Charles Darwin may be long dead, but his theories are alive and well in the swine flu epidemic.

Before an audience of about 100 at the Peabody Museum Auditorium Thursday night, Yale lecturer Carl Zimmer ’87 said evolution is at work as the fast mutation rate of swine flu makes it a public health hazard.

“I would hope that people will see how evolution is not something that happened three billion years ago,” Zimmer explained. “It’s something that happens every day.”

Zimmer said Darwin’s theory of biological evolution is relevant to understanding why the flu is difficult to control. This year, Zimmer noted, was the 150th anniversary of the publication of Darwin’s “On the Origin of Species,” which laid the groundwork for modern theories of how species develop. But Darwin didn’t know that viruses such as the flu also evolved, Zimmer said.

Zimmer said the speed at which seasonal and swine flu viruses evolve make it one of the most serious public health risks today. According to the Centers for Disease Control, 36,000 people in the United States die from the flu every year, not including the additional deaths caused by a prolonged pandemic.

Because the flu virus reproduces at a fast rate, Zimmer said, the process is “sloppy,” causing many mutations. While many of these mutations are fatal to the virus, some lead to strains of the virus that are resistant to antibodies and anti-viral drugs.

This compounds the challenge for researchers and evolutionary biologists who try to develop a vaccine against the flu every year, Zimmer said. No single method can be applied from year to year, Zimmer said, because there is no persistent or clear pattern in how the flu develops and spreads.

Combating H1N1 has been difficult because the swine flu virus was transferred to humans from pigs, Zimmer said. He explained that pigs are usually involved in the evolution of new strains of flu because they can contract viruses from a variety of species, including birds and humans. Three viruses combined together to form “classic swine,” Zimmer said, which then mutated to form the virus that scientists are scrambling to keep under control.

Zimmer said the close contact that animals have with each other in the United States, Zimmer said, creates the perfect conditions for the virus to reproduce and transfer from animal to animal.

Audience member Jakob Vinther GRD ’12 said he admires how Zimmer’s work has highlighted the effect of microbes on scientists’ view of evolution.

A member of the committee that organized the lecture, Frances Gaines, described the lecture as a “great match” for the “Disease Detectives” exhibit — an interactive exhibit that teaches visitors how to identify certain diseases — in the Peabody, which will be on display until Jan. 2010.

The lecture was part of the annual John H. Ostrom lecture series, named after John Ostrom, a geology professor at Yale from 1961 to 1992 who died in 2005.