Homo naledi

DH7, a juvenile.

*Homo naledi* is an extinct species of hominin that lived in South Africa during the Middle Pleistocene.

## History

On September 13, 2013, Rick Hunter and Steven Tucker discovered hominins in the Dinaledi Chamber of the Rising Star Cave, Cradle of Humankind. On the 24th, they returned to take photographs to show to Pedro Boshoff and Lee Berger on October 1st. Berger assembled the Underground Astronauts to them excavate the remains, consisting of Hannah Morris, Alia Gurtov, Marina Elliott, Elen Feuerriegel, Becca Peixotto and K. Lindsay (Eaves) Hunter. This team returned to the chambers for 4 weeks in a row, climbing through tight crawl spaces every day in order to commence excavation. Dinaledi is noted to have been entered once before in the 1990s. It is 80 meters in from the cave's main entrance and sits 12 meters down from a vertical drop and a 10 meter long passage 25-50 centimeters wide at its lowest. 1550 bones were collected from 15 H. naledi, with 9 immature and 6 adults from clay-rich sediment. IN 2015, H. naledi was named by Berger et al.. 737 anatomical elements were recovered, including skulls, jaws, ribs, teeth, limbs and the inner ear. Some were articulate or near-articulate. This makes it the richest hominin assemblage of Africa, with much of the ontogeny and sexes known.

The species name means "star" in Sotho since it was found from Rising Star, meaning "star man". John Hawks et al. (2017) reports 2 adults and a child from the Lesedi Chamber. On October 16, 2021, Lee Berger tweeted a teaser for a new hominin specimen, attaching a photo of a replica skull cropped just above the face, showing only the brow and the top of the braincase with several replica skulls in the back of identified hominins. On November 4, 2021, the announcement was made that a juvenile H. naledi skull was discovered in Dinaledi, nicknamed Leti. This discovery was spread using #ChildofDarkness, which was used alongside #Leti and #Homonaledi, at a 9.8/100 popularity at the time of description. In 2022, Berger brought John Hawks into the cavern for the first time, with the entrance expanded, and the discovery of additional remains, including a humerus and possible clavicle, were announced.

## Classification

In 2017, all the Dinaledi remains were dated to 335-236,000 years using electron spin resonance and uranium-thorium dating on 3 teeth and the matrix they were found in. They were previously assumed to be 1-2 million years old since no small-brained hominins yet known from Africa, and it was a shock that such a variety had survived until the MIddle Pleistocene. The genus has high variation. It is hypothesized to have branched from early *Homo* during the time of *Homo habilis*, *Homo rudolfensis* and *Homo sediba*. They lived with *Homo erectus* and the Florisbad skull (*"H. helmei"*). They could also be sister to the descendants of *Homo heidelbergensis*. If the latter is true, they would have branched at 900,000 years at the latest and at the Pliocene at the earliest. They may have also speciated after *Homo* and australopithecines interbred. The skull is closest to *Homo erectus*, which have led some to classify them as early *Homo erectus*. These *H. naledi* may have been an isolate population or they may have roamed all of Africa, which may lead to late *Homo erectus* specimens being referred if true.

"Homo erectus naledi" was a name made-up by Wikipedia users. It has not been used formally in literature or even proposed anywhere else.

Berger believes that, as technology and our fossil record advances, the braided stream model of human genetics and evolution will be quite complex. Specifically, he believes *H. naledi* introgressed with the *Homo erectus*/plesiomorphic *Homo sapiens* lineage to make up a large amount of the *Homo sapiens* genome. However, the figure he created to illustrate this concept lacks *Homo luzonensis* and several other species. He also believes *H. naledi* shares traits with *Homo sapiens* not seen in plesiomorphic forms of the latter and *Homo erectus*; however, he notes "incredible homoplasy" may be the culprit of these morphological details.

## Description

2 men from Dinaledi have cranial capacities of 560 centimeters; 2 women with 465 centimeters; and a man from Lesedi with 610. These are most similar to australopithecines and much lower than *Homo erectus* and even lower than apomorphic *Homo sapiens*. It has an encephalization of 4.5, the same as *Homo floresiensis* and much smaller than contemporaneous species. The skull is most akin to *Homo*, being slender with reduced post-orbital constriction and a frontal lobe very similar to all *Homo* and not similar to *Australopithecus*. This species is implicated to have made tools. used language and was social. It is unknown if the brain size is from the *Homo* LCA of if it was secondarily evolved later. The permanent 2nd molar erupts late in life alongside the premolars, which indicates they matured slower than *Homo sapiens*; the front teeth are similar to *Homo sapiens* in formation, in size to Pleistocene *Homo sapiens* and closest resemble *Homo* indet. from Swartkrans and Koobi Fora. The molar necks are proportionally similar to *Australopithecus afarensis* and *Paranthropus*. Several dental features are lacking and many individuals bear main cusps (mostly metacone and hypocone on the 2nd and 3rd molars and a Y-shaped hypoconulid on all 3 molars). On the contrary, many dental characters are similar to contemporaneous species, although a 2023 study clarifies that there are still enough distinctive traits from coeval forms to support distinction. The anvil of the ear resembles *Pan*, *Gorilla* and *Paranthropus* more than *Homo*. A large brow is similar to *Homo habilis* and *Homo erectus*, bearing a fissure that stretches just above the ridge. A pronounced occipital bun is included. Various facial characters are shared with *Homo rudolfensis*. Despite a smaller brain size, similar human-like organization suggests similar behaviours in *H. naledi*.

*H. naledi* is of size intermediate of *Australopithecus* and *Homo*. Men and women were around the same size, with men averaging 20% larger than women. DH7 is a juvenile similar with the growth rate of *Homo sediba* MH1 and the Turkana Boy. Since the dental development is so similar, a maturation rate may also be similar to *Homo sapiens*. If it grew faster, this specimen may be 8-11 years of age. If it grew slower, it may have been 11-15 years of age upon age. Only the 10th and 11th thoracic vertebrae are known, presumably from the same individual. They are proportionally similar to contemporaries, but they are the smallest known of any hominin. The transverse processes are most similar to *Homo neanderthalensis*. The neural canals are large, similar to *Homo sapiens*, *Homo neanderthalensis* and *Homo georgicus*. The 11th rib is straight like *Australopithecus afarensis* and the 12th is robust in cross section like *Homo neanderthalensis*. Also like Neanderthals, the 12th may have supported strong intercostal muscle above and a strong quadratus lumborum below. Unlike them, however, the diaphragm weakly attaches. This species appears to be small-bodies, though it is unknown if this specimen represents every individual or a one-off. The shoulders are like australopithecines , with the shoulder blade sitting higher up the back and farther from the midline with short clavicles and little-no humeral torsion. The elevated shoulder and clavicle suggests a narrow chest. The pelvis and legs are similar to *Australopithecus* (anterposteriorly compressed femoral necks, mediolaterally compressed tibiae and a somewhat circular fibular neck). These indicate a wide abdomen. These would not suggest efficient endurance in *H. naledi*, unlike *Homo erectus* and descendants. Rather, *H. naledi* may have been more arboreal.

The metacarpal of the thumb was well developed which suggests adaptation to holding large objects as well as manipulation, with strong crests to support the opponens pollicis and then muscles' which suggests precision pinch gripping. This is more similar to *Homo* than *Australopithecus*. Strong flexor pollicis longus with humanlike palm/finger pads were present, which allow forceful gripping between the thumb and fingers. Unlike other species, *H. naledi* has a small metacarpal joint compared to the thumb length and a flattened phalangeal joint. The distal thumb phalanx is robust and more similar to *Homo habilis* and *Paranthropus robustus*. Metacarpals of the other fingers ear adaptations similar to *Homo sapiens* and *Homo neanderthalensis* used to cup and manipulate, with the wrist similar as well. The proximal phalanges are curved, near identical to *Australopithecus afarensis* and *Homo habilis*, interpreted as for climbing and a supensory lifestyle. This curvature is seen in adults more, suggesting climbing was used as much if not more by adults or was a regular behaviour. The fingers are longer than any extinct hominin except *Ardipithecus ramidus* and Qafzeh 9. *H. naledi* had a gate identical to *Homo sapiens*. Strong insertion of the gluteus maximus, defined linea aspera, thick patellae, long tibiae and gracile fibulae ensured this and also indicate long distance travel. The foot is similar to apomorphic species and bears bipedal adaptions. The low-oriented heel is more comparable to non-human hominids and a low-declining ankle suggesting the ankle was slightly stiffer during the stance phase of walking. The incus is excluded from the Homo range of variation, further resembling *Paranthropus robustus* and chimpanzees.

## Paleobiology

### Technology

Though not associated with tools, H. naledi likely produced Acheulean or possibly Oldowan, possibly Middle Stone Age industries as well, since they have the same hand adaptations in other species that produce similar tools. It is the only human species to have had existed during the Middle Pleistocene, Highveld, possibly indicating they manufactured and maintained tradition during this time period. Industries such as stone cuttings likely occur independently multiple times in different populations throughout human evolution or transported over long-distance by their inventors or apprentices, where they taught their methods. In 2022, Berger revealed a series of new discoveries concerning the ecology of this taxon. First, he announced the discovery of two hearths (one large, one small) outside of the Dinaledi entrance chute as well as burnt antelope bones, and a large chamber located within a series of fissures whose floor is covered in burnt animal bones and charcoal (which had been discovered much earlier in the main system but disregarded as too scant) and soot on the ceiling of the Dinaledi chamber. This second chamber, untouched since its last "occupation", also bears stacked rocks on top of animal bones and a hearth site that was also used as waste disposal. Despite this, no skeletal *H. naledi* are found with culture and no culture with the skeletal remains, suggesting that the site was probably just used in ritual. Additionally, Berger speculates that this is no different than how modern societies go to great lengths when disposing of the dead, and that the site was probably not used for living. This marks the first bona fide culture, and suggests that even small-brained species could be culturally complex.

### Diet

Dental chipping and wearing indicates small hard objects were continually consumed, such as dirt and dust, with cup-shaped wearing in the back teeth caused by gritty particles. These may have come from unwashed tubers and roots. Additionally, these may be sue to aridity stirring dirt and dust onto food. *H, naledi* may have commonly ate larger, hard items such as seeds and nuts that were processed into smaller pieces. If this is true, *H. naledi* sat in a distinct niche from other species including *Australopithecus* and *Paranthropus*. The teeth of all 3 species show a high force exerted during consumption, perhaps to shear through plant or muscle fibers. However, teeth in *Homo* are incapable of high forces due to food processing arising.

### Paleopathologies

U.W. 101-1142 supports a bony lesion suggestive of a benign tumor that would have swelled, limited muscle function, raised the right end of the jaw and caused discomfort in life. Seasonal stressors likely caused dental defects during 1.6-2.8 and 4.3-7.6 months. These may be extreme temperatures causing food scarcity, extreme cold causing respiratory disease and apomorphic South African winters causing flu season and summers with pediatric diarrhea. Large predators likely preyed on H. naledi. They likely preferred the Blaaubank River to hunt. Alternatively, an absence in predators at Cradle of Humankind may be due to a gap in the fossil record.

Paul Dirks, Berger et al. (2015) concluded their bodies were carried and placed into Dinaledi as a mortuary act since they mostly intact and no evidence of predation are present. This would be the only explanation for how the bodies accumulated since no predators could reach Dinaledi, it is isolate and appears to have not been flooded, no evidence of a natural disaster are present and there is no hidden shaft for individuals to fall through. It is possible the bodies fell through a chute and slipped down due to irregularity in the surface and narrowness, falling onto a soft mud cushion. In both scenarios, they would have needed to use artificial light. The burial hypothesis is suggested by how the bodies were deposited at different times. Aurore Val (2016) states the bodies were mummified rather than buried, with the lack of long bone heads due to predation. She notes excluding natural forces is unjustified. Bones appear to bear damage done by beetles, their larvae and snails. However, the chamber does not bear the conditions ideal for snails and did not contain snail shells, so decomposition likely started before they entered the chamber. In 2017, Dirk, Berger et al. found an evidence for water flowing into the cave, finding it more likely they were buried, possibly by contemporary *Homo*. Nonetheless, mortuary practices for *H. naledi* are still possible. The burial may have been to remove bodies from settlement, prevent scavengers and/or due to grief. Charles Egeland (2018) finds the same thing Val (2016) does, noting the bodies accumulated similarly to how baboon carcasses do (via natural causes or predation).

### Locomotion

In 2022, Berger and team discovered footprints at Rising Star cave during fieldwork. They were identified as a likely pair of *Homo naledi*. The prints, though undescribed, appear very apomorphic. The iliac blade is similar to australopiths and the sacroiliac joint is enlarged. An ilium from the Lesedi chamber likely belonging to a juvenile is comparable in height of 4-11 year-old modern children.

## Paleoecology

A series of new discoveries have kicked off the "muddle in the middle", a paleoanthropological problem concerning the taxonomy of African Middle Pleistocene hominins including the Florisbad skull, *H. naledi*, Border Cave *Homo sapiens*, Kabwe 1 and related specimens of similar ages. At one point, Florisbad was considered *"Homo helmei"*, but recent studies suggest it is an 'early' plesiomorphic *Homo sapiens* similar to Jebel Irhoud and Eliye Springs. Additionally, Kabwe 1 is traditionally referred to *Homo heidelbergensis* after initially being named *"Homo rhodesiensis"*; however, a 2021 review suggests the former two names should be disused and Kabwe (plus other referred specimens) should now be called *Homo bodoensis*. Additionally, many of these specimens had poor dating, so their affinities are still blurry. Nonetheless, all of these were contemporaneous and overlapped with varying degrees.

## Notable Specimens

* DH1: The holotype; a partial calvaria, maxilla and near-complete mandible of a man.
* DH2-5: The paratypes, all partial calvaria.
* "Letimela" or "Leti" or the "Child of Darkness: A partial skull (28 fragments) and 6 teeth found ~12 meters outside of Dinaledi, representing a 4-6-year-old individual that lived 250,000 years. It's nickname, Leti, is the Setswana word "the lost one". The skull was encased in spider webs in a tight passage in 2017. It has a cranial capacity of 480-610, ~90-95% or an adult's. There is no evidence of predation or shifting sediment so it likely deposited in this remote position. There is no indication what sex Leti was. Leti is the first juvenile skull of *H. naledi*.

## Gallery

"Leti".
**Credit: Boniswa Khumalo.**"Leti"."Leti".
**Credit: John S. Mead (@Evo\_Explorer).**"Leti"."Leti"."Leti"."Leti"."Leti".**Credit: Elisabeth Daynès.**
## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 https://en.wikipedia.org/wiki/Homo\_naledi
2. ↑ https://twitter.com/LeeRberger/status/1449419025205927942
3. ↑ https://hashtagify.me/hashtag/childofdarkness
4. ↑ https://twitter.com/LeeRberger/status/1509145122381963271
5. ↑ https://johnhawks.net/weblog/fossils/naledi/homo-naledi-homo-erectus-2015.html
6. ↑ https://en.wikipedia.org/wiki/Talk:Homo\_erectus#H.\_erectus\_subspp.?
7. ↑ https://twitter.com/LeeRberger/status/1432042050908827653
8. ↑ https://twitter.com/LeeRberger/status/1432044410066423816
9. ↑ https://www.sciencedirect.com/science/article/pii/S0047248423000519?dgcid=coauthor
10. ↑ https://www.pnas.org/content/115/22/5738
11. ↑ https://www.sciencedirect.com/science/article/abs/pii/S0047248418300472
12. ↑ https://www.cbsnews.com/video/evidence-found-that-man-was-not-the-first-being-to-master-fire/
13. ↑ https://skulls-and-things.blogspot.com/2022/12/homo-naledi-fire-hearths-ritual-oh-my.html
14. ↑ https://twitter.com/LeeRberger/status/1502172157232570369
15. ↑ https://twitter.com/LeeRberger/status/1502935821703426050
16. ↑ https://onlinelibrary.wiley.com/doi/full/10.1002/ajpa.24522
17. ↑ https://en.wikipedia.org/wiki/Florisbad\_Skull
18. ↑ https://onlinelibrary.wiley.com/doi/10.1002/evan.21929
19. ↑ https://www.youtube.com/watch?v=C1SsIT6CLYo&ab\_channel=WitsUniversityOFFICIAL
20. ↑ https://www.tygodnikpowszechny.pl/letimela-169761
21. ↑ https://www.wits.ac.za/news/latest-news/research-news/2021/2021-11/a-child-of-darkness.html