Fathers

Fathers

1. Methods

   • Archival/Observational
     • Daly & Wilson (1982)
       • Study 1: videotapes of American child births; remarks on resemblance w/ father
         • unsolicited remarks, no demand characteristics
         • data collected in different context >> no experimenter bias
         • naturalistic & spontaneous
         • newsborns
       • Study 2: questionnaire on resemblance w/ Canadian new families
     • Consequences for investment
       • Anderson et al. (1999): survey on paternity certainty & college financing
       • Marlowe (1999): Hadza stepfathers invest less than genetic fathers; when number of fertile women & ratio of women:men increase in camp, paternal investment decreases
       • Alvergne et al. (2009): objective resemblance ~ paternal investment which in turn ~ nutritional status & growth
         • pos: olfactory cues, more realistic and consistent photos; assessed by Pp who are fathers; non-WEIRD sample, resource scarcity & competition among offspring; resource allocation depends on father >> relevant; avoids father's report of investment & resemblance (influenced by others' opinion and familiarity) or intention of investment; direct assessment of offspring fitness
         • Limit: low variability of paternal investment (mothers may have underreported b. social desirability, social norms or cultural beliefs or compensated); external raters were unfamiliar w/ faces
       • Gaulin & Schlegel (1980): cross-cultural sample of preindustrial societies; archival data; population level of paternity confidence ~ paternal investment; support for widened mother's brother hyp.
         • limit: third variable (knowing that he will need to invest, so makes certain paternity)? unexplained variance
       • Vonk et al. (2010): infant massage intervention increased perceived resemblance relative to control group; thus, rel. bw. paternal investment & perceived resemblance is bi-directional
     • Consequences for abuse
       • Daly & Wilson (1985): children living w/ one stepparent 40x more likely to be physically abused
       • Burch & Gallup (2000): domestically violent men perceived resemblance w/ child ~ quality of rel. w/ child, neg. ~ severity of injuries & frequency & severity of abuse of partner; same w/ their fathers
         • bad relationship might lead to perception of low resemblance?
   • Experiments
     • Bredart & French (1999): ages 1, 3 & 5; do not resemble father more
       • same limit. as Christfeld & Hill (1995)
     • Platek et al. (2002): morphed 2-year old toddler faces; men more likely to invest in self-morphs
       • limit: unrealistic shape + colour, familiarity, equity vs equality; hypothetical questions; intention> action; look older than 2-year old; used same- & opposite sex controls; undergrads
       • pros: manipulate resemblance;
     • Christenfeld & Hill (1995): 1-year olds more similar to fathers
       • mum might have chosen pictures; inconsistency in image quality; poor stimulus; raters are not fathers; not relevant to their life; artificial; social father might not be biological father; same race
       • 1, 10 & 20 year-olds
       • Critique oby Pagel (1997): did not test resemblance at birth; only need to sow enough doubt so father don't want to commit infanticide to offspring that might be his; does not require absolute anonymity; fathers in past not accustomed to viewing themselves in mirrors
     • Platek et al. (2003): men more likely to invest in self-morphs; respond to 25% morphs (beyond conscious recognition); no sex difference in matching
       • pros: different %; tested matching accuracy
       • same limitations as
     • DeBruine (2004): no sex differences in investment
       • limit: baby faces differ in baby schema features; undergrads (but Platek et al., 2004)
       • pros: 3.5-6 month-olds; same sex controls; unfamiliar morphs as frequent as self-morphs; diff. child faces for each question; neotonized faces, colour images >> more realistic; question more relevant to Pp; checked accuracy of matching
     • Platek et al. (2004): males select self-morph more often; fMRI w/ areas for inhibition of negative responses in males & areas for mentalizing in females
       • pros: high-resolution, colour; famous control to rule out familiarity; each face equally frequent;
       • limit: hypothetical, poor stimulus, intention > action; undergrads; self-face priming bias?
   • Self-report
     • Regalski & Gaulin (1993): interviews w/ Mexican parents & relatives
       • addition: looked at recent union & distance of relatives
       • median age: 47 days
     • McLain et al. (2000): 1-3 day old
       • Study 1: women more likely to comment on father's resemblance
         • control for image quality; no selection bias for pictures; take photos in diff. rooms; cover story; test ascribed vs actual resemblance w/ same faces
       • Study 2: more accurate matches of child w/ mother's photo
         • Genomic imprinting
     • Apicella & Marlowe (2007): survey at Heathrow Airport; self-perceived mate value ~mating effort; mating effort neg. ~ paternal investment; perceived resemblance & mate's perceived fidelity ~ investment
   • Comparative (other species)
     • Widdig (2007): paternal kin discrimination required for paternal care
       • more paternal care when high paternity certainty (wild guinea pigs has polygynous mating system) than when low paternity certainty (yellow-toothed guinea pig mates promiscuously)
       • some evidence that preference for familiar > unfamiliar indiv. regardless of relatedness, but captive animals & artificial set-up
       • maternal kin discrimination through familiarity (interact often)
       • potential mechanisms
         • familiarity hypothesis
           • mother-mediated
             • maternal control hyp. (influence offspring's association patterns)
             • mother's-codon-male-friend hyp. (mothers affiliate w/ father)
           • father-mediated
             • paternal care hyp. (father cares or paternal half-siblings at same time)
             • father-mothers-friendship hyp. (affiliates w/ mother; offspring grows up in proximity of paternal half-siblings)
           • via age proximity (no perfect skew where one male fathers all offspring in age cohort)
         • phenotype matching hypothesis
           • father present >> father used as template
           • father absent >> self-referent
           • male baboons help genetic offspring more than offspring from female they had sex w/ in fertile season but are not genetically related to
         • not mutually exclusive; no conclusive evidence; would need to control for familiarity to test phenotype matching
         • most likely cues:
           • odour (but decreasing reliance on smell dur. primate evolution b. trichromatic vision becomes more imp.)
           • facial appearance
           • accoustic characteristics of vocalisation
           • personality
       • how do paternal half-siblings recognize each other?

2. Paternity Uncertainty Background

   • General evolutionary theory = Inclusive fitness theory (Hamilton, 1964; adaptations are selected for and evolve because they promote inclusive fitness)
     • classical fitness
     • indirect fitness
     • costly behav. will be favoured only if it is preferentially directed towards related offspring
     • if indiv. put their helping behav. where their genes are, need to possess some proximate mechanism for kin recognition
   • mid-level theory: Theory of parental investment (the sex that invests greater resources will evolve to be choosier in mate selection; the other sex will be less choosy & more competitive w/ members of own sex)
     • Parental care favoured if it increases fitness of parent; favour offspring w/ higher return on parental investment
       • ability of offspring to convert parental care into fitness
       • genetic relatedness
   • Specific evolutionary hyp. (proposes existence of specific psychol. mechanism that is designed to solve a specific human adaptive problem)
     • predictions that follow can be tested empirically w/ several different methods >> cumulative weight of evidence
   • Buss (2004)
     • Paternity Uncertainty one reason why mothers care more for offspring than males
     • internal fertilization & concealed ovulation >> obscured reproductive status (not in estrus as in chimps when fertile)
       • women attractive during entire ovulatory cycles
       • cannot be mate guarded whole time
       • contextual cues for paternity:
         • promiscuity & premarital chastity >> female sexual loyalty/fidelity
         • sex w/ female around time of conception
       • perception of child's resemblance
         • kin recognition mechanisms, e.g. phenotype matching
     • maternity uncertainty but paternity uncertainty or probabilistic paternity certainty
   • because of concealed ovulation, internal fertilization & female infidelity, parental certainty is asymmetrical

3. Theory of concealing paternity

   • Pagel (1997)
     • Alternative hyp.: resembling one's parents at birth is developmentally impossible (but eye colour or other markings not difficult)
     • Population genetics model to explain neonatal appearance similarity to biological father in terms of fitness (cost of advertising paternity, consequential reduction in fitness, reduction in fitness due to paternity uncertainty >> decreased paternal effort, promiscuity); assuming anonymity or resemblance as ancestral condition
     • Concealing paternal identity is advantageous when domestic father is not likely to be the biological father and when costs of this are high (to avoid paternal neglect, abuse or infanticide)
     • under strict monogamy, badge not necessary (assuming that it is costly); given promiscuity, even small amounts of paternity uncertainty are sufficient to select against parent-infant resemblance
       • in US & UK, 5-30% of paternities misaligned (estimate based on blood tests)
     • force of selection against resemblance declines as child grows up b. infanticide by step-parent declines w/ age (main reason for infanticide is to reduce time until mother can conceive again so only useful while mother nurses)
   • Regalski & Gaulin (1993): divergent selection pressures; mothers evolve traits that elicit paternal care regardless of relatedness; father evolve traits that cause them to withhold paternal care from all but genetic offspring

4. Remarks on resemblance

5. Actual resemblance

6. Paternal investment as corr. w/ paternity certainty

7. Parental care

   • altricial vs precocial offspring
     • birth canal constraints head size >> post-utero brain growth >> premature until age 8
     • Rosenberg & Trevathan (2015): human babies have long gestation similar to prosocial great apes but larger babies w/ smaller brains >> extreme motor immaturity b. of encephalisation, but social learning abilities
     • humans secondarily altricial (Portman) >> longer cultural development
     • Mitteroecker & Fischer (2016): Caesarian section births have led to evolution of women w/ smaller pelvis

8. Paternal care (Fernandez-Duque et al., 2009)

   • Paternal care = behav. performed by a mature male that promote infants' dev., growth, well-being or survival & would not be performed in the absence of the young
   • found among owl monkeys, humans, tamarins & many other species that are only distantly related >> may evolve under different social & ecological cond.
   • proximate level: hormones (oxytocin , progesterone, estrogen & prolactin in females; vasopressin, prolactin & testosterone in males)
   • same neuroanatomical & neuroendocrine processes regulate pair-bonds, monogamy & paternal care
   • Gaulin & Schlegel (1980): males have 2 reproductive strategies (high investment in genetic offspring or broad procreation when genetic relatedness is ambiguous); if paternity is uncertain, invest in siblings' offspring or offspring he is more confident in