This finding supports the thesis that the initial driver of giraffe neck elongation was sexual selection.
Unearthed in northern China, the fossil of Discokeryx xiezhi belongs to a species unknown to date, which lived 17 million years ago, reports a study published in the journal Science.
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.
was most likely adapted to head-butting behaviors between malessuppose the researchers, who compare this behavior
to the fights of male giraffes with their necks. The latter – the current species – engage in domination struggles by swinging their heads, equipped with small horns, against the adversary with all their might.
The discovery of Chinese paleontologists is a decisive piece in a debate as old as that of paleontology: why does the giraffe have such a 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 combat is
probably the first reason why giraffes developed long neckswhich then provided them with an advantage for grazing foliage high up.
It is a perfect example of exaptation, that is to say of an advantage provided by an organ which will later prove useful for another use.explains to AFP the paleontologist Grégoire Metais, of the National Museum of Natural History, who salutes a
very nice study.
According to him, the giraffids have embarked on a
forward race for a long and reinforced neck. That
shows once again that sexual competition is one of the engines of evolution, which leads to morphological innovations that can be used for other purposes.
In the case of Discokeryx xiezhiits morphology represented
the most optimal adaptation for head-butting, when compared with current species engaging in this practice, according to the study.
As proof, computer modeling of the impact of headbutts, applied to other combative ruminants, such as the muskox, suggests that the Discokeryx xiezhi was linked to intense headbutting practice”,”text”:”very special head and neck morphology of Discokeryx xiezhi was linked to intense headbutting practice”}}’>very special morphology of the head and neck of Discokeryx xiezhi was linked to an intense practice of headbutting. And that this morphology gave him an incomparable ability to
absorb the energy of the impact and protect his brain.
The study also clearly establishes that this fossil was a giraffoid, which appeared about 20 million years ago, of which the only two species still existing are the giraffe and the okapi.
But then why Discokeryx xiezhi didn’t he also develop a long neck? Firstly because he did not need it: he lived through a remarkable episode of the Miocene, which saw a marked warming of the climate, allowing him to graze to his heart’s content. Then, because it was only
the beginning of the history of giraffes, recalls Mr. Metais. And that of the growth of their long necks.