1. Chapter 22
Human Evolution

2. Points to Ponder What is the chemical evolution of life?
What is biological evolution?
What is natural selection and what three elements are vital for this?
What was Darwin’s contribution to evolution?
What have we learned from the fossil record?
Explain the fossil, biogeographical, anatomical and biochemical evidence that supports the theory of evolution by common descent?
What are analogous, homologous and vestigial structures? Give examples of each.
How are humans classified?
What characteristics do primates have in common?
Explain the evolution of hominids.
Who is Lucy?
Explain the evolution of humans.
What are the 2 hypotheses for modern man?
Compare and contrast Cro-Magnons and Neandertals

3. Origin of life through chemical evolution
Steps of chemical evolution:
Gases of the primitive atmosphere formed small organic molecules
Molecules combined to form macromolecules
Only RNA might have been needed to form the first cells and is supported by the fact that RNA can act as enzymes called ribozymes (RNA-first hypothesis)
Protocells made of proteins and lipids could metabolize by using oceanic organic molecules but could not reproduce
The true cell can reproduce and has DNA as its genetic material

4. Origin of life through chemical evolution

5. 22.2 Biological evolution
Biological evolution
Biological evolution – change in population or species over time
2 important points:
Living things descended from a common ancestor and thus have common chemistry
Livings things adapt to their environment
Adaptation – a characteristic that makes an organism to survive and reproduce in its environment

6. Evidence to support the theory of evolution by common descent
22.2 Biological evolution
Evidence to support the theory of evolution by common descent
Fossils in the fossil record
Biogeographical evidence
Anatomical evidence
Biochemical evidence

7. 1. What are fossils? Fossils are the traces of past life
22.2 Biological evolution
1. What are fossils?
Fossils are the traces of past life
Fossils allow us to trace the descent of a particular group
Charles Darwin, an English naturalist, relied on fossils to formulate the theory of evolution
Transitional fossils have characteristics of two different groups

8. What have we learned from the fossil record?
22.2 Biological evolution
What have we learned from the fossil record?
Fossil record tells us that life progressed from simple to more complex
Prokaryotes are the first life forms seen in the fossil record followed by unicellular eukaryotes and then multicellular eukaryotes
Fishes evolved before terrestrial plants and animals
Nonflowering plants preceded flowering plants
Amphibians preceded reptiles
Dinosaurs are directly linked to birds

9. 22.2 Biological evolution
Fossils

10. 2. Biogeographical evidence
22.2 Biological evolution
2. Biogeographical evidence
Is the study of the distribution of plants and animals throughout the world
Supports the hypothesis that organisms originate in one locale and then may spread out
Different life forms are expected whenever geography separates them
Islands demonstrate this because they have many unique life forms because of geographic isolation

11. 22.2 Biological evolution
3. Anatomical evidence
Common descent hypothesis offers plausible explanation for anatomical similarities among living organisms
Homologous structures – structures anatomically similar that are inherited by a common ancestor
e.g. Vertebrate forelimbs
Analogous structures – structures that serve the same function but they do not share a common ancestry and thus are not constructed the same
e.g. Wings of a bird and wings of an insect
Vestigial structures – anatomical features fully developed in one group but are reduced and may have not function in another group
e.g. Whales have a vestigal pelvic girdle and legs

12. An example of homologous structures
22.2 Biological evolution
An example of homologous structures

13. 22.2 Biological evolution
4. Biochemical evidence
Almost all living things use the same biochemicals (e.g. DNA and ATP)
Living things use the same triplet code
Living things use the same 20 amino acids in their proteins
Living things share many of the same genes

14. 22.2 Biological evolution
Natural selection
A theory by Darwin that describes a mechanism by which a species becomes adapted to its environment
3 vital elements:
Variation – there must be physical variations that can be passed from generation to generation
Competition – there must be competition for limited resources (food, mates, shelter) and those better adapted will survive and reproduce
Adaptation – subsequent generations will see an increase in individuals with the same adaptations as long as the environment remains unchanged

15. 22.2 Biological evolution
Natural selection

16. The arrival of humans on earth
22.3 Classification of humans
The arrival of humans on earth

17. Primates Characteristics: Two suborders: Opposable thumb
22.3 Classification of humans
Primates
Characteristics:
Opposable thumb
Stereoscopic vision (depth perception)
Well-developed brain
Reduced # of offspring (usually a single birth) with an increased period of parental care
Emphasis on learned behavior and social interactions
Two suborders:
Prosimians – includes lemurs, tarsiers and lorises
Anthropoids – includes monkeys, apes and humans

18. 22.4 Evolution of hominids
Evolution of primates

19. 22.4 Evolution of hominids
Evolution of hominids
Hominids – human lineage on the evolutionary tree
Characteristics:
Bipedal
Flatter face with more pronounced chin
Brain size
Suggested fossils of the first hominids (~ 6-7 MYA):
Central African fossil ~7 MYA (Sahelanthropus tchadensis)
Eastern African fossil ~ 6 MYA (Orrorin tugenensis)
Eastern African fossil ~ MYA (Ardipithecus kadabba)
Hominids split from the ape line of descent ~ 7 MYA

20. 22.4 Evolution of hominids
Australopithecines
A group of hominids that evolved and diversified in Africa ~ 3 MYA
Some had slight frames and others were robust with massive jaws that fed on plant materials
Walked upright
Limbs proportions are ape-like
Small brain
Famous skeleton named “Lucy” is from this group
Australopithecus africanus has a large brain is is the most likely ancestral candidate for early Homo

21. 22.4 Evolution of hominids
Australopithecines

22. Characteristics of Homo
22.5 Evolution of humans
Characteristics of Homo
Brain size is 600 cm3 or greater
Evidence of tool use
Jaw and teeth resemble humans
Early Homo representatives:
Homo habilis
Homo erectus
Later Homo representatives:
Neandertals
Cro-Magnons

23. 22.5 Evolution of humans
Human evolution

24. Early Homo: Homo habilis
22.5 Evolution of humans
Early Homo: Homo habilis
Lived ~ MYA
Large brain with enlarged speech area
Omnivorous (hunters and gatherers)
Primitive tools
Culture may have existed

25. Early Homo: Homo erectus
22.5 Evolution of humans
Early Homo: Homo erectus
Lived ~ MYA
Larger brain than H. habilis
Flat face with the nose projected
Tall and stood erect
Striding gait
May have migrated from Africa to Europe and Asia
Advanced tools and fire (systematic hunters)
Language may have evolved

26. 22.5 Evolution of humans
Later Homo individual

27. Modern Humans: Homo sapiens
22.5 Evolution of humans
Modern Humans: Homo sapiens
2 hypotheses:
Multiregional continuity – suggests that modern humans evolved from H. erectus in several geographic places
Out-of-Africa hypothesis – modern humans evolved from H. erectus most likely only in Africa and later migrated to Europe and Asia (this hypothesis has the most support)

28. Hypotheses for modern human evolution
22.5 Evolution of humans
Hypotheses for modern human evolution

29. Neandertals Discovered in Germany ~2000 years ago Massive brow ridges
22.5 Evolution of humans
Neandertals
Discovered in Germany ~2000 years ago
Massive brow ridges
Nose, jaws and teeth protrude forward
Low and sloping forehead, no chin

30. Cro-Magnons Lived about 40,000 to 10,000 years ago
22.5 Evolution of humans
Cro-Magnons
Lived about 40,000 to 10,000 years ago
Oldest fossils to be designated Homo sapiens
Modern appearance
Advanced culture including art, tool and maybe language
Good cooperative hunters

31. 22.5 Evolution of humans
Human variation
Human variations between populations are called ethnicities
Variations evolved as adaptation to local environments:
Skin color: range of dark to light
Body shape: Bergmann’s rule and Allen’s rule

32. 22.5 Evolution of humans
Human variation