The giraffe’s extremely long neck is probably an adaptation to their fighting behavior with other members of the same species. An international research team concludes this from examining the fossil remains of an ancient giraffe. These animals banged their heads against each other during fights and subsequently developed a protective hood and extremely robust cervical vertebrae, as the scientists report in the journal Science.
The long necks of today’s giraffes could have developed in a similar way. They don’t bang their heads against each other like their ancestors did, but the bulls use their muscular necks to fight for mating privileges.
“The common notion that the long necks only developed in the course of evolution because the animals used them to reach leaves in the upper part of the trees may not go far enough,” explains co-author Manuela Aiglstorfer from the Natural History Museum in Mainz and the State Collection for Natural History Rhineland-Palatinate. “Perhaps this is just a side effect and combat strategy is the primary reason for the development of the long neck.”
The researchers suspect that the animals rammed their heads against each other in a similar way to today’s ibex or musk oxen. Such fights could also have occurred when courting females. In fact, the vertebral structure of the primordial giraffe was better adapted to the great force than is the case in today’s animals that fight in this way, the researchers write.
Today’s giraffes live on the African continent. Despite the extremely long neck, around two meters long, their cervical spine consists of only seven vertebrae, as in most mammals. “The cervical vertebrae of modern giraffes have a completely different structure than those of Discokeryx, they are aligned for length,” says Aiglstorfer. Why animals developed such long necks in the course of evolution has occupied scientists for centuries.
Some researchers assume that sexual selection drove the development: males with a strong, long neck won the fights for the females more often and passed their genes on to the next generation more often.
The theory that advantages in acquiring food were more important is more well-known: the evolutionary biologist Jean-Baptiste Lamarck suspected that a giraffe’s neck stretched over the course of its life because it always reached out for leaves growing at a great height. According to Lamarck, the newly acquired property was passed on to the offspring. This theory has since been disproved because acquired adaptations do not affect the genes that are the basis for the inheritance of physical traits in this way.
The most common hypothesis today goes back to Charles Darwin’s theory of evolution. According to this, individuals with a particularly long neck are born again and again by chance. Since they can reach more food than their shorter-necked counterparts, they have a better chance of survival and more offspring, to whom they pass on the genetic basis for the long neck. This is how a trait is expressed and the hereditary dispositions assert themselves in the gene pool.
The results didn’t disprove a link to diet, says Aiglstorfer. “But we show that in ruminants there can also be other significant influences that affect the structure of the cervical spine.”
