Research press release



Evolution: Before apes were bipeds



今回、Madelaine Bohmeたちは、完全な四肢骨が保存された新種の化石類人猿Danuvius guggenmosiについて記述している。この化石標本については、「extended limb clambering(四肢を伸ばした姿勢でのよじ登り)」と命名された新たな位置的行動の形態を示す証拠になるとBohmeたちは考えている。D. guggenmosiは、腕で枝にぶら下がることができたと考えられているが、脚より腕を多く使って移動する他の類人猿(例えば、テナガザルやオランウータン)とは異なり、後肢が真っすぐに保たれており、歩行に用いられた可能性がある。また、D. guggenmosiは、物をつかむことのできる第1趾を持っており、足の裏全体を地面につけて歩行していたと考えられる。

Bohmeたちは、類人猿が地上に降りる前に後肢で歩行し始めた過程がD. guggenmosiの化石によって例証されていると結論付けている。

The fossil of a previously unknown species of ape found in Germany is reported in a paper published this week in Nature. This specimen, which lived during the Miocene about 11.6 million years ago, sheds light on what apes may have been like before they were bipedal.

Many ideas have been proposed to explain the origin of hominin bipedalism and great ape suspension, but fossil evidence has been lacking. It has been suggested that hominin bipedalism evolved from a quadruped that puts its entire foot on the ground, similar to living monkeys, or from a more suspensory quadruped, most similar to extant chimpanzees.

Madelaine Bohme and colleagues describe a new fossil ape, named Danuvius guggenmosi, with complete limb bones. The authors suggest that this specimen provides evidence of a newly identified form of positional behaviour that they call ‘extended limb clambering’. This ape would have been able to hang from branches by its arms. However, unlike other apes such as gibbons or orangutans, which do not use their legs as much as their arms for locomotion, this species had hindlimbs that were held straight and could have been used to walk on. This ape also had a grasping big toe, which meant it would have walked on the sole of its feet.

The authors conclude that D. guggenmosi illustrates a way in which apes began to walk on their hind legs before they reached the ground.

doi: 10.1038/s41586-019-1731-0

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