Alan Turing's theory of how limbs and fingers form in the womb finally proven

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Alan Turing's theory of how limbs and fingers form in the womb finally proven

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British mathematician Alan Turing is famed for designing the machines that cracked German military codes in the Second World War and for pioneering artificial intelligence.

But one of his lesser known theories saw him turn his hand to mathematical biology - and the conclusion he came to has just been proven.

In 1952 he published a paper that offered a theory on the mathematics of patterns including zebra stripes and ridges on sand dunes - and his theory even explained how human fingers formed.

Like strips and dots in many animals, fingers can be considered as patterns. Alan Turing's model, first published in 1952, suggested that the development of limbs while humans were in the womb could be explained using mathematics, a theory that has now been proven by modern researchers

Turing, who died in 1954, discovered that a system with just two molecules could, in theory, create spotty or stripy patterns if they diffused and chemically interacted in just the right way.

His mathematical equations showed that starting from a system with no pattern the molecules could spontaneously self-organise their concentrations into a repetitive spatial pattern.

This theory has come to be accepted as an explanation of fairly simple patterns such as zebra stripes and even the ridges on sand dunes, but it can also explain how structures such as fingers are formed when a human is in the womb.

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Now a group of researchers from the Multicellular Systems Biology lab at the Centre for Genomic Regulation (CRG) in Barcelona has provided the long sought-for data which confirms that fingers and toes are patterned by this Turing mechanism.

The approach taken was that of systems biology - combining experimental work with computational modelling.

Their model predicted how the pattern of fingers should change during the development of a human, explaining how molecules align to produce certain organs based on Turing's theory.

When the same experiments were done on small pieces of limb bud tissue - structures formed in early limb development - cultured in a petri dish the same alterations in finger pattern were observed, confirming the computational prediction.

This result answers a long-standing question in the field, but it has consequences that go beyond the development of fingers.

It addresses a more general debate about how the millions of cells in our bodies are able to dynamically arrange themselves into the correct 3D structures, for example in our kidneys, hearts and other organs.

TURING'S DEATH AND THE SUSPICIOUS 'POISON APPLE'

On 8 June 1954, Turing's cleaner found him dead. A post-mortem examination established the cause of death was cyanide poisoning.

An inquest determined that he had committed suicide, and he was cremated at Woking Crematorium on 12 June.

Several scholars, and even his family, have suggested Turing's death was not suicide - and instead either an accident or linked to a conspiracy.

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 poison apple in the story.

The theory was supported in an article in The Guardian written by Turing's friend, the author Alan Garner, in 2011.

However, later evidence suggested that Turing habitually ate an apple before bed, and it was not unusual for it to be discarded half-eaten.

His mother is said to have thought the ingestion was accidental, cause by her son's storage of chemicals in his home.

Speaking on the 100th anniversary of Alan Turing's birth on 23rd June 2012, Professor of Philosophy Jack Copeland, University of Canterbury, Christchurch, New Zealand, questioned the evidence given to the inquiry in 1954.

He said there was no evidence of premeditation - there was no suicide note and he seemed to be in a cheerful mood in the days leading up to his death.

He added that Turing's career was at an all time high and that he would not want to intentionally kill himself.

He pointed out that his friend Robin Gandy stayed with Turing a week before his death and he remarked how happy Turing seemed.

Finally, the academic remarked that the inquest was so bad that Turing could even have been murdered.

Although it is is unclear who would have wanted to murder him Mr Copeland said his work at Bletchly Park was under strict secrecy until well after his death.

On the left is an illustration showing how molecules can align in certain patterns to produce limbs such as fingers, as predict by British mathematician Alan Turing (right) in 1952

Turing's theory also challenges the dominance of an important traditional idea called positional information, which states that cells know what to do because they all receive information about their 'coordinates' in space (a bit like longitude and latitude on a world map).

The research highlights instead that local self-organising mechanisms may be much more important in the development of organs than previously thought.

Arriving at the correct understanding of multicellular organisation is essential to develop effective strategies for regenerative medicine, and one day to possibly engineer replacement tissues for various organs.

In the shorter term, these results also explain why polydactyly -the development of extra fingers or toes - is such a common birth defect in humans; Turing systems are mathematically known to have slightly lower precision in regulating the number of 'stripes' than alternative models.

At first glance, the question of how an embryo develops seems unrelated to the problems of computing and algorithms with which Turing is more commonly associated.

In reality however, they were both expressions of his interest in how complex and clever biological 'machines' arise in nature.

In a sense, he sought the algorithms by which life builds itself.

It is perhaps fitting that this study, which has confirmed Turing's 62 year-old theory on embryology, required the development of a serious computer model.

It brings together two of his major life achievements into one result.

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