No good story about human design flaws can pass up a discussion of flatulence - and science has addressed the kind that would occur if everyone in the world drank a tall glass of milk at the same time.

Patel said one of her favorite examples of evolution in progress involves the gene that determines which adults can digest the sugars in milk and which adults cannot. From genetic studies it appears that so-called lactose intolerance was our ancestral state.

A few people, however, were genetically gifted with an enzyme called lactase, which breaks down lactose, and in groups that started drinking lots of milk around 10,000 years ago, that version of the gene started to take over.

Scientists recently sequenced the lactase gene and found three variations that allow adults to drink the milk of other animals. "It's the first clear evidence of convergent evolution," Patel said, though it's not known whether those lacking this innovation failed to pass on their genes because they suffered from lack of nutrition or just didn't get invited to any parties.

As for design, intelligent or otherwise, Shubin says the body only makes sense if viewed as a product of evolution. If it was designed, the designer could have done away with some of our relics of the past.

"This designer, if there was one, liked history, and he really liked fish."

Celebrating Evolution

With approaching anniversaries of Charles Darwin's birth (Feb. 12, 1809) and of publication in Philadelphia of his On the Origin of Species (November 1859), the University of Pennsylvania Museum of Archaeology and Anthropology is leading a celebration of evolution.

"Surviving: The Body of Evidence"

What it is: The Penn Museum's new, interactive exhibit - its most ambitious in decades, with six major sections - explores the process of evolution and how it made us what we are today.

If you go: The exhibit is open daily except Mondays through May 2009 at the museum, 33d and Spruce Streets. Admission is $8. Information: 215-898-4000.

Year of Evolution

Dozens of events are planned at various institutions over the next year (many of them in 2009).

A sampling:

Lecture: "The Importance of Lucy," by the hominid skeleton's discoverer, paleoanthropologist Donald Johanson (2 p.m. May 4 at the Penn Museum).

Exhibitions: The work of Charles Darwin (American Philosophical Society Museum) and of geneticist Gregor Mendel (Academy of Natural Sciences).

Movies: Evolution-related IMAX films (The Franklin).

For more information

Listings and links are posted at www.yearofevolution.org