Good comedians make their material do work in multiple venues, but telling the same joke over and over, to audiences who have heard the material before…well, that’s the definition of tired. Atheist, biologist, and blogger PZ Myers has been telling the same joke about “Paul Nelson Day” for many years now. April 7, dubbed “Paul Nelson Day” by Myers, commemorates Paul’s failure to explicate in exact quantitative terms the concept of “ontogenetic depth.”‘

Snicker. Hey, haven’t we heard this one before?

Oh yeah. Seven years ago, in April 2011 — we told you PZ’s jokes were approaching mandatory retirement age — Paul Nelson acknowledged that, as originally conceived, “ontogenetic depth” was impossible to measure.

Nonetheless, although currently impossible to measure because of its complexity, “ontogenetic depth” is still quite real. One can recognize and name a property without being able to determine it quantitatively.

Paul further explained that being unable to measure ontogenetic depth, if personally disappointing for Paul (who, in 2003, thought it was possible), is not good news for evolutionary theory. When it comes to the unsolved problem of the origin of developing animals, evolutionary theory needs to show how ontogenetic depth is constructed by undirected processes. The problem is not going away. It is inescapable, if one begins with single-celled or colonial eukaryotes.

You can read Paul’s detailed account from 2011, in a two-part series, here and here. In 2015, Paul revisited the same issue, in responding to evolutionary biologist Ursula Goodenough, here.

So, as a public service to any Evolution News reader who wonders if Paul Nelson ever answered PZ Myers, we provide the links above. We also recommend that Myers hire some new comedy writers.

Image: C. elegans, in a scene from How to Build a Worm, courtesy of Discovery Institute.