The Selfish Gene Chapter 2 by Richard
Dawkins the Replicators. In this chapter Dawkins uses Darwin's theory to explain
how simplicity can change into complexity, that is, how simple unordered
atoms can group themselves into complex patterns and end up as human beings.
Dawkins states that Darwin's theory is the only feasible scientific explanation
currently available and may explain how the process of evolution through natural
selection contributed to the creation of a special molecule called the Replicator.
Darwin's survival the fittest is a special case of what can be called the
Law of Survival of the Stables. The universe is populated by stable things.
Stable things are collections of atoms that last long enough to be worth naming.
Dawkins gives some examples such as rocks, galaxies, ocean waves as stable
patterns of atoms, and hemoglobin molecules as more complex
configurations. Complex atoms are being formed all over the universe since the Big
Bang initiated the universe. The simplest example of natural
selection is when random groups of atoms in the presence of energy falls into
stable patterns and it tends to stay that way.
Unstable groups of atoms tend to be short-lived and therefore rejected
through natural selection. However, this random process in slow
building of molecules is not enough to explain the existence of humans. We can
start by looking at the chemical conditions during the early days of
Earth before life began. We speculate that it is plausible that water, carbon
dioxide, methane, and ammonia would have been present during the early days of Earth
as we know they are currently present in other planets in our solar system.
Chemists that put these substances together and subject them to sources of
energy such as UV or electric sparks, in trying to artificially recreate
primordial lightning, found that after a few weeks, a weak brown soup containing
amino acids start to form. Previous to these experiments, amino acids were
thought to be a sign of the presence of life. Similar experiments have yielded
purine and pyrimidine, building blocks of the genetic molecule DNA.
This primeval soup would have been made around three to four thousand million
years ago, floating in the seas and form large
molecules. At some point, a special molecule called a replicator would have been
formed by accident. Dawkins states that this replicator molecule was extraordinary
not because of its size or complexity, but because it could recreate
copies of itself. The likelihood of this happening was
very improbable if we consider the lifetime of human beings, but becomes
more probable if we consider this across hundreds of millions of years. Dawkins
argues that replicators can be thought of like a mould or template.
As a mould, it would be a large molecule consisting of chains of building blocks
that attracted other building blocks available in the primeval soup. The
building blocks that are attached in this way would automatically arrange in a
sequence that mimics that of the replicator and therefore creates a copy.
The other possibility is that each building block had an affinity not for
its own kind but reciprocally for another kind. The replicator would then
act like a template, not for an identical copy, but a kind of negative copy that
would remake the exact copy of the original.
We do not know if the original replicator was positive negative (a
template) or positive positive (a mould) but modern replicators (the DNA) used positive
negative replication. The new replicators spread its copies rapidly through the sea
and made other larger molecules more rare. With a large population of identical
replicas, however, mistakes in the copying process will happen. Like copying books
by hand before the invention of the printing press,
'first generation' mistakes usually do not distort the meaning. However, copying
copies of copies of copies then introduces errors that start to become
more cumulative and serious. Although we do not know how accurately the original
replicator molecules made their copies, modern DNA molecules show a high
fidelity but sometimes still made mistakes.
It is these mistakes that makes evolution possible. Due to the errors, soon the primeval
soup became filled with non-identical replicas, but some were descended from
the same ancestors. We can assume some were more inherently stable than others
and had better longevity. Replicators with the property of high longevity
tended to become more numerous and hence there will be an evolutionary trend
towards replicators with greater longevity. Secondly, the speed of
replication, known as, fecundity would also make replicators of one kind more
numerous than others and therefore replicators would trend towards higher
fecundity. Thirdly, replicators with higher accuracy,
known as copying fidelity, would be positively selected as well, given if the
frequency of mistakes were too high, the replicators had a high chance of
producing unstable children and therefore losing them. Dawkins states that this
may be paradoxical because evolution relies on errors to evolve but argues
that nothing actually wants to evolve. Evolution is something that happens
despite the efforts of replicators to prevent it from happening. So if you were
to take a sample of the primeval soup at two different times, say millions of
years apart, there should be a larger proportion of varieties with higher
longevity, fecundity, and copying- fidelity, in the later sample than the
earlier one. Whether we call these original replicator molecules 'living'
things, Dawkins warned that words are only tools
for our use and whether they were living or not, we can assume they were the
ancestors of life. As a primeval soup cannot infinitely
produce replicated molecules due to finite resources, competition becomes an
important factor in survival. Miscopying that created higher or greater
stability, or allowed a way to reduce the stability of rivals was automatically
preserved and multiplied. For example, the ability to break up rival molecules
would allow molecule to obtain food and remove competing rivals. Other
replicators found ways to protect themselves chemically or by building
protective coats of physical protein walls around themselves. This may be how the
first living cell was formed. Replicators that survived built 'survival machines'
for themselves to live in, which got bigger and more elaborate. The process
was cumulative and progressive. After about four thousand million years,
replicators now live in huge colonies, safe inside large robotic machines -
inside different species. The replicators created us and so
preservation is the ultimate rationale for their existence. These replicators
are called genes and we (humans, animals, plants, bacteria, and viruses) are their
survival machines.
