been an evolutionary paradox: it has high heritability, but it is associated with decreased reproductive success. The causal genetic variants underlying schizophrenia are thought to be under weak negative selection. To unravel this paradox, many evolutionary explanations have been suggested for schizophrenia. We critically discuss the constellation of evolutionary hypotheses for schizophrenia, highlighting the lack of empirical support for most existing evolutionary hypotheses—with the exception of the relatively well supported evolutionary mismatch hypothesis. It posits that evolutionarily novel features of contemporary environments, such as chronic stress, low-grade systemic inflammation, and gut dysbiosis, increase susceptibility to schizophrenia. Environmental factors such as microbial infections (e.g., Toxoplasma gondii) can better predict the onset of schizophrenia than polygenic risk scores. However, researchers have not been able to explain why only a small minority of infected people develop schizophrenia. The new etiological synthesis of schizophrenia indicates that an interaction between host genotype, microbe infection, and chronic stress causes schizophrenia, with neuroinflammation and gut dysbiosis mediating this etiological pathway. Instead of just alleviating symptoms with drugs, the parasite x genotype x stress model emphasizes that schizophrenia treatment should focus on detecting and treating possible underlying microbial infection(s), neuroinflammation, gut dysbiosis, and chronic stress.</p