If you liked using the expression “you know, it’s a chicken and
egg problem”, then you would probably need to find an alternative for
expressing circular causality, because the chicken and egg conundrum is no
more. In fact, British scientists from
Warwick and Sheffield universities recently cracked it: it’s the chicken that
came first.
Well,
it’s probably a little more complicated than that, but the age-old riddle can now
be considered resolved. Because eggs can
be formed only with a protein molecule (called ovocleidin-17) found in chicken
ovaries. This means eggs have to be formed in chickens first. With the help of
supercomputers, the structure and function of this protein was determined. It
kick-starts crystallization of the egg shell by turning calcium carbonate into
calcite crystals. This can potentially help develop new materials , and stronger
artificial bones.
The
elucidation of the catch-22 puzzle came as a surprise to many, since eggs
existed before the chicken in the evolution of species. But here we are talking
of chicken eggs, not dinosaur eggs. The chicken and egg problem is not just cultural
vernacular, but has been a question that scientists and philosophers actually pondered
on, with ramifications about fundamental questions on life and its evolution.
Even in theology and creationism, the question has been hotly debated.
But the follow-up
question is where the chicken came from. Certainly not from across the road or through
the magic of creationism. It evolved. At one point from reptiles, that grew
wings to adapt. Evolution is basically
mutations in the genetic code. We have come a long way to understand life,
species and their origin – but still some questions evade us, and alternative
explanations, like “intelligent design” is often used to fill in the current
gaps. Let’s look at another chicken-and-egg mystery of nature: what came first,
DNA or proteins? But first, a quick primer on some basic biology.
Living systems
are made of basic building blocks called cells. A human being, for example, has
about ten trillions of them. The cell is a wonderful piece of machinery where
the basic processes of life occur. Let’s focus on two important constituents of
a cell: DNA and proteins. DNA stands for deoxyribonucleic acid. It is a
very long molecule, a long chain of building blocks
called nucleotides, of which there are four types: Adenine, Guanine, Cytosine
and Thymine, or simply A, G, C and T. In fact in DNA there are two chains (linked
in a long twisted ladder form) with every A in one chain is connected to a T in
the second, and every C is connected to a G. When the chains separate,
you have enough information to regenerate exact copies – and this is why
chickens procreate chickens, and you inherit your parents’ looks. The structure
of the DNA was the landmark discovery by Watson & Crick in 1953, which they
duly celebrated over beer in a pub in Cambridge, England because of their claim
to the “discovery of the secret of life”. Fifty years later, there was
cause for more celebration: the exact sequence of the 3 billion A-T or C-G
connections in the DNA of a human was deciphered. This code contains all
information about the human: from the color of the eye to the disposition to
believe in God or commit crime, some argue. These characteristics are encoded
by genes, which are pieces in the DNA code. The
human DNA is believed to contain about 20,000 genes, although this number is
constantly under revision.
The love affair between cryptography and life goes on.
The genes themselves encode something else: proteins. In fact, various short sequences
(of three nucleotides) encode another group of molecules called amino acids.
There are twenty of them that occur naturally. And specific sequences of amino
acids are specific proteins, like ovocleidin-17.
Proteins are molecules that underlie all activities in the cell and in life. Most
functions of the cell depend on proteins to perform them - including the
creation of proteins to begin with! In
fact, there are proteins (encoded in the DNA) that decode the message in the DNA
sequence (through a process called transcription) to replicate proteins. Which begs
the question: what comes first, the DNA that encodes all proteins? Or proteins
that read the DNA code?
This
is a (former) chicken and egg problem. It is also often used as evidence of “intelligent
design” that purports discontinuity in sequential evolution, where several
components have to simultaneously fuse together to create life as we know it. Nonetheless,
to many the lack of scientific rationalization hardly makes creationist “explanations”
valid.
Well, now the chicken and egg problem
does not seem to contradict Darwin’s evolution theory i.e. species change over
time by mutating their DNAs, with survival of the fittest variants. Our
national dodo bird for instance, was initially a dove/pigeon that on arrival in
Mauritius adapted over millions of years to an environment with no predators.
So, some argue that they traded their ability to fly for the capacity to store
larger amounts of fat that pull them through hard times: not that dumb after all,
thereby salvaging the much maligned reputation of our beloved bird as being a
stupid, overweight and lazy. The dodo is
now considered an evolutionary success; it adapted well to local
conditions, (just like its human counterparts I am tempted to add).
So, the dodo bird must
have preceded its egg. Given its newly acknowledged evolutionary superiority,
it would be interesting to find out the variant of the ovocleidin-17 protein in dodos that
helps the crystallization of its shell. This may be hard now since the dodo is extinct. So until we find a
way to reconstitute species from their DNA (like in Jurassic Park), “as dead as
the dodo” is one expression that is still alive and kicking for use.
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