toward a general theory of evolution addy pross department of chemistry, ben gurion university...
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Toward a General Theory of EvolutionToward a General Theory of Evolution
Addy Pross
Department of Chemistry, Ben Gurion UniversityBe’er Sheva, Israel
ILASOL - Dcember 25, 2011
How did life
emerge?
How to make
life?
What is life?
Chemistry-Biology Interface Chemistry-Biology Interface ProblematicProblematic
Still struggling to answer central life questions
General Theory of EvolutionGeneral Theory of Evolution
Based on the unique kinetic character of the replication reaction
Identifies a stability kind associated solely with replicating entities - dynamic kinetic stability
A. Pross (2003-11)
Attempts to extend and reformulate Darwinian thinking in chemical terms to help bridge between biological and chemical worlds.
Molecular ReplicationMolecular Replication
A + B + C + …..A + B + C + ….. T T Molecular Molecular
ReplicationReplication
Template mechanism
S. Spiegelman, 1967G. von Kiedrowski, 1986
L. Orgel, 1987 J. Rebek, 1994
M.R. Ghadiri, 1996G. F. Joyce, 1997
e.g., nucleic acids, peptides, synthetic molecules
Replication Reaction is Replication Reaction is AutocatalyticAutocatalytic
79 replication cycles would convert a single 79 replication cycles would convert a single molecule to a mole (molecule to a mole (227979 ~ 6. 10 ~ 6. 102323).).
a further 83 cycles would generate a mass a further 83 cycles would generate a mass equal to that of the earth, equal to that of the earth, 10102727gg!!
Replication is unsustainable
Autocatalysis - can exhibit exponential growth
T. Malthus, An Essay on the Principle of Population, 1798
Nature of StabilityNature of Stability
A system is stable if it is persistent ,unchanging over time.
Thermodynamic Stability – an inherent property of a chemical system
Kinetic Stability – depends on reaction rates and barrier heights
Dynamic Kinetic Stability - A stability kind associated solely with replicating entities.
A. Pross, J. Syst. Chem. 2011A. Pross, Chem. Eur. J. 2009
Dynamic Kinetic Stability (DKS)Dynamic Kinetic Stability (DKS)
dX/dt = kXM - gXdX/dt = kXM - gXX = replicator conc.X = replicator conc.
M = monomer conc.M = monomer conc.k,g = rate constants.k,g = rate constants.
Lotka, 1910Lotka, 1910
dX/dt = 0 would define a steady state steady state populationpopulation
If a replicating system is stable then its stability is of a dynamic kinetic kind
Replication is unsustainable, therefore for stability rate of replicator formation rate of decay ~=
Stability in ‘Regular’ and Stability in ‘Regular’ and Replicative WorldsReplicative Worlds
‘‘Regular’ chemical systems are stable Regular’ chemical systems are stable because they because they DO NOTDO NOT react. react.
Replicating chemical systems are stable Replicating chemical systems are stable (persistent) because they (persistent) because they DODO react – to make react – to make more of themselves!more of themselves!
DKS would apply to all stable replicating systems, biological and chemical.
A.Pross, Pure Appl. Chem. 2005
Selection Rules in ‘Regular’ Selection Rules in ‘Regular’ Chemical and Replicator WorldsChemical and Replicator Worlds
‘‘Regular’ Chemical WorldRegular’ Chemical World::
Thermodynamically Thermodynamically Thermodynamically Thermodynamically Less Stable Less Stable More Stable More Stable
Replicator WorldReplicator World::
Dynamic kineticallyDynamic kinetically Dynamic kinetically Dynamic kinetically Less Stable Less Stable More StableMore Stable
A. Pross, J. Syst. Chem. 2011A. Pross, Pure Appl. Chem. 2005
How Did Life EmergeHow Did Life Emerge??
Simple Simple LifeLife
ComplexComplex LifeLife
Biological Biological PhasePhase
ChemicalChemicalPhasePhase
DarwinianDarwinian theorytheory??
One single physicochemical process initiated by simple replicating entity
Process defined by drive toward greater DKS
Inanimate Inanimate matter matter
A. Pross, J. Syst. Chem. 2011
Evidence for Single ProcessEvidence for Single Process
Replication Mutation Selection EvolutionReplication Mutation Selection Evolution
Same pattern observed at chemical (molecular) levelSame pattern observed at chemical (molecular) levele.g., RNA oligomers in a test-tubee.g., RNA oligomers in a test-tube
S. Spiegelman et al., S. Spiegelman et al., PNASPNAS, 1967, 1967
D.P. Bartel, J.W. Szostak, D.P. Bartel, J.W. Szostak, ScienceScience, 1993, 1993M.C. Wright, G.F. Joyce, M.C. Wright, G.F. Joyce, ScienceScience, 1997, 1997
Both Both chemical chemical and and biologicalbiological phases phases exhibit similar underlying patternsexhibit similar underlying patterns
(1)(1) The essence of biology: The essence of biology:
Biological level:Biological level: prokaryotes evolved into eukaryotes prokaryotes evolved into eukaryotes single cells evolved into multi-cell organismssingle cells evolved into multi-cell organismsemergence of ecological networks emergence of ecological networks
ChemicalChemical (molecular) level:(molecular) level:emergence of cross-catalytic networksemergence of cross-catalytic networkse.g., e.g., self-replicating DNA oligomersself-replicating DNA oligomers
D. Sievers, G. D. Sievers, G. von Kiedrowski, Nature, 1994
(2)(2) ComplexificationComplexification
self-replicating peptides
M. R. Ghadiri et al., Nature, 1997 G. Ashkenasy et al., Chem. Eur. J, 2010
G.F. Joyce, T.A. Lincoln, Science, 2009
Complexification Enhances Complexification Enhances RNA ReplicationRNA Replication
Fast replication, self-sustained exponential growth
Slow replication, limited exponential growth
Complexification enhances replicating ability at the molecular level!
A’ + B’
A + B
Autocatalysis
Cross-catalysis
A + B TT
E
E’E
E’
Complexification PrincipleI’ll scratch your back if you’ll scratch mine….
Complexification enhances replicating ability at both chemical and biological levels - network formation.
Cooperation = Complexification
Unification of Chemical and Unification of Chemical and Biological PhasesBiological Phases
Simple Life
Complex Life
Chemical Chemical phasephase
Simple Replicating
System
One continuous process
BiologicalBiological phasephase
Low complexity High complexity
One process – one set of principles
Greater complexity is induced by the drive toward greater DKS
A. Pross, J. Syst. Chem. 2011
Darwinian ConceptsDarwinian Concepts Chemical ConceptsChemical Concepts natural selectionnatural selection
adaptationadaptation dynamic kinetic dynamic kinetic
stability (DKS) stability (DKS)
survival of the fittestsurvival of the fittest drive toward greater drive toward greater DKS DKS
Darwinian concepts firmly rooted in chemistry
A.Pross, J. Syst. Chem. 2011A.Pross, Chem. Eur. J. 2009
Darwinian conceptsDarwinian concepts -- Particular applications Particular applications of broader chemical conceptsof broader chemical concepts
kinetic selectionkinetic selection
fitness fitness
General Theory of EvolutionGeneral Theory of Evolution
Driving force - Driving force - towardtoward greatergreater DKSDKS
MechanismsMechanisms -- complexification complexification (primary) (primary)
- - selection selection (secondary)(secondary)
A. Pross, J. Syst. Chem. 2011
Extended theory embraces both biological and chemical systems
Evolutionary SequenceEvolutionary Sequence
Replication Mutation Selection EvolutionReplication Mutation Selection Evolution
Traditional Darwinian sequenceTraditional Darwinian sequence::
Replication Mutation ComplexificationReplication Mutation Complexification
New proposalNew proposal::
SelectionSelection EvolutionEvolution
Martin Nowak (2011): Cooperation – the third evolutionary principle in addition to mutation and selection
“Supercooperators” , 2011
Global Characteristics of Living Global Characteristics of Living SystemsSystems
Extraordinary complexity Extraordinary complexity Dynamic character Dynamic character Far-from-equilibrium stateFar-from-equilibrium state Teleonomy (purposeful nature)Teleonomy (purposeful nature) Homochiral characterHomochiral character DiversityDiversity
Can be understood through the DKS concept
A. Pross, J. Sys. Chem. 2011
Dynamic Kinetic Stability (DKS)Dynamic Kinetic Stability (DKS)
Dynamic Steady States Exist at Dynamic Steady States Exist at Various Levels of ComplexityVarious Levels of Complexity
At cell level At cell level twotwo levels of turnover levels of turnoverProtein degradation and re-synthesisProtein degradation and re-synthesis is a is a tightly regulated process. tightly regulated process.
intracellular protein intracellular protein tt1/2 1/2 == 11 mins - 48 hrs 11 mins - 48 hrs Hershko, Ciechanover & RoseHershko, Ciechanover & Rose (Nobel Prize, 2004) (Nobel Prize, 2004)
For molecular replicators there is For molecular replicators there is just just oneone level of turnover level of turnover
At the organismic level At the organismic level threethree levels of levels of turnoverturnover
Global Characteristics of Living Global Characteristics of Living SystemsSystems
Extraordinary complexity Extraordinary complexity Dynamic character Dynamic character Far-from-equilibrium stateFar-from-equilibrium state Teleonomy (purposeful nature)Teleonomy (purposeful nature) Homochiral characterHomochiral character DiversityDiversity
Can be understood through the DKS concept
A. Pross, J. Sys. Chem. 2011
A: A: In replicative world the stability that In replicative world the stability that counts is counts is dynamic kinetic stability (DKS)dynamic kinetic stability (DKS)..
How can How can highhigh stabilitystability of one kind lead to of one kind lead to low stability low stability of another kind?of another kind?
Q: Q: How could the evolutionary process How could the evolutionary process lead to the formation of lead to the formation of thermodynamically unstable systemsthermodynamically unstable systems??
A Key Step on Road to Complexity - A Key Step on Road to Complexity - Incorporating a Metabolic Capability Incorporating a Metabolic Capability
Metabolism = energy gathering capability
Non-Metabolic Metabolic Replicator Replicator
Dynamic Kinetically Dynamic Kinetically Dynamic Dynamic Kinetically Kinetically lessless stable stable moremore stable stable
N. Wagner, A.Pross, E.Tannenbaum, Biosystems, 2010
Metabolism is kinetically selected for
Consequences of MetabolismConsequences of Metabolism Metabolism (energy gathering) frees the
replicator from thermodynamic constraints.
The result: Thermodynamically unstable but dynamic kinetically stable replicating entities
With thermodynamic constraints eliminated, primary directive for chemical change becomes kinetic rather than thermodynamic.
The moment lifeThe moment life beganbegan……
Death – reversion to the thermodynamic world
Global Characteristics of Living Global Characteristics of Living SystemsSystems
Extraordinary complexity Extraordinary complexity Dynamic character Dynamic character Far-from-equilibrium stateFar-from-equilibrium state Teleonomy (purposeful nature)Teleonomy (purposeful nature) Homochiral characterHomochiral character DiversityDiversity
Can be understood through the DKS concept
A. Pross, J. Sys. Chem. 2011
Principle of Natural SelectionPrinciple of Natural Selection
Principle of DivergencePrinciple of Divergence
Darwin’s Two PrinciplesDarwin’s Two Principles
‘Regular’ (thermodynamic) Space
Topology of ‘Regular’ Chemical and Topology of ‘Regular’ Chemical and Replicator SpacesReplicator Spaces
Thermodynamic sink
Replicator (kinetic) Space
ConvergentConvergent DivergentDivergent
Topology of replicator space explains diversity
A. Pross, J. Syst. Chem. 2011
DKS clarifies Darwin’s Principle of Divergence
Implications of Different Implications of Different TopologiesTopologies
Regular systemsRegular systems::
History History inaccessibleinaccessible FutureFuture predictablepredictable
ReplicatorsReplicators::
History History accessibleaccessible Future Future unpredictableunpredictable
N. Wagner, A. Pross, Entropy 2011A. Pross, Pure Appl. Chem. 2005
Key ConclusionsKey ConclusionsDKS - the conceptual bridge between Chemistry
and Biology.
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• Unifies abiogenesis and biological evolution
• Integrates Darwinian theory into general chemical theory
• DKS – the driving force for evolution
• Explains life’s unusual characteristics
Life - an ever expanding dynamic network of chemical reactions derived from the replication reaction.
Prof. Emmanuel Tannenbaum – BGUProf. Emmanuel Tannenbaum – BGU Dr. Nathaniel Wagner – BGUDr. Nathaniel Wagner – BGU Dr. Nella Pross - BGUDr. Nella Pross - BGU
AcknowledgementsAcknowledgements