It is hard to deny that Haeckel’s embryos are an “icon of evolution,” true even if “icon” now evokes Jonathan Wells’ “travesty” of a book (see Matzke). The embryos were reproduced in a majority of high school and college biology textbooks from the mid-1930s through at least the 1960s (See table). Generations of students took away the incorrect but easy to accept and generally cool idea that we pass through a fish-like stage, complete with gill slits, on our way to becoming human.
Creationists, forever seeking advantage, took a 1997 journal article challenging the residual utility of Ernst Haeckel’s iconic embryos (Richardson et al.) and fashioned it into a pointy stick to poke their favorite straw man, the “scientific elite” (Pennisi, 1997; Behe, 1998; Wells, 1999; Freeman, 2001a,b; Ojala, 2004). With fresh charges of “fraud” and “fake,” these anti-evolutionists pricked a few scientists and historians. But the “prickees” fought back, and with context and nuance on their side, made quick work of the critics (Hopwood, 2006; Blackwell, 2007; Richards, 2009). Charges of fraud against Haeckel are as old as the drawings themselves, the defenders noted, just another out of date argument in the creationists’ pitiful quiver of half-truths and rhetorical manipulations.
But we must be careful: creationist attacks tend to generate simplified and emotional responses that can constrain critical thinking.
Haeckel’s “icon” was and remains a potent and problematic image (see Ken Miller and Joe Levine’s note). Though it is true that Haeckel’s “schematic” illustrations gave way to better representations starting in the late 1940s, biology textbooks continued to present embryos, always vertebrates, side-by-side or in a comparative grid. It’s an arrangement that was designed to communicate Haeckel’s belief that embryonic development and evolutionary history were linked and that evolution was progressive. It is easy to argue that it still does, despite the disclaimers authors usually offer.
What is most curious is that the rise in popularity of Haeckel’s embryos happened just as biologists were distancing themselves from the kind of broad morphologically-based conjecture the “icon” was designed to support. Less than 20% of early American biology textbooks (1907-1932) included all or part of Haeckel’s original grid. But by the 1940s and into the 1950s, upwards of 60% of high school textbooks featured copies or close variations of the 1874 original.
How do we explain this? Continue reading