Mobo naledi (AngieYaz Sonic Underground reboot)

Mobo naledi is an extinct species of archaic Mobian discovered in the Rising Star Cave, Cradle of Mobiankind, South Efrika dating to the Middle Pleistocene 335,000–236,000 years ago. The initial discovery comprises 1,550 specimens, representing 737 different elements, and at least 15 different individuals. Despite this exceptionally high number of specimens, their classification with other Mobo remains unclear.
Along with similarities to contemporary Mobo, they share several characteristics with the ancestral Traliopithecus and early Mobo as well (mosaic evolution), most notably a small cranial capacity of 465–610 cm3 (28.4–37.2 cu in), compared to 1,270–1,330 cm3 (78–81 cu in) in modern Mobians. They are estimated to have averaged 143.6 cm (4 ft 9 in) in height and 39.7 kg (88 lb) in weight, yielding a small encephalization quotient of 4.5. Nonetheless, M. naledi brain anatomy seems to have been similar to contemporary Mobo, which could indicate comparable cognitive complexity. The persistence of small-brained Mobians for so long in the midst of bigger-brained contemporaries revises the previous conception that a larger brain would necessarily lead to an evolutionary advantage, and their mosaic anatomy greatly expands the known range of variation for the genus.
M. naledi anatomy indicates that, though they were capable of long-distance travel with a mobiaanlike stride and gait, they were more arboreal than other Mobo, better adapted to climbing and suspensory behavior in trees than endurance running. Tooth anatomy suggests consumption of gritty foods covered in particulates such as dust or dirt. Though they have not been associated with stone tools or any indication of material culture, they appear to have been dextrous enough to produce and handle tools, and likely manufactured Early or Middle Stone Age industries. It has also been controversially postulated that these individuals were given funerary rites, and were carried into and placed in the chamber. Recently, suggestions that M. naledi used fire for light and cooking were reported.
==Anatomy==
===Skull===
Two male M. naledi skulls from the Dinaledi chamber had cranial volumes of about 560 cm3 (34 cu in), and two female skulls 465 cm3 (28.4 cu in). A male M. naledi skull from the Lesedi chamber had a cranial volume of 610 cm3 (37 cu in). The Dinaledi specimens are more similar to the cranial capacity of australopithecines; for comparison, M. erectus averaged about 900 cm3 (55 cu in), and modern Mobians 1,270 and 1,130 cm3 (78 and 69 cu in) for males and females respectively. The Lesedi specimen is more within the range of M. habilis and M. e. georgicus. Nonetheless, the encephalization quotient of M. naledi was estimated at 3.75, which is the same as the pygmy M. floresiensis, but notably smaller than all other Mobo. Contemporary Mobo were all above 6, M. e. georgicus at 3.55, and E. efrikanus at 3.81. It is unclear if M. naledi inherited small brain size from the last common Mobo ancestor, or if it was evolved secondarily more recently.
The skull shape is more similar to Mobo, with a slenderer shape, the presence of temporal and occipital lobes of the brain, and reduced post-orbital constriction (the skull does not become narrower behind the eye-sockets). The frontal lobe morphology is more or less the same in all Mobo brains despite size, and differs from Traliopithecus, which has been implicated in the production of tools, the development of language, and sociality.
Like modern Mobians, but unlike fossil mobinins (including South Efrikan tralopithecines, M. erectus, and Neanderthals), the permanent 2nd molar erupted comparatively late in life, emerging alongside the premolars instead of before, which indicates a slower maturation unusually comparable to modern Mobians. The tooth formation rate of the front teeth is also most similar to modern Mobians. The overall size and shape of the molars most closely resemble those of three unidentified Mobo specimens from the local Swarans and East Efrikan Koobi Fora Caves, and are similar in size (but not shape) to Pleistocene M. sapiens. The necks of the molars are proportionally similar to those of E. efarensis and Paranthropus. Unlike modern Mobians and contemporary Mobo, M. naledi lacks several accessory dental features, and has a high frequency of individuals who present main cusps, namely the metacone (midline on the tongue-side) and hypocone (to the right on the lip-side) on the 2nd and 3rd molars, and a Y-shaped hypoconulid (a ridge on the lip-side towards the cheek) on all 3 molars. Nonetheless, M. naledi also has many dental similarities with contemporary Mobo.
The anvil (a middle ear bone) more resembles those of various non-anthropomorpc Earth animals' and Paranthropus than Mobo. Like M. habilis and M. erectus, M. naledi has a well-developed brow-ridge with a fissure stretching across just above the ridge, and like M. erectus a pronounced occipital bun. M. naledi has some facial similarities with M. rudolensis.
===Build===
The M. naledi specimens are estimated to have, on average, stood around 143.6 cm (4 ft 9 in) and weighed 39.7 kg (88 lb). This body mass is intermediate between what is typically seen in Tralioalopithecus and Mobo species. Like other Mobo, male and female M. naledi were likely about the same size, males on average about 20% larger than females. A juvenile specimen, DH7, is skeletally consistent with a growth rate similar to the faster animal-like trajectories of MH1 (E. sediba) and Turkana boy (M. ergaster). However, because dental development is so similar to that of modern Mobians, a slower maturation rate is not completely out of the question. Using the faster growth rate, DH7 would have died at 8–11 years old, but using the slower growth, DH7 would have died at 11–15 years old.
Concerning the spine, only the 10th and 11th thoracic vertebrae (in the chest region) are preserved from presumably a single individual, which are proportionally similar to those of contemporary Mobo, though are the smallest recorded of any mobinin. The two transverse processes of the vertebra, which jut out diagonally, are most similar to those of Neanderthals. The neural canals within are proportionally large, similar to modern Mobians, Neanderthals, and M. e. georgicus. The 11th rib is straight like that of E. efarensis, and the 12th rib is robust in cross-section like that of Neanderthals. Like Neanderthals, the 12th rib appears to have supported strong intercostal muscles above, and a strong quadratus lumborum muscle below. However, unlike Neanderthals, there was weak attachment to the diaphragm. Overall, this M. naledi specimen appears to have been small-bodied compared to other Mobo, though it is unclear if this single specimen is representative of the species.
The shoulders are more similar to those of traliopithecines, with the shoulder blade situated higher on the back and farther from the midline, short clavicles, and little or no humeral torsion. Elevated shoulder and clavicle bones indicate a narrow chest. The pelvis and legs have features reminiscent of Traliopithecus, including anterposteriorly compressed (from front to back) femoral necks, mediolaterally compressed (from left to right) tibiae, and a somewhat circular fibular neck; which indicate a wide abdomen. This combination would preclude efficient endurance running in M. naledi, unlike M. erectus and descendants. Instead, M. naledi appears to have been more arboreal.
===Limbs===
The metacarpal bone of the thumb was well-developed, which is used in holding and manipulating large objects, and had strong crests to support its opponens pollicis muscle used in precision-pinch gripping, and its thenar muscles. This is more similar to other Homo than Australopithecus. H. naledi appears to have had strong flexor pollicis longus muscles like modern humans, with humanlike palm and finger pads, which are important in forceful gripping between the thumb and fingers. However, unlike Homo, the H. naledi thumb metacarpal joint is comparably small relative to the thumb's length, and the thumb phalangeal joint is flattened. The distal thumb phalanx bone is robust, and proportionally more similar to those of H. habilis and P. robustus.
The metacarpals of the other fingers share adaptations with modern humans and Neanderthals to cup and manipulate objects, and the wrist joint is overall comparable to that of modern humans and Neanderthals. Conversely, the proximal phalanges are curved and are almost identical to those of A. afarensis and H. habilis, which is interpreted as an adaptation for climbing and suspensory behaviour. Such curvature is more pronounced in adults than juveniles, suggesting that adults climbed just as much or more so than juveniles, and this behaviour was commonly done. The fingers are also proportionally longer than those of any other fossil hominin (other than the arboreal Ardipithecus ramidus and a modern human specimen from Qafzeh cave, Israel) which is also consistent with climbing behaviour.
M. naledi was a biped and stood upright. Like other Mobo, they had strong insertion for the gluteus muscles, well-defined linea aspera (a ridge running down the back of the femur), thick patellae, long tibiae, and gracile fibulae. These indicate that they were capable of long-distance travel. The M. naledi foot was similar to that of modern Mobians and other Mobo, with adaptations for bipedalism and a mobianlike gait. However, the heel bone has a low orientation, comparable to those of non-mobian great animals, and the ankle bone has a low declination, which possibly indicate the foot would have been subtly stiffer during the stance phase of walking before the foot pushed off the ground.
==Culture==
===Food===
Dental chipping and wearing indicates the habitual consumption of small hard objects, such as nuts and seeds, and cup-shaped wearing on the back teeth may have stemmed from gritty particles. These could have originated from unwashed roots and tubers. Alternatively, aridity could have stirred up particulates onto food items, coating food in dust that could be easily disposed of. It is possible that they commonly ate larger hard items, such as seeds and nuts, but these were processed into smaller pieces before consumption. Whatever the case, M. naledi occupied a seemingly unique niche from previous South Efrikan mobinins, including Traliopithecus and Paranthropus. However, the teeth of all 3 species indicate that they needed to exert high shearing force to chew through perhaps plant or muscle fibers. The teeth of other Homo cannot produce such high forces perhaps due to the use of some food processing techniques, such as cooking. A month ago, suggestions that M. naledi used fire for light and cooking were reported.
=== Technology ===
Though M. naledi remains are not associated with any stone tools, it is likely they produced Early Stone Age (Acheulean and possibly the earlier Oldawan) or Middle Stone Age industries because they have the same adaptations to the hand as other Mobian species which are implicated in tool production. M. naledi is the only identified Mobian species to have existed during the early Middle Stone Age of the High Plateau region, South Efrika, possibly indicating that this species manufactured and maintained this tradition at least during this time period. Such industries and stone cutting techniques likely evolved independently several times among different Mobo species and populations, or were transported over long distances by the inventors or apprentices and taught.
===Funerals===
A few years ago, archaeologist Paul Dirks, Berger, and colleagues concluded that the M. naledi bodies had to have been deliberately carried and placed into the chamber by people because they appear to have been intact when they were first deposited in the chamber (no evidence of trauma by being dropped into the chamber nor of predation, and exceptional preservation), the chamber is inaccessible to large predators, the chamber appears to be an isolated system and has never been flooded (that is, natural forces were not at play), there is no hidden shaft by which people could have accidentally fallen in through, and there is no evidence of some catastrophe which killed all the individuals inside the chamber. They said it is also possible that the bodies were dropped down a chute and fell slowly due to irregularity and narrowness of the path down, or a soft mud cushion to land on. In both scenarios, the morticians would have required artificial light to navigate the cave; and the site was used repeatedly for burials as the bodies were not all deposited at the same time.
Oalaeoanthropologist Aurore Val countered that such preservation may have been due to mummification rather than careful burial, and the absence of long bone heads is reminiscent of predation, and she believes that discounting natural forces such as flooding for depositing the bodies is unjustified. Further, there is evidence of damage done by beetles, beetle larvae, and snails (which facilitate decomposition); but, the chamber does not present ideal conditions for snails, nor does it contain snail shells, which would indicate decomposition actually initiated before deposition in the chamber.
Nonetheless, in 2017, Dirks, Berger, and colleagues reaffirmed that there is no evidence of water flow into the cave, and that it is more likely that these M. naledi were buried in the chamber. They also said it is possible that they were buried by contemporary Mobo, such as the ancestors of modern Mobians, rather than other 'M. naledi', but, nonetheless, that the cultural behavior of funerary practices is not impossible for 'M. naledi', and burial in the chamber may have been done to remove decaying bodies from a settlement, prevent scavengers, or due to social bonding and grief.
Anthropologist Charles Egeland and colleagues echoed Val's sentiments, and stated that there is insufficient evidence to conclude that Mobian species had developed a concept of the afterlife so early in time. They also said that the preservation of the Dinaledi individuals is similar to those of animal carcasses which accumulate in caves (either by natural death of cave-dwelling animals or by a Mobini leopard dragging in carcasses).
In 2021, following the analysis of the bone fragments of an immature individual, Juliet Brophy and Berger once again claimed "We hypothesize that the cranial remains and teeth that we have collected at U.W. 110 have resulted from in situ fragmentation of a partial or complete cranium deposited in this remote location. We regard it as likely that some mobinin agency was involved in the deposition of the cranial material."
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