The discovery of Homo naledi has expanded the range of phenotypic variation in Homo, leading to new questions surrounding the mosaic nature of morphological evolution.
Though currently undated, its unique morphological pattern and possible phylogenetic relationships to other hominin taxa suggest a complex evolutionary scenario. Here, geometric morphometric analyses were performed onÂ
±á.Ìý²Ô²¹±ô±ð»å¾±Â cranial and mandibular remains to investigate its morphological relationship with species ofÂ
HomoÌý²¹²Ô»åÌý
Australopithecus. Generalized Procrustes analysis was conducted to placeÂ
±á.Ìý²Ô²¹±ô±ð»å¾±Â within the pattern of known hominin skull diversity, distributions of Procrustes distances among individuals to compareÂ
±á.Ìý²Ô²¹±ô±ð»å¾±Ìý²¹²Ô»åÌý
Homo erectus, and neighbour joining trees to investigate the potential phenetic relationships between groups. The goal is to address a set of hypotheses relating to the uniqueness ofÂ
±á.Ìý²Ô²¹±ô±ð»å¾±, its affinity withÂ
±á.Ìý±ð°ù±ð³¦³Ù³Ü²õ, and the age of the fossils based on skull morphology. The results indicate that, cranially,Â
±á.Ìý²Ô²¹±ô±ð»å¾±aligns with members of the genusÂ
Homo, with closest affiliations toÂ
±á.Ìý±ð°ù±ð³¦³Ù³Ü²õ. The mandibular results are less clear;Â
±á.Ìý²Ô²¹±ô±ð»å¾±Â closely associates with a number of taxa, including some australopiths. However, results also show that althoughÂ
±á.Ìý²Ô²¹±ô±ð»å¾±Â shares similarities withÂ
±á.Ìý±ð°ù±ð³¦³Ù³Ü²õ, some distances from this taxon - especially small-brained members of this taxon - are extreme. The neighbor joining trees placeÂ
±á.Ìý²Ô²¹±ô±ð»å¾±Â firmly withinÂ
Homo. The trees based on cranial morphology again indicate a close relationship betweenÂ
±á.Ìý²Ô²¹±ô±ð»å¾±Ìý²¹²Ô»åÌý
±á.Ìý±ð°ù±ð³¦³Ù³Ü²õ, whereas the mandibular tree placesÂ
±á.Ìý²Ô²¹±ô±ð»å¾±Â closer to basalÂ
Homo, suggesting a deeper antiquity. Altogether, these results emphasize the unique combination of features (
±á.Ìý±ð°ù±ð³¦³Ù³Ü²õ-like cranium, less derived mandible) definingÂ
±á.Ìý²Ô²¹±ô±ð»å¾±. The results also highlight the variability withinÂ
Homo, calling for a greater focus on the cause of this variability, and emphasizing the importance of using the total morphological package for species diagnoses.
Lauren Schroeder et al
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