The terms we know in the Drake equation make it very difficult to say it is unlikely for intelligence to arise more than once. ~100 billion stars * ~100 billion

The terms we know in the Drake equation make it very difficult to say it is unlikely for intelligence to arise more than once. ~100 billion stars * ~100 billion galaxies in the observable universe. Exoplanet surveys seem to be suggesting at least one planet per star on average. In addition, chemical self replication seems to happen fairly easily given the right chemical conditions, which don't appear to require much more than liquid water.