You may have heard of Alan Turing, father
of computer science and the mathematical genius
who cracked the German Enigma Code during
World War II -- a feat that Winston Churchill
once remarked was “the secret weapon that
won the war.”
But what you probably didn’t know was that
during his short lifetime, Alan Turing also
proposed a theory to help explain a series
of patterns that recur over and over again
throughout the natural world -- like the spherical
organization of cells in an embryo, the spiral
arrangement of petals on a flower, the whorled
tentacle pattern of a Hydra, the waves on
a sand dune, the spots on a leopard and even
the stripes on a zebra.
Turing’s desire to understand nature’s
recurring patterns stemmed from his fascination
with Embryology.
Turing wanted to know how the small, uniform
ball of cells in an embryo could differentiate
and morph into a fully formed, complex being.
His hunch was that there had to be some mathematical
principle underpinning the recurring patterns
in an embryo’s development.
So in 1952, Turing published a paper called
“The Chemical Basis of Morphogenesis”.
Within it, he proposed that the diversity
of patterns we see in nature can be explained
by a mathematical model, called the “reaction-diffusion
system”.
Essentially the system can be broken down
like this: let’s say we have two identical
cells within an embryo.
In the mix are two chemicals that can either
activate or inhibit a specific reaction within
an embryo’s cells.
Turing called these “morphogens.”
As these morphogens diffuse through the embryo
they causing the cells around them to transform,
ultimately creating patterns like spots, stripes,
spirals, hexagons and whorls.
But this is just one example of the “reaction-diffusion
system” at work.
Morphogens can really be any two opposing
components that work together to stop and
start a reaction, like chemicals, genes or
proteins.
Morphogens can really be any two chemical
substances that work together to stop and
start a reaction, like hormones, proteins
or acids.
And changing the rate at which these components
interact, diffuse and decay determines the
way those elemental patterns like waves, spots
and stripes appear.
Today, many theoretical biologists and mathematicians
believe that Turing's system could also be
applied to the patterns found in the vegetation
on a landscape, weather systems, and even
to the formation of galaxies.
Sadly, Turing never found out whether his
theory was right.
In an age of intolerance, he took his own
life in 1954, following a conviction for “gross
indecency”, the charge for being openly
gay.
And for a long time afterward his ambitious
model was forgotten.
But in the sixty years that have passed, some
experimental data has to emerged to prove
that Turing really was onto something.
Perhaps the biggest breakthrough to date is
a 2012 study that applied Turing’s model
to the formation of digits in the paws of
mouse embryos.
It turns out that of digits are, on a fundamental
level, a series of stripes.
During the early stages of development within
an embryo, the paw or hand is a continuous
plate of tissue.
But over time, the cells change to either
form digits, or to die and create the spaces
between them.
What researchers found was that the entire
process fit the reaction-diffusion system
proposed by Turing.
actually conducted by three morphogens - which
in this case were three genes.
In this case, two genes controlled the production
of morphogens that formed digits, while a
third gene controlled the production of morphogens
that caused cell death, forming the gaps between
digits.
In other words, those three genetic pathways,
working in opposition to each other, create
the “stripes” that are digits and gaps.
What researchers called, the perfect example
of Turing’s “reaction-diffusion system”.
Of course, more research is needed to determine
whether Turing’s model could really be applied
to all the patterns that we see in the natural
world.
But at the very least, Alan Turing should
be remembered as a mathematically visionary
who changed the way we see our world.
Another trailblazing mathematician called
Ada Lovelace, became the world’s first computer
programmer.
Watch this episode to learn more about how
Ada is partly responsible for all the amazing
computer tech we rely on today.
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