Tree responsibly: Part 1

A few years ago I was at a talk that opened with an evolutionary context for the study and had a tree that looked about like this:

I thought ruh-roh, I feel some basal-ancient-ladderness coming on.  And sure enough it was primitive [living] taxa from there on out. This got me thinking about the relationship between tree drawing and tree thinking. This relationship is well established in the science education literature, which has demonstrated that certain tree formats are more likely to trigger misconceptions about evolution (e.g., Novick et al. 2011). Viewers are likely to see the tips that are literally 'lower' on a tree like the one above as being evolutionarily lower*.  Moreover, they are likely to interpret this diagram not as a branching history but as a replacement series with a progressive evolutionary story.  Heck, it is almost begging readers to view evolution as a timeline. If you let it keep slipping, that’s right where you end up.

Going, going, gone.

It is then a very short hop for viewers to interpret that ‘tree’ as something like this.

As I have argued before, this terrible depiction of evolution and its many off-shoots (like this) are not only misleading but downright dangerous. Not to beat a dead horse, but none of the other extant apes (e.g., gorillas, chimps, bonobos) are our ancestors, as implied by this figure (see this great blog by Fabio Mendes for a more complete discussion). In fact, we can’t even be very sure which of the many extinct hominins actually sits on the lineage that gave rise to Homo sapiens (i.e., actually could be correctly referred to as an ancestor).

In exploring the relationship between tree diagrams and tree-thinking in science ed research, there has been a strong emphasis on diagonal trees versus rectangular trees, which often go by “tree” and “ladder” format, respectively. I prefer to stick with diagonal (as in the top diagram) and rectangular (below), because let’s be honest, a rectangular tree can be made to look just as ladder-y as a diagonal tree.

                                                       My Ladder-y Rectangular Tree

What is scary to me is the ladder-y trees seems to be exploding, faster than stick-in-the-muds like me can complain about how they trigger evolutionary misconceptions and make the jobs of evolutionary biologists even harder. Worse yet, these ladder-y trees are often presented the context of trying to expand access to information about phylogenies and evolution. I won’t enumerate them here, but let’s just say that I’ve got sort of a mental burn-book of phylogeny figures that fall in this more-harm-than-good zone**. In part II of this blog entry, I’ll talk about how I think we can improve the state of affairs.

*This is not a thing. Calling a group of organisms 'lower' is just as nails-on-a-chalkboard to me as basal.

*(I realize that I'm making tons of weird hyphenated adjectives today.  That's why it's just a blog.