Human Variation and Adaptation

Historical Views of Human Variation  Early human classification  Biological determinism  Eugenics - "race improvement“

Human classification

Human ancestry Australopithecus- Lucy Homo habilis- “handy man” Homo erectus- “upright man” Homo sapiens neanderthalis- early modern man ( one variation) Homo sapiens sapiens- modern man

Australopithecus

Homo habilis

Homo erectus

Homo neanderthalensis

A Subjective Mess

Biological Determinism Belief that human behavior is determined by genes or physiology Taking measurements to determine tendency to commit crimes

Traditional Concept of Race  Since the 1600s, race = ethnicity  Biological fallacy but social reality  Race is a taxonomic level below species in humans (biology)  There are more genetic variation within one race than other “different” races.  Ethnicity = culture ( Polish, Irish etc)

Racism  Based on false belief that intellect and cultural factors are inherited with physical characteristics.  Assumes that one's own group is superior.  A cultural phenomenon found worldwide.

Intelligence  Genetic and environmental factors contribute to intelligence.  Many psychologists say IQ scores measure life experience.  Innate differences in abilities reflect small variation within populations, little differences within races.

Crystallized intelligence- experience, education and training Fluid intelligence- on-the-spot reasoning visual intelligence-visualize, remember and manipulate in “your mind’s eye” Processing speed- scanning, focus, attention Short term memory ( working memory)- day to day recall, remembering numbers, list s

Human Polymorphisms  Polymorphisms  Genetic trait with 2+ alleles.  Used as a tool to understand evolutionary processes.  Clinal Distributions  A cline is a gradual change in the frequency of a trait or allele in populations dispersed over geographical space.  Example: The distribution of the A, B, and O blood alleles

Clinal Distribution

Adaptive Significance of Human Variation  Human variation is the result of adaptations to environmental conditions.  Physiological response to the environment operates at two levels: 1. Long-term evolutionary changes characterize all individuals within a population or species. 2. Short-term, temporary physiological response is called acclimatization.

Evolutionary Interactions Affecting the Frequency of the Sickle-cell Allele

Skin Color  Influenced by three substances:  Hemoglobin, when it is carrying oxygen, gives a reddish tinge to the skin.  Carotene, a plant pigment which the body synthesizes into vitamin A, provides a yellowish cast.  Melanin, has the ability to absorb ultraviolet radiation preventing damage to DNA.

Pigmentation and Geographical Divisions  Before 1500, skin color in populations followed a geographical distribution, particularly in the Old World.  Populations with the greatest amount of pigmentation are found in the tropics.  Populations with lighter skin color are associated with more northern latitudes.

Thermal Environment ..  Humans are found in a wide variety of thermal environments, ranging from 120° F to -60° F.  Human Response to Heat  Long-term adaptations to heat evolved in our ancestors:  Sweat Glands  Vasodilation

Human Response to Cold Short-term responses to cold:  Metabolic rate and shivering  Narrowing of blood vessels to reduce blood flow from the skin, vasoconstriction.  Increases in metabolic rate to release energy in the form of heat.

High Altitude  Multiple factors produce stress on the human body at higher altitudes:  Hypoxia (reduced available oxygen)  Intense solar radiation  Cold  Low humidity  Wind (which amplifies cold stress)

Impact of Infectious Disease  Before the 20th century, infectious disease #1 limiting factor.  Since the 1940s,antibiotics reduced mortality rates.  In the late 1960s,war against infectious was disease won.  Between 1980 and 1992 deaths from infectious disease increased by 58%.  Increases may be due to overuse of antibiotics.

Defining eugenics: “Improving human genetic qualities”  Eugenics is a social philosophy which advocates the improvement of human hereditary traits through various forms of intervention.

Concepts in Eugenics  Intelligence and social class  Miscegenation (racial purity)  Genetic defects

Where did Eugenics originate from?  Term eugenics literally means “well-born”  It was introduced in the 1880s by Sir Francis Galton, a cousin of Charles Darwin and the father of modern statistics.  Sir Francis Galton coined the term eugenics in 1883 from the Greek eugenes, and promoted the idea of improving the physical and mental makeup of the human species by selective parenthood.

Categories of Eugenics It is mainly divided into two categories.  Positive eugenics - Encouraging reproduction of those genetically ‘fit’  Negative eugenics - Aims to prevent those deemed physically, mentally or morally unfit to procreate. Generally by sterilization or segregation

Early Eugenicists  Believed genetics were the cause of problems for the human gene pool  They thought eugenic would eliminate diseases permanently  They tried to eliminate the genes of feeble-mindedness- including manic depression, immortality, alcoholism, rebelliousness, criminality, laziness, prostitution.  Charles B. Davenport (founder of eugenic record office in NY) suggested that people with “bad genes” should be sterilized in order to prevent their reproduction and for the society to save money

Eugenics in the ’s  The Eugenic Record office  researched by gathering pedigree  Rules lead onto forbidding marriage, segregation in institutions, reduce the number of immigrants and sexual sterilization of allegedly “unfit parents”. 

Eugenics Propaganda

Pedigree from early 1900s

Public service announcement

 Positive vs. Negative Eugenics  encouraging vs. restricting reproduction  Nazi Germany and the Soviet Union between 1936 and 1968

Governments and Eugenics in the 20 th Century  Genetic screening  Birth control  Promotion differential birth rates  Marriage restrictions  Segregation (racial and mentally ill)  Forced abortions or pregnancies  Genocide

Methods of Eugenics  Mandatory eugenics: government- mandated  Promotional voluntary eugenics: suggested to the general population  Private eugenics: voluntary participation

Basic ethical issue:  Pro: Eugenics is a social responsibility, an altruistic stance of a society, meant to create healthier and more intelligent people, to save resources, and lessen human suffering.  Alexander Graham Bell, George Bernard Shaw, and Margaret Sanger  Con: Eugenics is based on pseudoscience and leads to discrimination, such as in Nazi Germany.  Winston Churchill  Is there a middle ground?

Eugenics Then and Now  Then: Focus on selective breeding.  Now: Focus on prenatal testing and screening, genetic counseling, birth control, in vitro fertilization, and genetic engineering.

 Disability Rights Movement (1960- now) -independent living = equality (not medical “fixes”)  British National Party (1996) wanted to outlaw mixed race relationships  Gene doping (2008)- non-therapeutic use of cells, genes or genetic modifications to enhance performance  In vitro fertilization (2015)- parents want the right to discard unwanted embryos based on gender Modern Eugenics- still controversial

Ethical Dilemmas  Should embryos with medical conditions that can be effectively managed by medical intervention be discarded? If so, which conditions?  What distinguishes a true “genetic disease” from an unwanted genetic condition?  Should parents be allowed to choose certain traits for their children? If so, which ones?