Why babies look like their daddies: paternity uncertainty and the evolution of self-deception in evaluating family resemblance

It has been suggested that in a socially monogamous system where fathers invest in their mate's offspring but paternity is far from certain, it will be adaptive on the part of infants to conceal their father's identity; but the opposite claim has also been made that this is against the genetic interests of the fathers, and a high frequency of adulterine births will select instead for paternal resemblance. In this article, I present a simple theoretical model that suggests that neonatal anonymity benefits fathers, mothers, and children. Once anonymity becomes established, however, all babies start paying the cost of paternity uncertainty, that is, the reduction in paternal care due to fathers not knowing whether they have truly sired their mate's offspring. By diminishing the fitness of babies, such a cost bounces back as lowered fitness for parents as well. We should then expect the evolution of maternal strategies directed to decrease paternity uncertainty, in the form of instinctive and unsolicited comments on babies' resemblance to their putative fathers. In contradiction to the widespread belief that it would be in fathers' interest to be skeptical of these allegations, the model suggests that, under conditions of infant anonymity, fathers will actually promote their own fitness by believing their spouses. Received in revised form: 5 September 2001 Electronic Publication     

Expression of male-typical behavior in adult female pseudohermaphroditic rhesus: Comparisons with normal males and neonatally gonadectomized males and females

Two types of pseudohermaphroditic female rhesus produced by exposure to either testosterone propionate (TP) or dihydrotestosterone propionate (DHTP) prior to birth were ovariectomized postpuberally and evaluated for the display of male-typical sexual behavior in response to exogenous TP in adulthood (2 mg/kg/day for 12 weeks). Their performance in standardized tests with estrogenized female partners was compared to that of neonatally gonadectomized males and females identically tested and treated with exogenous TP as adults. In addition intact adult males not given exogenous TP were tested with the same estrogenized female partners. There were no reliable differences between the two types of pseudohermaphrodites on any measure of behavior shown during the tests. Accordingly results were combined. Reliable behavioral changes induced by the TP given in adulthood were limited to increases in purse-lip responses, the induced increases were similar in pseudohermaphrodites and castrated males, and increases were reliably greater in these two groups of subjects than in females. Pseudohermaphrodites and castrated males did not differ reliably from intact males in performance of purse-lip gestures during TP treatment. In the performance of mounting, however, pseudohermaphrodites and castrated males remained consistently below the standard of the intact males. The estrogenized female partners displayed proceptive responses most frequently to the intact males and least frequently to the females. Their proceptive responses with castrated males resembled their performance with intact males, but with pseudohermaphrodites their proceptive responses more closely resembled their performance with females. Receptive behavior of the female partners was displayed most frequently to intact males, at intermediate levels to castrated males, and least often to pseudohermaphrodites. Results are completely consistent with the notion that androgens in high concentrations before birth alter mechanisms related to the later display of masculine behavior. These alterations in behavioral mechanisms are of such a nature that the display of male-typical behavior induced by androgens in adulthood is more pronounced and more frequent than it would have been otherwise. The alterations in masculine behavior observed in pseudohermaphroditic rhesus are not different in kind or scope than those reported extensively for lower mammals.(ABSTRACT TRUNCATED AT 400 WORDS)     

Sex,money, and paternity: The evolutionary psychology of domestic violence

Three hundred sixty-five women, with children between six and 12 years of age, were interviewed and tested on various issues theoretically related to domestic violence. The sample was stratified into three subsamples of volunteer women recruited from: (1) a temporary shelter for battered women, (2) the local community and screened specifically for the reported presence of domestic violence, (3) the same community sources and screened only for the reported presence of children of the specified age group. Factor analytic structural equation models were constructed for the predictors of violence by the woman's main sexual partner toward the woman and towards the woman's child. Common factors were constructed for the four major dimensions of domestic violence— verbal, physical, escalated, and sexual—and for the three major predictors of domestic violence—sex, money, and paternity. The sex factor indexed the general quality of the sexual relationship dynamics, the money factor indexed the couple's socioeconomic relations, and the paternity factor indexed the genetic stakes held in the family by the woman's main sexual partner. These three factors jointly accounted for 60% of the variance in violence toward the woman. Violence towards the woman—the only significant direct effect—accounted for 26% of the variance in violence toward the child. These findings suggest that the principal perpetrators of domestic violence may be competitively disadvantaged males, pursuing coercive sexual and parental strategies without regard to the deleterious indirect effects upon their own genetic offspring.     

Individual differences in aggressiveness of female hamsters: response to intact and castrated males and to females

The aggressive behaviour of female hamsters was studied while they were housed in large enclosures with males and in brief tests with males or females. Some females are not aggressive with any male, whereas others are very aggressive toward all males in both testing conditions. Females that are not aggressive toward intact males may be very aggressive toward castrated males or females. When the animals are housed together for long periods of time, males dominate only if they are much heavier. Male dominance takes a relatively long time to establish and often there is an equivocal period characterized by reversals of dominance. Female dominance is rapidly established. Unless the male is much heavier, the female determines the presence or absence of agonistic behaviour.     

Giant females and dwarf males: a comparative study of nuptial organs in female Chondracanthidae (Crustacea: Copepoda)

Male chondracanthids attach to specific structures located near the genital apertures of the female and the term nuptial organ is proposed for these structures. The morphology of the nuptial organ in Acanthochondria cornuta, A. limandae, Acanthochondrites annulatus, Blias prionoti, Chondracanthodes deflexus, Chondracanthus lophii, Lernentoma asellina and Pseudoblias lyrifera is described. Nuptial organs in C. lophii contain glandular tissue and appear capable of producing a secretion. In addition to providing a site for male attachment these organs may have other possible functions, which are discussed.     

Dispersal, philopatry, and genetic relatedness in a social carnivore: comparing males and females

A balance must be maintained between the proportion of individuals dispersing and the proportion remaining philopatric such that inbreeding and resource competition are minimized. Yet the relative importance of dispersal and philopatric behaviour is uncertain, especially for species with complex social systems. We examine the influence of dispersal on genetic relationships of a white-nosed coati ( Nasua narica : Procyonidae) population from Panama. Field studies of the coati indicate a social system in which all females are highly philopatric and live in bands while all adult males become solitary at maturity, but do not disperse from the home range of their natal band. Based on analyses of multilocus DNA fingerprints, we confirm that female philopatry is the rule, long-distance dispersal is rare, and that relatedness between most bands is low. However, some new bands result from fission events and these bands retain relatively high relatedness to one another for several years. Adult males inhabiting the home range of a band are closely related to band members. In contrast, males and band members whose ranges do not overlap are unrelated or only slightly related. Adult males are also more closely related to other males whose home ranges they overlap extensively than to males whose home ranges they overlap only slightly. These results indicate that males initially disperse from their natal bands to reduce resource competition and not to avoid inbreeding. Inbreeding avoidance, if it occurs, results from more extensive range movements by males during the mating season.     

Sex-role reversal revisited: choosy females and ornamented, competitive males in a pipefish

In the pipefish Syngnathus typhle sex roles are reversed, thatis, females compete more intensely than males over mates. However,competition over mates among individuals of one sex does notnecessarily prevent members of that same sex from being choosy,and choosiness in the other sex does not prevent competitionwithin it. In an experiment we allowed a female pipefish tochoose freely between two males, after which we released themales and let the three interact. Comparisons with earlier resultsshow that both sexes courted partners and competed with consexuals.However, females courted more often than did males, and courtshipwas more frequent in treatments involving large individualsthan in treatments with small individuals. Males competed amongthemselves for access to mates but for a shorter duration thanfemales in the same situation. Males displayed an ornament towardsfemales but not to males during mating competition. Females,however, used their ornament in both contexts. Females did notalways mate with the male of their previously made choice, whichwe interpret as females being constrained by male-male competition,male motivation to mate, or both. Thus, in this sex-role reversedspecies, mate choice in the more competitive sex may be circumventedand even overruled by mate competition and mating willingnessin the least competitive sex. Hence, sex roles should not beconsidered as sexes being either choosy or competitive but ratherthat males and females may exhibit different combinations ofchoice and competition.     

Predation, sensitivity, and sex: why female black rhinoceroses outlive males

Among sexually dimorphic, polygynous mammals, adult femalestend to outlive males and respond more strongly to predatorsthan males. We asked whether a monomorphic, polygynous speciesvirtually immune to predation due to large size (black rhinoceros,Diceros bicornis) conforms to this pattern. Data on 193 interactionswith lions (Panthera leo) and spotted hyenas (Crocuta crocuta)in two nonhabituated populations in Namibia studied from 1991to 1993 revealed that: (1) females were more vigilant or aggressivethan males to either of the potential predators; and (2) whethersolitary or with calves, females attacked more often than males.Although solitary females tended to be more aggressive to lionsthan to hyenas, neither females with calves or males seemedto discriminate between the two carnivores. We also simulatedthe behavior of human predators (poachers) during 69 encounterswith rhinoceroses. While both sexes abandoned local sites becauseof our presence, females ran farther than males, covering upto 40 km in a day. These findings implicate a behavioral mechanismto explain why secondary sex ratios favor females - males aremore prone to human predation, a prediction consistent withdata from 12 populations throughout Africa. Black rhinocerosesappear to be an unanticipated exception to the well-establishedpattern of male-biased mortality in polygynous mammals; in theabsence of intense human predation (a recent event), male mortalityfails to exceed that of females, suggesting that intrasexualcompetition in a polygynous mammal: may not be the primary causeof unbalanced secondary sex ratios. Our results on the causesof sex differences in mortality and in responsiveness to differentpredators reinforce the relevance of behavioral ecology to conservation;such information is necessary for planning how best to minimizenegative human influences on the few remaining wild Africanrhinos.     

Sexes,species, and genomes: why males and females are not like humans and chimpanzees

This paper describes, analyzes, and critiques the construction of separate “male” and “female” genomes in current human genome research. Comparative genomic work on human sex differences conceives of the sexes as like different species, with different genomes. I argue that this construct is empirically unsound, distortive to research, and ethically questionable. I propose a conceptual model of biological sex that clarifies the distinction between species and sexes as genetic classes. The dynamic interdependence of the sexes makes them “dyadic kinds” that are not like species, which are “individual kinds.” The concept of sex as a “dyadic kind” may be fruitful as a remedy to the tendency to conceive of the sexes as distinct, binary classes in biological research on sex more generally.     

Reactions to children's faces: Males are more affected by resemblance than females are, and so are their brains

The detection of genetic relatedness (i.e., kinship) affects the social, parental, and sexual behavior of many species. In humans, self-referent phenotype matching based on facial resemblance may indicate kinship, and it has been demonstrated that facial resemblance increases perceptions of trustworthiness and attractiveness [Proc. R. Soc. Lond., B Biol. Sci. 269 (2002) 1307–1312; Proc. R. Soc. Lond., B Biol. Sci. (in press)]. However, investigations of sex differences in reaction to facial resemblance have produced mixed results [Evol. Hum. Behav. 25 (2004) 142–154; Evol. Hum. Behav. 23 (2002) 159–166; Evol. Hum. Behav. 24 (2003) 81–87]. Here, we replicate the effects of Platek et al. [Evol. Hum. Behav. 23 (2002) 159–166] using high-resolution color morphing. We also extend these findings using functional magnetic resonance imaging (fMRI) to demonstrate a possible neural mechanism that may account for the observed sex difference. These data support the hypothesis that human males may use and favor facial resemblance as a paternity cue.     

An extinct Eocene taxon of the daisy family (Asteraceae): evolutionary, ecological and biogeographical implications

Background and Aims

Morphological, molecular and biogeographical information bearing on early evolution of the sunflower alliance of families suggests that the clade containing the extant daisy family (Asteraceae) differentiated in South America during the Eocene, although palaeontological studies on this continent failed to reveal conclusive support for this hypothesis. Here we describe in detail Raiguenrayun cura gen. & sp. nov., an exceptionally well preserved capitulescence of Asteraceae recovered from Eocene deposits of northwestern Patagonia, Argentina.

Methods

The fossil was collected from the 47·5 million-year-old Huitrera Formation at the Estancia Don Hipólito locality, Río Negro Province, Argentina.

Key Results

The arrangement of the capitula in a cymose capitulescence, the many-flowered capitula with multiseriate–imbricate involucral bracts and the pappus-like structures indicate a close morphological relationship with Asteraceae. Raiguenrayun cura and the associated pollen Mutisiapollis telleriae do not match exactly any living member of the family, and clearly represent extinct taxa. They share a mosaic of morphological features today recognized in taxa phylogenetically close to the root of Asteraceae, such as Stifftieae, Wunderlichioideae and Gochnatieae (Mutisioideae sensu lato) and Dicomeae and Oldenburgieae (Carduoideae), today endemic to or mainly distributed in South America and Africa, respectively.

Conclusions

This is the first fossil genus of Asteraceae based on an outstandingly preserved capitulescence that might represent the ancestor of Mutisioideae–Carduoideae. It might have evolved in southern South America some time during the early Palaeogene and subsequently entered Africa, before the biogeographical isolation of these continents became much more pronounced. The new fossil represents the first reliable point for calibration, favouring an earlier date to the split between Barnadesioideae and the rest of Asteraceae than previously thought, which can be traced back at least 47·5 million years. This is the oldest well dated member of Asteraceae and perhaps the earliest indirect evidence for bird pollination in the family.     

Melodic males and flashy females: Geographic variation in male and female reproductive behavior in red‐eyed treefrogs (Agalychnis callidryas)

Geographic variation in courtship behavior can affect reproductive success of divergent phenotypes via mate choice. Over time, this can lead to reproductive isolation and ultimately to speciation. The Neotropical red‐eyed treefrog (Agalychnis callidryas) exhibits high levels of phenotypic variation among populations in Costa Rica and Panama, including differences in color pattern, body size, and skin peptides. To test the extent of behavioral premating isolation among differentiated populations, we quantified male advertisement calls from six sites and female responses to male stimuli (acoustic and visual signals) from four sites. Our results show that both male advertisement calls and female behavior vary among populations: Discriminant function analyses can predict the population of origin for 99.3% ± 0.7 of males based on male call (dominant frequency and bandwidth) and 76.1% ± 6.6 of females based on female response behavior (frequency and duration of visual displays). Further, female mate choice trials (n = 69) showed that population divergence in male signals is coupled with female preference for local male stimuli. Combined, these results suggest that evolved differences among populations in male call properties and female response signals could have consequences for reproductive isolation. Finally, population variation in male and female behavior was not well explained by geographic or genetic distance, indicating a role for localized selection and/or drift. The interplay between male courtship and female responses may facilitate the evolution of local variants in courtship style, thus accelerating premating isolation via assortative mating.     

Female dimorphism and mating behaviour in a damselfly, Ischnura ramburi: females mimicking males

Females of the damselfly Ischnura ramburi exhibit a simple genetic colour dimorphism in which one form is cryptic (heteromorph), and the other closely resembles the more conspicuously colourful males (andromorph). Andromorphs also mimic male behaviour in interactions with males. Consequently they copulate half as often as do heteromorphs, which may give them a frequency-dependent selective advantage. Assuming that females need only mate once, excessive copulations, which average 3 h in duration, waste time for heteromorphs and may expose them to increased predation. The peculiar biology and mating behaviour of ischnurans provides a possible evolutionary context for this mimicry. The polymorphism is probably balanced by a frequency-independent selective disadvantage suffered by the more conspicuous andromorphs, through increased predation.     

Sperm (ejaculate) competition in Drosophila melanogaster, and the reproductive value of females to males in relation to female age and mating status

• 1 In double mating experiments with Drosophila melanogaster in which one male had been irradiated, it was confirmed that sperm displacement is extensive, i.e. the second male to mate displaces most of the previously-stored sperm.
• 2 The predominance of the second ejaculate over the first increases with the interval between the two matings, from about P₂= 0.83 (second mating on the first day after the first mating) to about P₂= 0.99 (interval between mating = 14 days) where P₂ is the proportion of offspring fathered by the second male.
• 3 A more accurate method for calculating P₂ values is developed for experiments in which sperm are ‘labelled’ by irradiation treatment (equation 1).
• 4 Observations of the reducing egg production of the female throughout life were also obtained. A model is examined which incorporates both the sperm competition and egg production data to predict the reproductive value to a male of a mating with a given type of female, varying in age and mating status. The relative value (in terms of probable numbers of progeny gained) of a mating with a virgin or 4 day post-mating female is about twice that of a 14 day post-mating female, mainly because of the fecundity difference.
• 5 Some evolutionary aspects of sperm competition and multiple mating in insects are reviewed and discussed.

     

Reckless males, rational females: dynamic trade-off between food and shelter in the marine isopod Idotea balthica

Habitat choice of herbivores is expected to be a resolution of a trade-off between food and shelter. The resolution of this trade-off may, however, be dynamic within a species because distinct phenotypes may value these factors differently and the value may vary temporally. We studied this hypothesis in the marine herbivore Idotea balthica (Isopoda), by simultaneously manipulating both food and shelter, and investigated whether the resolution of the trade-off differed between sexes, colour morphs and day and night (i.e. high and low predation risk). Isopods chose between exposing and concealing backgrounds in which the quantity or quality of food varied. When choosing between the backgrounds in the absence of food, females preferred the concealment more than males did. However, in a trade-off situation the isopods traded shelter for food, and females more so than males. Thus, males' lower preference for the shelter was not counterbalanced by a stronger preference for food. The microhabitat use also differed between night and day showing adaptation to diurnally fluctuating predation risk. We suggest that microhabitat utilization of females is more strongly tied to variation in risk and resources than that of males, for whom other factors, such as seeking mates, may be more important.     

The epidemiology and transmission of AIDS: A hypothesis linking behavioural and biological determinants to time,person and place

Epidemiologically, the Acquired Immune Deficiency Syndrome, AIDS, is transmitted and distributed in the USA and Europe almost entirely in well-defined subsets of populations engaging in, or subjected to, the effects of behaviours which carry high risks of genital and systemic infections. The persons predominantly affected are those engaging in promiscuous homosexual and bisexual activity, regular use of addictive drugs, and their sexual and recreational partners. In such persons and in subsets of populations with corresponding life-styles, the risk of AIDS increases by orders of magnitude. Because of continuity of risk behaviour and of associated indicator infections, the incidence of AIDS over 3–5 year periods is predictable to within 10% of actual totals of registered cases in the USA and UK. Secondary transmission of AIDS beyond these groups is minimal or, in many locations, absent. There is no indication of appreciable spread by heterosexual transmission to the general population.The Human Immunodeficiency Virus, HIV, is transmissible to some extent in general populations, and more so among promiscuous persons. It may cause viraemia, lymphadenopathy and latent infection (HIV disease) in anyone. In persons engaging in risk behaviours which themselves alter or suppress immune responses, it can interact with MHC, antibodies to other organisms and to semen, and other allogenic antigens to initiate a programmed death of CD4 lymphocytes and other defensive cells, as in graft-host rejections. This occurs also in haemophiliacs receiving transfusions of blood products, and is more pronounced in persons with reactive HLA haplotypes. The susceptibility of particular subsets of populations to AIDS is thereby largely explained. But these changes occur in the absence of HIV, and so do Kaposi's sarcoma, lymphadenopathies and opportunistic infections which are regarded as main indicators of AIDS. The hypothesis that HIV-1 can do all this by itself and thereby cause AIDS is falsifiable on biological as well as epidemiological grounds.An alternative hypothesis is proposed, linking the incidence of AIDS to the evolution of contemporary risk behaviour in particular communities and locations in the USA, UK and probably in most of Europe. It does not pretend to explain the reported incidence of AIDS in Africa and other developing regions where data are insufficient to provide validation of the pattern of disease and contributory variables.The immediate, practical implication of this alternative hypothesis is that existing programmes for the control of AIDS are wrongly orientated, extremely wasteful of effort and expenditure, and in some respects harmful.     

Extrapair paternity in the blue tit (Parus caeruleus) : female choice, male charateristics, and offspring quality

Extrapair paternity is common in many birds, and it is now generallyaccepted that female choice plays an important role. However,die benefits that females obtain from extrapair paternity aremuch less dear. To test the hypothesis that females obtain indirectfitness benefits, we studied paternity in a blue tit populationover 4 years. Extrapair paternity occurred in 31-47% of allnests and accounted for 11-14% of all offspring. Most malesthat fathered extrapair young did not lose paternity themselves,males never "exchanged" paternity, and within nests the extrapairoffspring were usually fathered by a single male. Comparisonsbetween males that did and did not lose paternity and pairwisecomparisons between the extrapair male(s) and the within-pairmale showed that successful males had longer tarsi and sangon average longer strophes during the dawn chorus. Successfulmales weighed less (relative to their size) during the nettlingstage, but nevertheless they survived better. Male age did notinfluence their likelihood of losing paternity, but extrapairmales were usually older than the within-pair male they cuckolded.Within nests with mixed paternity, extrapair young were morelikely to survive than within-pair young in cases of partialbrood mortality. Our data also suggest that extrapair offspringwere more likely to be males. Because extrapair males were usuallyclose neighbors, male quality should be considered relativeto the quality of the neighbors. Despite this, we found consistencyin female choice over years. Our observations provide supportfor the hypothesis that female blue tits engage in extrapaircopulations to obtain good genes for their offspring.     

Imitating the cost of males: A hypothesis for coexistence of all‐female sperm‐dependent species and their sexual host

All‐female sperm‐dependent species are particular asexual organisms that must coexist with a closely related sexual host for reproduction. However, demographic advantages of asexual over sexual species that have to produce male individuals could lead both to extinction. The unresolved question of their coexistence still challenges and fascinates evolutionary biologists. As an alternative hypothesis, we propose those asexual organisms are afflicted by a demographic cost analogous to the production of males to prevent exclusion of the host. Previously proposed hypotheses stated that asexual individuals relied on a lower fecundity than sexual females to cope with demographic advantage. In contrast, we propose that both sexual and asexual species display the same number of offspring, but half of asexual individuals imitate the cost of sex by occupying ecological niches but producing no offspring. Simulations of population growth in closed systems under different demographic scenarios revealed that only the presence of nonreproductive individuals in asexual females can result in long‐term coexistence. This hypothesis is supported by the fact that half of the females in some sperm‐dependent organisms did not reproduce clonally.