“The evolution of cooperation in groups of non-kin in humans has been … the subject of debate ...

...fundamental questions remain about the … nature of the cognitive mechanisms that underpin human cooperative psychology and whether there are stable individual differences in these mechanisms.

Experimental results of the kind reported here can be useful for clarifying whether the assumption of stable types in the realm of human cooperation as assumed by simulations is justified, and, if it is, how best to characterize these types.”

Kurzban & Houser (2005): Experiments investigating cooperative types in humans: A complement to evolutionary theory and simulations. PNAS. Boris & Patrick

“In line with types used in simulations and observed in other experimental contexts, we consider the hypothesis that people are one of three stable types: ”

• Cooperators: contribute to generating group benefits at a cost to self

• Free-riders: who do not incur these costs

• Reciprocators: who respond to others’ behavior by using a conditional strategy (such as tit-for-tat)

Kurzban & Houser (2005): Experiments investigating cooperative types in humans: A complement to evolutionary theory and simulations. PNAS. Boris & Patrick

Von Rueden et al (2008): The multiple dimensions of male social status in an Amazonian society. Evol. Hum. Behav.

Maddie & Caitlane

Predictions:Physical size winning dyadic fights

Number of allies winning group conflicts

Acculturation community influence

Prosocial behavior community influence

Social status will increase until 40’s, then decline, with each proxy declining at a different rate

Fiddick & Erlich (2010): Giving it all away: altruism and answers to the Wason selection task. Evol. Hum. Behav. Ngoc & Laura

Our minds consist primarily of “a constellation of specialized mechanisms that have domain-specific procedures, operate over domain-specific representations, or both” Cosmides and Tooby (1994)

Cosmides 1989: cheater detection is one such mechanism. Used Wason selection task.

Subsequent studies: altruist detection is another such mechanism, perhaps subserving both.

Problem 1: confounds in instructions (“giving it all away”)

Problem 2: altruist detection makes no theoretical sense

Musso et al (2003): Broca’s area and the language instinct. Nature Neuroscience. Kyle & Victor

Purpose: To investigate the system underlying the acquisition of new linguistic competence

Chomsky hypothesis = Universal Grammar

Alternative hypothesis: The human mind is a general learning tool without specialized structures

Prediction: by Chomsky hypothesis, individuals should use Broca’s area in learning new ‘real’ language but not in learning new ‘unreal’ language

Schug et al (2010): Emotional expressivity as a signal of cooperation. Evolution & Human Behavior. Carol & Adrian

Hypothesis: emotional expressivity is a honest (reliable) signal of a cooperative disposition because emotional responses are involuntary and cannot be faked.

More specifically: cooperators are likely to show more emotion, both positive and negative.

Involuntary nature of emotional expression is taken as a given, not treated as adaptive. Presumably the ability to pick up on these signals would be adaptive, but that’s not tested here, only whether the degree of emotional expression predicts cooperativeness.

Healy & Ellis (2007): Birth order etc: Tests of the family-niche model of personality. Evolution & Human Behavior.

Maddie & Dylan

Test hypothesis about personality differences between 1st- and 2nd-born siblings.

Primary hypothesis: 1st-borns are more responsible, achieving, etc,. second borns more rebellious and unconventional.

Secondary hypothesis: 2nd-born males hypomasculinized, therefore bigger differences between male than female sibling pairs.

Healy & Ellis (2007): Birth order etc: Tests of the family-niche model of personality. Evolution & Human Behavior.

Maddie & Dylan

Test hypothesis about personality differences between 1st- and 2nd-born siblings.

Primary hypothesis: 1st-borns are more responsible, achieving, etc,. second borns more rebellious and unconventional.

Secondary hypothesis: 2nd-born males hypomasculinized, therefore bigger differences between male than female sibling pairs.

Salmon et al (2008): Ancestral mechanisms in modern environments: Impact of competition and stressors on body image and dieting behavior. Human Nature. Tiffany & Alex

Evolutionary hypothesis: anorexia is an adaptation for exerting control over reproduction, specifically by suspending menstruation (ovulation). Idea is that in times of unfavorable social or ecological conditions, woman could delay reproduction until situation or ability to deal with it improves. In short, in EEA, adjusting body fat was a way of modulating reproduction.

Miller – Costly Display Theory

Culture is more than a system for transmitting useful technical knowledge and group-benefiting traditions down through the generations. It can also “be considered an arena for various courtship displays in which individuals try to attract and retain sexual partners.  When a young male rock star stands up in front of a crowd and produces some pieces of human ‘culture’ known as songs, he is not improving his survival prospects.  Nor is he engaging in some bizarre maladaptive behaviour that requires some new process of ‘cultural evolution’ to explain.  Rather, he is doing something that fulfils exactly the same function as a male nightingale singing or a male peacock showing off his tail.  He is attracting sexual partners”.  Miller 1999

Question: Why is most publicly generated ‘cultural’ behaviour is produced by young males points towards its courtship function.

“This cultural courtship model proposes that sexual selection through mate choice by both our male and female ancestors was a major evolutionary force in shaping human culture, i.e. the genetically inherited capacities for behaviours such as language, art, and music.  These behaviours, according to this model, function mainly as courtship displays to attract sexual partners, and show many of the same design features shared by other courtship displays in other species.  In short, human culture is mainly a set of adaptations for courtship.  This hypothesis doesn’t really come from Nietzsche, of course, or from Freud.  Rather, it is a relatively simple application of standard Darwinian sexual selection theory to a somewhat puzzling set of behavioural phenomena in one rather pretentious species of primate”.

Miller 1999

Miller – Costly Display Theory

Nettle & Clegg (2006): Schizotypy, creativity and mating success in humans. Proc. Royal Society. Grant & Brooke

Miller’s hypothesis: Costly displays of quality function to attract mates

Prediction: artistic production correlated with high number/quality of sexual partners

Gerdes et al (2009): Spiders are special. Evolution & Human Behavior. Michael, Alex & Lindsay

Preparedness hypothesis: we should be strongly inclined to fear dangerous things (learn quickly etc).

Authors examine an apparent exception to this hypothesis: spiders are more feared than bees & wasps despite being less dangerous.

Positive aspects of bees (especially in EEA) might be a partial answer to this paradox.

Authors just raise a problem, but provide no answers.

Hypothesis: kin influence individuals to make decisions that advances the individual’s fitness and their relatives’ inclusive fitness.

Proxy is fairly weak, as they rely on role-playing about what a woman might do rather than providing actual data on this point.

But it is a clear evolutionary alternative to the standard (r vs k selection) hypothesis that decrease in fertility in modern societies reflects a shift to a strategy of investing more in a few kids rather than having lots of kids.

Newson et al (2007): Influences on communication about reproduction: the cultural evolution of low fertility. Evolution & Human Behavior. Kyle & Victor

Model for attractiveness of indicator trait and prevalence of schizophrenia