"I think artificial intelligence will, for decades to come, be less of a worry than real stupidity", Martin Rees tells The Economist 

Martin Rees on the Future of Science and Humanity

https://www.youtube.com/watch?v=DNNgjY_bewg

than

Pronunciation /ð(ə)n//ðan/

CONJUNCTION & PREPOSITION

• 1Introducing the second element in a comparison.

  as preposition ‘he was much smaller than his son’

  ‘Jack doesn't know any more than I do’
• 2Used in expressions introducing an exception or contrast.

  as preposition ‘he claims not to own anything other than his home’

  as conjunction ‘they observe rather than act’
• 3conjunction Used in expressions indicating one thing happening immediately after another.

  ‘scarcely was the work completed than it was abandoned’

Usage

Traditional grammar holds that personal pronouns following than should be in the subjective rather than the objective case: he is smaller than she rather than he is smaller than her. This is based on an analysis of than by which than is a conjunction and the personal pronoun (‘she’) is standing in for a full clause: he is smaller than she is. However, it is arguable that than in this context is not a conjunction but a preposition, similar grammatically to words like with, between, or for. In this case the personal pronoun is objective: he is smaller than her is standard in just the same way as, for example, I work with her is standard (not I work with she). Whatever the grammatical analysis, the evidence confirms that sentences like he is smaller than she are uncommon in modern English and only ever found in formal contexts. Uses such as he is smaller than her, on the other hand, are almost universally accepted. For more explanation see personal pronoun and between

Origin

Old English than(ne), thon(ne), thænne, originally the same word as then.