There are some ideas in science that ultimately get forgotten, although they must have seemed pretty important at the time. Louis Agassiz’s idea of evolution being driven by cycles of catastrophic events and “new creations” is one such example, and I’m certain that his name recognition today is probably not what he hoped it would be. Still, while a good many hypotheses have been relegated to the trash bin of history, I think it’s important to look back and take note of scientific ideas that never quite made it, and Gerhard Heilmann’s 1927 opus The Origin of Birds contains such a wonderful illustration that I couldn’t resist sharing it.
I could write about what’s wrong with Heilmann’s hypothesis that birds evolved from archosaurs like Ornithosuchus and Euparkeria, but for now I will pass over this topic, especially since at the time he wrote the book he was not privy to the fantastic fossils coming out of China which have further solidified the relationship with dinosaurs and birds (Heilmann does note the closeness of small theropods and birds, although in the end he decides on the “pseudosuchians” as the best contenders). No, instead I want to bring into focus something Heilmann did right; refuting the notion that birds evolved from ornithiscian (“bird-hipped”) dinosaurs like Iguanodon and Camptosaurus. Besides the obvious issues with the time scale (the ornithiscian dinosaurs in question are younger than their proposed descendant, Archaeopteryx [or, Heilmann notes, Archaeornis, which was later found to be the same as Archaeopteryx]), the Iguanodon-bird link seemed entirely based upon the structure of the hip, other scientists so enamored with the bones that they disregarded everything else, producing some terrible “just-so” stories. Heilmann writes (p. 143);
Before proceeding, we take out one of the books accompanying us on our expedition. The title is “Extinct Animals” (London 1909), and, on opening it we happen to catch sight of a rather astonishing passage, p. 202: “In fact it is now certain that reptiles similar to the Iguanadon were the stock from which birds have been derived, the front limb having become probably first a swimming flipper or paddle, and then later an organ for beating the air and raising the creature out of the water for a brief flight. From such a beginning came the feather-bearing wing of modern birds.”
Dear me! How evident! we exclaim. The origin and evolution of the entire class of birds presented in a nutshell, and not the slightest doubt as to the correctness of the conclusion: “In fact it is now certain.” Hands off! All further investigations superfluous; we may just as well pack up again.
But are we really justified in relying upon our authority? we muse, turning to the title page, bearing the author’s name. We are struck with awe as we read: “E. Ray Lankester, M.A., LL. D., K.C.B., F.R.S., Late Director of the Natural History Department of the British Museum; Correspondent of the Institute of France.” And in the preface we further read: “This volume is a corrected shorthand report of the course of lectures adapted to a juvenile audience given by me at the Royal Institution, London.”
Well, then there can be no doubt whatever. No scientist, of course, would tell anybody, especially young people, what was not absolutely reliable. A pity, though, that he has not furnished us with an illustration, too, of this interesting process of evolution; it would have been a grateful task to draw the reptile “similar to the Iguanodon,” standing half-way in water, waving its paddle-like organs in the air, “raising the creature out of the water for a brief flight.”
Heilmann goes on to further desconstruct Mr. Lankester, but I couldn’t help but laugh out loud when I imagined a flippered Iguanodon and read Heilmann’s sarcastic response. Indeed, while the book may be old and full of technical language involving the names of bones (which Heilmann graciously depicts and labels throughout; it is a beautiful work) it surpasses many of the “popular” science books I have read recently, where authors are stingy with illustrations (did I mention Heilmann largely supplied his own for the book, in addition to writing it?) and are so concerned with using general terminology and metaphor that they trip over themselves. This is not true of all old books, of course, (Gosse’s Omphalos nearly killed me) but right or wrong Heilmann’s work has instantly become one of my most favorite works, and if you can find it I reccomend you get ahold of it.
In any case, there are far more stories to tell and old ideas to be inspected than anyone fully has time for, but I do think the history of science should be just as important to current students of nature as the newest Science or Nature paper. Some old ideas actually come back to life or appear to have elements of truth to them, and even if they do not (like a penguin/Iguanodon) they can serve to keep us humble; future researchers may end up laughing at our lofty ideas as well.