2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
American paleoanthropologists carried out a morphological analysis of the first metacarpal bones of Homo naledi and compared them with samples of modern humans, great apes, monkeys and fossil hominids. Scientists have concluded that the thumbs of the Dinaledi people represent an example of a transitional state in the evolution and adaptation of the human thumb, with a number of features indicating a similarity to the bones of the African Australopithecus. The article was published in the Journal of Human Evolution.
In 2013, on the territory of the UNESCO World Heritage Site Cradle of Humanity in the Rising Star Cave, paleoanthropologists discovered more than one and a half thousand fossils - almost a whole skeleton and the remains of fourteen more individuals of different sexes and ages. The scientific team described these findings as a new species of ancient people - a man from Dinaledi (Homo naledi), who supposedly lived about 335-236 thousand years ago. People from Dinaledi had a height of about 1.5 meters, the intermediate brain volume between a skilled person (H. habilis) and australopithecines (Australopithecus) - from 465 to 560 cubic centimeters.
The morphological features of this species are archaic in many aspects and occupy an intermediate place between people and their ancestors (you can read more in our blog "Ice man - is he a man?"). At the same time, the surprisingly small sizes of molars turned out to be comparable to the teeth of modern humans, significantly inferior to all Australopithecines, archaic Homo and even the Floresian man (H. floresiensis). The first study of the metacarpal bones and the wrist joint showed that they are similar to those of modern humans and Neanderthals.
Lucyna Bowland, together with colleagues from the University of Arkansas, performed a morphological analysis of the first metacarpals of H. naledi and compared them with similar findings from other hominids. Scientists noted that today there are seven known such bones from the Dinaledi chamber. In general, the hands of this species exhibit a mixture of archaic and progressive features, including pronounced insertion of the deep flexor tendon into the distal phalanx of the thumb, Cro-Magnon and Neanderthal geometry of the carpometacarpal joint.
Scientists compared the first metacarpal bones of H. naledi with those of H. sapiens (n = 178), modern apes (n = 86), representatives of the monkey primate species Cercopithecus lomamiensis (n = 59), and fossil hominins (n = 14).
Research has shown that the unusual body morphology of the metacarpals of H. naledi distinguishes them from nearly all other hominins. A distinctive combination of most of the features, according to scientists, could be considered autapomorphic. However, the similarity between the samples from Dinaledi and A. africanus suggests that such a morphology may have been characteristic of at least some Australopithecines. Researchers believe that H. naledi thumb morphology represents an example of a transitional state in the evolution and adaptation of the human thumb.
The distinctive features of the thumbs of H. naledi, according to paleoanthropologists, are narrow promaximal ends with expanding muscles of the distal phalanges. In this aspect, they are similar to the bones of the African Australopithecus. The promaximal pineal gland was found to be gracile and most similar to C. lomamiensis, chimpanzee (Pan), orangutan (Pongo), Afar australopithecus (A. afarensis) and Australopithecus sediba (A. sediba).
Earlier at N + 1, they talked about the creation of a 3D map of the Rising Star cave systems, where the remains of H. naledi were found. In addition, paleoanthropologists, using morphological analysis, found that the structure of the brain of H. naledi is closer to H. habilis and H. erectus than to Australopithecines. To learn more about the study of the teeth of representations of this species, please visit our blog "Homo naledi's Gritty Teeth Gritted".
