614
17 Life in the Universe
The above three conditions are sufficient. This can be shown by computer
modeling. Physical modeling in an experimental laboratory is more difficult, as
the critical step of evolving code, within an encapsulated life form, to hold the
information need for replication, takes a long time in human lifespans.
Modeling shows that the steps to life occur with time sequencing of ordering
and the formation of complexity in spurts and jumps. 1 Spurts occur when a ‘door’
opens with the right combination of catalysts and synthesizing pathways, so that
the production of organized subsystems dramatically increases. Starting with liquid
water and basic elements present on the Earth, the organic building blocks naturally
form in the soup. As we have seen, the ordering of subsystems in an open system
(the soup) is a natural and even expected process as heat energy is released to the
environment. Experiments of the type of Miller-Urey in 1952 2 using mixtures of
carbon dioxide, methane, ammonia, and liquid water, together with electric sparks,
amply demonstrate how one can get organic molecules in short order, including
all the amino acids. About 3.6 billion years ago, favorable conditions would have
existed within certain water pools on the surface of the Earth, and near sea vents at
the bottom in the ocean. The next step on the Earth is the linking of monomers, such
as amino acids, to make polymers, such as proteins, and the linking of nucleotides
to make ribonucleic acid chains. The linking process of nucleotides is catalyzed
naturally on some rock crystalline surfaces.
The following step probably took eons, but at some point in time, the first RNA
molecule formed which contained the coding to make replication catalysts. This was
a watershed event, since such a molecule could then reproduce copiously in a soup
of nucleotides. Variability and mutability in structure made competition possible,
and evolution followed.
We still have open questions regarding the minimal requirements for life to form.
The life-forming materials must have some entities which can form bonds with
others. Those bonded systems must be able to bond with a multitude of entities in
order to contain the instructions for replication. They also must be able to synthesize
their own structure and any auxiliary catalysts and other functional units that have
evolved, using the surrounding environmental material (‘food stuff’). There must
be a source of energy capable of breaking typical bonds perhaps with the help of a
catalyst. The energy released as kinetic motion must have a way of being dissipated.
Can life exist with only carbon, hydrogen, and oxygen as the material elements, and
no others?
For life on Earth, ‘CHOPS-N-things’ (Carbon, Hydrogen, Oxygen, Phosphorus,
Sulfur, Nitrogen) started us off. 3 The flow of solar energy that amounts to 240 W/m 2
1 Spurts also characterize ‘thresholds’ in ordering theory (see Chap. 15). For life systems, the
sequence of spurts and lulls is called ‘punctuated evolution’.
2 Stanley L. Miller, Production of Amino Acids Under Possible Primitive Earth Conditions, Science
117:3046, 528–529 (1953); Stanlely L. Miller and Harold C. Urey, Organic Compound Synthesis
on the Primitive Earth, Science 130:3370, 245–251 (1959).
3 More than half of the dry weight of a biological cell is carbon.
17 Life in the Universe
The above three conditions are sufficient. This can be shown by computer
modeling. Physical modeling in an experimental laboratory is more difficult, as
the critical step of evolving code, within an encapsulated life form, to hold the
information need for replication, takes a long time in human lifespans.
Modeling shows that the steps to life occur with time sequencing of ordering
and the formation of complexity in spurts and jumps. 1 Spurts occur when a ‘door’
opens with the right combination of catalysts and synthesizing pathways, so that
the production of organized subsystems dramatically increases. Starting with liquid
water and basic elements present on the Earth, the organic building blocks naturally
form in the soup. As we have seen, the ordering of subsystems in an open system
(the soup) is a natural and even expected process as heat energy is released to the
environment. Experiments of the type of Miller-Urey in 1952 2 using mixtures of
carbon dioxide, methane, ammonia, and liquid water, together with electric sparks,
amply demonstrate how one can get organic molecules in short order, including
all the amino acids. About 3.6 billion years ago, favorable conditions would have
existed within certain water pools on the surface of the Earth, and near sea vents at
the bottom in the ocean. The next step on the Earth is the linking of monomers, such
as amino acids, to make polymers, such as proteins, and the linking of nucleotides
to make ribonucleic acid chains. The linking process of nucleotides is catalyzed
naturally on some rock crystalline surfaces.
The following step probably took eons, but at some point in time, the first RNA
molecule formed which contained the coding to make replication catalysts. This was
a watershed event, since such a molecule could then reproduce copiously in a soup
of nucleotides. Variability and mutability in structure made competition possible,
and evolution followed.
We still have open questions regarding the minimal requirements for life to form.
The life-forming materials must have some entities which can form bonds with
others. Those bonded systems must be able to bond with a multitude of entities in
order to contain the instructions for replication. They also must be able to synthesize
their own structure and any auxiliary catalysts and other functional units that have
evolved, using the surrounding environmental material (‘food stuff’). There must
be a source of energy capable of breaking typical bonds perhaps with the help of a
catalyst. The energy released as kinetic motion must have a way of being dissipated.
Can life exist with only carbon, hydrogen, and oxygen as the material elements, and
no others?
For life on Earth, ‘CHOPS-N-things’ (Carbon, Hydrogen, Oxygen, Phosphorus,
Sulfur, Nitrogen) started us off. 3 The flow of solar energy that amounts to 240 W/m 2
1 Spurts also characterize ‘thresholds’ in ordering theory (see Chap. 15). For life systems, the
sequence of spurts and lulls is called ‘punctuated evolution’.
2 Stanley L. Miller, Production of Amino Acids Under Possible Primitive Earth Conditions, Science
117:3046, 528–529 (1953); Stanlely L. Miller and Harold C. Urey, Organic Compound Synthesis
on the Primitive Earth, Science 130:3370, 245–251 (1959).
3 More than half of the dry weight of a biological cell is carbon.