The poet's family was first sent to northeast China and then to Xinjiang, an arid and remote desert region on the country's border with Russia, Pakistan and Afghanistan, where Ai's father had to clean public latrines.
Ai Dan, the artist's younger brother, said he believed those early years of exile and upheaval were a pivotal moment in the formation of Ai. "He had a miserable childhood - not materially, but psychologically and emotionally. Other people don't understand why my brother is so stubborn, given that we are from a better-off family. I think the root is his unhappy childhood."
With the death of Mao and the end of the Cultural Revolution in 1976, the family returned home. Ai signed up for the Beijing Film Academy and studied alongside Zhang Yimou, who would go on to become China's best-known cinema director.
But the young artist yearned to spread his wings and soon lost interest in the course. In 1981, aged 24, he made his way to New York and set up camp on the Lower East Side. He befriended beat poet Allen Ginsberg and eventually turned away from painting towards sculpture and photography. He documented his adoptive home in a decade-long collection of some 10,000 pictures.
Ai also developed an obsession with art galleries and blackjack, making regular trips to Atlantic City to bankroll his fledgling career as an artist.
After more than a decade in the US, he returned to China in 1993 to be with his sick father. There, he met his future wife, the artist Lu Qing, and became an influential figure on the domestic art scene, publishing a trilogy of underground art books called The Black, White and Grey Cover Books.
The first hints of Ai's superstar status came in 2000, when he curated a now celebrated exhibition of avant-garde artists during Shanghai's Biennale. Its title was F*** Off. "It taunted the authorities to shut it down, with artworks that included allegedly poisonous gases and acts of cannibalism," Lee Ambrozy writes in the introduction to a 2011 collection of the artist's writings. "Eventually it was closed, but not until it was seen by all the right people."
As Ai's fame spread, he also began his transformation into one of the Communist party's most acerbic and fearless critics. In 2006, he started a blog, initially focused largely on art and architecture, but which increasingly became an outlet for his frustrations about social issues, one-party rule and Beijing's disregard for human rights and free speech.
"The internet thrilled him because he saw it as a real and free platform for expression," said his brother. "He wanted to express his views, his resistance and his contempt."
Censors closed the blog down in 2009, but Ai simply took his message to Twitter, where he now boasts around 260,000 followers. The internet was the artist's key weapon when he launched one of his most sensitive campaigns in the wake of the devastating 2008 Sichuan earthquake, which claimed some 90,000 Chinese lives.
More than 5000 children died in the disaster, many crushed to death when poorly built schools, which many blamed on corrupt and incompetent officials, collapsed on them. Incensed, Ai set about gathering their names and publishing them online. He established a "Citizen's Inquiry" into the causes of so many young dying and eventually conceived a giant art installation to remember them. The work was built from 9000 children's backpacks, used to spell out a quote from the mother of one victim. "She lived happily for seven years in this world," the message said.
It was typical Ai: creative, confrontational and, in one-party China, brave. "He is a man with attitude," said Zhao Zhao, another outspoken artist who was his assistant for seven years.
But Ai's campaigning went down badly with his country's stability-obsessed leaders. His situation deteriorated further in 2011 after security forces launched a pre-emptive crackdown on activists it feared were trying to mobilise a "Jasmine Revolution" to topple the party. Ai took to Twitter to denounce the campaign of arrests. On February 24 that year, he posted a thinly veiled attack on the Government's paranoid approach that said: "I didn't care about jasmine at first but people who are scared by jasmine sent out information about how harmful jasmine is often ... which makes me realise that jasmine is what scares them the most."
Just over a month later, Ai was seized by police as he arrived at Beijing airport. He was spirited off into detention and spent the next 81 days behind bars, triggering an international campaign for his release.
"They were extreme conditions, created by a system that thinks it is above the law and has become a kind of monstrous machine," he later wrote.
Yet as Ai's political troubles mounted at home, his international fame ballooned. In 2010, the Tate Modern had invited him to fill its Turbine Hall with Sunflower Seeds, a 10-tonne sculpture made up of 8 million porcelain sunflower seeds. The following year, he was named the most powerful figure in the global art community by Art Review. That left the Communist party smarting. "China has many artists who have sufficient ability," a Government spokesperson fumed. "We feel that a selection that is based purely on a political bias and perspective has violated the objectives of the magazine."
Ai's detention did little to take the political edge off his art. An exhibition in Berlin last year was entitled Ai Weiwei - Evidence and featured a foam-padded replica of the cell in which he was held. Yet in recent months, the artist has appeared more cautious in his criticism of the Government, perhaps in response to advice from his mother.
"I'm scared. I've seen your writings. Some of your words are really harsh," she tells her son in Andreas Johnsen's 2013 documentary The Fake Case. "You criticise them too much. If this were 1957, they would have killed you already. I'm worried about you."
There were hints this year that Ai's period of forced confinement was coming to an end. In June, he was allowed to put on his first solo exhibition in China, for which he rebuilt a Ming dynasty temple in Beijing's 798 Art District.
The Global Times, a Government-controlled tabloid, urged the dissident artist in an editorial to spend his time helping "boost public interest in modern art", not politics.
Asked why he thought his passport had been returned, the artist said: "This is not something I can say."
But with a major party crackdown under way, there is no hint that it represents any kind of political opening. Xi Jinping is waging a ferocious campaign against dissent designed to strengthen the party's grip on power.
Since early July, more than 240 people have been detained or questioned as part of a police offensive against human rights lawyers, at least one whom has defended Ai Weiwei.
Ai was guarded when asked about the crackdown. "Of course, I am concerned about it," the normally outspoken artist said, before falling silent. It was an uncharacteristic hush - and one that is unlikely to last for long.
- Observer
