Of sexual dimension of giraffe neck

There are subjects that the columnist must approach with caution. Highly flammable, preceded by centuries of controversy, they place us in unstable balance on the shoulders of the giants. But how to resist an article of the review Science Science who ensures a fascinating, ancestral question, which brings the child and the scientist together: the origin of the long neck of the giraffe.

In the absence of a satisfactory hypothesis, the Greeks had kicked in touch: his dress and appearance testified to the union of a leopard and a camel. Not convinced, Carl von Linné (1707-1778) named her anyway, in 1758, Giraffa Camelopardalis, her current scientific name, borrowing in the Arabic Zirafa.

which did not settle the question of the neck. After various eccentric hypotheses, the origin of its dimension symbolized the confrontation of two schools. In order of entry on the scene, Jean-Baptiste de Lamarck (1744-1829) drew the first. For him, the giraffe, eager to reach the leaves located in height, had stretched his neck and transmitted this character acquired to his girafons. And so on on thousands of generations. No, replied a few decades later Charles Darwin (1809-1882): like humans, giraffes are more or less large, and the largest have been favored, lived longer, benefited from greater descendants. A “natural selection” model.

Both agreed in any case on the central role of access to food. In 1996, however, two South African zoologists, Robert Simmons and Lue Schippers, proposed another hypothesis: that of sexual selection. To attract the favors of the females, the males compete with neck. Like the large woods of deer, the disproportionate cervical vertebrae would have been favored. As proof, the neck of males is larger. To this theory called “Necks for Sex”, much replied that the sexual dimorphism of the giraffes was nothing exceptional and invited the two revolutionaries to return to comb the animal.

ancestor close to the Okapi

The article published in Science, Thursday, June 2, by a Sino-Swiss team, however, takes up this theory. It is based on the discovery, in 1996, by Professor Jin Meng, of the Academy of Chinese Sciences, of a fossil of 16.9 million years old, in the Xinjiang desert: a skull and four vertebrae . “He immediately saw that it was a strange animal, but he first thought of a bovid,” said Shiqi Wang, first author of the article. Paleontologists continued excavations, accumulated equipment and it was in 2015 that a major study was launched. “A colossal work” bringing together “geochemistry, stress analysis, analysis of head appendages in histology, analysis of internal cranial structures”, details Loïc Costeur, curator at the museum of natural history of Basel. He was responsible for the inner ear, an element which turned out to be essential to the attribution of the fossil to the family of the Giraffidés.

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/Media reports.