Tales of the barnacle goose

Occasionally one comes across odd stories in the late medieval literature on natural history, and one is inclined to dismiss them as fablous stories born of credulous superstition. But they illustrate a much more important phenomenon - the shift from seeing nature as a source of moral lessons to seeing nature as something worth studying for its own sake. One such is the tale of the Barnacle Goose.

The Barnacle Goose, Branta leucopsis, is a small (less than 2kg) black and white goose of the order Anseriformes. It lives during the winter months in the Atlantic coasts of Scotland and Ireland, but it breeds in the Arctic, usually in Iceland or Greenland.

The fact that it was never seen to breed gave rise to a myth that it was in fact spontaneously generated from molluscs, the Goose Barnacle, or Goose Neck Barnacle, Lepas anatifera, a deep water mollusc that is occasionally washed up on shore attached to pieces of driftwood. Its shell resembles a goose head, and is attached to the substrate by a long stalk somewhat resembling a bird's neck.

Around the end of the 12th century, Bishop Giraldus Cambrensis (Gerald of Wales) published a book Topographia Hiberniae, after King John's successful invasion of parts of Ireland. In it, he described how Irish churchmen would eat the Barnacle Goose during fasts because "these birds [are] not flesh nor being born of the flesh", for "they are born at first like pieces of gum on logs of timber washed by the waves. Then enclosed in shells of a free form they hang by their beaks as if from the moss clinging to the wood and so at length in process of time obtaining a sure covering of feathers, they either dive off into the waters or fly away into free air. . . I have myself seen many times with my own eyes more than a thousand minute corpuscles of this kind of bird hanging to one log on the shore of the sea, enclosed in shells and already formed". And so the myth was born, and spread around Europe.

Spontaneous generation was a commonly held belief, dating back to Aristotle, that modern complex organisms could, under the right conditions, be made out of nonliving stuff. What is interesting is that these organisms had an ordinary lifecycle, of sorts, but they always arose in a predictable fashion, without divine intervention. It was just that they lacked parents. Gerald used the Barnacle Goose story to try to argue to Jews that the Immaculate Conception of Jesus was proven possible. There was a moral lesson in this otherwise marvellous event.

About 200 years later, there was a marvellous man named Frederick II of Hohenstaufen, Holy Roman Emperor, King of Sicily and Jerusalem. I have blogged about him before, but it's worth quoting his observations and comments about the Barnacle Goose:

There is also a small species known as the barnacle goose, arrayed in motley plumage ..., of whose nesting haunts we have no certain knowledge. There is, however, a curious popular tradition that they spring from dead trees. It is said that in the far north old ships are to be found in whose rotting hulls a worm is born that develops into the barnacle goose. This goose hangs from the dead wood by its beak until it is old and strong enough to fly. We have made prolonged research into the origin and truth of this legend and even sent special envoys to the North with orders to bring back specimens of those mythical timbers for our inspection. When we examined them we did observe shell-like formations clinging to the rotten wood, but these bore no resemblance to any avian body. We therefore doubt the truth of this legend in the absence of corroborating evidence. In our opinion this superstition arose from the fact that barnacle geese breed in such remote latitudes that men, in ignorance of their real nesting place, invented this explanation.

The goose migrates to Ireland and Scotland via the Scandanavian countries, so it became thought that they did their transmutation in that region. What Frederick happened to receive from his envoys was one of those driftwood planks, possibly with the Goose Barnacle attached. As it happens, though, these barnacles are more common in the region where the myth arose, so perhaps they went to Britain or Ireland. And he was absolutely right that the Barnacle Goose breeds in "remote latitudes.

Albert the Great also addressed the Barnacle Goose question, noting that he and his friends had bred one with a domestic goose, and that the spontaneous generation account is "altogether absurd as I and many of my friends have seen them pair and lay eggs and hatch chicks". So the spontaneous generation myth is done and dusted by the mid-14th century.

Or was it? Several authors, including Joseph Justus Scaliger and Hector Boethius repeated the claim in the 16th century, with Scaliger asserting, as Giraldus had, that he had seen this with his own eyes. What he saw, as had Giraldus, was of course the goose barnacles, and the similarity of form between the geese and the barnacles was sufficient to imply that they were related, on the "calculus of probabilities" as another author said in a similar context.

What is happening here? Well there are several explanations. One is that Frederick, being excommunicated twice (!) was not regarded as reliable in orthodox terms, and the tradition itself had a strong theological component. Frederick was excommunicated for challenging the Pope's authority to crown emperors rather than doctrinal heresy, but that might have been enough to tar him. Moreover, his work, which was about breeding and training hawks and falcons, was distributed only among the aristotcracy - this was before printing, remember, and such manuscripts were regarded as valuable in the extreme. But I think that the fact that "everybody knows" that spontaneous generation occurred was sufficient for his and Albert's observations and clear inferences to be ignored.

The persistence of the myth for theological reasons is due to the long-standing tradition, which began with the Physiologus in the second century, of drawing moral lessons from nature to underpin theological points, just as Giraldus had done. Until the rise of natural history as an end in itself, in the early 17th century, nature was just God's second Book. And we still do this today, as witness the claims by the modern physiologists that the Emperor penguin's breeding habits somehow reinforce the idea that monogamy is God's will (ignoring the fact that the penguins change their breeding partners each year. Let's see that in the Marriage Acts!).

Social, moral and theological concerns do not generate good science. They lead us to make inferences that reinforce prior assumptions, values and prejudices. The long tradition early in the Christian era of using nature only as a source of illustrations for moral tales may or may not have impeded the development of science but at the best it failed to help it. I think there's a moral there...

Finally, let it be noted that Frederick and Albert are instances of honest attempts to understand the world about them. They didn't always get it right (although Frederick, being restricted to a single investigable subject, was a lot more right than Albert, who included fabulous beasts in his bestiary), but they tried, and did so intelligently. I do not think that it is coincidence that the two late espousers of the myth were protestants. Luther's antipathy to reason and science is well known. Not that Catholicism is that much better, but during the middle ages there was a lot less control over and censure of heterodoxy in natural history than later.

And I reiterate my prior comment: people were not stupid before Darwin, nor did they suddently become smart after him. Science will not cure the reliance on myth.