Reborn ales of yore
One recent bit of historical mashing on the highly drinkable end of the spectrum has been taken up by Yards Brewing, with their reinvention of a "small beer" (not to be confused with the weak small beer that's made from second runnings) as described by George Washington. Where else can you go and enjoy the "ales of the revolution" over lunch other than at the City Tavern in Philadelphia? Beer brewed with spruce tips in the place of hops is actually quite common in a number of olden styles. From ancient Scotch ales through the Age of Discovery through the colonists, spruce and pine have been used in unhopped ales to counteract the malt's sweetness much like the Finnish use juniper in their sahti.
On the other hand, you have your projects that aim to replicate the times when beer was just what happened to last nights' uneaten gruel. Consider this before embarking on your own ancient beer brewing expedition. The question you should ask yourself before you begin is, "Do I want to enjoy the fruits of my labor, or would I prefer to be disgusted by the lengths at which my forefathers went to get loaded?"
Rather than leave some stale bread in a bowl of water next to a drafty window, consider investigating the Sumerian Beer Project handled by Anchor Brewing in San Francisco. Consulting the same University of Pennsylvania professor Dr. Solomon Katz who worked on Midas Touch, they set off to brew according to the guidelines posited in the Hymn of Ninkasi. Most infamously known for its being the earliest written acknowledgement of brewing, the hymn was used by Fritz & Co. as the basis for their own Ninkasi ale. Their approach, using the data gleaned from these various sources to brew "essay" beers, seems to be quite reasonable. Rather than stripping down to their loincloths and fashioning crude gruelbooze from their kids' uneaten oatmeal, they - and Dogfish Head, for that matter - have taken the line between art and science that brewers love to tread, and used it to help them bring something ancient to life.
Think about that while you're sweating over your 5 gallons of pre-hopped pale malt extract and smack-pack yeast, oh fancypants brewer from the future.
"It is an attempt, a try, an essay. We do not claim to be correct in all details, but we have made a sincere effort to bring the art and craft of today's brewer to bear on the mystery of how the ancient beers of earliest man might have been made over 5000 years ago."