Chapter 5 Biology, Culture and Society

Chapter Outline  Heredity  Behavioral Genetics  The Growth Revolution  Hormones and Behavior  DNA and Culture  Humans and Other Animals

Genotype and Phenotype  The genotype is the total of the genetic instructions an organism receives from its parents.  The phenotype is what we see when we look at an organism.

Genotype and Phenotype  The genotype is genetic potential.  The phenotype is the outcome of the combination of the genotype and the environment.

The Growth Revolution  Men born in 1956–1962 were 3 times as likely as men born in 1906–1915 to reach a height of 6’ or taller.  1/3 of those born in 1906–1915 were under 5’7”. Fewer than 10% of those born in 1956– 1962 were 5’7”.  A century ago, most people did not reach their full adult height until age 25.  Today, most people stop growing by 18.

Trends in the Height of Americans Year of Birth 1906– – –1962 Malespercent over 6’ under 5’7” Females over 5’5” under 5’3”

The Growth Revolution  To ask why humans suddenly began to get so large so fast raises the wrong question.  The right question is, what kept humans so small and delayed their maturation for so long?  This rapid change in the phenotype of human beings reveals the previously unfulfilled potential of the human genotype.

Inadequate Nutrition  Until modern times, most people ate meager diets that were deficient in vitamins and proteins.  Most people lived almost exclusively on bread, mush and soup made from grain.  Their poor diet made people more susceptible to illness and contagious diseases.

Testosterone and Behavior Men with higher levels of testosterone are more likely to:  Get divorced  Physically abuse their wives  Engage in extramarital sex  Have many sexual partners  Have problems with alcoholism

Testosterone and Behavior Men with higher levels of testosterone are more likely to:  Use drugs  Have been punished while in military service  Have been a juvenile delinquent  Get in trouble with the law as an adult  Be unemployed

Testosterone and Behavior Men with higher levels of testosterone are less likely to:  Get married  Become highly educated  Obtain a high-status occupation

Jane Goodall’s Primary Rules of Fieldwork 1. Record everything you notice, always, and file it so you can find it again. 2. After you have drawn a conclusion, search for evidence that you are wrong. 3. Never, ever think you understand everything that’s going on.

Crows and Tool Use  Three Oxford zoologists demonstrated that crows can use tools.  A female crow, captured as a juvenile bird, bent a wire to form a hook and used it to lift food from a vertical plastic pipe.