Human Evolution

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Human Evolution

• D.3Chapter 15

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D.3.1 Outline a method for dating rocks and
fossils using radioisotopes, with reference to
14C and 40K

• Fossils, or the rocks containing fossils can be
  dated using radioisotopes
• When an atom of a radioisotope decays, it changes
  into another isotope and gives off radiation
• Isotopes different number of neutrons in an
  element

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D.3.1 Outline a method for dating rocks and
fossils using radioisotopes, with reference to
14C and 40K

• Radiocarbon dating the of surviving 14C atoms
  in a sample is measured
• Useful in dating samples that are between
  1000-100,000 years old
• C-14 and C-12 are present in living organisms
• Once an organism dies it no longer takes in C-14
  and the existing C-14 decays

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D.3.1 Outline a method for dating rocks and
fossils using radioisotopes, with reference to
14C and 40K

• Potassium-argon dating the of surviving 40K
  atoms and daughter 40Ar atoms are measured
• Used to measure the age of rocks
• Useful in dating samples older than100,000 years
  old.

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D.3.2 Define half-life

• The number of years it takes 50 of the sample to
  decay
• 14C half-life is 5730 years
• 40K half-life is 1.3 billion years

half lives years passed original radioisotope remaining
1 5730 50
2 11460 25
3 17190 12.5
4 22920 6.25
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D.3.3 Deduce the approximate age of materials
based on a sample decay curve for a radioisotope

• To be done in radioactive decay lab

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D.3.4 Describe the major anatomical features
that define humans as primates

• Opposable thumbs allows for grasping hands and
  feet
• Long, thin, straight fingers fine motor skills
• Fingernails instead of claws
• Shoulder flexibility (socket) for greater
  mobility (swinging in trees)
• Forward-facing eyes stereoscopic (3D) vision and
  depth perception
• Extensive care of young

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D.3.5 Outline the trends illustrated by the
fossils of . . .
Approximate dates Distribution
Ardipithecus ramidus 5.8-4.4 MYA Ethiopia
Australopithecus afarensis Lucy 4-2.5 MYA Eastern Africa
Australopithecus africanus 3-2.5 MYA Southern Africa
Homo habilis 2.4-1.6 MYA Tanzania, Kenya, Ethiopia, S. Africa
Homo erectus 1.8M 100,000 YA Europe, India, China, Indonesia
Homo neanderthalensis 200,000 30,000 YA Europe, W. Asia
Homo sapiens 140,000 70,000 YA Africa, Europe, Asia
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D.3.6 State that, at various stages in hominid
evolution, several species may have coexisted

• Examples
• Homo neanderthalensis and Homo sapiens
• A. afarensis and A. africanus

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D.3.7 Discuss the incompleteness of the fossil
record and the resulting uncertainties about
human evolution

• Incompleteness due to
• Bits and pieces of skulls skeletons discovered
• Discrepancy in the number of fossils found for
  each species
• Estimations in characteristics (cranial capacity)
  are imprecise due to differences between males,
  females, and juveniles
• Oldest fossils are most difficult to find because
  they degenerate over time

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D.3.7 Discuss the incompleteness of the fossil
record and the resulting uncertainties about
human evolution

• Incompleteness results in slightly different
  timelines of human evolution with different dates
  and phylogenetic connections between species

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D.3.8 Discuss the correlation between the change
in diet and increase in brain size during hominid
evolution

• The consequence of a larger brain is the need for
  more energy
• Early hominids were foragers and ate fruit
  nuts, and only on occasion meat
• As tools became more sophisticated, hunting
  techniques improved availability of meat
  increased

Meat in diet complex tools bigger brain
sizes
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D.3.9 Distinguish between genetic evolution and
cultural evolution

• Genetic evolution inherited characteristics
• Body morphology (cranial capacity, skull shape,
  height, robustness)
• Number of chromosomes
• Biochemicals (blood proteins)
• These (features of hominids) are passed on
  through chromosomes.

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D.3.9 Distinguish between genetic evolution and
cultural evolution

• Cultural evolution acquired characteristics
• Language (spoken and written)
• Customs and rituals (ethnic or religious)
• Art (sculpture, pottery, painting)
• Technology (comfort, obtaining food, warfare)
• These can be passed on within a social group or
  family.

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Note The whole process of the increase in
hominid cranial capacity was through natural
selection. - over-production of offspring -
variation in a population so some offspring
had bigger brains - bigger brains could have
meant better problem solving skills thus
better fitness due to an ability to find food
and shelter more successfully - better fitness
would increase the chances of survival -
those who survived passed on their genes to
the next generation
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D.3.10 Discuss the relative importance of
genetic and cultural evolution in the recent
evolution of humans

• As brain size increased, so did the quality of
  tool-making
• Genetic evolution preceded cultural evolution
• Genetic evolution was really important up until
  Homo sapiens
• After that, cultural evolution increased in
  importance
• For the last several thousand years, humans have
  altered the environment so much that we dont
  need to genetically evolve
• We evolve tools (cultural) to better solve
  problems