Giraffes are quite distinctive due to their extremely long necks.

Charles Darwin suggested the “competing browsers hypothesis,” which basically says that the elongated necks evolved because they enabled giraffes to reach food that competitors could not. It makes sense, but was this really what happened?

Chinese researchers offered a new explanation for the evolutionary mystery of giraffes’ long necks: They were elongated by head-bashing combat in competition for mates.

The study published in the journal Science on June 2 revealed that giraffes use their two-to-three-meter-long swinging necks to hurl their heavy skulls — equipped with small ossicones and osteomas — against the weak parts of competitors. As a result, the longer the neck, the greater the damage to the opponent.

In 1996, a team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) under the Chinese Academy of Sciences discovered a 17-million-year-old fossil in the vast Gobi wilderness in northwest China’s Xinjiang Uygur Autonomous Region.

The fossil, belonging to a large ruminant, features disk-shaped headgear equipped with a helmet-like horny cap, and particularly complex head and neck joints.

IVPP researchers and their collaborators named it Discokeryx xiezhi and conducted their study on the strange early giraffoid.

“Both living giraffes and Discokeryx xiezhi belong to the Giraffoidea, a superfamily. Although their skull and neck morphologies differ greatly, both are associated with male courtship struggles and both have evolved in an extreme direction,” said Wang Shiqi, first author of the study.

The research team 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 toward extreme differences in morphology, thus indicating that courtship struggles are more intense and diverse in giraffes than in other ruminants.

Research indicated that Discokeryx xiezhi was living in open grasslands and may have migrated seasonally. For animals of the time, the grassland environment was more barren and less comfortable than the forest environment. The violent fighting behavior of Discokeryx xiezhi may have been related to survival-related stress caused by the environment.

长颈鹿最特别的就是它们的长脖子。

达尔文提出了“觅食优势假说”，认为进化出长脖子的特征让长颈鹿得以吃到它的竞争对手够不着的食物。这似乎有道理，但事实真是如此吗？

近日，一项中国科学家进行的研究揭开了这个谜题：长颈鹿长脖子形成是由雄性间的求偶竞争推动的。

6月2日发表在《科学》上的一篇研究表明，长颈鹿甩动它们2到3米长的脖子挥舞沉重的头颅 —— 长着一对角和骨瘤 —— 作为武器来攻击对手身上的弱点。所以，脖子越长就能给对手更大打击。

1996年，中国科学院古脊椎动物与古人类研究所的考察队伍在中国西北部新疆的茫茫戈壁之中，发现了一具距今1700万年的神秘化石。

这是一件大型反刍动物的化石，脑颅骨壁异常厚实。其脑袋顶上长着一个巨大的圆盘，完全覆盖了头顶，就像一顶帽子，具有非常复杂的头颈和颈间关节。

古脊椎所的研究人员和合作者们给它命名为獬豸盘角鹿，并研究这种早期长颈鹿类动物。

研究论文的第一作者王世骐说：“现存的长颈鹿和獬豸盘角鹿都属于长颈鹿科，尽管它们的头骨和颈部构造非常不同，两者同样面临雄性求偶竞争，然后身体朝着极端的方向进化。”

研究人员比较了不同类反刍动物的角的形态，包括长颈鹿、牛、羊、鹿和叉角羚。他们发现和其它动物相比，不同个体长颈鹿角的构造有极大差异，从而证明长颈鹿的求偶竞争比其它反刍动物更为激烈。

研究表明，獬豸盘角鹿生活在开放的草原上，需要季节性迁徙。对于当时的动物来说，草原相对贫瘠，也不如森林环境舒适。它们的激烈打斗行为可能和环境导致的生存压力有关。

(chinadaily.com.cn)

Words to Learn 相关词汇

【假设】jiǎshè hypothesis a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation

【形态学】 xíngtàixué morphology the study of the shapes and arrangement of parts of organisms, in order to determine their function, their development, and how they may have been shaped by evolution