Evolution (lecture 3)

Evolutionary Developmental Science

• "nothing makes sense except in the light of evolution" -Theodosius Dobzhansky

• Evolution theory is a theory that explains the diversity and function of all living things

• After life evolution always begins

• Evolution is a theory, but so is gravity

Charles Darwin

• Evolutionary theory is most associated with him

• Explains a wide range of life forms that existed

• Earlier theories existed e.g., Lamarkianism (inherits traits that change over a lifespan)

• Came up with theories of natural and sexual selection

5 components of Darwin's evolution by Natural Selection:

1. More offspring are born that survive to reproduce

2. Individuals vary based on different traits

3. Certain traits are more likely to be passed onto offsprings (via genes)

4. Off spring likely inherit these traits

5. Environment change/conditions have changed leading to a new species

• This knowledge of evolution gives the fundamental meaning of life

• We now know what the biological meaning of life is

  • Pass on genes to future generations

Evolutionary Fallacies

• Survival of the fittest- Fitness in biology means number of offspring; evolution is really survival of those who produce the most successful lineages

• Group selection- evolution acts at the end level of the individual, not the species

• Evolution progress from simple to complex forms of life

• Evolution is pre-determined

Fit vs. Unfit

• In the long run, unfit people will be able to produce way more offspring than fit people

• Not about being fit, bit being able to reproduce faster

• About passing your genes onto the off spring

  • NOT YOUR SPECIES

Group vs. Individual

• Individuals have a larger population than the group

Higher and lower genes

• Evolution has 1 goal- to move toward an even more complex way of life (more complex forms of life)

  • Evolution is random- a mutation is as likely to retreat from a greater complexity

• More complex forms of life are better

  • 1/4 animal species are beetles

Evolutionary Psychology

• According to Tooby and Cosmides, e.p.,

  • Involves domain specific mechanism

  • That are at least partly inheritable

  • That solved problems in the EEA (the past evolutionary environment)

• Note: this allows for experience nurture and culture to influence cognitive mechanisms

Critiques of EP

• Doesn’t reveal specific cognitive mechanisms its more of a guide than a manual

• Depends in an accurate guess based on limit info about EEA

  • We need to look at the past to help the future

• Just-so stories

• Too simplistic- ignores human change and other environmental factors

Evolutionary pitfalls

• Determines fallacy- if some one is evolved or in our genes it cannot be changed

  • WRONG: male aggression

• Naturalistic fallacy- if someone is evolved or comes from nature, it must be morally good and/or accepted

  • WRONG: war

Childhood as an adaptation

• ~50% of children dies before adulthood

• Surviving childhood is crucial for evolutionary pressure

• Therefore, childhood is an adaptation in and of itself (e.g., limited attention, poor metaknowledge, curiosity, attachment, play, etc.,)

Genes: interplay of heredity and environment

• Both heredity and environment influence the individuals characteristics

• When scientists first begun to investigate the contributions of heredity and environment, they generally emphasized one factor or the other as the prime influence- both matter

  • Nature with nurture

  • Nature through nurture

Model of interaction

• 3 key elements

  1. Genotype: The genetic material an individual inherits

  2. Phenotype: the observable expression of the genotype, including body, characteristics, and behaviour

  3. Environment: includes every aspect of the individual and their surrounding other than genes

Fundamental relations

1. Parents contribution to the child's genotype

2. Contribution of the child's genotype to their phenotype

3. Contribution of the child's environment to their phenotype

4. Influence of the child's phenotype on their environment

Relationship between parents and child's genotypes

• Genetic material is passed on through chromosomes-long threadlike molecules made up of DNA

• Genes are sections of chromosomes that code for a particular protein sequence an/or have a particular effect on other genes

Mechanisms contributing to genetic identity

• Mutations: changes in the sections of DNA caused by random or environmental factors

• Random assortment: The shuffling of the 23 pairs of chromosomes in the sperm and egg; chance determines which member of the pair goes into the new sperm and egg

• Crossing over: the process by which sections of DNA switch from one chromosomes to another during meiosis increasing genetic variability

Alleles

About 1/3 of human genes have 2 or more different forms, known as alleles

• The Dominate alleles are the forms that are expressed if present

• The Resistive alleles are the not expressed if a dominate allele is present

• If a person with 2 of the same alleles  for a trait is describes as homozygous

• A person with Different alleles for a trait is called heterozygous

  • This causes proteins to be different

Sex chromosomes

Determines individuals sex

• Females have 2 X chromosomes in the 23rd pair, whereas males have an X and Y chromosome

• A gene on the Y chromosome  encodes the protein that triggers the formation of the tests which subsequently produce testosterone, which in turn over the molding of male

The male disadvantage

• The Y chromosome has only about one third as many genes as the X chromosome

• The recessive genes are more commonly found in the X gene

• Because many alleles on the X chromosome don't have a corresponding allele on the Y chromosome that could suppress the action males are more likely than females to suffer a variety of inherited disorders caused by recessive alleles than the X chromosomes (i.e., colour blindness)

Genetic origins of human diseases & disorders

• Over 5,000 human diseases and disorders are presently known to have genetic origins

• Recessive gene: PKU, Sickle-cell anemia, cystitis fibrosis

• Single dominate gene (rare): Huntington's disease

• Sex-linked inheritance: Fragile-X syndrome, hemophilia

• Errors in meiosis: (resulting in a zygene, fewer or more than normal chromosomes) Down syndrome, Klinefelter

• In some cases, as with sickle-cell anemia, a gene can have both

  • Deleterious effect: a debilitating blood disorder when both allenes are present

  • Benefits: protection against malaria, a blood parasite that cant live or grow within oval blood cells

• Many syndromes are known to have a genetic basis, but the specific genetic mechanism has not been established

  • Dyslexia, Tourette, autism, cystic fibrosis (cholera), ADHD, depression, schizophrenia, and anxiety

Polygenic Inheritance

• When traits are governed by more than one gene

• Applies to most traits and behaviours of interest to scientists

In the case of PKU

• Children born with Phenylketonuria (PKU)- a disorder that is related to a defective gene on chromosome 12- are unable to metabolize phenylalanine (amino acid) (like lactose intolerance but way more severe)

• Do genes dictate who we are?

  • It is interactive- Gene * environment interaction

• With early diagnosis and a properly restricted diet, however mental retardation resulting from PKU or avoided

Regulator genes

• Largely control the continuous switching on and off of genes that underlie development across the life span

  • A gene influences development and behaviours only when it is turned on

  • e.g., Some one who is 5'4'' and some one who is 6'5'' have the same genes for height, but one was turned on longer than the other

• Once thought to be relatively useless stretches of DNA, regulator genes now appear to be major force in evolution and development

• Because there appears to be a tool kit for building bodies - any bodies, and it’s the regulator genes unlimitedly decide the final product

Dandelion kids vs. Orchid Kids

• Low MAOA (Dandelions)

  • "no earmuffs"

  • Can "Grow anywhere"

• High MAOA (Orchids)

  • "earmuffs on"

  • Need a specific environment

Epigenetics

• How genes and environment work together to produce and develop an organism

• Most likely the future of development studies

• Its a reductionist approach that is extremely challenging to do in humans

• Don’t change DNA

  • No changes

  • Patterns in behaviour change is because of the environment not sperm or eggs

The Evolution and Development of the Brain

• The evolution of the human brain

  • Size matters

  • Humans have much bigger brains than is expected for body size

  • Encephalization quotient

• Humans have more cortical neurons

• Size of humans cortex is much bigger

• Humans are born to learn (why it is so much bigger)

Development of the Brain (0-21 years old)

1. Proliferation (neurogenesis) : Making of new neurons

2. Migration : Moving to its correct spot

3. Differentiation : Finding the right spot

4. Synaptogenesis : Creating links

5. Cell death: Killing the parts that aren't being used

6. Synaptic rearrangement : rearranging things

• Using parts of your brain is like using your muscles

• Flexible brain system

• Constantly changing

• Visual cortex develops at about one year

• Prefrontal cortex done developing in adulthood

• Neuroplasticity and the role of experience in brain development

  • Placidity- the ability of the brain to change

    • Experience- expected synaptogenesis

  • Synapses are formed and maintained by species-typical experiences (hearing language)

    • Experience-  deepened synaptogenesis

  • Synapses are formed as a result of unique experiences of the individual (losing a parent)

• Brain injury during development

• Kennard effect- young brains tend to "heal better"

• We trade off placidity for efficiency