From spotty leopards to stripy zebras, nature has no shortage of distinct patterns on animals and plants.
Now, the age-old question of how these patterns developed may have finally been solved.
Scientists have shown that the same physical process that helps remove dirt from laundry could play a role in how tropical fish get their colourful spots and stripes.
For their study, the team at the University of Colorado Boulder drew on the groundbreaking work of British computer pioneer Alan Turing, dating back more than 70 years.
They believe their findings could help develop new materials and even new drugs.
The age-old question of how the leopard got his spots and zebras earned their stripes may finally have been solved (stock image)
In 1952, before biologists discovered the double helix structure of DNA, Alan Turing proposed a bold theory of how animals got their patterns
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Benjamin Alessio, lead author of the study, said: ‘Many biological questions are fundamentally the same question: how do organisms develop complicated patterns and shapes when everything starts off from a spherical clump of cells?
‘Our work uses a simple physical and chemical mechanism to explain a complicated biological phenomenon.’
Biologists have previously shown that many animals evolved to have coat patterns to camouflage themselves or attract mates.
While genes encode pattern information such as the colour of a leopard’s spots, genetics alone do not explain where exactly the spots will develop.
In 1952, before biologists discovered the double helix structure of DNA, Alan Turing proposed a bold theory of how animals got their patterns.
Turing, who is widely considered to be the father of theoretical computer science and artificial intelligence, hypothesised that as tissues develop, they produce chemical agents.
Those agents diffuse through tissue in a process similar to adding milk to coffee.
While some of the agents react with each other, forming spots, others inhibit the spread and reaction of the agents, forming space between spots.
The study came about after Mr Alessio visited the Birch Aquarium in San Diego, where he was impressed by the sharpness of the boxfish’s intricate pattern
Turing’s theory suggested that instead of complex genetic processes, the simple reaction-diffusion model could be enough to explain the basics of biological pattern formation.
Dr Ankur Gupta, an author of the study, said: ‘Surely Turing’s mechanism can produce patterns, but diffusion doesn’t yield sharp patterns.’
As an example, Dr Gupta points to the fact that when milk diffuses in coffee, it flows in all directions with a fuzzy outline.
The study came about after Mr Alessio visited the Birch Aquarium in San Diego, where he was impressed by the sharpness of the boxfish’s intricate pattern.
It’s made of a purple dot surrounded by a distinct hexagonal yellow outline with thick black spacing in between.
Mr Alessio thought Turing’s theory alone would not be able to explain the sharp outlines of the hexagons.
But the pattern reminded him of computer simulations he had been conducting, where particles do form sharply defined stripes.
Mr Alessio, a member of the Gupta research group, wondered if the process – known as diffusiophoresis – plays a role in nature’s pattern formation.
Diffusiophoresis happens when a molecule moves through liquid in response to changes, such as differences in concentrations, and accelerates the movement of other types of molecules in the same environment.
The team ran a simulation of the purple and black hexagonal pattern seen on the ornate boxfish skin (left) using only the Turing equations. The computer produced a picture of blurry purple dots with a faint black outline (centre). Then the researchers modified the equations to incorporate diffusiophoresis. The result turned out to be much more similar to the bright and sharp bi-colour hexagonal pattern seen on the fish (right)
While it may seem like an obscure concept to non-scientists, the research team explained that it’s actually how laundry gets clean.
A recent study showed that rinsing soap-soaked clothes in clean water removes the dirt faster than rinsing soap-soaked clothes in soapy water.
That is because when soap diffuses out of the fabric into water with lower soap concentration, the movement of soap molecules draws out the dirt.
But when the clothes are put in soapy water, the lack of a difference in soap concentration causes the dirt to stay in place.
The movement of molecules during diffusiophoresis, as Dr Gupta and Mr Alessio observed in their simulations, always follows a clear trajectory and gives rise to patterns with sharp outlines.
To see if it may play a role in giving animals their vivid patterns, the team ran a simulation of the purple and black hexagonal pattern seen on the ornate boxfish skin using only the Turing equations.
The computer produced a picture of blurry purple dots with a faint black outline.
Then the researchers modified the equations to incorporate diffusiophoresis.
The result turned out to be much more similar to the bright and sharp bi-colour hexagonal pattern seen on the fish.
The team’s theory suggests that when chemical agents diffuse through tissue as Turing described, they also drag pigment-producing cells with them through diffusiophoresis – just like soap pulls dirt out of laundry.
The pigment cells form spots and stripes with a much sharper outline.
Decades after Turing proposed his seminal theory, scientists have used the mechanism to explain many other patterns in biology, such as the arrangement of hair follicles in mice and the ridges in the roof of the mouth of mammals.
Dr Gupta hopes the new study, and more research being conducted by his team, can also improve the understanding of pattern formation, inspiring scientists to develop innovative materials and even medicines.
He added: ‘Our findings emphasise diffusiophoresis may have been underappreciated in the field of pattern formation.
‘This work not only has the potential for applications in the fields of engineering and materials science but also opens up the opportunity to investigate the role of diffusiophoresis in biological processes, such as embryo formation and tumour formation.’
Who was Alan Turing? Pioneering scientist who helped crack Hitler’s enigma machine only to be convicted for homosexuality after WWII
Alan Turing (pictured) was a British mathematician best known for his work cracking the enigma code during the Second World War
Alan Turing was a British mathematician born on June 23, 1912 In Maida Vale, London, to father Julius, a civil servant, and mother Ethel, the daughter of a railway engineer.
His talents were recognised early on at school but he struggled with his teachers when he began boarding at Sherborne School aged 13 because he was too fixated on science.
Turing continued to excel at maths but his time at Sherborne was also rocked by the death of his close friend Christopher Morcom from tuberculosis. Morcom was described as Turing’s ‘first love’ and he remained close with his mother following his death, writing to her on Morcom’s birthday each year.
He then moved on to Cambridge where he studied at King’s College, graduating with a first class degree in mathematics.
During the Second World War, Turing was pivotal in cracking the Enigma codes used by the German military to encrypt their messages.
His work gave Allied leaders vital information about the movement and intentions of Hitler’s forces.
Historians credit the work of Turing and his fellow codebreakers at Bletchley Park in Buckinghamshire with shortening the war by up to two years, saving countless lives, and he was awarded an OBE in 1946 for his services.
Turing is also widely seen as the father of computer science and artificial intelligence due to his groundbreaking work in mathematics in the 1930s.
He was able to prove a ‘universal computing machine’ would be able to perform equations if they were presented as an algorithm – and had a paper published on the subject in 1936 in the Proceedings of the London Mathematical Society Journal when he was aged just 23.
But he was disgraced in 1952 when he was convicted for homosexual activity, which was illegal at the time and would not be decriminalised until 1967.
To avoid prison, Turing agreed to ‘chemical castration’ – hormonal treatment designed to reduce libido.
As well as physical and emotional damage, his conviction had led to the removal of his security clearance and meant he was no longer able to work for GCHQ, the successor to the Government Code and Cypher School, based at Bletchley Park.
Turing was awarded an OBE in 1946 for his codebreaking work at Bletchley Park, pictured, which is credited with ending World War II two years early
Then In 1954, aged 41, he died of cyanide poisoning. An inquest recorded a verdict of suicide, although his mother and others maintained that his death was accidental.
When his body was discovered, an apple laid half-eaten next to his bed. It was never tested for cyanide but it is speculated it was the source of the fatal dose.
Some more peculiar theories suggest Turing was ‘obsessed’ with fairytale Snow White and the Seven Dwarfs and his death was inspired by the poisoned apple in the story.
Following a public outcry over his treatment and conviction, the then Prime Minister Gordon Brown issued a public apology in 2009.
He then received a posthumous Royal pardon in 2014, only the fourth to be issued since the end of the Second World War.
It was requested by Justice Secretary Chris Grayling, who described Turing as a national hero who fell foul of the law because of his sexuality.
An e-petition demanding a pardon for Turing had previously received 37,404 signatures.
A 2017 law, that retroactively pardoned all men cautioned or convicted for homosexual acts under historical legislation, was named in his honour.
