2. Dynamical coexistence of molecules Eörs Szathmáry Collegium Budapest (Institute for Advanced Study)

3. The major transitions (1995) * * * * * These transitions are regarded to be ‘difficult’

4. Difficulty of a transition Selection limited (special environment) Pre-emption: first comer  selective overkill Variation-limited: improbable series of rare variations (genetic code, eukaryotic nucleocytoplasm, etc.)

5. Difficult transitions are ‘unique’ Operational definition: all organisms sharing the trait go back to a common ancestor after the transition These unique transitions are usually irreversible (no cell without a genetic code, no bacterium derived from a eukaryote can be found today)

6. A common theme: origin of higher levels of evolution hereditary traits affecting survival and/or reproduction 1.multiplication 2.heredity 3.variation

7. Increase in complexity (a)Duplication and divergence (b)‘symbiosis’ (c)epigenesis

8. Egalitarian and fraternal major transitions (Queller, 1997)

9. The formose ‘reaction’: non- informational replication formaldehyd e glycolaldehyde autocatalysi s Butlerow, 1861

10. Von Kiedrowski’s replicator

11. Classification of replicators Limited heredity Unlimited heredity Holisticformose ModularVon Kiedrowski genes Limited(# of individuals) >,  (# of types) Umlimited(# of individuals) << (# of types)

12. Eigen’s paradox (1971) Early replication must have been error- prone Error threshold sets the limit of maximal genome size to <100 nucleotides Not enough for several genes Unlinked genes will compete Genome collapses Resolution???

13. Molecular hypercycle (Eigen, 1971) autocatalysis heterocatalytic aid

14. Parasites in the hypercycle (Maynard Smith, 1979) parasite short circuit

15. Population structure is necessary! Good-bye to the well-stirred flow reactor Adhesion to surface or compartmentation Hypercycles (with more than 4 members) spiral on the surface and resist parasites, BUT Are not resistant to short-circuits Collapse if the adhesive surface is patchy Only compartmentation saves them

16. The stochastic corrector model for compartmentation Szathmáry, E. & Demeter L. (1987) Group selection of early replicators and the origin of life. J. theor Biol. 128, 463-486. Grey, D., Hutson, V. & Szathmáry, E. (1995) A re-examination of the stochastic corrector model. Proc. R. Soc. Lond. B 262, 29-35.

17. The stochastic corrector model (1986, ’87, ’95, 2002) metabolic gene replicas e membrane

18. Dynamics of the SC model Independently reassorting genes Selection for optimal gene composition between compartments Competition among genes within the same compartment Stochasticity in replication and fission generates variation on which natural selection acts A stationary compartment population emerges

19. Group selection of early replicators Many more compartments than templates within any compartment No migration (fusion) between compartments Each compartment has only one parent Group selection is very efficient Selection for replication synchrony

20. Bubbles and permeability We do not know where lipids able to form membranes had come from!!!

21. A ‘metabolic’ system on the surface (2000)

22. A cellular automaton simulation Reaction: template replication Diffusion (Toffoli- Margolus algorithm) Metabolic neighbourhood respected Metabolic Replication Grey sites: neighbourhood Black: empty site X: potential mothers

23. Parasite on metabolism Parasites do not kill the system Can be selected for to perform useful function

24. Nature 420, 360-363 (2002).

25. Maximum as a function of molecule length Target and replicase efficiency Copying fidelity Trade-off among all three traits: worst case

26. Evolution of replicases on the rocks All functions coevolve and improve despite the tradeoffs Increased diffusion destroys the system Reciprocal altruism on the rocks

27. ‘Stationary’ population parasites efficient replicases