Transcript Lecture 05b: Mass extinctions and hominid evolution

Destruction and creation
Goals
Learn about the K-T boundary
• Asteroid impacts and mass extinctions
• Hominid evolution
• Ethics of artificial life
•
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The K-T boundary
Where we left off on our discussion of evolution of life on
Earth…
1. Eukaryotes evolved with symbiont prokaryote-organelles (2.1 b.y.a.);
2. Oxygen levels and other stresses had encouraged the Cambrian
Explosion of multicellular life (545 m.y.a.);
Biodiversity was extraordinary; the Burgess Creek Shale (post
Cambrian Explosion) shows arthropods from about 25 subphyla, only
4 of which persist today;
3. Life invaded land (475 m.y.a.);
4. Organisms developed the resistance to desiccation, and invaded the
land (400 m.y.a.);
5. Dinosaurs and mammals (245 m.y.a.).
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The K-T boundary
245 MYA, terrestrial biodiversity was high.
65 MYA, a major extinction event occurred on a global basis, at the end of the
Cretaceous Period, and beginning of the Tertiary Period.
Examples of effects:
Heavy losses:
Moderate losses:
Microbes: significant losses
Fish: only 10-20% losses
Marine inverts: 60% losses (genera)
Fungi: benefits!
Terrestrial inverts: major losses
Amphibians: minor losses
Terrestrial plants: huge losses
Reptiles: minor losses
Dinosaurs: extinct
Summary:
Ancestral birds: heavy losses
Plants and animals: 75% species loss
Mammals: moderate losses
Plant and animal kill: 99% by individual!
What had happened?
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K-T boundary characteristics
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Global in occurrence;
High in iridium and other rare metals (osmium, gold, etc);
Quartz in layer shows shock characteristics (high P, T);
It contains rock droplets that were once molten;
Its carbon layers suggest soot once occurred at a global scale.
Evidence suggests a gigantic meteoric impact
– Impact site: Yucatán Peninsula (200 km Chicxulub crater);
– Object a comet or asteroid 10 km in diameter;
– 100,000,000 megaton bomb (most massive human bomb was 50
megatons);
– Glowing debris on global scale;
– Global tsunami events;
– Months of smoke and ash, resulting in global winter;
– Subsequent possible greenhouse phase;
– Possible oceanic poisoning by nitrites.
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The big five mass extinctions
Ordovician-Silurian periods
440-450 MYA: 2nd largest; claimed 27% (families), 57% (genera).
Likely due to climate changes; not an impact.
Late Devonian period
360-375 MYA: Part of a series, claimed 19% (families), 50%
(genera), 70% (species). Instigated the arrival of amphibians.
Permian-Triassic periods
251 MYA: Largest; 57% (families), 83% (genera). Opened the way
for dinosaurs by removing amphibians and mammal-like reptiles.
Triassic-Jurassic periods
205 MYA: 23% (families), 48% (genera).
Cretaceous-Tertiary periods
65 MYA: 75% (species).
Current times
1900s to 2100: 50% (species). Caused by humans.
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The extinction that takes us out
Causes:
More asteroids/comets
Supernovae
Ecological collapse
Magnetic field reversals
Gamma-ray bursts
Global volcanism
What about the next impact event?
Global kill rate: ???: ??% (families), ??% (genera).
Our space and military programs would be unable to respond effectively.
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Hominid evolution
We now take the audacious step of applying the
same techniques throughout the scientific
process—the techniques that have created
vaccines, ipods, and spacecraft—and study the
evolution of our own species.
Some basic misconceptions on (hominid) evolution
– “It’s just a theory;”
– There are no missing links;
– We did not evolve from monkeys, orangutans, gorillas,
chimpanzees, or bonobos;
– Anthropologists are not in huge disagreement on the basic
concepts of biological evolution (Project Steve).
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Hominid evolution
An extensive record now exists of the development of humans over
the last several million years. There are many players, and new
fossils are being discovered frequently.
Most new fossils are simply repeat findings of previously known
hominids.
Some fossil Australopithecus and Homo species
T1, A. africanus, 2.6 My
T2, A. africanus, 2.5 My
T3, H. habilis, 1.9 My
T4, H. habilis, 1.8 My
T5, H. rudolfensis, 1.8 My
T6, H. erectus, 1.75 My
B1, H. ergaster (early H. erectus), 1.75 My
B2, H. heidelbergensis, 300,000 – 125,000 y
B3, H. sapiens neanderthalensis, 70,000 y
B4, H. sapiens neanderthalensis, 60,000 y
B5, H. sapiens neanderthalensis, 45,000 y
B6, H. sapiens sapiens, Cro-Magnon, 30,000 y
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We are all Africans
The prevailing (but not only theory) is that while the Earth has had a
number of species of hominids, three entities were widespread until
recently:
H. sapiens neanderthalensis: Europe
H. erectus: Asia
H. sapiens: Africa
It seems that Homo sapiens sapiens
emigrated from Africa, and displaced
the other species/subspecies.
Note: we did not evolve from existing
apes!
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Critical future mileposts in our evolution
Cultural evolution modifies evolutionary processes
Rise of agriculture;
Rise of easy transportation modifies gene flow;
Rate of cultural evolution dwarfs biological evolution.
Technological evolution rules evolutionary processes
Genetic engineering of plants and lower organisms commonplace;
Creation of artificial life in progress (Craig Venter’s Mycoplasma mycoides);
2014 insertion of dNaM-d5SICS (called “XY”) artificial base pair into E. coli;
Genetic engineering of humans is inevitable
Ilya Ivanov inseminated female chimps with human
sperm in 1927.
He prepared to inseminate five human females with
orangutan sperm in 1929.
He was interrupted only by changes in Soviet politics.
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Critical future mileposts in our evolution
Impending crises approach (we shall see)
– Resource exhaustion?
– Technological singularity?
Moore’s law—the # of transistors on a chip doubles every two
years.
When CAD-facilitated computer construction reaches a point
comparable to human intelligence, machine evolution will exceed
human evolution.
And we all know what that means…
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