Franklin Stahl, of “the Most Beautiful Experiment,” Dies at 95
Franklin Stahl. Image: Wikimedia Commons
by Andrew Moseman
Franklin Stahl, who passed away on April 2, 2025, at age 95, enjoyed a decades-long career as a researcher in molecular biology and genetics. But he will live on in the history books for an insightful project he worked on as a Caltech postdoc in the 1950s—one dubbed “the most beautiful experiment in biology.”
Stahl was one half of the famous Meselson-Stahl experiment of 1958; the other half was graduate Matthew Meselson (PhD ’57), who earned his PhD under famed Caltech professor and Nobel Laureate Linus Pauling.
As Stahl’s obituary in The New York Times explains:
“The two biologists proved a theory advanced by the Nobel Prize winners James Watson and Francis Crick, who discovered DNA’s helical structure in 1953. Watson and Crick posited in the journal Nature that DNA replicates in a so-called semi-conservative fashion.
“In 1958, Dr. Meselson and Dr. Stahl, postdoctoral fellows in Linus Pauling’s laboratory at the California Institute of Technology in Pasadena, Calif., proved that Watson and Crick were correct, by using an experiment that was celebrated for its design, execution and results. …
“The experiment demonstrated that after DNA unwinds and is replicated, each new DNA molecule contains one original, or parental, strand and one newly copied strand. Dr. Stahl and Dr. Meselson proved this by using E. coli bacteria, which reproduce rapidly.”
In 2018, Caltech magazine looked back on the seminal experiment performed on our Pasadena campus. As writer Lori Dajose (BS ’05) explained:
The experiment addressed a question that constituted a century-old roadblock to understanding how the structure of DNA led to its functions—inheritance, mutation, and information storage for protein synthesis. “While it was conceptually simple—simply distinguishing old from new—it was technically original and elegant, and more importantly it gave a clear answer,” says [Caltech professor of chemistry and biology Judith] Campbell. “Meselson and Stahl’s findings also provided insight into how to experimentally trace genetic information, eventually even paving the way for whole-genome sequencing.”
Read our full story, The Most Beautiful Experiment.