What makes us who we are? Nature and Nurture Based on “Nature via Nurture” by Matt Ridley (2003)

Genes code for proteins. Cells function because of proteins. Fig 16.10 Genes code for proteins. Cells function because of proteins. Organisms are collections of cells. Protein

The connection between genes and traits is rarely direct. Fig 16.10 The connection between genes and traits is rarely direct. Protein

Mostly Nurture-Imprinting: exposure to movement (environment) sets “mother”

Mostly Nature- X/Y chromosomes in humans: genes = traits XX

Your DNA comes in pairs...

X/Y chromosomes in humans: genes = traits XX

Twin studies have been used to determine the heritability of various traits.

Types of twins: http://pennhealth.com/health_info/pregnancy/000199.htm

Twin studies have been used to determine the heritability of various traits, but there are some caveats: How many twins have been studied? How different are the environments?

Correlation of weight and relatedness Correlation of weight (BMI) % Identical twins reared together 80 Identical twins reared apart 72 Fraternal twins reared together 43 Biological siblings 34 Parents and children living together 26 Adopted children and parents 4 Unrelated children living together 1 *But food preference shows little genetic correlation The nature of environmental influences on weight and obesity: A behavior genetic analysis. Grilo, Carlos M.; Pogue-Geile, Michael F.; Psychological Bulletin, Vol 110(3), Nov 1991. pp. 520-537. And two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999)

Intelligence Correlation of IQ Inheritance : % The same person tested twice 87 Identical twins reared together 86 Identical twins reared apart 76 Fraternal twins reared together 55 Biological siblings 47 Parents and children living together 40 Parents and children living apart 31 Adopted children living together 0 Unrelated people living apart 0 From two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999)

When the environment is equal (everyone has access to resources), genetic differences are magnified. When environments are different (only a few have access to resources), environmental differences are magnified.

Proof or disproof? Correlation of IQ Inheritance : % The same person tested twice 87 Identical twins reared together 86 Identical twins reared apart 76 Fraternal twins reared together 55 Biological siblings 47 Parents and children living together 40 Parents and children living apart 31 Adopted children living together 0 Unrelated people living apart 0 From two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999)

Can we see a genetic basis for complex behaviors?

Voles Prairie Monogamous Both parents care for young Montane Nonmonogamous Mother cares for young briefly

Oxytocin Encourages bonding between individuals Water/salt balance (hormone) Encourages bonding between individuals Water/salt balance Contraction of womb and milk production

Hormones are molecules produced in one cell and signal another.

Oxytocin Encourages bonding between individuals Water/salt balance (hormone) Encourages bonding between individuals Water/salt balance Contraction of womb and milk production

Voles Prairie Monogamous Both parents care for young Montane Nonmonogamous Mother cares for young briefly

Same levels of oxytocin Voles Prairie Monogamous Both parents care for young Montane Nonmonogamous Mother cares for young briefly Same levels of oxytocin

Hormones are molecules produced in one cell and signal another.

Same levels of oxytocin Voles Prairie Monogamous Both parents care for young More receptors Montane Nonmonogamous Mother cares for young briefly Less receptors Same levels of oxytocin

Voles Prairie Monogamous Both parents care for young More receptors ? Montane Nonmonogamous Mother cares for young briefly Less receptors ? Same levels of oxytocin Inject hormone into brain

Voles Prairie Monogamous Both parents care for young More receptors Montane Nonmonogamous Mother cares for young briefly Less receptors Same levels of oxytocin Inject hormone into brain

Same levels of oxytocin Voles Prairie Monogamous Both parents care for young More oxytocin receptors ? Montane Nonmonogamous Mother cares for young briefly Less oxytocin receptors ? Same levels of oxytocin Block receptors

Same levels of oxytocin Voles Prairie Monogamous Both parents care for young More oxytocin receptors Nonmonogamous Montane Nonmonogamous Mother cares for young briefly Less oxytocin receptors Same levels of oxytocin Block receptors

Voles Prairie Monogamous Both parents care for young More oxytocin receptors Montane Nonmonogamous Mother cares for young briefly Less oxytocin receptors Monogamous Same levels of oxytocin Increase levels of receptors (genetically) in ventral pallidum

Same levels of oxytocin Voles Prairie Monogamous Both parents care for young More receptors Montane Nonmonogamous Mother cares for young briefly Less receptors Same levels of oxytocin

Nature and Nurture: Next... Are traits coded for by genes fixed while traits coded for by the environment are under our control?

Next: Evolution