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intro to kin recognition

Although not often considered, humans both produce cues to kinship that vary with genetic relatedness and have perceptual abilities to detect these cues in others and assess that relatedness. The potential functions of these abilities are discussed.


what is kin recognition?

Kin recognition is an unobservable internal process of assessing genetic relatednes


how can kin recognition be inferred?

is inferred by kin discrimination, the observable differential treatment of conspecifics based on cues that vary with relatedness


e.g.'s of kin recognition in animals

• Lots of species have a way of regulating their behaviour in order to enhance their own inclusive fitness

Some animals remarkably good at this

Japanese quails (Bateson, 1982)

Ostriches and eggs (Bertram, 1977)

Honey bees (Page and Erikson, 1984)


what does kin selection aim to actually achieve?

better inclusive fitness


kin recognition in Japanese Quails

• Japanese quails and mate choice (Bateson, 1982)- if given a sibling, 1st cousin or unrelated bird that they’ve never met before- more likely to preferentially mate with 1st cousin- optimal relatedness in breeding pairs- defo treated differently if related.


kin recognition in ostriches

• Ostriches and eggs (Bertram, 1977)
o Engage on co-operative nesting
o Sits on eggs of other females
o If not enough room kicks out eggs of other females rather than their own


kin recognition in honey bees

• Honey bees and larvae (Page and Erikson, 1984)
o More likely to feed larvae to turn into queens pick ones more related to themselves


mammals and kin recognition

• Numerous examples of mammals preferring to socialise with, avoid conflict with relatives


what two broad things can we use to know relatedness

Social cues
and phenotype matching


what two social cues are there?

proximity-e.g. nearest thing when born and association- spending lots of time together


what did hamilton posit in terms of phenotype matching/

Hamilton posited that genes should affect ‘(1) some perceptible feature of the organism, (2) the perception of that feature, and (3) the social response consequent upon what was perceived’ (1964).


what does an understanding of kin phenotype recognition consist of nowadays?

an understanding of kin recognition involves three components: the production of unique phenotypic cues, or ‘labels’, the perception of these labels and their degree of correspondence with a ‘recognition template’ (these components are the mechanism of recognition), and the action taken by an animal as a function of the similarity between its template and an encountered phenotype (Mateo 2003, 2004)


what could lead us to believe that we recognise kin through facial features?

Humans have entire visual areas devoted to facial recognition thus would serve that one way we recognise kin is through facial features.


evidence for genetic relatedness in facial features

Mothers can recognize photographs of their infants within 33 h of birth, and strangers can match photographs of mothers to their infants, suggesting a physical resemblance among kin (Porter et al. 1984) – thus strangers perceptions are based on phenotype matching.
People can also match faces of siblings to whom they are not related (Maloney & Dal Martello 2006) and assess the relatedness of pairs of close and distant kin (e.g., grandparents and grandchildren, aunts and nephews/nieces; Kaminski et al. 2009).
Thus, there appear to be cues to genetic relatedness in facial features.


what examples are there suggesting there is a visual modality to kin recognition?

-genetic relatedness cues in faces

-we trust more faces that are our own

-more attracted to faces that look genetically different

all these suggest that there is something we can tell about genetics from the face


evidence that we trust self-familiar faces more

o DeBruine (2002)
o Used facial morphing to create self-similarity in a stranger’s face- calculate 2D structure of base face and participant and then morph colour info into morph of the two people uses hair and clothes of the base face.
o Participants co-operate with their own self-morph and some others’ self-morph. Look at how much someone co-operates with themselves controlling for how much the other person also wants to co-operate with them (some people may just generally look nicer and more trust worthy)
o Play a trust game- and found that they are sig more likely to trust self-morphs than non-self morphs. If look at fairness (ie. when on other side of trust game and if you then cheat or give someone a fair amount) there is no difference to self and non-self so maybe people are just generally giving especially middle class uni students.

• Krupp et al., 2012
o Public goods game- everyone puts money into pot- that pot is then multiplied and divided between players- best way to play is to cheat it and not put money in but get the money out (free-riding)
o People were placed into groups of 4 where there were 2 co-operators and a free rider- got to see pics of who playing with- either 3 strangers, 2 strangers 1 self-resembling or 2 self-resembling, 1 stranger.
o The more self-resembling faces within ‘group’ the greater public goods contributions- the more people are trusting- trust own relatives more
o No change in costly punishment (e.g. can pay a pound and find out who the free rider is to take money off of them)


menstruation and facial preference for own looking faces study

• DeBruine, Jones & Perrett (2005)
o Menstrual cycle study- looking at how preference for self and others changes across the menstrual cycle
o Young and female, mature and female, young and male, mature and male
o Luteal phase (middle of the second half of menstrual cycle), follicular (2nd week of menstrual cycle) can become pregnant in the follicular stage but not in luteal phase. In luteal phase there is a high rise in progesterone waiting for a fertilised ovum.
o Follicular phase- these is no self-similarity preference nor aversion
o In luteal phase- preference for self-similar faces and this is particularly strong for female faces (mostly straight women).
o Why might spike in progesterone lead to preference for self-similar faces- progesterone goes up in luteal phase progesterone only goes up more when pregnant- preference for female kin network when hormones are telling you that you might be pregnant. Body is hormonally half way there when in luteal stage- female kin extremely important when pregnant.


what is a potential issue with studies that show preference to self-familiar faces?

Don’t have mirrors how can you know what you look like if you don’t have a mirror? People have argued that all you need is a still dark pool and this is probably not that true- mechanism must build on something else…


what do experimenters who manipulate faces to look like self hope they are manipulating? but what is still the issue with this

Can build a model of self-similarity without a mirror by basing on a template of those related to you
Use kin to form image of self-similarity recognise kin based on self-similar faces which leads back to using kin to form image of self-similarity—is arguably very circular. This doesn’t work if this is your only way of detecting kin and only way to correctly regulate behaviour towards kin as need something else to correctly build template in the first place.


if need to know kin before kin recognition template is created then what does this suggest? but who argues against this and why?

So is it all about familiarity?
DeBruine argues this is not true- because same study with famous and non-famous faces i.e. are you more likely to trust someone you don’t know but who looks very like a celebrity than you are to trust someone you don’t know and who looks like nobody you know. Morphs of highly familiar but not related individuals didn’t produce the same behaviours. But haven’t acc met many of these celebrities maybe you need real interaction and not just visual association


what brain imagining research also supports DeBruine's research on kin recognition in faces?

Detection of resemblance in children’s faces activates the left frontal cortex in men, but not women, suggesting possible decision-making processes involved in assessment of paternity and possible investment (Platek et al. 2004). Kin faces (versus unknown faces) activate regions involved in self-face recognition (e.g., anterior cingulate gyrus and medial frontal gyrus), whereas kin versus friend faces activate posterior cingulate and cuneus, again suggesting a need to process for identification (Platek & Kemp 2009). Multiple mechanisms for discriminating kin faces may have been favored by selection due to the need for fast and accurate recognition.

but still there must be an initial mechanism to know kin to begin.


what is kin recognition by smell called?

Olfactory cues


olfactory cues in animals

Olfactory cues are known to covary with genetic relatedness in a variety of taxa (e.g. birds: Coffin et al., 2011; mammals Halpin 1986)


olfactory cues in humans evidence?

• Infants rapidly recognise the mother’s scent when they are born- partly because they have been in utero swallowing and breathing amniotic fluid which is itself carrying chemical compounds to do with mother’s diet so already exposed to mothers scent- newborn babies can orient to mothers scent.
• Parents can recognise own offspring by scent-
o Porter and Moore (1981)
o Children slept in t shirts for 3 nights (unscented scent and detergent)
o Parents smelled the t shirts
o 19/14 siblings recognised each other’s smell
o 17/18 tests on mothers achieved recognition
o 8/9 recognised both their children
o Study 2- 16/18 parents could recognise and discriminate between their offspring.


argument against olfactory cues in humans?

argued that it may just be familiarity?

o Hold and Schleidt (1977)- found that partners recognised each other’s smell just because become familiar with that smell
o So partly we just learn smells and is a by-product of a social cue.


what is evidence that odors can actually be cues to kin in humans?

Fathers, grandmothers, and aunts can also identify their related infant with little prior contact (Porter et al. 1986- so suggests that it is smell to an extent- suggesting a shared genetic component in the odors of family members.

Odor-based recognition of kin can go beyond simple familiarity with individual’s cues, however. People can match the odors of mothers and their children, despite being unrelated to the odor donors, indicating discrimination based on phenotype matching. That husbands and wives cannot be reliably matched by odor indicates that odor recognition is mediated through shared genes rather than a shared environment (Porter et al. 1985)

Accordingly, extended periods of separation do not diminish the ability to recognize kin (Porter et al. 1986)


what is evidence that odors can actually be cues to kin in animals?

an habituation–discrimination study using rats shows that human odors covary directly with genetic relatedness, with close kin (e.g., mother, sister) having more similar odors than distant kin (e.g., aunt, niece, grandmother), which in turn have more similar odors than non-kin (Ables et al. 2007).


what would provide additional information to the fact that odors may be cues to kin relatedness?

that odors influence human social interactions

(evidence in parents and in mate choice)


evidence of odors influencing social interactions for parents

-mothers who are better able to recognize their infant’s odor also report better nursing experiences and positive mothering attitudes (Fleming et al. 1995)
- Fathers have greater attachment and show more affection toward offspring they can identify by odor. In contrast, mothers use more punishment with offspring whose odors they cannot identify and use less punishment with children with odors they rate as pleasant (Dubas et al. 2009).