I find the study to be absolutely stunning. The data matrix of characters that they’ve assembled is jaw-dropping and, when combined with DNA sequence data, undoubtedly provides one of the best estimates of evolutionary relationships within placental mammals to date.

Just to put into perspective what an incredible amount of work coding over 4,500 characters for nearly 90 different species is, I once looked at a “mere” 200 characters for 35 species (for my Masters project) and it was six weeks straight of sitting in various natural history museums for 8+ hours a day. Incredibly arduous and not really that exciting. Kinda dusty too. Now scale that up by a factor of over 20!

What’s lost in the results, however, was the effort in coming up with the 4,500 characters in the first place. I’ve heard rumours of how it took years for them just to come up with the character list itself. That seems hard to believe, but you have to remember that they had to come up with a list of characters and character definitions that fits everything from a bumblebee bat to a blue whale and all the weird and wonderful forms in between (e.g., beavers, elephants, seals, sloths, meerkats, even humans). That’s a lot of diversity to try and summarize.

To make matters worse, they often had to do a lot of detective work because the same structure could often go under a half dozen aliases, with the name/definition often being peculiar to a particular taxonomic group. So, there was a lot of science going on here as well in trying to decide if a particular flange on the top of the femur in something like a walrus was evolutionarily the same structure as a ridge in a similar position on the femur of an aardvark! And, if so, then what should they call it?