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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