I encountered it by way of Michael Shermer's reply to this year's Edge question "What should we be worrying about?" His answer, the Is/Ought Problem.
Which I came to by way of a related post by Mr. Shermer (in which he seems to be channeling Sam Harris) at Skepticblog, where we learn he is writing a book on the topic of the Is/Ought Problem titled, The Moral Arc of Science. No wonder that's what he's worrying about this year.
That unconvincing post nonetheless contains a link to a well-reasoned counterpoint by Massimo Pigliucci (for the win) at his Rationally Speaking blog.
A footnote in Massimo's post to take us to Steven Novella's Neurologica blog here and here.
This hopscotch of a thread in turn takes me back to Robert Wright in The Moral Animal.
Me, I'm inclined to think that we've been "doing" morality since long before we had words to describe it. Of course for as long as long as we could talk about it we've been arguing about whether or not we're moral because gods tell us to be, because we make up our own rules, or because morality is an emergent and ever evolving property of our cosmos.
What say you?