The Origin of Birds is an early synopsis of bird evolution written in 1926 by Gerhard Heilmann, a Danish artist and amateur zoologist. The book was born from a series of articles published between 1913 and 1916 in Danish, and although republished as a book it received mainly criticism from established scientists and got little attention within Denmark. The English edition of 1926, however, became highly influential at the time due to the breadth of evidence synthesized as well as the artwork used to support its arguments.Nieuwland (2004) pp. 1–11. It was considered the last word on the subject of bird evolution for several decades after its publication.Shipman (1998) p. 110.
Through the course of the research represented in the book, Heilmann considers and eventually rejects the possibility of all living and several extinct groups of reptiles as potential ancestors for modern birds, including crocodilians, pterosaurs and several groups of dinosaurs.Weishampel, Dodson & Osmólska (2004) p. 220. Despite his acknowledgment that some of the smaller Jurassic theropods had many similarities to Archaeopteryx and modern birds, he determined that they were unlikely to be direct bird ancestors and that they were instead closely–related offshoots,Ries (2007) pp. 1–19. and concluded that the similarities were a result of convergent evolution rather than direct ancestry.Alexander & Vogel (2004) p. 197. Based essentially on a process of elimination, Heilmann arrives at the conclusion that birds must be descended from thecodonts, a group of archosaurs that lived during the Permian and Triassic periods. Although this conclusion was later shown to be inaccurate, The Origin of Birds was regarded as a masterful piece of scholarship at the time and set the international agenda for research in bird evolution for nearly half a century, and much of its research remains of interest.
Background
When Heilmann began his research in the early 1900s, the early bird Archaeopteryx was only known from three fossils found in the limestone quarries of Solnhofen near Eichstätt, Germany. The three fossils consisted of two nearly complete skeletons found in 1861 and 1877 and a single feather from 1860. They had been discovered just a few decades after the discovery of the dinosaurs, and as some dinosaurs appeared somewhat birdlike, Archaeopteryx was regarded as a possible "missing link" between reptiles and birds by many paleontologists at the time.
The similarities between Archaeopteryx, known dinosaurs and extant birds were examined and emphasized, with Thomas Huxley championing the idea that Archaeopteryx as well as modern birds had more in common with theropod dinosaurs than any other group of animals. This was at the time in opposition to the view of anatomist Sir Richard Owen of the British Museum, who viewed Archaeopteryx as no different taxonomically from modern birds. Huxley's work was controversial, and this climate of uncertainty and contention about bird origins persisted well into the beginning of the 20th century.Long (2008) pp. 3–4.
While the dinosaur-bird connection (or lack thereof) was being pursued in paleontology, the problem of the evolution of flight was under scrutiny as well. It was observed that a number of animals with moderate flying or gliding ability, such as bats, flying lizards and flying squirrels have arboreal lifestyles. This led to the idea that the ancestors of birds must have gradually acquired the ability to fly from leaping among branches in the tops of trees. The Hungarian paleontologist Franz Nopcsa proposed an alternate hypothesis in 1907, arguing that the ancestors of birds were fast-running, bipedal animals related to theropod dinosaurs. When Heilmann came onto the paleontology scene, these two sets of conflicting theories provided the framework for his research and eventual conclusions.
Publication
Between 1913 and 1916, Gerhard Heilmann published a series of articles in the journal of the Danish Ornithological Society, all heavily illustrated and dealing with the question of the origin of birds. He first proposed the idea of a popular treatise on bird evolution in 1912 to Otto Helms, the editor of the journal of the Danish Ornithological Society. Helms supported the idea but recommended that Heilmann first seek professional advice on the topic.Ries (2010) pp. 69–91. Despite the lack of formal training in zoology, Heilmann succeeded in amassing his research with the help of several others, including the expert in prehistoric animals at the Zoological Museum in Copenhagen, Adolf Herluf Winge, and the biologist D'Arcy Wentworth Thompson of the University of Dundee. Winge, though initially showing interest in Heilmann's work, later proved to be a source of frustration by refusing to engage Heilmann in depth on various scientific queries. Heilmann eventually broke off contact, expressing some bitterness at the apparent change of heart, which Heilmann later ascribed to Winge's belief in Lamarckism.
Heilmann's original articles were publicly ignored by Danish zoologists, but caused considerable unrest behind the scenes. Danish zoologist R.H. Stamm, for example, mocked Heilmann in private letters to Helms shortly after the publication of his first article. Other Danish zoologists openly expressed their disdain for Heilmann's work as well, including the professors of zoology in Copenhagen University J.E.V. Boas and Hector Jungersen. Despite this, Helms continued to steadfastly support Heilmann and his ideas, which eventually began to gain attention from abroad. In April 1913, the American expert in fossil birds R. W. Shufeldt came across Heilmann's first article by chance. Shufeldt, who was married to a Norwegian, could understand some Danish and was able to interpret Heilmann's work and initiated contact with him shortly thereafter. This opened up the opportunity for international correspondence with distinguished paleontologists for Heilmann, which was instrumental to the recognition of his work outside of Denmark.
Heilmann's articles were later collected and published as a book in Danish in 1916 with the title as in his series, Vor Nuvaerende Viden om Fuglenes Afstamming ("our present knowledge about the origin of birds").Salomonsen (1946) pp. 146–149. This met the same lack of interest and is thought to have been a result of publishing in Danish, as this made it inaccessible to many scientists working in the U.S. and much of Europe. The field of paleontology at the time was dominated by American and English scientists, and the discipline in continental Europe was dominated by Germany and to a lesser degree France.
Consequently, and at the urging of Shufeldt, Heilmann devoted much of the next few years attempting to find an English–language publisher willing to undertake a translation of his work. None of the larger publishers he approached were willing to do so unless Heilmann himself was prepared to finance it, which he was unable to do. In the meantime, Heilmann took the opportunity to revise and improve his manuscript, which included information he acquired from examining the Berlin specimen of Archaeopteryx for the first time in 1923 at the invitation of Josef Felix Pompeckj, a professor at the Natural History Museum in Berlin. Examining this important specimen in person allowed Heilmann to add some additional details and revisions to his understanding of the hip, the skull, and the flight feathers. With the help of the English paleontologist Arthur Smith Woodward of the British Museum, he finally met success in finding a small London publisher willing to produce an English version of his manuscript in 1926.
Editions While most of the original material was published in the journal of the Danish Ornithological Society between the years of 1913 and 1916, the first English version of the book was published in London in 1926 by H. F. & G. Witherby. It was published in the United States the following year by D. Appleton & Company. The book was reprinted in 1972 by Dover Publications, Inc.,Worldcat.org with the only change being the grayscale reproduction of several illustrations originally published in color.Heilmann (1926)
The English and Danish editions differed in several significant ways. The English edition was somewhat shorter and more concise, and included newer information that Heilmann had acquired by studying the actual fossils of Archaeopteryx in Berlin, as well as from foreign scientists who sent him photographs and plaster casts. It also contained considerably less harsh language towards Boas and others with whom he disagreed. Curiously, the English edition did not contain the transformational sequences inspired by D'Arcy Thompson, though Heilmann still briefly acknowledged the use of his methods in reconstructing his Proavis.
Book outline
Heilmann's book was divided into four main parts. The first three draw evidence for bird evolution from the fossil record, from the embryos of birds and other animals, and from living birds, respectively. The fourth and most groundbreaking section examines several groups of extinct animals in order to determine the probable root of modern birds.
Part I: Some Fossil Birds
In the first section, Heilmann examines in exquisite detail the fossil remains of several extinct birds, including Hesperornis, Ichthyornis, Archaeopteryx, and "Archaeornis", the name used commonly at the time for the Berlin specimen, which was then thought to represent a separate genus. Throughout this section are many finely detailed and labeled renderings of different parts of the skeletal anatomy of these birds, as well as other groups of extinct reptiles and some modern birds. Heilmann's attention to detail in his artwork is inspired at least in part by his dissatisfaction with anatomical renderings of these animals in scholarly works of the time, which he deemed as "unsatisfactory" and "containing misleading errors."Heilmann (1926) p. 3.
Early in this section Heilmann embarks on a thorough description of the Berlin Archaeopteryx specimen, which includes detailed comparisons to specific aspects of modern birds. Following a comparison of its skull to that of Aetosaurus, Euparkeria, and a modern pigeon, Heilmann states that he disagrees with the scientific consensus of the time that the skull of Archaeopteryx is that of a true bird. He writes that the reptilian features of the skull are much more pronounced, citing features of the teeth, fenestrae, and jaw structure as being undeniably un-birdlike.Heilmann (1926) pp. 5–9. Heilmann found that much of Archaeopteryx'''s anatomy, in fact, was decidedly reptilian and generally opposed to that of modern birds. This included the pelvis, which lacks a pectineal process and has a very different os sacrum from modern birds,Heilmann (1926) pp. 15–21. as well as the carpus, which Heilmann wrote exhibited the same phenomena found in the wrists of modern reptiles.Heilmann (1926) pp. 22–23. Its tail was also noted by Heilmann as being extremely reptilian and resembling nothing known of modern birds.Heilmann (1926) p. 30.