February 12th is Charles Darwin’s birthday; this year he turns 209.
There are many ways to celebrate. You could crack open your old copy of On the Origin of Species, his groundbreaking work describing the theory of evolution. You could book a trip to Down House, where he lived and raised his family. Or, if you’re looking for something impactful, make a contribution to defend evolution education (for a good birthday present you can even do it in his name).
An additional way to celebrate is with music. Darwin-themed songs have been highlighted before, and this is a wonderful option to explore. However, in this post I am proposing a playlist of another sort, in which it is the songs’ arrangement, rather than their content, that honors Darwin.
Today, evolutionary relationships are often represented using a diagram called a phylogenetic tree. (In fact, Darwin sketched one as early as 1837.) In a phylogenetic tree, organisms are placed at the tips of lines called branches. At certain positions in the diagram, adjacent branches intersect. These points of intersection are called nodes. A node represents a common ancestor—a point in the past when a single ancestral population split to give rise to two separate lineages. Clusters of intersecting branches, incorporating all of the species that are descended from a given ancestor, are called clades.
My playlist is organized in exactly the same way. It has 16 songs, each named for a different biological organism. Each song is positioned at the end of a branch; these branches, in turn, are arranged to reflect genealogical relationships.
I selected my songs based on two considerations. First, I wanted a diverse range of organisms, belonging to several different phyla. At the same time, I also wanted to restrict my playlist to famous songs—titles that most people would recognize immediately.
At the top of my list, “Who Let the Dogs Out” is paired with “Hungry Like the Wolf,” reflecting a close evolutionary relationship between dogs and wolves.
Positions 3 and 4 of the playlist are occupied by two more distantly-related carnivores: “The Fox” (better known as “What does the Fox Say?”) and “Eye of the Tiger.”
At positions 5-7 is a second clade of mammals, which diverged from the carnivores approximately 100 million years ago. This clade consists of a lagomorph-themed song: “White Rabbit,” together with a pair of songs named for primates: “Piano Man” and “Shock the Monkey.”
Bird-themed songs form a clade at positions 8-10: “Blackbird,” “When Doves Cry,” and “Peacock.”
Invertebrates occupy positions 11-13. Two arthropods, “Rock Lobster” and “Fireflies,” are paired; a mollusk-themed song, “Octopus’ Garden,” is present on an adjacent branch.
The remaining branches, rounding out the playlist, are devoted to plants and plant products: The Presidents of the United States of America’s “Peaches,” Eric Clapton’s “Cocaine” (cocaine is derived from any of several plants in the genus Erythroxylum), and Maroon 5’s “Sugar.”
The only thing more fun than this playlist is the process of creating one of your own. And you can do that, just like I did, in five easy steps.
1) Select your songs
Your selection criteria—and musical tastes—will likely differ from mine. You might also wish to challenge yourself by honing in on one specific section of the tree of life. Consider, for example, a playlist that is devoted just to flowering plants, or just to protostomes, or just to vertebrates.
2) Convert your song titles to species names. (Sites like Wikipedia can help.) In this conversion, for example, “Peaches” becomes “Prunus persica.”
3) Save a list of the species in .txt format
4) Visit TimeTree.org
Scroll to the bottom of the page. At “Load a List of Species,” upload your .txt list. Then, Bam!, Time Tree will generate a phylogenetic tree.
5) Recreate the tree replacing the species names with the song titles
And then, Voilà!: You have a playlist.
As you play around with your playlist, you should also remember: equivalent trees can be written in many different ways. So feel free to headline your playlist with whatever song you’d like: “The Yellow Rose of Texas,” “Hound Dog,” “I Am the Walrus,” whatever. Then tweak the arrangements of the other songs accordingly. And you’ll still have a perfectly accurate tree.
Whatever your plans for February 12th, I hope that you’ll consider making a phylogenetic playlist a part of the celebration. Use mine—you are very welcome to it. Or else build one of your own.
As you listen to your playlist, reflect upon the deep familial connections that link all forms of life. Think, too, about Darwin: the author of the revolutionary conceptual framework that underlies your playlist—the same framework that today enables us to make sense of biology.
And wish him, with all your heart, a happy 209th.
Bio: Rachel Rodman has a Ph.D. in Arabidopsis genetics, and presently aspires to recontextualize all of art, literature, and popular culture in the form of a phylogenetic tree. Won’t you help her?