Psychology- Chapter 3- Lecture 10
Slide 4- Premises of Evolution
- According to evolution, there is no static world; everything in the environment is always changing
- Because the environment is changing, the animals and beings in the environment are also changing
- These changes are gradual. Gradual across generations but if generations pass very quickly (e.g. insects like
cockroaches that have many generations of change within a few weeks.)
- Gradual meaning across generations
- All organisms descended from a single common ancestor. Over time, different species evolved, each adapted to
their own ecological niche.
- The debatable question remains Could we have evolved from monkeys? or Could all animals, including
humans, have evolved from the same protozoa?
- Natural selection not only causes changes during changing environments, it also prevents changes in static
- The environment and change in the environment that fuels evolution.
- If there is a lot of environmental change then there will be a lot of evolution. If the environment is static (not
changing) there will be slow evolution.
- Humans vs Whales: If you look at the skeleton of a whales fin, you would see a striking resemblance to the
skeleton of a human hand. This is actually common among many animals. Most of the skeletal features are quite
- This idea made many scientist studying evolution think, maybe this common feature is the sign of a common
ancestor. At the same time, this idea made religious people say, this common feature is the signature of Gods
Slide 5- Process of Natural Seletion
- We have this notion of Survival of the Fittest- not physical fit, but fit with the environment.
- Organisms that fit with the environment are able to get resources from the environment that they need to
- If your characteristics allow you to do well in your environment then you will be attractive to others and thus
increasing the likelihood of you procreating and passing on your genetic make-up continuing. called
- Two processes that are important for evolution to proceed:
1. You need species that have VARIATION- there needs to be a variety in a species so that you can
choose the characteristics that you would like to pursue and pass on.
Genotypes vs. Phenotypes: The variability that you see with your eyes, in both behaviour and
physical characteristics, is not identical to the underlying genetic variability
Certain genetic predispositions that you have may or may not present themselves
For example: Alcoholism- there is a notion that there is a genetic predisposition to alcoholism
If your father drank, and your grandfather drank, you will probably have a gene that is common
among alcoholics. If scientists catch this, they will tell you that you have a genetic disposition to
alcoholism. This does not mean you are bound to become an alcoholic, it means that it will be
natural and easy for you to become an alcoholic as opposed to someone who does not carry that
specific gene. When put under stress, people with this genetic disposition turn to alcohol because
they feel it comforting but this can be controlled (behaviour phenotype).
The environment can shape the way genetic influences play out. o 2. If there is variance and limited resources then there will be COMPETITION
Competition is very important.
If everyone in the world was able to have everything to survive, then variance would not matter
As soon as there is a limited amount of resources (food, shelter, mates), then there is
competition for that and variability will start to matter.
Then the fittest most able to have success in that environment will have the most chances to
- THERFORE: To assume Natural Selection, you have to assume variability and competition in that environment.
Slide 6- Natural Selection in Human Evolution
- Something like 98% of our DNA is identical to that of chimpanzees and gorillas
- There is a strong fossil record showing ancestors between us and typical monkey-like animals, ancestors that are
no longer around
- Timeline is from the textbook
- Clan of the Cave Bear Movie
- There are many things causing problems to earth. Scientists agree that the biggest problem that Earth has is
humans. We have been able to rise above evolution and create our own environment.
- For most other animals, the environment is the environment that nature created for them and they have to
adapt and live within the niches that nature provides.
- Humans created their own environment so that they are able to live where ever (eg: underwater, in space, etc).
- Humans are able to get around the competitive forces and expand as a species in a way that no other species
- The suggested reason for this is BIPEDIALISM:
the fact that we are able to walk on our hind legs in a very organized way. That probably
happened over time.
There are some dogs that can stand on their hind legs for a little while.
The claim is that before humans, some monkeys had learned to stand on their hind legs for a bit
and that gave them huge advantage. When standing, they had the advantage of being able to use
their hands during fights and, since they had opposable thumbs, they could pick up stones and
sticks to help defend themselves. This advantage helped them get more food, more mates, which
lead to their genetic makeup being passed on to the next generations. This process continued
until we reached a point where we can stand as straight as we can now.
- We are not evolving towards something; we evolve to become fit with the environment.
- A characteristic that neither helps nor hinders the reproductive success in the environment, it tends to stay. (ex.
Men having nipples)
- Humans also had a lot of ENCEPHALIZATION of the brain:
There is middle part that keeps us alive with the basic functions
There is also an outer cortex area where a lot of the complex behaviour seem to come from (eg:
the ability to strategize, plan, be creative)
We have a lot more of this middle part of the brain compared to other animals
Looking at fossil records, you see that the size of the skull keep increasing especially in the frontal
area were that planning happens.
Language was also extremely critical for information and knowledge to be passed on through
time and space. Language allowed humans to share their knowledge and that allowed knowledge
to spread. This made the species, as a whole, very strong compared to other species.
Slide 7- Genetics and Heredity
- When Darwin wrote his findings, the field of genetics did not exist
- He knew that traits seemed to be passed down through generations but he didnt know why.
- Now we know how things get passed down from parents to children and it is the study of Genetics
- In the textbook, the words heredity and genetics are used interchangeably.
- Heredity is a vague tern to refer to the extend which we inherited things from our predecessors; our family.
- Genetics is a specific term to explain the biological process underlying heredity
- So heredity is more general and heredity is more specific
- The critical point is that your physical traits and your behaviour traits (psychological traits) are partly determined
by what you inherit from your parents
- This is kind of the opposite idea of the tabula rasa or the blank slate, where our experiences defined who we
Slide 8- Basic Principles of Genetics
- The pattern of the coding of adenine, thymine, guanine and cytosine determine the behaviour and features of
the human being (or animal)
Slide 9 Heredity, Variability, and Chromosomes
- Each parent gives us 23 chromosomes which gives is 23 pairs. Each pair controls different things
- The 23 pairs of chromosomes split into two groups with one member of each pair joining each group allowing
for 2 or 8,388,608 different combos of sperm or ova per person allowing 70 trillion possible kids per couple!!
Slide 10- Whats the Big Deal About Sex?
- Why do humans and other mammal have couples that procreate with each other as opposed to randomized
- Even with the same partner you still cause variability it is virtually impossible to have the same kid twice.
- If you produce by cell division, you produce the same clone every time- this type of breeding does not create
- Why is this important (not to have clones)
- When you have variability, it brings in a form of protection
- Eg: Cockroachs!