Ah, I guess I made up that it was The Constant... what I must have been thinking of is the episode on Lysenkoism by the legendary Melvyn Bragg on In Our Time.
Apologies for leading you astray at first. I couldn't find it FOR THE LIFE OF ME either.
If you guys aren't already fans of In Our Time, I'm delighted to be the one to turn you on to it. It's the Liberal Arts education you didn't get in school... And I say that as someone who GOT a Lib Arts education.
There are over a thousand episodes and it's all a brilliant quick study on an unbelievable variety of subjects.