Download The Origin and Maintenance of Life

The Origin and Maintenance of
Life
Nicolas Kosoy
Outline
• What is life?
– John Maynard Smith on Life and Evolution
• Why living systems are important to us?
• Conclusions
What is Life?
• John Maynard Smith-Origin of Life
– http://www.youtube.com/watch?v=JhXCl-nIOTc
Origin of Life (Theories, Oparin: 1924)
• Theory of Spontaneous Generation
– “Maggots in rotting meat … are generated
spontaneously from decaying materials”
• Theory of Panspermia
– Cosmozoa cast off by celestial bodies carried
germs of microorganisms
• Primordial Soup
Origin of Life (replication)
• Replication of molecules in the absence of
proteins
– How did it happen?
• Imagine a molecular quasi-species (replicating
RNA without recombination but with mutation,
leading to different traits)
– If mutation is very high, then population is a random
collection of sequences
– If mutation is low, the population would be centred
around optimal mutation
Hypercycles (Maynard-Smith, 1979)
• Replicate the
message GSTQ
• Assuming a
count of 5bits
per letter,
leading to 75
bits in total, a
max of 25 bits
per word and
an error of
1/50 per bit
Hypercycles (cont.)
• Organisation will then arise by gradual
differentiation of a single quasi-species into
two or more;
• Selection process will favour mutations
making the hypercycle more efficient
• Compartmentalization of hypecycles in
membranes
Characteristics of Life (Maynard-Smith ,
1999)
• Genotype and phenotype are clearly distinct,
separating replication from development;
• The genetic system is capable of transmitting an
indefinitely large number of different message;
• There is no one-to-one mapping between
particular nucleotides, codons or genes and
particular parts of the body;
• Heredity is digital and not analog;
• Development is symbolic
“It is tempting to argue that these features are
necessary for the evolution of complex
organisms, and will turn out to be true of any
that have evolved elsewhere in the universe. But
this may merely reflect the fact that we lack the
ability to imagine a world fundamentally
different from the one we know.” (MaynardSmith, 1999: 398)
Why living systems are important?
• The economy grows within the finite and non
growing ecosystem, there is an opportunity
cost to growth;
• The costs arise because the economy is a
dissipative structure sustained by a metabolic
flow from and back to the environment
– This flow, called “throughput”, begins with the
depletion of low-entropy useful resources from
the environment and ends with the return of highentropy polluting wastes (Daly, 2006)
Why…? (cont)
• If the throughput remains within the natural
capacity of the ecosystem to absorb wastes
and regenerate resources, then the scale of
the economy is considered “sustainable”;
– Nonrenewable resources cannot be exploited in a
sustainable- yield manner;
– Uncertainty about what exploitation levels
sustainable, gives rise to the “precautionary
principle”
Why…? (cont)
• As growth pushes us from an empty world to a
full world, the limiting factor in production will
increasingly become natural capital
• The identity of the limiting factor changes
from manmade to natural capital
– economizing efforts and policies must change
accordingly
– becomes more important to study the nature of
environmental goods and services
Conclusions
• Life is an evolutionary process taking place over
hundreds of millions of years and whose main
characteristics are function and natural selection;
• Information is passed from on generation to the
other, but there is no matching between the
information that passes and the information
exhibited by one generation;
• Life is the origin of the economic process,
degrading life also implies the degradation of
value
Conclusions
• Living systems define a hard limit to our social
metabolism;
• Non linearity and uncertainty are inherent
conditions of all living systems;
• Managing living systems does not mean
simplifying them but understanding the
relationships between variables and trade-offs
between outcomes.
Thank You