The giraffe did not always have a long neck, but it always favored the headbutt to defend its position, as evidenced by the discovery of a giraffoid fossil, equipped with a real cranial shield. The specimen was found in northern China.
The discovery of “Discokeryx xiezhi” reinforces the thesis that the initial driver of giraffe neck elongation was sexual selection. The specimen is the first representative of a new species, the fossil of which lived regarding 17 million years ago, reports a study published in the journal Science last week.
This ruminant the size of a large deer had a thick bony disc at the top of the skull and a neck with formidable cervical vertebrae allowing it to withstand violent frontal shocks, according to paleontologist Shi-Qi Wang, from the Chinese Academy of Sciences, first author of the article.
This particular morphology “was probably adapted to head-butting behaviors between males”, suppose the researchers, who compare this behavior “to the fights of male giraffes with their necks”. The latter engage in struggles for domination by swinging their heads, equipped with small horns, once morest the adversary with all their might.
The fights between males at the origin of the elongation of the neck of the giraffes. [Y. WANG AND X. GUO]
Sexual competition
The discovery of Chinese paleontologists sheds a decisive piece on the cause of the giraffe’s long neck. Paleontologists have long defended the thesis of ecological advantage, according to which this long neck gave its holder a decisive advantage in reaching high foliage. More recent and highly disputed, the other theory postulates that a long and powerful neck influences the outcome of fights between males and has therefore favored its growth.
The study by Shi-Qi Wang and his colleagues agrees with this last thesis. This kind of fighting is “probably the first reason giraffes developed long necks”, which later provided them with an advantage for browsing foliage at heights.
This “shows once once more that sexual competition is one of the engines of evolution, which leads to morphological innovations that can be used for other purposes”, explained to AFP paleontologist Grégoire Metais, from the national museum of ‘natural History.
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