Transcript Evolution of Culture Capacity - Palomar Community College

Evolution of Culture
Capacity
Human Evolution
Theory of Natural Selection
Theory formulated by Charles Darwin.
Changes in living organisms occur over
time as a result of reproduction.
The most convincing scientific explanation
of the variety and history of life on earth.
Theory of Natural Selection
No two living things, even those of the
same species, are alike.
Sources of variation:
Mutation
Sexual reproduction
Genetic drift
The chemical structure
of DNA consists of two
long backbones made of
alternating sugar and
phosphate molecules.
There are two
pools of genetic
variation,
hidden and
expressed.
This computer simulation demonstrates that genetic drift causes isolated
populations to become genetically different from one another.
Figure 03.23
Theory of Natural Selection
Most creatures did not survive long
enough to have offspring.
Creatures who won the struggle for
survival passed traits that led to their
success to their offspring.
Life in a nutshell: the cells of organisms are composed of a
large number of very complicated chemicals
Stabilizing selection favors the intermediate phenotype out of a range of phenotypes. The
extremes in variation are selected against. Example: Human infants weighing significantly less
or more than 7.5 pounds have higher rates of infant mortality. Selection works against both
extremes.
Types of
Natural
Selection
Directional Selection tends to favor phenotypes at one extreme of the range of variation.
Insecticide resistance is an example. DDT was a widely used insecticide. After a few years of
extensive use, DDT lost its effectiveness on insects. Resistance to DDT is a genetic trait that the
presence of DDT in the environment made into a favored trait. Only those insects resistant to
DDT survived, leading over time to populations largely resistant to DDT.
Disruptive Selection favors individuals at both extremes of variation: selection is against the
middle of the curve. This causes a discontinuity of the variations, causing two or more morphs or
distinct phenotypes. The African swallowtail butterfly (Papilo dardanus) produces two distinct
morphs, both of which resemble brightly colored but distasteful butterflies of other species. Each
morph gains protection from predation although it is in fact quite edible.
Common
Examples
of
Selection
In Action
Selection
Pressures can be
observed in
local microenvironments
where severe
conditions
prevail
The same mechanisms are
at work in developing new
crops through artificial
selection.
Selection can carry a population far beyond the original
range of variation.
Illustration of Artificial Selection for Oil Content in Corn.
Selection For Oil Content
Selection Against Oil content
HARDY-WEINBERG EQUILIBRIUM
THEORY
A MATHEMATICAL MODEL OF AN IDEAL
POPULATION IN WHICH GENE FREQUENCIES
ARE.NOT INFLUENCED BY EVOLUTIONARY
PROCESSES. THE MODEL.MAKES THE
FOLLOWING ASSUMPTIONS:
A LARGE (INFINITELY?) POPULATION.
NO MUTATION
NO MIGRATION
NO SELECTI ON
COMPLETELY RANDOM.MATINGS
EVOLUTION TERMINOLOGY
GENE POOL: THE TOTAL NUMBER OF ALLELES IN
A POPULATION. THE GENE POOL REPRESENTS
THE AVAILABLE GENETIC VARIATION.
BREEDING ISLOLATES: A POPULATION THAT IS
ISOLATED, OR SEMI- ISOLOATED, FROM OTHER
POPULATIONS FOR GEOGRAPHIC, BEHAVIORAL,
OR OTHER.REASONS.
ENDOGAMY: MATING WITHINA SOCI.AL GROUP.
EXOGAMY: MATING OUTSIDE A SOCIAL GROUP.
Gene flow among
populations destroys
differences between
them.
Figure 04.02a
Island 1
Island 2
Island 1
Now suppose two
populations of finches
live on different islands,
one wet and one dry,
with no gene flow
between the two islands
Figure 04.02b
Island 2
In the Galápagos, selection maintains three species of ground finches
despite the fact that there is substantial gene flow among them
Figure 04.03
EVOLUTION TERMINOLOGY
NEGATIVE ASSORTIVE MATING: INDIVIDUALS
OF UNLIKE PHENOTYPE MATE MORE OFTEN
THAN THOSE OF SIMILAR PHENOTYPES.
POSITIVE-ASSORTIVE MATING: INDIVIDUALS
OF LIKE PHENOTYPE MATE MORE OFTEN THAN
THOSE OF SIMILAR PHENOTYPES.
INBREEDING: THE SYSTEMATIC SELECTION OF
MATES FROM CLOSE GENETIC RELATIVES.
CONSANGUINITY: THE DEGREE OF RELATION
BETWEEN INDIVIDUALS.
Types of Speciation
Allopatric speciation
occurs when a species is
divided into two
reproductively isolated
populations that
subsequently diverge. If
the divergent populations
regain contact, they
cannot interbreed and
two new species exist.
Figure 04.10
Parapatric speciation
occurs when a species
experiences different
environments in different
parts of its geographic
range. Natural selection
causes different
populations of the
species to diverge while
adapting to these
different surroundings,
and eventually
reproductive isolation is
achieved.
Sympatric speciation
occurs when selection
strongly favors different
adaptations to a similar
environment within a
single species.
EVOLUTION TERMINOLOGY
FOUNDER EFFECT: THIS OCCURS WHEN
A.VERY SMALL NUMBER OF INDIVIDUALS
(AND THEREFORE A VERY SMALL GENE
POOL) ARE THE ONLY INDIVIDUALS TO
CONTRIBUTE GENES TO THE .FOLLOWING
GENERATIONS.
An illustration of
sampling variation.
Anagenesis and Cladogenesis
There are two types of change. These are depicted here as
anagenesis and cladogenesis. The latter, of course, implies the
process of speciation. The former relates to changes over time in a
species.
There are three terms that you should know relative to evolution.
These are: Divergent Evolution, Convergent Evolution, and
Parallel Evolution. The keys to understanding the differences
between these terms is to contrast ancestry, adaptations, and
eventual forms. If you do this, you will find these terms easy to
understand.
DIVERGENT EVOLUTION
Evolution of DIFFERENT adaptive traits in forms that were once
related but then diverged, developing along different lines.
In terms of ancestry, adaptation and form:
there is similar ancestry,
different adaptations and
resulting different forms.
CONVERGENT EVOLUTION
Evolution of SIMILAR adaptive traits
In terms of ancestry, adaptation and form - consider convergent
evolution to reflect
different ancestries,
similar adaptations and
resulting similar forms.
PARALLEL EVOLUTION
Evolution of similar adaptive traits in forms that were once related
but then diverged, developing along similar lines.
In terms of ancestry, adaptation and form: there is
similar ancestry,
similar adaptations and
resulting similar forms.
Debates on Evolution
Most debate about evolution is
religious rather then scientific.
Evolution challenges religious creation
stories.
In 1950, the Catholic Church declared
evolution compatible with Christianity.
Common Ancestors
Humans, gorillas and chimpanzees evolved
from common ancestors.
All animals are equally evolved in different
ways and under different circumstances.
Human ancestors diverged from those of
chimpanzees and gorillas 5 to 8 m.y.a.
Primates
For our purposes, Primates have the following features:
Limbs and Locomotion
1.
2.
3.
4.
5.
Retention of Five Digits (pentadactyly)
Nails instead of claws on at least some digits.
Flexible hands and feet with considerable prehensility
Retention of the Clavicle
A tendency towards erect posture, especially in the upper body
•
Teeth and Diet
1. A generalized dental pattern
2. A lack of specialization in diet
Senses, Brain, and Behavior
1.
2.
3.
4.
A reduction of the snout
An increased emphasis on vision
Expansion and increased complexity of the brain
A more efficient means of fetal nourishment, lengthening of the entire life-cycle,
especially of gestation and infancy.
5. Dependency on highly flexible learned behavior
6. Adult males often associate with the group permanently
Grades of Primate Evolution
Suborder Prosimii
Grade One: Tree Shrews (primitive mammalian grade)
•Live in southeast Asia, India to Indonesia
•Have claws, not nails, on all digits
•Have grasping hands
•Probably resemble some of the earliest primates
Grade Two: Lemurs and Lorises
•Lemurs: Only on the island of Madagascar. Extinct elsewhere
•Lorises: Very similar to Lemurs, but are distributed over much of
Southern Africa
Summary of the Prosimians: 1. Have nails on at least one digit 2. Well developed vision
but not completely stereoscopic. 3. Prolonged life spans 4. Projecting nose 5. Welldeveloped sense of smell 6. Expressionless faces 6. Grooming dentition 7. Unelaborated
social structure.
Suborder Anthropoidea
Grade Four: Monkeys
A. New world Monkeys: Ceboidea
•Exclusively Arboreal
•Southern Mexico, Central America, South America
•Some have prehensile tails
B. Old world Monkeys: Cercopithecoidea
•The most widely distributed of all primates other than humans
•2.1.2.3 dental formula
•All quadrapedal, mainly arboreal
•No prehensile tails in adults
Grade Five: Hominoids
A. Lesser Apes: Gibbons and Siamangs
B. Great Apes: Orangutans, Gorillas, Chimps
C. Humans
Primate Social Behavior
Core of society is the bond between mothers
and their offspring.
Play becomes central to the interaction of
older primates with their age-mates.
Primates have displays of aggression and
means of reconciliation.
Primate Social Behavior
Mother-Infant Relationship: The basic social unit in all primates.
Males may consort with females for mating, but they may
or may not participate as members of a social unit.
In most other animals infants are left behind in dens or nests.
In Primates:
1. Infants cling to mothers while they move about.
2. The bond is often for life, and is reflected in adult grooming
behavior.
The role of the mother-infant attachment is not just one of social
stability, it is absolutely essential for the proper development of
primate infants.
What are some of the basic types of non-human
primate social groups?
1. ONE
a.
b.
c.
d.
e.
f.
MALE GROUPS
A single adult male, several adult females and their offspring.
The most common primate mating structure
Only one male actively breeds.
Usually formed by a male or males joining a kin group of females.
Females usually form the permanent nucleus of the group.
Examples: Guenons, Orangs, Gorillas, pottos (some), spider monkeys (some), patas.
2. MULTIMALE GROUPS
a. Several adult males, several adult females and their young.
b. Several of the males reproduce.
c. The presence of several males may lead to tension and to a dominance hierarchy.
d. Examples: Lemurs(some), macaques, mangabeys, savanna baboons, vervets, chimpanzees.
3. FAMILY, or MONOGAMOUS
a. A mated pair and their young.
b. Usually arboreal
c. Minimal sexual dimorphism
d. Frequently territorial; Adults do not tolerate other adults of the same sex.
e. Not found among the great apes, and least common of breeding structures in non-human
primates.
f. Examples: gibbons, indris, tarsiers, owl monkeys, titis, pottos, marmosets(some).
ASPECTS OF SOCIAL BEHAVIOR
Grooming: The manual cleaning of skin and fur.
1. Almost all primates groom one another
2. Grooming occurs in other species but SOCIAL grooming is a
unique primate activity and plays an important role in the
life of most primates.
3.
Eases interaction between male/female and lower/higher
ranks: “social lubricant”
4. The social cement for all primates: helps maintain social
organization of the group.
5. Often reciprocal with roles interchanged; groomer becomes
the groomee
ASPECTS OF SOCIAL BEHAVIOR
Displays: Stereotyped behavior what serves to
communicate emotional signals.
1. Animals often display when excited
2. They use displays
a. when outsiders are present
b. in reaction to another member of the
group.
ASPECTS OF SOCIAL BEHAVIOR
Dominance (dominance hierarchy): The physical
domination of some members of a group by
other members.
1. Measured by priority access to a desired
object such as food or a mate.
2. The dominant individual is given priority
in confrontations.
3. Dominant individuals compete more
successfully in the group than others: net
reproductive success.
Primate Tool Use
Females first develop tool-using skills
and become more adept than males.
Tool use is learned behavior and
passed along by the social group.
Some groups of chimpanzees do some
activities and others do not.
Examples of Primate Tool Use
Use sticks to threaten others or defend
themselves.
Use water to separate grains of wheat
from sand.
Use twigs or blades of grass to fish
termites from their mounds.
Early Human Ancestors
Few in number and geographically
confined to Africa.
Did not depend heavily on tools, and
left few material remains.
Spread from African origins to inhabit
most of the globe.
Evolution of Humans
Humans have adapted to many
different climates and ecosystems.
All humans are members of the
biological family Hominidae.
Humans fall into two genera:
Australopithecus and Homo.
Homo Habilis
•Expanded cranial capacity
(relative to africanus).
•Reduced postcanine tooth size.
•The presence of a precision
grip (determined from the hand
bones present in OH 7), which
provides the anatomical basis
for tool-making.
Homo Habilis
Found in Africa between 2.5 and 1.8
million years ago.
Made sophisticated sets of tools as
early as 2.3 million years ago.
Stone rings indicate that habilis
probably built shelters for protection.
Homo erectus
•An increase in brain size (erectus
approximately 900 cc., sapiens approximately
1350 cc.).
•A reduction in postcanine dentition, and a
correlated decrease in jaw size.
•Vertical shortening of the face.
•Shortening of armbones (especially the
forearm) to come to a very humanlike limb
proportions (postcranial proportions are very
similar to tropically adapted modern humans).
•The development of a more barrel-shaped
chest.
•The formation of an external nose.
•Reached modern human size in terms of
height.
Homo erectus
Found in Africa, Asia, and Europe between
1.8 million and about 200,000 years ago.
Became increasingly dependent on culture
to survive in the Ice Age.
Capable of controlling and using fire.
Lived by hunting, scavenging, and
gathering.
Neandertals
Amud 1
•Flat zygomatic arch.
•The supraorbital torus projects at midline.
•Retreating chin.
•A long low brain case. .
•An occipital bun.
•A broad and projecting nose.
•Larger cranial capacity (but due to larger body size,
Neanderthals are less encephalized than modern humans).
Neandertals
Members of a population of archaic Homo
sapiens.
Lived between 130,000 and 35,000 years
ago.
Pollen found in graves show bodies were
buried with flowers, suggesting rituals and
belief in the afterlife.
Homo sapiens sapiens
•A high, rounded cranium.
•A steep forehead.
•Large cranial capacity (1600 cc.).
•A short face with rectangular orbitals.
•A tall and narrow nasal opening.
•A parabolic palate.
•A prominent mental eminence.
Homo sapiens sapiens
Tools were more sophisticated and efficient
than any prior species.
Left symbolic and artistic remains in form
of cave paintings and Venus figures.
Turned to the domestication of plants and
animals about 10,000 years ago.
Human Variation
Human traits change in frequency
geographically.
Blood type and skin color vary
geographically.
The sickle cell gene is common in
areas that have a high incidence of
malaria.