Origins and Early Evolution
of Life
Richard Vann
CBI 206/ANESTH 445
Physiology and Medicine of Extreme Environments
Spring 2013
1
Origin of Life Topics
• Who, when, what, where, how, why
• Discussion
2
Panspermia &
Spontaneous Generation
Anaximander
611-547 BC
Anaxagoras
500?-428 BC
Aristotle
384-322 BC
•Panspermia: life exists throughout the universe
•Spontaneous generation: life forms by the action
of the sun on the primordial terrestrial slime
3
Recipe for Mice:
Jan Baptista van Helmont (1580-1644)
• Put a soiled shirt and grains of
wheat in a jar and let them
ferment
• Mice form after 21 days
• No experimental evidence
provided
4
Friedrich Wöhler & Urea (1828)
• Organic and non-living compounds are different
(“élan vital, life force, will-to-live”)
• Wöhler made urea by heating
ammonium cyanate
• "I can no longer, so to speak, hold
my chemical water and must tell
you that I can make urea without
needing a kidney, whether of
man or dog."
• A founder of organic chemistry
5
Death of Spontaneous Generation:
Louis Pasteur (1859)
• Living systems arise biotically from other living systems
6
Charles Darwin (1871)
“But if (& oh what a big if) we
could conceive in some warm
little pond with all sorts of
ammonia & phosphoric salts, light, heat, electricity, etc.
present, that a protein
compound was chemically
formed, ready to undergo still
more complex changes …”
- letter to Joseph Hooker7
Aleksandr Oparin (1924)
•Early atmosphere was strongly
reducing
•CH4, NH3, H2O , H2 (no O2)
•Sunlight reacted with non-living
chemicals in the “primeval soup”
•Unique, abiogenic, spontaneous
generation of life
•No difference between a living
organism and lifeless matter
8
J.B.S. Haldane (1929)
“When ultra-violet light acts on a
mixture of water, carbon dioxide and
ammonia, a vast variety of organic
substances are made, including
sugars and apparently some of the
materials from which proteins are
built up … [B]efore the origin of life
they must have accumulated till the
primitive oceans reached the
consistency of hot dilute soup.”
9
Harold Urey
1893-1981
Stanley Miller
1930-2007
10
Miller-Urey Ocean-Atmosphere (1953)
11
Miller (1953). Production of amino acids under
possible primitive Earth conditions. Science 117: 528.
12
Space
• Radio astronomy found evidence of organic
molecules on space dust
• Laboratory simulations of deep space created
organic molecules
• Collisions of comets with primitive Earth
• Murchison meteorite in Australia 1969
contained organic molecules
13
Exogenesis and Mars
• Mars may have been habitable a
billion years before Earth
• A meteorite from Mars recovered
in 1984 was claimed to contain
fossil life but this is disputed
• The question of exogenesis from
Mars to Earth is unresolved 14
Hydrothermal Volcanic Vents
DSV Alvin (1977)
Giant Clams
Hydrothermal vents
Tube Worms
15
Corliss, Baross & Hoffman. 1981. An hypothesis concerning
the relationship between submarine hot springs and the
origin of life on Earth. Oceanolgica Acta 4 (Suppl): 59-69.
16
Deep, Hot Biosphere
Yellowstone (1966)
Rock-Eating Bacteria
Thermophiles
Laboratory Simulations
• Reactants: N2, CO2, S, Fe
• Minerals: Fe-S, Ni-S
• Products: NH3, amino acids,
peptide bonds, C-fixation Fecomplexes
17
Origin of Primordial Molecules
- Deamer (2002)
18
Timeline
~13.7 bya
~11.5
~4.6
~4.4
~4.4-3.9
~4.2-4.0
4.0-3.7
~3.5
~0.5
~1 mya
“Big Bang” (atomic evolution)
Supernovae & heavy elements
Sun, solar system & Earth
Oceans formed
Chemical evolution
Earliest life at hydrothermal vents?
Earliest life at sea level?
Earliest fossils (Apex chert, WestAus)
Organic evolution (‘naked genes’)
19
Social evolution (humans)
When was Earth Ready for Life?
- Schopf (2002)
Sterilizing Meteor Storms
Origin of
Sustained Life
Oldest Fossils:
Stromatolites
Success
of Life
4.5
Planetary
Birth
4.0 3.9
3.5
Billions of Years Ago (bya)
3.0
20
Life and the Atmosphere
STERILIZING
METEOR STORMS
CHEMICAL
EVOLUTION
OXYGEN
CATASTROPHE
SUSTAINED
LIFE
OLDEST FOSSILS:
STROMATOLITES
EUKARYOTES
O2
metab
BIF
21
3.9 – 3.5 bya
Time
Many
early
life
forms
(temperature, O2 Catastrophe
anaerobic,
radiation,
arsenic,
salt)
LUCA
Present
Biochemistry
(ATP,
Krebs cycle,
RNA, DNA)
22
NASA Definition of Life
• “A self-sustaining chemical system
capable of Darwinian evolution”
–Self-sustaining (energy production)
–Chemical system (cell membranes)
–Darwinian evolution (replication)
• What’s the driving force that makes
this system run?
23
Energy and Complexity
- Chaisson (2001)
Stars
Planets
Large animals
Human brain
Society
2 erg/g/sec
75
20,000
74,000
500,000
24
Sagaminopteron Ornatum
25
Thermodynamics
• 1st Law: energy is conserved, not created or
destroyed
– all forms of energy are inter-convertible
• 2nd Law: heat flows from higher to lower temp
– Energy conversions are never complete
• Some energy is always lost to the environment as wasted
heat (ΔQ)
– Entropy (S) = wasted heat divided by the
environmental temperature (ΔS=ΔQ/T)
• Entropy is generated with each energy conversion
• The entropy of a closed system always increases
• Entropy is “time’s arrow”
26
Entropy Generation Rate
- Silva (2008)
27
Entropy (S) and “Heat-Death”
Universe
∆Suniverse > 0
dS/dt > 0
Energy
Life
∆Slife = 0
• Life is
maintained by
energy input
from the
universe &
entropy export
to the universe
• Does time stop
when dS/dt=0?
28
How Did Early Life Get Energy?
• Heterotroph – the ‘premordial soup’ provided
high energy complex molecules that had been
abiotically synthesized (Oparin & Haldane).
– Modern heterotrophs eat other organisms.
• Autotroph – energy derived from oxidation of
ammonia to nitrous & nitric acid, sulfur to
sulfurate, iron to iron oxide, and methane to
carbon dioxide & hydrogen.
29
Reverse TCA Cycle
2 CO2 + 4 H2
no catalyst:
very slow
2 H2O + C2O2 (acetate)
30
Iron-Sulfur World
- Günter Wächtershäuser
• Life originated on mineral surfaces
near deep hydrothermal vents
(“primordial sandwich”)
• 1st cells were lipid bubbles on
mineral surfaces
• Metabolism predated genetics
with iron sulfides as energy source
(chemoautotrophs)
• Photoautotrophs evolved as
chemical energy was deleted
• Autocatalytic & self-replicating
metabolism
31
Thioester World
- de Duve
• Thioester bonds are high energy & played the
role of ATP in early life
• Thioesters are intermediates in the ancient
processes leading to ATP
• Thioesters evolved into ATP
32
Driving Force: Entropy & Probability
• Heat is molecular motion
• Most probable configuration has greatest entropy
Less probable (S1)
More probable (S2)
S1 < S 2
• Attractive & repulsive intermolecular forces
determine the most probable configuration
More probable (S4)
Less probable (S3)
S3 < S4
33
Simulation of Self-Assembly
http://complex.upf.es/~harold/lipid_world/index.html
Before self-assembly (low S)
After self-assembly (high S)
34
Self-Assembly of Liposomes
- Bangham (1961); Deamer (1997, 2002)
Murchinson
Meteorite
extract
Murchinson
Liposomes
35
Biological Self-Assembly
• Lipid bi-layer membranes
• Structure guided by attractive & repulsive
forces (“lock-and-key”)
Antibody & antigen
Substrate & enzyme
36
Lipid World
- Serge, Ben-Eli, Deamer, Lancet (2000)
• Coacervates. 1-100 μ “proto-cells”
(Oparin 1932)
• Microspheres formed by heatpolymerized amino acids (Fox
1957)
• Murchison carbonaceous
meteorite (Deamer 1997).
Catalytic activity, replication, etc.
37
also proposed.
Tobacco Mosaic Virus (TMV)
• TMV self-assembly from separated protein & RNA
38
Darwinian Evolution
- Darwin (1959)
• Modified progeny of ‘A’
are better adapted to
the environment &
survive
• Subsequent generations
of ‘B’ – ‘F’ are
unmodified & become
extinct
• Track ‘A’s genealogy into
deep time to find LUCA
• Fossil record too limited
39
Systematics or Phylogenetics
- Haeckel (1866)
• Commonality of traits
– Animals – consumers
– Plants – producers
– Protists – reducers
Evolutionary
time
• Eucaryote* – nucleus, etc.
• Prokaryote* – no nucleus
* Stanier (1961)
[common
biochemistry]
• LUCA
• Fossils–no! Genetic code?
40
DNA Code
Cytosine
Guanine
Adenine
Thymine
41
RNA World
• RNA-based life predated DNA life
• RNA can act as its own catalyst (‘ribozyme’) so
proteins were unnecessary
• RNA evolved into DNA which is more stable
• Ribosomal RNA (rRNA) is a remnant of the
RNA World
• Problems: RNA chemically fragile, difficult to
synthesize abiotically, limited catalysis
42
Pre-RNA Worlds
• Alternative nucleic acids
– RNA precursors: threose nucleic acid (TNA), PNA
(peptose), GNA (glycol)
• PAH (Polycyclic Aromatic
Hydrocarbon) World
– PAHs are amphiphilic and might
self-organize in stacks as a
nucleic acid backbone
43
Clay World
- Cairns-Smith (1985)
• Proto-life was inorganic and existed on solid
surfaces such as clays
• Clays catalyzed formation of complex organic
molecules
• Clays acted as template for RNA self-assembly
and evolved into RNA
• Natural selection enhanced their replication
potential
44
Ribosome
- Woese (1981)
• Site of protein synthesis in all cells
– Functionally constant over time
• Ribosomal RNA 16S
– RNA “dictionaries” → phylogenetic trees
– Genotype → phenotype (cell membranes)
45
Phylogenetic Tree of Life (16S rRNA)
- Woese (1990)
‘progenotes’
46
Horizontal Gene Transfer (HGT)
• ‘Infective heredity’
• Endosymbiosis
– Mitochondria (1.7-2 bya)
– Plastids (1.5 bya)
• Antibiotic resistance
– Plasmids
• Viruses
47
Artificial HGT (Social Evolution)
- Craig Venter
• Sequence yeast cell genome (Myoplasma
mycoides)
• Synthesize M. mycoides genome from lab
chemicals
• Transplant synthetic genome into recipient cell
(M. capricolum)
• Test viability of synthetic cell
• Next find minimal viable synthetic genome
• Applications – bio-fuels, vaccines, drugs, etc.
48
• What are the limitations of the field?
• What came first: metabolism or replication?
• What would be the result if you could re-run
evolution again beginning from the Big Bang?
• What would be the result if you re-ran
evolution from the Big Bang 1,000 times?
• Is laboratory investigation of the creation of
some form of life valuable?
• If you were in charge of an origin of life lab,
where might you focus your efforts?
49