“A musical about yeast?”

That’s the question most likely on your mind.

Yes, it’s a musical about yeast, but also a musical about life, evolution, greed, corruption, exploration, and, yes, love.

In fact, it’s surprising how influential love is in our evolutionary history.

At least that’s what Mark Hollmann (music and lyrics) and Grog Kotis (book and lyrics) maintain in their earnest, yet slightly off-centered, new musical about the very first life forms on the earth — of which we are all descendants. It’s a mostly successful effort, modeled off their previous hit, Urinetown.

How do I summarize the plot? Well – there’s this kingdom of inter-related yeasts, ruled by “Jan the Elder” (Joseph Anthony Foronda). This colony of primordial seabed ooze is in trouble, mostly caused be their food supply of salt running low. Various yeasts are plotting and vying to overthrow, or just kill, the Elder. In the meantime, fresh-faced yeasts Jan the Sweet (Melanie Brezill) and Jan the Second (Andrew Keltz) have fallen in love, with the Second risking his life to rise beyond the boarders of their close-knit colony to see what exists above. What he discovers drastically shakes up stasis, impacting the history of the world to come.

It’s a goofy plot, though deeply rooted in the earliest forms of Greek theatre, “employing archetypal characters, music and dance, simple costumes and mighty emotions to tell an epic story,” as director PJ Paparelli explains in his notes.

The show could easily turn into the hot mess that was Earth TTFN?! — another recent sci-fi comedy that featured offbeat villains and heroes (read that review here). Whenever it began to creep in that direction, it always pulled back with a genuine laugh, witty one-liner or toe-tapping song. In addition, the cast includes some classy Chicago actors such as Barbara Robertson (see my previous tribute post on her here) and Foronda (who’s starred on Broadway and the Donmar Warehouse) to anchor the proceedings.

In addition, Melanie Brezill as Jan the Sweet is quickly becoming a hot little actress after starring in Caroline, or Change at Court Theatre last fall, and more recently, Once on This Island at Porchlight.

Kotis and Hollmann’s mostly sung-through rock store successfully drives the zany and emotive narrative. After an energetic opening number delivered by the awesome ensemble of 15, the score continues with some hits, along with a few repetitive misses. (After a while, all the numbers explaining how so-and-so will carry out their evil doings seem to blend together.) And some of the lyrics are quite mundane, eliciting unintended laughs. Robertson, who is a true stand-out as the witchy, blind narrator, gets the best number, featured in the second act.

For whatever reason, there are many similarities to the writing duo’s previous hit, Urinetown — from the wise and omniscient narrator, to the young and naive hero whose quest to save the world doesn’t pan out as planned, right down to the hand-clapping gospel-influenced finale number. It might raise an eyebrow from a few savvy theatre-goers, but most probably won’t notice or care. The show is a good time.

Set designer Walt Spangler (he of the oppressive floating house that starred in Goodman’s Desire Under the Elms) has transformed ATC’s space to resemble nothing like it was when I last was there for their amazing production of Hedwig. Now, there’s a surprisingly large stage with multiple levels for actors to appear on and climb up to — often while singing. And along with lighting designer Jesse Klug, Spangler has raided the world’s supply of black lights to create a unique, multi-layered effect.

Paul Spadone’s costume design makes clever use of a fluorescent green poncho. However, more than a few actors got caught on the scenery with these cape-like ensembles, or simply tripped over them. In fact, there was a lot of falling and tripping the night I saw it. While some of it was distracting stage business, some of it was genuine. Speaking of abused actors, I also felt bad for what they were required to wear as their finale costumes. No one looks good in pink Spandex bodysuits. No one.

Yeast Nation is a fun night. Just keep an open mind and clap along with the highly accessible score, and you’ll enjoy your visit with your primordial ancestors.

Yeast Nation will play to October 18 at the American Theater Company’s home at 1909 W Byron Street, Chicago. For more information, visit www.atcweb.org.