ABOUT A105

INSTRUCTOR

SYLLABUS

TOPIC SCHEDULE

GRADES

STUDENT
CODE of ETHICS

ASSIGNMENTS

ACTIVITIES

BACK TO LECTURES

SCHOLAR LINKS

RETURN TO A105
 

 A105 Human Origins and Prehistory
Lecture 3

Lecture 3, Spring 2002 

I.  Four Forces of Evolution
                 Gene flow -- movement of genes into a population.

                 Genetic drift -- random shift in gene frequencies.   Founder effect.  Influences small populations the most.
 

                 Mutation -- random genetic change, for any reason (radiation,
                       copying error, etc.). 
 

                 Natural selection -- produces adaptations through differential survival and differential reproduction.
 
 
 

II. Other evolutionary concepts.
          Adaptive radiation – rapid diversifying of a group.  
 
 

Convergent evolution -- similar adaptation without recent ancestry. 
 
 

P arallel evolution -- similar adaptation in related lineages.  
  

III.  Evolution in Action: Altruism & Infanticide.  CONCEPT: Adaptation.
Selection acts at the level of the individual, BUT many seemingly altruistic acts benefit related individuals. 
 
 
 

Actions that are bad for species can be explained in terms of their advantage to the individual that takes these actions. 

  

IV. Limits on Reproduction in Primates. 
Selection operates by favoring individuals who are good at reproducing.
What do individuals need to do to be successful reproducers?  It is different for males and females.
 
 
 

Has implications for behavior and body structures.  In particular, efficiency and energy conservation are extremely important.  When we look at how bodies work at doing this job, we are talking about functional morphology. 
 

V. Functional Morphology

The body as a system of levers, with three components. 
Rigid bones = framework 
Ligaments = hinges 
Muscles drive the movements. 
 

Bones
Strong in compression -- by weight, as strong as steel. 
Weak in tension. 
Shapes evolve to reduce stress placed on bones, and to ensure that any stress will be compression rather than tension. 

Ligaments allow only certain kinds of movement. 
Bone shapes determine the range of possible movements, not muscles. 
Bodies evolve to reduce muscle action, because it burns energy. 

Bodies evolve to conserve energy, by bearing weight off muscles and reducing the need to use muscles. Means bearing weight on bones, having joints lock in posture. 

VI. Basic Osteology
Basic Osteological Terms 
               Cranial = head 
               Postcranial = “after” the head…or, below the neck. 
               Distal = further away from the middle of the body. 
               Proximal = closer to the middle. 

Cranial Bones 
The cranium is made up of the vault (braincase) and the face. 
The lower jaw is the mandible, the hardest bone in the skeleton. 
There are other cranial bones, but we will not worry about them here.
 
 

Teeth: 
Incisors, canines, premolars, molars.  Dental formula: Number of each type of tooth in each quadrant.

Postcranial Skeleton
Vertebral column
Ribs
Pelvis
Limbs
 
 
 

VII: Introduction to Modern Nonhuman Primates
     Taxonomy and Primate Evolutionary Trends 

Taxon = a group of related animals 
Taxonomy = the science of naming and organizing living organisms. 
Primates represent an order in the class of mammals. 
Other orders include Carnivora, Rodentia. 

The Order Primates
Very diverse – 200 species. 
Size ranges from 2 ounces to over 400 pounds. 
Wide range of brain sizes also. 
Wide range of shapes. 
Wide range of social behavior. 

What is a Primate?
We can describe them in terms of several evolutionary trends. 
Most if not all of these trends are related to adaptation to life in the trees  -- arboreality . 

Skeleton and Locomotion
1.  Generalized skeleton and limb structure. 

2.  Prehensile hands and feet with 5 digits – good grasping ability. 

3.  Erect posture in the upper body. 

Diet and Teeth
4.  High-quality diet.  Fruits, nuts common; omnivory 
. 
5.  Generalized teeth.  Primates have all 4 tooth types 

Primate Senses
6. Less reliance on olfaction (smell); more reliance on sight.

7. Eyes frontated (face front) so fields of vision overlap.

8. Color vision.

Brains and Behavior
9.  Large brains, especially in relation to body size.

10. Diurnal (active during the day).

11. K-selected life history (slower life cycle, fewer offspring with more investment in each).
 

Think about how each of these trends would be helpful to an animal living in the trees, moving about and finding food.
.