1. Ch22: Human Evolution

2. Evolution Vs. Intelligent Design
Change in heritable traits within a population over successive generations
Supported by scientific evidence
Intelligent Design
Concept that “certain features of the universe and of living things are best explained by an intelligent cause”
Can not be supported or rejected by research

3. Geological Time

4. Chemical Evolution
Atmospheric gases reacted and produces small organic molecules
Stanley Miller performed an experiment to support this hypothesis
Small organic molecules joined to produce organic macromolecules
Organic macromolecules formed the first Protocell.
Lipid-protein membrane
Heterotroph – takes in preformed food
Fermenter- created energy without oxygen
Protocells incorporated RNA (& then DNA) to create a True cell.
Cell was able to reproduce & pass on its genetic information.

6. Biological Evolution
Biological evolution is a change in life forms between generations.
Two aspects of biological evolution:
Common descent – all living descended from a common ancestor
Explains unity of all living things (i.e. all living things are made up of cells and have the same biochemistry)
Adaptation – modification in structure, function, or behavior to better suit the environment
Explains the diversity of life

7. Charles Darwin
A naturalist that formulated the theory of evolution based on the following evidence:
Biogeographical – even though there were suitable environments for certain plants & animals they were not distributed everywhere.
Anatomical
Homologous structures – anatomical parts that are similar, but have different functions; these anatomical similarities indicate common descent.
Analogous structures – have the same function, but are anatomically different; thus, there is no common descent
Fossils – remains or traces of past life that has been preserved in the earth’s crust.

8. Homologous Structures

9. Additional Evidence
Biochemical Evidence – almost all living organisms use the same basic biochemical molecules.
DNA – genetic information
Organisms that are closely related have a higher percentage of similar DNA
Proteins – same 20 amino acids
ATP – molecule for energy

10. Evolutionary Mechanisms
Natural Selection - the process by which a species becomes adapted to its environment.
Sexual Selection – the process by which certain individuals are chosen to mate.
Genetic Drift – random changes in gene frequency in a population

11. Evolutionary Mechanisms
Evolutionary Mechanisms are dependent on:
Mutations – changes in chromosome structure
Genetic Recombination – changes in alleles combinations often due to crossing-over
Gene flow – movement of alleles of genes into or out of a population by migration and interbreeding.

12. Natural Selection
Variation - physical variations can be passed from generation to generation
Competition - the environment “selects” these better adapted members to have offspring and to pass on this characteristic
Adaptation - subsequent generation include more individuals that are adapted in the same way to the environment.

13. Sexual Selection
Intrasexual competition – same sex individual fight to mate with females
Intersexual competition – females (or males) choose certain mates based on certain characteristics.

14. Human Evolution: Humans are Primates
Characteristics of Primates:
Grasping fingers and toes, some with opposable thumbs
Well-developed brain
Nails
Single birth
Extended period of parental care
Emphasis on learned behavior
Two Suborders:
Prosimians—lemurs, tarsiers, and lorises.
Anthropoids—monkeys, apes, and humans

15. Evolution of Hominids Hominid – humans Family branch
Bipedal posture (walking on two feet)
Flat face
Brain size
Australopithecines - a group of individuals that evolved and diversified in Africa.
Hominids lived about 3 MYA
Walked erect
Small brain compared to us, but large brain compared to other primates
Limb proportions are ape-like
Australopithecus africanus with its large brain is the best ancestral candidate for early Homo

16. Evolution of Homo
Homo habilis - may be the ancestor to modern humans ( MYA)
Made tools
Large brain
Dentition
Omnivores (plant gatherers and hunters)
May have had the rudiments of a culture
Homo erectus – may have evolved from Homo habilis ( MYA)
Striding gait
Made well-fashioned tools
Control of fire
Migrated into Europe and Asia

17. Evolution of Modern Humans
Multiregional Continuity Hypothesis – evolution of modern humans was essentially similar in many different places.
Out-of-Africa Hypothesis – evolution of H.sapiens evolved from H.erectus only in Africa and then H.sapiens migrated to Europe & Asia

18. We are one Species
Biological definition of a species – Any group of organisms able to interbreed and bear fertile offspring.