Crossing A Line

Environmental & Science Education, STEM, Biological Evolution, History of Science, Nature of Science, Art and Environment

Ed Hessler 

Perhaps you've heard of the Wallace Line, "a hypothetical boundary separating the biogeographical regions of Asia and Australia." The co-developer of the theory of evolution with Charles Darwin, Alfred Russel Wallace, had noticed striking differences between species found in Australia and Papua New Guinea and Southeast Asia. This is readily seen when considering the differences between the two regions. "South and east of the line marsupials and monotremes are found, unlike the placental mammals found north and west of it."  

In a teaching unit for grades 5 - 8, the National Geographic has a good map of the line. For information about the Weber line see the Wiki entry on Max Carl Wilhelm Weber.

The Wallace Line is mentioned in a fascinating essay by Rebecca Mead (The New Yorker July 5, 2021) primarily about Heather Dalton, an art historian who now lives in Melbourne, Australia. When she was a graduate student, while thumbing through an art book, Dalton noticed a feature in a painting that caught her eye. It was in the Renaissance painting, "Madonna della Vittoria," by Andrea Mantegna, completed in 1496. It is a large painting of more than 2.74 m (9')  in length and your eye is directed downward but near the top is "white bird with a black beak...and an impressive greenish-yellow crest." Her time in Australia led her to identify it as a "sulfur - crested cockatoo," which she expresses more colorfully.

Cocakatoos are not migratory and are restricted to the south and east of Wallace line. The Wiki entry includes a photograph of the yellow-crested cockatoo. Dalton wondered "'How did a bird from Australasia end up in a fifteen - century Italian painting?"' This led to a publication in 2014 arguing that "the bird's presence...illuminated the sophistication of ancient trade routes between Australasia and the rest of the world." It turns out that this is not the only painting that "hints of at least indirect contact with Australasia. Around 1561, Flemish painter Joris Hoefnagel "shows a furry gray creature seated on a gilded throne, gnawing on a branch." Dalton thinks it is probably a tree kangaroo.  The painting is titled "A  Sloth."                                                                                                                                                                                                                                                               

Aristotle remarked on the ability of parrots (from Indian trade routes) to mimic and they began showing up in European art later. Aristotle, reports Mead, noted that "they were 'even more outrageous after drinking wine.Painters and others did not explore the implications of the cockatoo's "geographical origin," indeed most didn't think much about the bird at all or why it was there.

In 1988, on the occasion of a bicentenary "of the establishment of a British penal colony in Australia, Dalton wrote an article "about the country's vigorous trade in beche-de-mer, or sea cucumber."  It is related to starfish and "was harvested off the northern coast of Australia and then sold in Chinese markets." She returned to the subject later noting that "The fishermen, who had gathered sea cucumbers in shallow waters had formed one end of a significant mercantile link between coastal Australia and Asia, but they had been largely overlook in the narrative of Australia's national founding," on favoring '"the digger, the pastoralist, and the drover.'"

Dalton told Mead that she "'was very interested in the idea that everything is about trade and economics, and the idea that we make discoveries for some national reason is something that you claim later.'"

Dalton has not found the cockatoo in any other of Mantegna's paintings or of contemporaries or can she show that it is only a representation of another image. The painter did own a large birdcage but there is no evidence of the acquisition of a cockatoo. Dalton considers the possibilities of trade and Mead provocatively discusses the prospects.

Mead draws attention to research by Finnish zoologist Pekka Niemela who was given access to a "rare manuscript in the collection of the Vatican Library in which he found the same cockatoo or a close relative.The illustrations not only reveal the "original coloring" but suggest it was a female (reddish flecks in the eye's iris). This attention to detail amazed me.

A collaboration between Dalton and Niemala led to a publication tracking down the provenance of Frederick II's cockatoo sent to him by the "'Sultan of Babylon' -- the ruler of Egypt, Al - Malike al - Kamil. Frederick II was the Holy Roman Emperor, 1241 to 1244. The route ends in Cairo from China via Australasia. The evidence is very strong since it includes a paper trail. By the way the two leaders exchanged many gifts, shows "of poer and prestige.

Mead's essay may be read here. Please give yourself a treat and do just that. It is a wonderful story, a tale of scientific sleuthing, evidence and hypotheses.