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Care to draw a line where nature starts and finishes?
Human beings are part of nature. If something is designed by
human beings, it automatically was created as part of nature. So there
is never a sharp line between "designed" and "formed."
Even when a human beings has directly assembled an artifact,
the human itself is the result of an undirected process.
As an example, in the current time human beings are always put
together by undirected processes. The process by which an embryo grows
is undirected. Unlike the watch, there is never a time that one could
say, "Ahaa, that section of the embryo was directly put together by a
deity." So the "human artifact" was created by an intentional
purpose, which was originally formed through an undirected process.
Whether the first step is intentional or undirected is not a
1. Panspermia: is the hypothesis that "seeds" of life exist already in
the Universe, that life on Earth may have originated through these
"seeds", and that they may deliver or have delivered life to other
2. Exogenesis: is a more limited hypothesis that proposes life on
Earth was transferred from elsewhere in the Universe but makes no
prediction about how widespread it is. Because the term "panspermia"
is more well-known, it tends to be used in reference to what would
properly be called exogenesis.
3. Directed panspermia: During the 1960s, Crick became concerned with
the origins of the genetic code. In 1966, Crick took the place of
Leslie Orgel at a meeting where Orgel was to talk about the origin of
life. Crick speculated about possible stages by which an initially
simple code with a few amino acid types might have evolved into the
more complex code used by existing organisms. At that time, everyone
thought of proteins as the only kind of enzymes and ribozymes had not
yet been found. Many molecular biologists were puzzled by the problem
of the origin of a protein replicating system that is as complex as
that which exists in organisms currently inhabiting Earth. In the
early 1970s, Crick and Orgel further speculated about the possibility
that the production of living systems from molecules may have been a
very rare event in the universe, but once it had developed it could be
spread by intelligent life forms using space travel technology, a
process they called “Directed Panspermia”. In a retrospective
article, Crick and Orgel noted that they had been overly
pessimistic about the chances of abiogenesis on Earth when they had
assumed that some kind of self-replicating protein system was the
molecular origin of life. Now it is easier to imagine an RNA world and
the origin of life in the form of some self-replicating polymer
Abiogenesis (Greek a-bio-genesis, "non biological origins") is the
formation of life from non-living matter. Today the term is primarily
used to refer to hypotheses about the chemical origin of life, such as
from a 'primeval soup' or in the vicinity of hydrothermal vents, and
most probably through a number of intermediate steps, such as non-
living but self-replicating molecules (biopoiesis). The current models
of abiogenesis are still being scientifically tested.
In the natural sciences, abiogenesis, the question of the origin of
life, is the study of how life on Earth might have emerged from non-
life sometime between 4.4 billion years ago, when liquid water first
flowed on the Earth, and 2.7 billion years ago when the earliest
incontrovertible evidence of life is found in the form of stable
There is no truly "standard model" of the origin of life. But most
currently accepted models build in one way or another upon a number of
discoveries about the origin of molecular and cellular components for
life, which are listed in a rough order of postulated emergence:
Plausible pre-biotic conditions result in the creation of certain
basic small molecules (monomers) of life, such as amino acids. This
was demonstrated in the Miller-Urey experiment by Stanley L. Miller
and Harold C. Urey in 1953.
Phospholipids (of an appropriate length) can spontaneously form lipid
bilayers, a basic component of the cell membrane.
The polymerization of nucleotides into random RNA molecules might have
resulted in self-replicating ribozymes (RNA world hypothesis).
Selection pressures for catalytic efficiency and diversity result in
ribozymes which catalyse peptidyl transfer (hence formation of small
proteins), since oligopeptides complex with RNA to form better
catalysts. Thus the first ribosome is born, and protein synthesis
becomes more prevalent.
Proteins outcompete ribozymes in catalytic ability, and therefore
become the dominant biopolymer. Nucleic acids are restricted to
predominantly genomic use.
RNA world hypothesis states that RNA was, before the emergence of the
first cell, the dominant, and probably the only, form of life. The
phrase "The RNA World" was first used by Walter Gilbert in 1986.
This hypothesis is supported by RNA's ability to participate in the
storage, transmission, and duplication of genetic information,
similarly to DNA, coupled with its ability to act as a ribozyme
(similar to an enzyme), catalyzing certain reactions. From the point
of view of reproduction, molecules exist for two basic purposes: self-
replication and catalysis assisting self-replication. DNA is capable
of self-replication, but only assisted by proteins. Proteins are
excellent catalysts, but fail to catalyze processes complex enough to
recreate themselves, individually. RNA is capable of both catalysis
and self-replication. [My favorote theory]