It is commonly thought that the giraffe evolved to grow its neck six feet long so it could reach the leaves on the tallest branches.
But a new study by Chinese experts says the mammal’s distinctive neck evolved over millions of years because it was an effective weapon.
The researchers came to this conclusion after an analysis of the fossils of a “strange” species of giraffe called Discokeryx xiezhi, which roamed the Xinjiang region in the northwest. China 17 million years ago.
The results suggest that giraffes developed long necks to hit other males in the fight for a female, because longer one neck allowed them to generate more power and speed.
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Fossils of a strange early giraffe have revealed key driving forces in giraffe evolution, Chinese researchers say. This illustration depicts two fighting males of the earliest extinct giraffo species (Discokeryx xiezhi, foreground) and two fighting males of the modern northern giraffe (Giraffa camelopardalis, background)
D. XIEZHI: A FIRST ‘STRANGE’ GIRAFFOID
Discokeryx xiezhi is an extinct species in the Giraffoidea superfamily.
He lived in the Xinjiang region of China up to 17 million years ago.
Researchers describe it as “odd,” because it had a stockier neck than today’s giraffes, and also a single, dome-shaped ossicone on its head.
He had very complex head-neck joints suitable for hitting an opponent in a fight for his teammates.
Unlike modern giraffes, D. xiezhi had only one ossicone, the bony structure covered with skin at the top of the head, but was more like a dome or a disk in shape.
D. xiezhi is so named because its unique ossicone resembles that of the xiezhi, a one-horned creature from ancient Chinese mythology.
The new study was led by researchers from the Institute of Paleontology and Paleoanthropology of Vertebrates (IVPP) of the Chinese Academy of Sciences in Beijing.
“Both living giraffes and Discokeryx xiezhi belong to the Giraffoidea, a superfamily,” said study author Wang Shiqi of IVPP.
“Although their skull and neck morphologies differ greatly, both are associated with male courtship fights and both have evolved in an extreme direction.”
Today, a giraffe’s neck can be six feet long – taller than the average man – and it can weigh up to 600 pounds.
Millions of years ago, the giraffe had a stockier neck, but competition for food has led to the constant increase in neck length over many generations.
The longer necks allowed giraffes to search for edible leaves on treetops in African savannah woodlands that would otherwise be out of reach, according to Charles Darwin’s theory of natural selection.
The theory suggested that giraffes with longer necks were able to access the food needed to survive and pass their genetic code on to subsequent generations.
However, with increasing observation of giraffe behavior, scientists have begun to realize that the neck serves as a weapon in male courtship competition.
This is evident in the clips circulating online today, which show two males brutally beating each other.
D. xiezhi is so named because its unique ossicone resembles that of the xiezhi, a one-horned creature from ancient Chinese mythology (pictured here as a sculpture in the Forbidden City in Beijing, China)
The distinctive long neck of the modern giraffe – the tallest land animal and largest ruminant on Earth – has long been considered a classic example of adaptive evolution and natural selection since Darwin first wrote the concepts
GIRAFFES CHOOSE SIMILAR SIZE OPPONENTS FOR A FAIR FIGHT
In an honorable example of fair play, giraffes choose opponents of similar size to ensure a “square,” a study reveals.
From the observations in South AfricaUniversity of Manchester researchers found that males practiced head butts with males of similar stature.
Male giraffes fight for “access to large numbers of females” by throwing their ossicones – the two skin-covered bony structures at the top of their heads – at their opponents, using their long necks as leverage.
Longer necks tend to generate more speed and power, so the longer the neck, the greater the damage to the opponent.
Indeed, male giraffe neck size is directly related to social hierarchy, and courtship competition is the driving force behind the evolution of long necks.
The fossils in this study were found in the lower Miocene “strata” (a layer of rock or sediment) about 17 million years ago on the northern edge of the Junggar Basin in Xinjiang.
A complete skull and four cervical vertebrae belonging to Discokeryx xiezhi were part of the find.
Analysis indicates that ancient species had helmet-shaped headdresses, more like a dome than a sharp point, and particularly complex head and neck joints.
The researchers found that the complicated joints between the skull and the cervical vertebrae of the species were particularly adapted to the high-speed head-to-head impact.
This structure was much more effective than that of live animals, such as the musk ox, which adapt well to head impact.
In fact, D. xiezhi may have been the best adapted vertebrate ever to head impact, the researchers think.
The findings suggest that the ability to hit an opponent with the neck and the associated survival benefits have been a key part of giraffe morphology for millions of years.
Computer modeling shows the “complicated” joints between the skull and the vertebrae of Discokeryx xiezhi
In the photo, two giraffes face off in a head-to-head position. Longer necks tend to generate more speed and power, so the longer the neck, the greater the damage to the opponent
The wildlife community in the Junggar Basin, Xinjiang, China, about 17 million years ago is depicted. Discokeryx xiezhi are in the middle
The research team also compared the horn morphology of several groups of ruminants, including giraffoids, cattle, sheep, deer and pronghorns.
They found that horn diversity in giraffes is much greater than in other groups, with a tendency towards extreme differences in morphology.
This indicates that courtship fights are generally more intense and different in giraffes than in other ruminants.
The findings also suggest that D. xiezhi lived in open, dry grasslands and may have migrated seasonally.
For the animals of the time, the environment of the meadows was more arid and less comfortable than the forest environment.
Indeed, the species’ violent fighting may have been related to survival stress caused by the environment.
The new study was published in the journal Science.
EXPERTS CONFIRM THAT THERE ARE FOUR DISTINCT SPECIES OF GIRAFFE
Efforts to map the genome of giraffes have confirmed that there are four distinct species and they are as different from each other as brown bears are compared to polar bears.
Efforts to map the genome of giraffes have confirmed that there are four distinct species, and they are as different from each other as brown bears and polar bears.
Visually, they are hardly distinguishable, according to scientists from the LOEWE Center for Translational Biodiversity Genomics in Frankfurt, Germany, who carried out the genetic analyzes.
While they look the same, there are genetically four distinct species of giraffes and seven subspecies, explained lead author Dr Axel Janke.
According to their comprehensive genome analyzes, the four giraffe lineages have evolved separately for thousands of years.
Widespread from north to south Africa, the four distinct species of giraffe are: Northern Giraffe, Reticulated Giraffe, Masai Giraffe, and Southern Giraffe.
Southern Giraffe (Giraffa Giraffa)
Found in: Angola, Namibia, Zimbabwe, South Africa, Zambia
Subspecies: Angolan giraffe, South African giraffe
Masai giraffe (G. tippelskirchi)
Found in: Kenya, Tanzania, Zambia
Reticulated giraffe (G. reticulata)
Found in: Kenya, Somalia, Ethiopia
Northern giraffe (G. camelopardalis)
Found in: Chad, Central African Republic, Cameroon, Democratic Republic of the Congo, South Sudan
Subspecies: Kordofan giraffe, Nubian giraffe, West African giraffe