Research press release


Nature Communications

Palaeontology: Early Miocene apes evolved in tropical forest



今回、Lauren Michelたちは、ルシンガ島(ケニア)で発見された中新世前期の環境指標(例えば、化石植物や化石土壌)とProconsulの化石の解析を行った。ルシンガ島は、中新世前期に由来する古生物学的情報の重要な情報源となっている。Michelたちは、この化石には、密集した根株と保存状態の良好な葉が含まれており、その大半が常緑樹の葉であることを報告している。この古生物学的データからは、年間平均気温が摂氏22.6~34.5度の範囲内にあり、降水量も比較的多かったことが示唆されている。以上をまとめると、今回示された証拠は、Proconsulが赤道アフリカの高温、湿潤な季節的気候の熱帯密林に生息していたことを示唆している。


Proconsul, a genus of early apes linked to the origin of the ape-human lineage, lived in a dense tropical forest, according to research published in Nature Communications. Previous evidence has suggested that Proconsul may have lived in a variety of habitats, including open spaces, but this work helps to confirm that some members of the genus definitively lived in dense, closed-canopy forests. This finding indicates the importance of arboreal settings in the early evolution of distant human ancestors.

Hominoids originated and diversified in Afro-Arabia 28-18 million years ago during the late Oligocene and Early Miocene. Knowledge of the environment that these ancestral apes lived in can help us to understand the selective pressures that gave rise to early humans. There are, however, very few instances where well-preserved fossil hominoid remains co-occur with a discrete set of palaeoenvironmental indicators, making it difficult to directly tie individual species to specific habitats.

Lauren Michel and colleagues analysed Early Miocene environmental indicators, such as fossil plants and fossil soils, and remains of Proconsul from Rusinga Island, in Kenya - an area that contains key sources of palaeobiological information from the Early Miocene. The authors report that the fossil remains include densely clustered tree stumps, and well preserved leaves from predominantly evergreen species. The palaeoclimate data suggest that the annual temperature ranged from 22.6-34.5oC, and the precipitation was relatively high. Together, this evidence implies that Proconsul lived in dense tropical forest set in a warm, wet, and seasonal local climate in equatorial Africa.

This work supports the hypothesis that Proconsul lived in closed canopy forests and also highlights that these hominoids were already adapted to live in both open and closed conditions.

doi: 10.1038/ncomms4236

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