In this activity, you’ll be using your powers of observation and classification to create your own cladograms!
What is a cladogram? A cladogram is a type of diagram that is used to show common ancestry among a group of organisms. A cladogram is similar to a family tree because it shows generational relationships. Most family trees, however, only go back a few generations. Even royal families (who are particularly interested in their ancestry!) only go back about 500 years or so. Cladograms are used to understand ancestry that goes back thousands–even millions–of years!
Unfortunately for science, we don’t have perfect records of all organisms that have ever existed. All we have is the fossil record and our knowledge of species that can still be studied in person today. Scientists use thousands of data points about location, size, bone structure, behavior, and many other characteristics to say, “I think these two species share a common ancestor!” This website shows what is probably the biggest cladogram of all: it shows how scientists believe all life on Earth is related!
Here’s an example of a cladogram showing how closely different canine species are related:
The further away two canines are from one another, the more time has passed since their common ancestor lived. Dogs and grey wolves shared a common ancestor recently, while the dhole and the coyote shared an ancestor a very long time ago. You can think of cladograms as family trees that only show cousins!
Science has the cladograms for all existing species pretty locked down at this point. That’s why your challenge is to create your own cladogram on some made-up “species”!
Look at these shapes. How are they similar? How are they different? Which ones are more different than the others, and by how much? You can compare size, shape, color, or all three! How long ago did Circles and Squares share a common ancestor? Bonus points for writing your reasoning!
Not feeling these shapes? Think of your own “species group”! Here is an example cladogram that uses garden tools instead of shapes or living things:
Remember, these cladograms are fictional! You can use reasoning to justify the relationships you come up with, but there isn’t really a “wrong” answer. If you want to look at some extremely detailed cladograms for plastic bread tags, here’s a link!