In defense of a hypothesis

Bruce MacFadden is telling a story as if it happened to him. It is the story of the evolution of horses and the portrayal of their evolution in museums across the United States. Fossil horses are one of the finest examples of evolution found anywhere in the fossil record. He knows this story extremely well even though it is riddled with specific terms, processes, and details that are hard to understand and/or remember even in isolation, without the context of how it all fits together. This story has been evolving for over thirty years, starting with his work as an undergraduate. But it is not done. In fact, it may never be complete. What he understands makes sense to him now, but each new finding and fresh analysis changes the story, and affirms or challenges what he understands.

Bruce giving his talk at the Smithsonian Tropical Research Institute
Bruce giving his talk at the Smithsonian Tropical Research Institute (Photo: Jeff Gage, University of Florida)

Bruce’s claim is that the information communicated about horse evolution is more often wrong than right. Their evolution is phylogenic, meaning that their lineage has branched off such that, at times, there were several daughter species living concurrently. The depiction of their evolution found in museums and textbooks often shows what he calls orthogenesis, or “straight line evolution”, where one species evolves directly into another. Why the exhibits and texts show it this way is somewhat of a mystery. It has been over a hundred years since horse evolution was proven to be phylogenic. Is it just easier to portray this way? Is it to save space in museum exhibits and textbooks


At the start of Q & A, immediately following a warm applause for Bruce’s talk, one after another audience member poked at what they perceived as holes in Bruce’s work. He was on the defensive, and the attacks were aggressive. To one commenter, he replied “I’d love to argue with you more about that over a beer”, to which the commenter replied, “I’d love that”.  This is science, and this is the way it goes.  When you put yourself out there, you expose any vulnerable pieces of your claims, or even in the way you told your story. I’d imagine word choice is critical, and I am now understanding better the careful way of communication that I have noticed when Bruce speaks technically.

One of the most significant shifts of the Common Core standards in ELA and Math is the need for students to be able to use evidence to defend their point of view.  In ELA,College and Career Readiness Anchor Standard for Writing 1  starts out “Write arguments to support claims in an analysis of substantive topics…”, and in Math, Mathematical Practice 3 is to “Construct viable arguments and critique the reasoning of others.” Similarly, the Next Generation Science StandardsScience and Engineering Practices have identified eight practices of science and engineering that are essential for all students to learn. Number seven on the list is “engaging in argument from evidence.” This is a skill that ALL students need to be able to apply to ALL of their learning. Watching Bruce brought the importance of these standards to life.

At last, some clear interdisciplinary alignment of what students need to know and be able to do.



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