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Khan Academy “Evidence for Evolution” Video Pushes the Fake Fossil Horses Series

Casey Luskin
Image: Pliohippus Pernix, by Claire H. from New York City, USA, CC BY-SA 2.0 , via Wikimedia Commons.

I’ve been reviewing the Khan Academy video on “Evidence for Evolution,” which misleads students and teachers with some seriously outdated science about biological origins. See my two earlier posts, here and here, detailing the video’s treatment of what biologist Jonathan Wells calls “icons of evolution,” long ago discredited lines of evidence that never seem to go away. After using circular arguments for common ancestry based upon homology, the Khan Academy video goes on to push another evolutionary icon: fossil horses. 

Khan draws straight arrows from one species of fossil horses to the next and says “there is a constant change and we can see it directly through the fossil record.” The video even shows a continuous cross-section of rock strata and draws lines on it as if we find this “gradual” sequence of horses in the same unit — in the same location over long periods of time, thus showing evolution in operation at a “very, very gradual pace.” 

Problems with the Classic Series

But in the famed series, the horse fossils don’t evolve in a straight line, nor are they found in the same place, nor do they show a continuous direction of change. Jonathan Wells tackled this in his book Icons of Evolution

By the 1920s it was already becoming clear that the evolution of the horse was much more complicated than [paleontologist Othniel Charles] Marsh’s linear picture implied. Paleontologist William Matthew and his graduate student, Ruben Stirton, established that several extinct horse species coexisted with the Protohippus, and that the history of horses ranged back and forth over several continents. The fossil record of horses looked less like a straight line and more like Darwin’s branching tree. 

In 1944 Simpson wrote that the “general picture of horse evolution is very different from most current ideas of orthogenesis.” In particular, its branching-tree pattern is “flatly inconsistent with the idea of any inherent rectilinearity.” Furthermore, the trends that had seemed to support orthogenesis were illusory. For example, the trend toward larger size was not seen in all of the extinct sidebranches, some of which actually reversed direction and became smaller. Even the revised picture of horse evolution is oversimplified. Among other things, Miohippus actually appears in the fossil record before Mesohippus, though it persists after it.

Despite having been revised, the picture of horse evolution still includes a line connecting Hyracotherium with its supposed descendants, all the way up to the modern horse. 

p. 199

Here, Wells is critiquing the classic series of horse intermediates, but similar problems plague the Khan Academy narrative. The video draws straight arrows from one species to the next, misleadingly making it appear that Merychippus lived from “~16-12 Ma” and was immediately succeeded by Pliohippus that lived from “~12-5 Ma.” The straight lines imply a nice, neat succession of ancestor and descendent species. 

Reality is far more complicated. The online paleobiology database Fossilworks dates Merychippus to “15.97 to 5.332 Ma” and Pliohippus from as early as 15.97 to as recent as 4.9 Ma. There may be some inconsistency in the database’s nomenclature, but the point is that these taxa most definitely overlapped significantly in time and one species did not “succeed” the other in some nice, neat, gradualistic direct ancestor-descendant evolutionary sequence.  

Even if the Series Were True

Perhaps the biggest problem with arguments based upon the horse series isn’t so much that it’s a fake series but that even if it were a true sequence, it doesn’t show large-scale evolution. Even Khan admits that some of the fossils in the classic series look “very close” to one another. Here’s what the curriculum Discovering Intelligent Design says on this topic:

Horses are another group of fossils commonly cited in support of macroevolution — as one evolutionary biologist claimed, “horses are a poster child of evolution.” Textbooks and museums often display charts showing horse fossils. They typically start with smaller four-toed creatures, which grow larger and lose toes until the series ends with modern horses, which have hooves.

Aside from the fact that the horse body plan does not significantly evolve throughout the series, there is a significant problem with this evolutionary story: it’s an imaginary lineage. In the actual fossil record, some of the earlier horses are larger than later ones. Additionally, the fossils portrayed in the supposed lineage span different continents, separated by vast expanses of ocean.

Both location and sequence conflict with the evolutionary series as it is often portrayed. Even a prominent evolutionary website admits that the horse fossils merely “represent branches on the tree and not a direct line of descent leading to modern horses.”

Some defenders of Darwinism will say in response that a messy, branching evolutionary tree nevertheless demonstrates evolution. Perhaps, but then why do textbooks and museums feel the need to manipulate the horse fossil record?

Niles Eldredge called the series “speculative,” and finds it “lamentable” that it “has been presented as the literal truth in textbook after textbook.” Likewise, one technical book on evolution called classical portrayals of horse evolution “not accurate,” and admitted they “put the chart before the horse.” 

pp. 179-180

Attacking a Straw Man

As with homology, Khan resorts to dysteological arguments against creation. He states: “This is strong evidence for evolution. The animals we see today weren’t just created all of a sudden and haven’t changed since then.” Here, Khan is attacking a straw man. No Darwin skeptic I’ve ever met says that species or taxa can’t undergo small-scale changes, including changes in size. Even if horses have undergone evolution, it’s small-scale change. So the story is not only much more complicated but also much less Darwinian or macroevolutionary than Khan Academy makes it out to be.

Something similar comes at the end of the video when it cites antibiotic resistance as evidence for evolution. Yes, this is an example of evolution, but no Darwin skeptic I’m aware of denies that antibiotic resistance occurs or that it is a real problem in medicine today. But as I have explained elsewhere (see “Antibiotic Resistance Revisited”), this too is small-scale evolution that does not produce new features and frequently breaks important features, exacting a fitness cost from the antibiotic-resistant organism. This evidence for small-scale change may be evidence for evolution, but it isn’t the kind of Darwinian macroevolution that Khan Academy wants its viewers to believe in. 

Moreover, to create drugs that outsmart evolving bacteria or cancer cells, biomedical researchers must use a process of intelligent design. They create drug cocktails that bank upon the fact that there are limits to how much living things can evolve on their own. Far from being evidence for Darwinian theory, antibiotic resistant bacteria point to what Michael Behe has called “the edge of evolution,” beyond which unguided Darwinian processes are powerless.

Next, I’ll conclude this series by examining another old evolutionary chestnut in the video: the argument for common ancestry based on human-chimp genetic similarity.