Lecture #19. Evolution of Humans. Next Week: Habitability! Chpt 7

Transcription

1 Lecture #19 Evolution of Humans Next Week: Habitability! Chpt 7

2 Recent Asteroid in the News Asteroid 2012 DA14 discovered a few weeks ago 40-meter wide rock February 16, 2013, it will pass about 27,000 km from the center of the Earth (roughly 21,000 km from the surface)

3 Solar Flares

4 Human Evolution How did humans evolve? Are we (or something like us) inevitable?

5 Humans Eukarya Animalia Chordata Mammalia Primate Hominidae Homo Sapiens

6 Life: ~ Mya

7 When conditions are good, why does life take over so rapidly? If a new cell can double itself every hour. How long would it take to reach 10 trillion (1013) cells (about the number in a human body, more or less) A) 12 hours B) 2 days (44 hours) C) 2 weeks D) 2 months How long before it reaches the mass of the Earth? (cell ~ g, earth ~ 1028 g 1040 cells) 5.5 days (133 hours)

8 Domain: Eukarya ~ Mya

9 Oxygen Life releases oxygen into the ocean As long as there is reduced iron in the ocean BIFs 1800 Mya Dissolved iron used up... oxygen moves into the atmosphere In total the Earth will be habitable for 5-6 billion years. 2 billion of those the Earth was inhabited but there wasn't much evidence for this in the atmosphere (oxygen) What does this mean for the detection of life elsewhere?

10 Kingdon: Animalia ~ Mya Molecular Clock n Wray, Levinton, Shapiro (1996) estimated that then Anelids Chordates split mya! (Generly now considered too early) There is very little fossil evidence for complex life before the Cambrian (550 Mya)

11 Forming Animals Stage 1: Body Plan Comb Jelly Sea Sponge Roundish Flatworm Urbilateria

12 Stage 2: Diversity Cambrian Explosion 550 Mya If it took a few hundred million years to go from animals to the diversity seen in the Cambrian... does that mean that animal life must become complex? Causes for Diversity Snowball Earth More Continent Formation

13 Phylum: Chordata ~ Mya Earliest Chrodate fossile: 560 Mya Flinders Range Imagine a tadpole about six centimetres Probably crawled on the oceans floor not swam

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15 Class: Mamalia ~200 Mya appeared in the Late Triassic Over 70 million years after the first therapsids (hair, lactation) Very much the beneficiaries of mass extinctions!

16 Mass Extinctions

17 Mass Extinctions: Possible Causes Large impacts: Random or somehow regular intervals? Climate change from high rate of volcanism? Magnetic field collapse allows more charged particles to hit Earth, increasing mutation rates? Nearby supernovas eject cosmic rays, increasing mutation rates? We know these extinction events were important for our ancestors becoming dominant... Is this a necessity? Or is this just survivors bias?

18 Order: Primates ~65 Mya Oldest Fossils Plesiadapis (55 58 mya)

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20 Family: Homidae ~14 Mya Family of Gorillas, Orangutans, Chimps Toumaï" Sahelanthropus tchadensis Discovered in Chad Earliest Hominine Fossil (post chimp split) 7 Mya

21 Genus: Homo Mya

22 Homo Habilis Handy Man Mya Larger Brain Case, Smaller Face/Teeth Oldest stone tools slightly older than genus Homo

23 Homo Floresiensis (Hobbits) 95,000-17,000 years ago Flores, Indonesia 3ft 6 in tall, large feet Used stone tools May have used fire

24 Homo neaderthalensis (Netanderthal) 200,000-28,000 years ago Europe and southwest asia Brains larger than ours (bigger bodies) Sophisticate Tools, Fire Symbolic Behavior (jewelry, burying dead) Interbreeding with homo sapians?

25 Species: Homo Sapiens 0.2 Mya (200,000 years ago)

26 Is Intelligence Inevitable?

27 Animals and Tools Many Animals are know to use tools and to fashion them

28 Humanoids and Tools Good Evidence For Stone Tools for 2.5 MY Evidence for Fire for 2-3 MY No Modern Humans until 200,000 years No Bronze age until 5000 years ago!

29 Quantifying Intelligence Encephalation Quotient

30 Could intelligent life have formed more quickly? Chris McKay (NASA Ames) Intelligent life could have arose 100 Myr Plate Tectonics hindered the emergence of an oxygen Atmosphere Why have we said plate tectonics are important? Climate Regulation over Billions of Years If you could get intelligent life in 100 Myr, would it matter if climate can be regulated over Gyr?

31 Reminders Next Monday Habitability Read Homework #5 is posted (Due next Friday)