Currently, the most high-profile person on the autistic spectrum in Britain is a garden designer with flamboyantly pink hair and muscly, tattooed arms. Star of Channel 4’s latest makeover show, The Autistic Gardener, Alan Gardner is just three years younger than my autistic older brother, but if you sat these two middle-aged men next to each other it would be very hard to see what they have in common. While one is charmingly articulate, capable of negotiating with private clients and a production company to create both beautiful gardens and engaging television, the other requires considerable support and is minimally verbal. How can the same word describe both these men?

There’s a clue in the dates when they were diagnosed – my brother in 1961, at the age of three, with what was then called “childhood psychosis”, and Alan Gardner only two years ago with Asperger syndrome. The fact that Gardner could have reached his 50s without a diagnosis doesn’t mean that autism didn’t affect his life, but it speaks volumes on how awareness of the autistic spectrum and its definition have changed over the last 50 years.

Neurotribes by Steve Silberman explores in fascinating, near-encyclopedic depth how autism has evolved. It’s a gripping narrative written with journalistic verve. First defined as a rare disorder of childhood in 1943, today autistic spectrum disorders are estimated to affect about one in 100 people of all ages in the UK (in the US, the figure is one in 68). Silberman combines portraits of autistic individuals with a forensic exploration of the disorder’s history and also delineates the current political and cultural battles that divide professionals and parents, self-advocates and charities.

Silberman, an American journalist, came to the subject from an unusual perspective. Most books on autism are written by practitioners, parents or people on the spectrum themselves. Silberman is none of these – he specialises in writing about technology and the digital industry for Wired magazine and the New Yorker. It was only after interviewing several Silicon Valley innovators and finding that they had autistic children that his curiosity was piqued. The resulting article, The Geek Syndrome (Wired, 2001), posited the theory that Silicon Valley had become a hot spot for autism diagnoses because nerdy programmers and engineers met there and had children while carrying a “genetic predisposition” for the disorder.

After the article was published, Silberman received more mail about it than about anything else he’d written. He was intrigued that while some of his correspondents saw autism as a tragic disability severely compromising their children’s future, others saw particular strengths and unique skills in their unusual sons and daughters. They also recognised some of their children’s traits in themselves. He went in search of the deep history of autism. It was a journey that led him to explore not only America’s infatuation with Freud, then with behaviourism, but also the murky archives of Nazi-era Vienna and the legacy of eugenics.

It’s long been a puzzle that two seemingly unconnected paediatricians of Austrian origin, one based in Baltimore (Leo Kanner) and the other in Vienna (Hans Asperger), simultaneously observed the unusual behaviour of children brought to them by worried parents and coined an identical label to describe them – autistic – in 1943. Silberman uses his investigative skills to find the buried connections between the two doctors, the overlaps in mentors and colleagues, as well as revealing their profound differences in approach.

He also explores the longstanding question of whether the children the two paediatricians observed really shared the same disorder. For a long time, it was thought that Kanner’s autistic children were far more disabled by their condition. They had delayed or nonexistent speech, while Asperger described his charges as “little professors” – fluent if pedantic speakers with idiosyncratic interests. In reality, not all of Asperger’s autistic patients were obviously intelligent and they displayed a wide range of deficits as well as strengths. But for tactical reasons he chose in his presentation paper to describe the four most able boys. He stressed their potential (with appropriate education) to achieve in life. Asperger was probably trying to protect his autistic charges at a time when Nazi eugenic policy viewed physically and mentally disabled children as “lives unworthy of life”. Under the T2 “euthanasia” programme, more than 5,000 such children were killed by lethal injection or starvation.

Silberman presents a vivid and sympathetic portrait of Hans Asperger; he was enlightened, kindly and modest, and his ability to do good work under a terrible regime was remarkable. He was alert to signs of “autistic intelligence” and saw traits in artists and scientists, observing: “Not everything that steps out of line, and is thus ‘abnormal’, must necessarily be ‘inferior’.” If Asperger’s 1940s writing had not languished in relatively unread German texts until translated in 1981, attitudes to autism might have been more positively framed.

Silberman is far more critical of Kanner, an ambitious émigré to the US who would become a popular authority on child rearing. For too long Kanner adhered to his definition of autism as a rare childhood condition with very strict diagnostic criteria. He was far from being a Freudian, but laid a degree of blame on toxic parenting. He described the educated parents who brought their children to him as “emotional refrigerators”, whose lack of warmth contributed to their sons’ and daughters’ retreat into their own worlds. Although Kanner later moved away from this position and acknowledged that autism was inborn, not psychogenic, the damage was done. My parents’ generation found themselves dealing not only with the challenges of bringing up an autistic child in an era when few schools would accept such children, but also battling their guilt on the psychoanalyst’s couch.

There are a few villains in Silberman’s wide-ranging account: the extreme advocates of behaviourism with their use of punishing regimes to “extinguish” autistic traits in terrified children; the campaigners who mistakenly pinned autism’s cause on the MMR vaccine; US charities that portray autism as a catastrophic disease that scientists must work ceaselessly to prevent, cure or eliminate.

But there are more heroes, too. Silberman dedicates his book to the British pioneer Dr Lorna Wing, the parent and psychiatrist responsible for the idea that autism is a spectrum condition. He paints portraits of scientists, inventors and engineers (historic and present-day) whose autistic perspectives have enhanced their work. He describes families and adults who have learned to live happily with autism and find its strengths. There’s a wonderfully detailed chapter on how the film Rain Man evolved from a chance encounter between a documentary maker and an eccentric man with learning difficulties.

Silberman also highlights the campaigning work being done today by autistic self-advocates (modelled on the gay and deaf rights movements) to reframe autism as a “difference” to be accepted and accommodated, rather than eradicated. We’ve come a long way since the 1960s, when my parents fought to set up a school for autistic children and Alan Gardner was bullied in mainstream education. But we still have a long way to go to understand how one word can usefully cover such a diverse and expanding range of people.

Neurotribes is published by Allen & Unwin (£16.99). Click here to order a copy for £12.99