psych

AnimBehavLect2NatSelect1.pdf

Introducing Evolutionary Theory

Lecture 2 Dr. Francine Dolins University of Michigan-Dearborn

Topics of Discussion

  Issues and pitfalls in evolutionary thinking: think critically!

  Before Darwin   Darwin’s Theory of Evolution by Natural Selection   Genes and the Modern Synthesis   Average and Inclusive Fitness and ‘The Selfish Gene

Theory’   Ethology and understanding evolution of behavior

Armchair Thinking or “Just so” stories

Excerpt, Buss (2002), Evolution of Desire

Before Darwin   species seen as immutable (unchangeable); created by

higher being   explanation:

  differences between species —physical & behavioral characteristics

  similarities between species —physical & behavioral characteristics, and in embryological development

  the functionality/ apparent purposefulness of parts of organisms

  Lamarck — inheritance of acquired characteristics   giraffes necks: how did they get to be so long?   Epigenetics: support for Lamarck in the 21st century!

Galapagos Finches …Darwin on beetles…

Darwin’s influences and theory   H.M.S. Beagle, Galapagos Islands and its finches

  http://www.britannica.com/EBchecked/topic-art/223745/74641/Fourteen-species-of- Galapagos-finches-that-evolved-from-a-common

  Why variation of traits in birds that were alike and inhabited the same environment?

  Thomas Malthus: An Essay on the Principle of Population (1798) population growth & decline.

  Darwin applied Malthus’ principles:   Larger populations exist than can survive and reproduce leading to

a struggle for survival.   Those with favorable traits selected for, survive, and pass on those

traits to offspring.   Certain favorable traits become more prevalent in a population.   We refer to this population as a “gene pool”.

Darwin’s influences and theory continued The Theory of Natural Selection (Darwin, also Alfred Russell

Wallace) based on:   variation — in physical & behavioral characteristics/traits of

an individual (the ‘tapestry’ of evolution)   adaptation — favorable traits selected for by the environment

promoting better survival and passing on of genes   inheritance — only some of these variations are inherited   selection — based on the adaptive nature of traits   competition for limited resources (mates, food, nest sites,

etc) within & between species   reproductive success is the measure or currency of evolution

What is ‘Selection’   FOUR types of selection in Evolution:

  Natural   Sexual   Kin   Group   (Artificial selection: only human-induced, not part of evolution)

  The mechanism of selection is adaptation to a given habitat or environment = an ecological niche.

Evolution by Natural Selection Thus, Evolution by Natural Selection is:

A biological process in which, from the variation of characteristics in a given population, favorable traits are selected for that enhance an individual’s adaptation to its environment.

These traits, and therefore these adaptations to surviving in a given environment, are passed on to viable offspring, increasing the frequency of these genes in the gene pool and the population.

Why a “given” population” Why “viable” offspring?

Mechanisms of Natural Selection within a lifetime and over generations

  William Hamilton (& George Williams)   AVERAGE FITNESS: sum of an individual’s own reproductive

success during their lifetime (e.g., how many viable offspring survive to reproduce)

  INCLUSIVE FITNESS: sum of an individual’s own reproductive success (= average fitness) + the reproductive success of genetic relatives + the reproductive success of relatives over generations, weighted by the degree of relatedness

  e.g. 0.5 for siblings; 0.5 for offspring; 0.25 for grandchildren   ‘The Selfish Gene Theory’(Richard Dawkins, 1976):

=> Evolution works on the molecular level   to express ideas of Hamilton & Williams about average and

inclusive fitness

Natural Selection in Humans

http://news.sciencemag.org/sciencenow/2012/04/ natural-selection-is-still-with-.html

Darwin’s theory: some important points •  Evolution is not ‘forward-looking’, ‘intentional’ or ‘goal-directed’; a blind watch-

maker (Dawkins) •  Evolution is gradual [What is ‘gradual’? Everything is relative!]

  evolution can be relative, occurring in ‘spurts’ with periods of stasis [Punctuated Equilibrium; Stephen Jay Gould]

  each and every step in the gradual evolution of a feature or trait must be ‘advantageous’ (ultimately, in respect of reproduction) — e.g. ‘partial wings’, ‘partial eyes’

  The problem of the dung beetle: Crypticity - What is the good of looking 1/3rd like a piece of dung? [Stephen Jay Gould]

•  Evolution does not work to perfection but is often “optimal” •  All species can be seen as being connected by the same lineage: a large bush, not a

ladder. [See sketch of Darwin’s evolutionary tree] •  Evolution is not a moral process (e.g. infanticide). •  Evolution works by reproduction (e.g. sexual reproduction to maintain variation in

populations).

Darwin’s evolutionary tree

The great ape evolutionary tree (from Corballis, 1999)

Genes and the modern synthesis   Introduction

  natural selection is not the only form of evolution, but it’s the only one we know that produces complex design

  Darwin didn’t have a coherent theory of inheritance, & didn’t know the nature of the mechanism of inheritance ...

  genes   Gregor Mendel and his experiments with variations in sweet

pea plants   genotype, phenotype (see next slide); DNA; Crick & Watson   the units of inheritance — the vehicles for the transmission of

information through lineages of organisms   the information that genes transmit constitutes the instructions

for the design of those organisms

Genotype and Phenotype

  Genotype = the make-up (total) of one’s genes (a “genome”)

  Phenotype = the make-up of one’s genes + the interaction with the environment;   all observable characteristics   e.g., hair and eye color   including some behaviors

Ethology and the evolution of behavior

  Behavior leaves behind no fossils   Darwin: theory applies to behavior as well as to physical

structures   all behavior depends on physical structures   artificial selection/ breeding of species for behavioral

characteristics   Ethology: the study of behavior in the subject’s natural environment

  e.g., imprinting & Konrad Lorenz   Niko Tinbergen & the 4 ‘whys’ of behavior: (see next slide)

Niko Tinbergen & the four ‘whys’ of behavior

  immediate causes: according to the behavior’s SURVIVAL VALUE and CAUSATION of the behavior

  developmental causes: DEVELOPMENT of the behavior

  adaptive function: according to the behavior’s FUNCTIONAL VALUE

  evolutionary origins: EVOLUTIONARY HISTORY of the species

Why is a behavior shown?

Two levels for studying behavior   Proximate level

  Questions about HOW behavior happens   Tend to focus on the internal mechanisms of behavior

  Ultimate level   Questions about WHY a behavior occurs   Deals with the evolutionary value of a behavior

“How” questions about proximate causes   What is the causal relationship between the animal’s genes and its

behavior?   Is the trait to some extent inherited from its parents?   Does the diet of the animal during development influence how it

acts as an adult?   What stimuli trigger the response, and how are these stimuli

detected?

“Why” questions about ultimate causes   Has the behavior evolved over time?   If so, why did the changes take place?   What was the original step in the historical process that led to the

current behavior?   What is the purpose, the function, of the behavior?   Does the behavior help the individual to better survive in order to

reproduce?

Causes

  Proximate   Genetic-developmental

mechanisms   Effects of heredity on behavior   G-E interactions underlying the

development of S-M mechanisms   Sensory-motor (S-M)

mechanisms   Nervous system detection of

environ. stimuli   Hormone systems for adjusting

responsiveness to environ. stimuli   Skeletal-muscular systems for

carrying out responses

  Ultimate   Historical pathways leading

to current behavior   Events occurring over

evolution from the origin of a trait to present

  Selective processes shaping the history of a behavioral trait   Past and current usefulness of

the behavior in reproductive terms

Proximate and Ultimate not Mutually Exclusive, but Continuous

Any questions?

WWW links

The BBC Evolution Web Site: http://www.bbc.co.uk/education/darwin/

The Evolutionist Online Magazine: http://www.lse.ac.uk/Depts/cpnss/darwin/evo/ interviews with a selection of today’s leading evolutionary thinkers

Darwin and Darwinism: http://www.human-nature.com/darwin/index.html

Additional reading

  Barrett, L., Dunbar, R., Lycett, J. (2002). Human Evolutionary Psychology. Princeton, NJ: Princeton University Press. Chapter 2

  Jolly, A. (2001). Lucy's Legacy: Sex and Intelligence in Human Evolution. Boston: Harvard University Press. Section I, Chapter 2

  Buss, D.M. (1999). Chapters 1 & 2: The new science of evolutionary psychology. Evolutionary psychology: The new science of the mind. Boston, MA: Allyn & Bacon

  Cosmides, L. & Tooby, J. (1997). Evolutionary psychology: A primer. [ http://www.psych.ucsb.edu/research/cep/primer.html ]

  Miele, F. (1996). The (Im)moral animal: A quick and dirty guide to evolutionary psychology and the nature of human nature. Skeptic, 4, 42-49. [http://www.skeptic.com/magazine.html]

References and further reading

Buss, D.M. (1999). Evolutionary psychology: The new science of the mind. Boston: Allyn & Bacon. — Chap. 1

Cartwright, J. (2000). Evolution and human behaviour: Darwinian perspectives on human nature. Basingstoke & London: Macmillan. — Chapters 2 & 3 (+ Chap. 1).

Corballis, M.C. (1999). Phylogeny from apes to humans. In M.C. Corballis & S.E.G. Lea (Eds.), The descent of mind: Psychological perspectives on hominid evolution (pp.40-70). Oxford: Oxford University Press.

Darwin, C. (1859). On the origin of species by means of natural selection. London: John Murray. — edited excerpts in: Ridley, Mark (Ed.) (1994). A Darwin selection. (Revised edition.) London: Fontana Press. — pp.84-126

Dawkins, R. (1976). The selfish gene. Oxford: Oxford University Press.

References and further reading

Dawkins, R. (1986). The blind watchmaker. London: Longman/Penguin. Ideally, you should read the whole book! But at least “Chapter 2: Good design.”

Dawkins, R. (1995). River out of Eden: A Darwinian view of life. London: Weidenfeld & Nicolson. — Chapter 1: The digital river.

Dennett, D.C. (1995). Darwin's dangerous idea. Evolution and the meanings of life. New York: Simon & Schuster. — Chapter Two: An idea is born (pp.35-60)

Maynard Smith, J. (1975). The theory of evolution. 3rd edition. Harmondsworth, Middlesex: Penguin. — Chapter 1: Adaptation; & Chapter 2: Natural selection

Sober, E. (1993). Philosophy of biology. Boulder, CO: Westview Press. — Chapt 1: What is evolutionary theory?

Sterelny, K. & Griffiths, P.E. (1999). Sex and death: An introduction to philosophy of biology. Chicago: Chicago University Press. — Chapters 2, 3 & 4

Williams, G.C. (1996). Plan and purpose in nature. London: Weidenfeld & Nicolson/ Phoenix. — Chapters 1, 2 & 3