U2: EVOLUTION GENETICS AND EXPERIENCE
1. Natural Selection and - Our Zeitgeist is the general intellectual climate of our culture, influencing
Understanding our Brains how we think.
- Natural selection suggests that the heritable traits associated with survival
and reproduction are the most likely to be passed on to future generations.
- All of an organism’s characteristics have functional significance
o Ex. Eagles are able to catch and eat prey because of strong
talons and beaks
- These behaviours aren’t inherited but what is inherited is a brain that
allows the behaviour to occur.
- Functionalism is the principle that the best way to understand a biological
phenomenon is to understand its useful functions for the organism.
2. Rules for Human Evolution 1. Evolution doesn’t proceed in a straight line
2. Homo sapiens are not the supreme organisms in evolution
3. Evolution is not always slow
4. Present species are only a fraction of all species that have evolved on
Earth – only tips of branches of evolutionary bush have survived.
5. Evolution is not perfect
6. Evolution is not always adaptive, nonadaptive evolutionary
byproducts are called spandrels -phenotypic characteristic that is a
byproduct of the evolution of some other characteristic, rather than a
direct product of adaptive selection.
o Ex. Human belly button have no adaptive function and is the by
product of the umbilical cord
7. Structures or behaviours evolve in response to one type of
evolutionary pressure but later perform a different function
o Ex. Feathers were initially for temperature regulation but later
evolved for flight.
8. Similarities between species don’t imply a common evolutionary
origin. Homologous structures have a common evolutionary origin
and analogous structures with different but convergent evolutionary
Evolution of Vertebrates
- Chordates are animals with dorsal nerve cords
- Vertebrates are spinal bones that protect dorsal nerve cords.
Evolution of Amphibians
- The advantages of land transformed fins and gills of fishes to legs and
- Thus, the first amphibians evolved.
Evolution of Reptiles - Reptiles were the first vertebrates to lay shell-covered eggs and to be
covered by dry scales
Evolution of Mammals & humankind
- New class of vertebrates evolved from line of reptiles that fed their young
using secretions from mammary glands.
- Eventually stopped laying eggs and nurtured their young in the watery
environment of their bodies.
- Hominins are primates of the family that includes humans
- This family has 2 genera– (1) Homo and (2) Australopithecus
3. Evolution of the Human Brain - There is no relationship between size and intellectual capacity in humans.
- Evolution of the human brain has:
1. Increased in size during course of evolution
2. Most of this increase occurred in the cerebrum
3. Increased cerebrum size is accompanied by increased convolutions/folds
of the cortex.
- It’s important to consider evolution of the brain stem (reflexes) separately
from the evolution of the cerebellum (cerebral hemispheres)
4. Genetics & Applications
Human Genome Project - Goals were to identify all the approx. 20 000-25000 genes in DNA,
determine sequences of all 3 billion chemical base pairs and address the
ethical, legal and social issues that may arise from the project.
- Discovered human genome only has 34 000 genes, only 50% more than a
mouse and 3x that of a fruit fly.
- Our complexity appears to be due to refinements in gene expression rather
than in a huge increase in number of genes involved.
- Improved diagnosis of disease, earlier detection of genetic predisposition
of diseases, gene therapy
Energy sources and environmental - Creating new biofuels, develop environmental monitoring techniques to
applications detect pollutants.
Gene knockout - Creation of organisms that lack a specific gene to measure neural or
- Useful for learning about a gene that has been sequenced but has unknown
- The problems with this technique are: