paginate with :order AND :include?

My two goals:
1) display last 10 posts in reverse chronological order
2) link to the author without hitting the database 2n-1 times

These work:
  def list
    @post_pages, @posts = paginate :posts, :order => "created_at DESC",
:per_page => 10
  end

  def list
    @post_pages, @posts = paginate :posts, :per_page => 10, :include =>
:person
  end

This doesn't:
  def list
    @post_pages, @posts = paginate :posts, :order => "created_at DESC",
:per_page => 10, :include => :person
  end

I get a "Column 'created_at' in order clause is ambiguous" error. I'm
not sure but I thought it was be possible to order the posts and then
join the person table. Otherwise I will hit the database with each
post. Does anyone have a solution to this? Thanks in advance!