Watch : Musk, Ma Square Off On AI, Mars and Aliens

Elon Musk was in China on Thursday, but not to talk Tesla and its new factory in the country.

Instead, the chief executive talked artificial intelligence on stage next to Alibaba founder Jack Ma, and doubled down on his warnings that the technology could pose grave risks to human society as we know it.

Jack Ma believes artificial intelligence poses no threat to humanity, but Elon Musk called that “famous last words” as the billionaire tech tycoons faced off Thursday (Aug 29) in an occasionally animated debate on futurism in Shanghai.

The Chinese co-founder of Alibaba and the maverick industrialist behind Tesla and SpaceX frequently pulled pained expressions and raised eyebrows as they kicked off an AI conference with a dialogue that challenged attendees to keep up, veering from technology to Mars, death, and jobs.