just for Njosh
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04_natural_selection_s17.pdf.docx1/26/17
1/26/17
1/26/17
6 Distinctive
Human Characteristics
1. Life span
2. Juvenile dependence
3. Multigenerational resource flows
4. Concealed ovulation/monogamous bond
5. Male provisioning
6. Brain size and cognitive competencies
There are others (e.g., bipedal, language) but these are less relevant to biosocial development in families
To understand why (and how) the six distinctive human traits have evolved, we need to take a brief detour into evolutionary biology—or evolutionary theory.
Understanding evolutionary theory helps us appreciate the adaptive functions of traits (“why”) and the process (“how”) by which traits evolve.
Recall
Families and paternal care have evolved because they provide socio-ecological adaptive (fitness) benefits (i.e., survival and reproduction).
Our biology and culture have evolved to support the formation and maintenance of families and paternal care.
Evolutionary Framework
Evolutionary Framework
provides a way to build
the understanding of
“
Why”
Evolution by Natural Selection:
Darwin and Wallace
Darwin
1809
-
1882
Wallace
1823
-
1913
Darwin and Wallace
independently developed the idea of
Natural Selection
Some examples:
-
Language
-
Fashion
species come and go
through
time
while
they exist they
change
Evolution = change over time
-
Organisms
species come and go
through
time
while
they exist they
change
Evolution = change over time
Why/How
do
organisms evolve?
Natural Selection
Darwin’s Reasoning:
1. Population capacity to grow is infinite but environmental capacity to support population is finite (resources, “carrying capacity”)
2. Variation in traits among members of a population leads to differences in reproduction and/or survival
3. Variation in traits is heritable (offspring resemble parents)
Evolution
—
not new
•
change over time
Evolution by Natural Selection
-
new
•
process by which forms of life having traits that better enable them to
adapt
to specific
environmental pressures
, will tend
to
survive
and
reproduce
in greater numbers than others of their kind,
thus
ensuring the perpetuation of those favorable traits in succeeding
generations
•
“
Survival of the Fittest
”
Fitness= the extent to which your traits (genes) are represented in
subsequent
generations
Punchline
:
Natural Selection produces
adaptations
!
Cause of K
-
T
Extinction?
In the natural
world, change is
constant
The Galapagos Finches: Natural Selection
The Beak of the Finch: Speciation of finches on the Galapagos
http
:
//
www.youtube.com
/
watch?v
=
mcM23M
-
CCog&feature=
youtu.be
http://
www.youtube.com
/
watch?v
=
xkwRTIKXaxg
How does Evolution (by Natural Selection) really work?
Video
Processes of Evolution
· Evolution is defined as a change over time in one or more traits in a population (e.g., average beak length in a population of hummingbirds)
· Not all evolutionary changes are adaptations
· Only evolutionary change in a population through the process of natural selection, acting on
individuals (“differential survival/ reproduction”), leads to adaptations
· In other words, only natural selection produces “adaptations”
· Natural Selection is the main evolutionary process
Products of Evolution
1. Adaptations
Inherited and reliably developing characteristic that came into existence through natural selection because they helped to solve problems of survival or reproduction better than alternative designs existing in the population during the period of their evolution
2. By-products
Characteristics that do not solve adaptive problems and do not have functional design; they are “carried along” with characteristics that do have functional design because they happen to be coupled with those adaptations
3. Noise
· Random effects produced by forces such as chance mutations, sudden and unprecedented changes in the environment, or chance effects during development
Features of
Adaptations
· Function
· The adaptive problem it evolved to solve
· Efficiency
· Solving the problem in an proficient manner
· Economy
· Solving the problem in a cost-effective manner
Precision
The component parts are specialized for achieving a particular end
Reliability
Solves the problem dependably in context in which an organism encounters the adaptive problem
In sum, Adaptations exhibit specialization
Example of Specialization
from
Animal Behavior
by J.
Alcock
, citing research by A. Dixon
g
alago
spp
l
oris
spp
s
low
loris
macaque
m
armoset
spp
mandrill
patas
m
armoset
spp
g
alago
spp
g
alago
spp
Contemplate your navel
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Discussion Questions Rubric Participation /2 2pts= automatic for participation Spelling/Grammar /2 2pts= only 1-2 errors Critical Thought Low Level /2 2pts=includes one perspective or example Critical Thought High Level /2 2pts=includes additional perspective, reasoning/ argument, or applies course concepts TOTAL POINTS= 8/8 |
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