Abscheulich!

Natural History, March, 2000 by Stephen Jay Gould

To cut to the quick of this drama: Haeckel had exaggerated the similarities by idealizations and omissions. He also, in some cases--in a procedure that can only be called fraudulent --simply copied the same figure over and over again. At certain stages in early development, vertebrate embryos do look more alike, at least in gross anatomical features easily observed with the human eye, than do the adult tortoises, chickens, cows, and humans that will develop from them. But these early embryos also differ far more substantially, one from the other, than Haeckel's figures show. Moreover, Haeckel's drawings never fooled expert embryologists, who recognized his fudgings right from the start.

At this point, a relatively straightforward factual story, blessed with a simple moral message as well, becomes considerably more complex, given the foibles and practices of the oddest primate of all. Haeckel's drawings, despite their noted inaccuracies, entered into the most impenetrable and permanent of all quasi-scientific literatures: standard student textbooks of biology. I do not know how the transfer occurred in this particular case, but the general (and highly troubling) principles can be easily identified. Authors of textbooks cannot be experts in all subdisciplines of their subject. They should be more careful, and they should rely more on primary literature and the testimony of expert colleagues, but shortcuts tempt us all, particularly in the midst of elaborate projects under tight deadlines.

Therefore, textbook authors often follow two suboptimal routes that usually yield adequate results but can also engender serious trouble: they copy from previous textbooks, and they borrow from the most widely available popular sources. No one ever surpassed Haeckel in fame and availability as a Darwinian spokesman and a noted professor at the University of Jena. So textbook authors borrowed his famous drawings of embryonic development, probably quite unaware of their noted inaccuracies and outright falsifications--or (to be honest about dirty laundry too often kept hidden) perhaps well enough aware, they then rationalized with the ever tempting and ever dangerous argument "Oh well, it's close enough to reality for student consumption, and it does illustrate a general truth with permissible idealization." (I am a generous realist on most matters of human foibles. But I confess to raging fundamentalism on this issue. The smallest compromise in dumbing down by inaccuracy destroys integrity and places an author upon a slippery slope of no return.)

Once ensconced in textbooks, misinformation becomes cocooned and effectively permanent, because, as stated above, textbooks copy from previous texts. (I have written two essays on this lamentable practice: one on the amusingly perennial description of the eohippus, or "dawn horse," as the size of a fox terrier, even though most authors, including yours truly, have no idea of the dimensions or appearance of this breed; and the other on the persistent claim that elongating giraffe necks provide our best illustration of Darwinian natural selection versus Lamarckian use and disuse when, in fact, no meaningful data exist on the evolution of this justly celebrated structure.)