Chapter 3

1. Chapter 3 Evolution, Heredity, and Behaviour Chapter 1 – Evolution, Heredity and Behaviour

2. EvolutionTheory Darwin proposed the idea of biological evolution … the notion that populations of organisms change over time in a manner that ends up making them more suited to their environment This has lead scientists in many areas (but especially biology and psychology) to consider the adaptive significance of the physical and behavioural characteristics of their subjects A distinction is often drawn between: (1) ultimate causes - events and conditions which, over generations, have shaped the behaviour of our species, versus (2) proximate causes - immediate environmental variables that effect behaviour Steve’s “Its really a woman’s world” example Chapter 1 – Evolution, Heredity and Behaviour

3. Brief History of Darwin Collected many species of animals during his voyage on the “Beagle” and sent many of the specimens back to England for later study Was fascinated by how well animals and plants seemed adapted to their environment Also became interested in artificial selection … a procedure by which certain animals are mated to produce offspring with desirable characteristics Wondered if a similar process might also occur in nature … a natural selection Began collecting data to support his theory of natural selection … but did not publish his ideas or data for 20 years … until prompted by finding out that somebody named Wallace had a similar theory Published his ideas in a book called “Origin of the Species” … a best seller then, and now Chapter 1 – Evolution, Heredity and Behaviour

4. Premises of Evolution The 4 basic premises of Darwin’s theory of evolution 1) The plant and animal communities of the world are dynamic, constantly changing the physical and behavioural characteristics 2) Evolution is gradual. Changes arise through slow and steady environmental changes. Sudden changes challenge a species’ ability to adapt 3) All organisms descended from a single common ancestor. Over time, different species evolved, each adapted to their own ecological surroundings 4) Natural selection not only causes changes during changing environments, it also prevents changes during static environmental conditions Us versus the whales example Chapter 1 – Evolution, Heredity and Behaviour

5. Process of Natural Selection While “survival of the fittest” is part of evolution theory … fit does not mean physically fit. Rather fitness is defined in terms of reproductive success which is measured as the number of viable offspring an organism can produce relative to the organisms that it competes for resources with. Two processes affect changes to a species 1) Variation - individuals vary in terms of their physical and behavioural characteristics. This variation is often discussed in terms of differences in genotypes (an individuals genetic make-up) and phenotypes (an individuals physical characteristics and behaviour phenotypes are the result of the interaction between an organisms genotype and its environment 2) Competition - competition for food and mates is critical for insuring natural selection. If there were no competition, fitness would not matter Chapter 1 – Evolution, Heredity and Behaviour

6. Natural Selection in Human Evolution Does natural selection apply to humans as well as to other animals? There is now strong genetic evidence that we have a common with the gorillas and chimpanzees Steve, show that time line thing here, and mention “Clan of the Cave Bear” As a species we are somewhat “out of control”. Our strong evolutionary success can be linked to two events in our past: 1) Development of Bipedialism - thereby freeing up the hands for all sorts of mischief (e.g., tool making, weapons, building in general) 2) Encephalization of the Brain - The larger brain allowed more brain area to be expended on cognitive operations like thinking, reasoning, and decision making another important things it allows is planning … the ability to plan for and predict future events … oh, and language too! Chapter 1 – Evolution, Heredity and Behaviour

7. Genetics and Heredity Darwin’s work lead the way to new fields of research including genetics, the examination of the structure and function of genes, including the manner in which genes are passed between generations Included in this is the study of how genes affect an organisms physical and behavioural makeup Related to this is the issue of heredity, the sum of the traits and tendencies inherited from one’s parents, grandparents, and so on Chapter 1 – Evolution, Heredity and Behaviour

8. Basic Principles of Genetics “Genes are segments of genetic material called DNA (deoxyribonucleic acid) - strands of sugar and phosphate that are connected by nucleotide molecules of adenine, thymine, guanine, and cytosine” DNA is in the form of a twisted ladder, with the sugar and phosphate forming the sides, and all those nucleotide things forming the rings The sequence of the nucleotide molecules directs the protein synthesis that control the biological and physical development of the body … and behaviour?? > cool book … “The Double Helix” Chapter 1 – Evolution, Heredity and Behaviour

9. Heredity, Variability, & Chromosomes Genes are located on chromosomes, and each chromosome contains a different sequence of genes We inherit 23 chromosomes from each of our parents, giving us 23 pairs. Different pairs control different things, for example one pair determines gender characteristics Sexual reproduction involves the union of a sperm and an ova … each of which are formed through a special form of cell division called meiosis The 23 pairs of chromosomes split into two groups with one member of each pair joining each group … allowing for 223 or 8,388,608 different combos of sperm or ova per person … allowing 70 trillion possible kids per couple!! Chapter 1 – Evolution, Heredity and Behaviour

10. What’s the Big Deal About Sex? The vast majority of organisms reproduce via a sexual process of some sort … why sex?? As seen by the previous “couple” number, the need for two individuals to jointly create one greatly increases the genetic diversity of the organism … make it more able to evolve if evolution is necessary Nasty bug example - yuck! Chapter 1 – Evolution, Heredity and Behaviour

11. Genetics and Psychology Chapter 1 – Evolution, Heredity and Behaviour

12. Genetics and Psychology The image to the left is a colorblindness test - colorblindness is determined primarily through genetics … can you see the shapes? OK, now for another example … the taste test! The moral? Our perception of the world is largely determined by our genetic make-up. How far do genetics go in explaining human experience and behaviour? Chapter 1 – Evolution, Heredity and Behaviour

13. The Example of Alcoholism Alcoholism can obviously be a very destructive “disease” … how much is it due to genetic factors? Twin Studies - Concordance rate for alcoholism is higher for MZ than for DZ twins (76 vs 61 for males, 36 vs 25 for females) This is true even when the kids are not raised by their biological parents Chapter 1 – Evolution, Heredity and Behaviour

14. The Challenge of Altruism As a final look at Evolution Theory, let’s consider the challenge that is posed by altruistic behaviours An altruistic behaviour is one in which an organism does something that puts itself at risk, in order to aid another Many animals (including humans) perform altruistic acts - for example, howling wolves warning of predators Surely these behaviors defy the notions of Evolution Theory, right? Turtle soup chef coming!! Run for your lives!! Ahh!! Chapter 1 – Evolution, Heredity and Behaviour

15. First Reply to the Challenge - Inclusive Fitness Hamilton (1964) argued that evolution is not really focused on the reproductive success of the “individual” but rather focuses on the reproductive success of the “gene” Often times, altruistic acts are directed towards close family members who share many of the same geners … especially towards children Thus, although the altruistic act may hurt one individual carrying a certain gene, in doing so it may serve the “greater good” of preserving the same genes in related individuals This notion is termed inclusive fitness Chapter 1 – Evolution, Heredity and Behaviour

16. Second Reply - Reciprocal Altruism But not all altruistic acts are directed at family members, what of the acts directed at total strangers? Trivers (1971) claims that Evolution Theory also has an answer to that … reciprocal altruism This notion is that an individual considering performing an altruistic act towards a stranger will do so if the potential benefits of the acts outweigh the risk If the benefits do outweigh the costs, then the individual can increase their reproductive success by performing the act and does so … a somewhat dark view of altruism eh? Chapter 1 – Evolution, Heredity and Behaviour

17. Summary of Chapter 3 There is no doubt that our genes affect the manner in which be perceive and relate to the world around us Evolution Theory provides a theoretical framework for understanding (a) how we as humans have come to be as we are and (b) why we may act as we do in certain situations Often, when one proposes a theory of human behaviour, they include some discussion of their theory in terms of Evolutionary Adaptiveness … e.g., inhibition of return Chapter 1 – Evolution, Heredity and Behaviour

18. Inhibition of Return Example + Chapter 1 – Evolution, Heredity and Behaviour

19. Inhibition of Return Example * Chapter 1 – Evolution, Heredity and Behaviour

20. Inhibition of Return Example + Chapter 1 – Evolution, Heredity and Behaviour

21. Inhibition of Return Example A Subjects are faster when the target is in a new area of the screen, than if it is in the area that was flashed, why? Chapter 1 – Evolution, Heredity and Behaviour