How Did Humans Evolve

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How Did Humans Evolve?

• Early primate lifestyles mostly tree dwelling
• Additional ecological niches on the ground near
  the forest
• Problem Exploit the new niches without getting
  eaten
• Use only biological adaptations to accomplish this

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But First, Some Background Information

• Living systems chemical reactions that use
  energy from outside sources to stay organized
  otherwise, everything wears out and runs down
• All living systems contain computer programs (DNA
  and/or RNA) to run them, and usually cellular
  structures and an energy source

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Photosynthesis

• Cells with chlorophyll capture photons from the
  sun and then use the energy to combine carbon
  dioxide and water to make sugar (glucose), more
  water, and oxygen.
• 6CO2 (cars make it) 12 H2O photons (sunlight)
  C6H12O6 (we eat it) 6H2O (we drink it) 6O2
  (we breath it).
• Glucose (sometimes combined with nitrogen and
  phosphorus) is used to make carbohydrates,
  proteins, and fats.
• Cells stay alive by breaking down glucose into
  carbon dioxide and water and storing the energy
  in a chemical form (ATP) to be used later. This
  is called respiration.

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Organization of the Living.
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Biological Organization

• Cells (neurons)
• Tissues (cerebellum)
• Organs (brain)
• Organism (snapping turtle)
• Populations (species all snappers in an area)
• Community (snappers, fish, crawfish, hawks, Lilly
  pads)
• Ecosystem (community pond)
• Landscape (pond forest)

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Ecology

• Derived from the Greek word eco meaning house
  and logy meaning study.
• Divides the world into biotic or living and
  abiotic or physical.
• Ecology is the study of organisms and their
  interactions with other organisms and with the
  abiotic world.

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Food Chain
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Food Chains in an Ecosystem

• Diatoms eaten by copepods eaten by sardines eaten
  by herring eaten by flounders eaten by people.
• Antarctic food web includes algae eaten by krill
  (shrimp) eaten by whales.
• Ozone hole (caused by CFCs) damages algae this
  reduces krill and thus, whales.

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Energy Flow Through a Food Chain
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Eco Pyramids

• Numbers of producers gt numbers of primary
  consumersgt numbers of secondary consumers (10,000
  plants to 10 mice to 1 hawk).
• Biomass pyramid is more accurate (grams/meter
  squared).
• Energy pyramid is most accurate (Kcal/meter
  squared/year).

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Organismal Pyramid
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Interactions Among Organisms

• Predation includes animals eating plants, other
  animals, and plants eating animals and other
  plants
• Predation drives co-evolution of weapons and
  countermeasures (bats sonar versus tuned moth
  ear and life or death brain circuits)
• Ambush and escape traits arise randomly and
  are selected by natural selection

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Ambush Versus Escape Traits

• Ambush strategies include stealth (cats), power
  (bears), extraordinary senses (raptors),
  camouflage (mantis), mimicry (fireflies).
• Escape strategies include schooling (fish),
  hiding (rabbits), speed (antelope), mimicry
  (snakes), and drugs and poisons in animals and
  plants (bufotensin in toads opium, nicotine, and
  curare in plants).
• Milkweed produces cardiac glycosides that are
  deadly to most insects, yet monarch butterfly
  caterpillars feed exclusively on milkweeds and
  concentrate the poisons as protection against
  predators.

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Ecological Niche

• Ecological niche is an organisms role in the
  ecosystem and includes its habitat, what it eats,
  who eats it, the competition, and its
  relationships with the physical environment
  (water, temperature, salinity, etc.)
• Competition narrows an organisms fundamental
  niche down to its realized niche or actual
  lifestyle.

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Two Men Enter, One Man Leaves
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Competitive Exclusion and Resource Partitioning

• Competitive exclusion maintains that no two
  species can occupy the same exact niche in the
  same community.
• One species prevails under a given set of
  conditions such as Paramecium aurealia versus
  Paramecium caudatum (Two men enter, one man
  leaves!).
• But resources can be partitioned to support
  similar species (warblers in forage in different
  parts of a spruce tree)
• Richer habitats contain more niches and can
  support more species and thus support more
  biodiversity.

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Resource Partitioning
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EvolutionPopulation Changes Over Time

• Darwin discovered that diversification of species
  occurs during evolution.
• Adaptation is a process by which an evolutionary
  modification improves an organisms chances of
  survival and reproduction in a given environment.
• Natural selection is the mechanism that drives
  adaptation.

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Natural Selection

• Species overproduce offspring.
• Heritable variations occur in populations.
• Some variations are adaptive, others are
  maladaptive, while others are neutral.
• Resource availability limits population growth
  not all offspring survive to reproduce.
• Those that do reproduce are more adapted to a
  given environment their traits will be
  genetically passed on to their offspring.
• Over time, changes in genetic traits in a
  population produce new species.

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Evolution of Traits

• Human body types have evolved via adaptation to
  different climates
• Thin, tall people are adapted to living in
  temperate open grasslands. They need high surface
  area to volume ratio to radiate heat and
  increased height to see over long distances.
• Thin, smaller people are adapted to living in
  wooded and forested areas in a tropical climate.
• Thick people have a small surface area to volume
  ratio they hold heat and are adapted to living
  in cold climates with hills and mountains to
  traverse.

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Now, Apply Ecology and Evolution Principles to
Human Evolution

• What are/were primate niches?
• How and why did those niches change 4 million
  years ago?
• Who evolved to take advantage of these new
  niches?
• What physical adaptations enabled new species to
  colonize new niches?