ケニア・リフト・バレーのネオゲン・ホミニド・パレオ環境の同位体証拠
まとめ
初期の人類の双足性は,草原への移動によって引き起こされなかったかもしれない. 安定炭素同位体の分析により,東アフリカでは何百万年にもわたってC3とC4の植物が混在していたことが明らかになった.
科学分野:
- パレオエコロジー (古生態学)
- 古人類学は,古人類学である.
- イソトープ地球化学 イソトープ地球化学
背景:
- 初期のホミニドの双足性は,東アフリカにおける生息地の変化とよく関連している.
- この遷移は,理論的には1200万年から500万年前に起こったと考えられています.
- この変化は,森林からより開放的な草原環境への移行であると考えられていました.
研究 の 目的:
- ミオセンの後半期の東アフリカの古生物学環境を調査する.
- C4草原へのシフトが,初期のヒト類の進化の間に起こったかどうかを判断する.
- オープンな生息地への反応として二足が進化したという仮説を検証するために.
主な方法:
- 安定した炭素同位体組成の分析 (デルタ 13C).
- ケニアのトゥーゲンヒルズ (Tugen Hills) のパレオソール炭酸と有機物の調査.
- 過去の植生組成 (C3対C4植物) の再構築.
主要な成果:
- C3とC4の植物が混在した異質な環境は,少なくとも1550万年もの間存在しています.
- オープンな草原はリフト・バレーのこの地域を支配しなかった.
- C3が優勢である生息地からC4が優勢である生息地への移行を裏付ける証拠はありません.
結論:
- 東アフリカにおける初期のホミニド進化の環境条件は,生態学的に多様であった.
- 双脚性を単に草原への移動と結びつける伝統的な仮説は,このデータによって支持されていません.
- ホミノイドはモザイクの景色で進化した可能性が高いが,それは露天草原だけではなかった.
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