Circumstantial evidence rarely stands up in a court of law. In science, correlation has a little more credence, especially when it leads to a testable hypothesis. By 1978, people had been studying microtubules for a dozen years and nonmuscle actin filaments for about nine years. There were “plenty of examples in electron micrographs where microtubule and actin filaments were in the same place in the cell,” says Thomas Pollard (Yale University, New Haven, CT).
But, he notes, no one had investigated whether the polymer filaments actually interacted with each other and, if so, by what molecular connections. After seeing more provocative but still circumstantial images at a summer Woods Hole Marine Biological Laboratory course, Linda Griffith, then a graduate student at UCLA, asked Pollard if she could transfer to his Harvard laboratory to test the idea.
The two used a rather low-tech viscometer that measured...
