Author : Wahid Ahmad
On
September 13, 2013, cavers Rick Hunter and Steven Tucker discovered hominin
fossils in the Dinaledi Chamber of South Africa's Rising Star Cave system. They
returned on September 24 to take photographs, which they showed to South
African paleoanthropologists Pedro Boshoff and Lee Berger. Berger organized an
excavation team, including Hunter and Tucker, known as the "Underground
Astronauts."
The
Dinaledi Chamber is about 80 meters from the main cave entrance, accessible via
a 12-meter vertical drop. The main passage leading to the chamber narrows to around
a foot at its narrowest point.
The
excavation yielded over 1,550 bone fragments from at least fifteen individuals,
including nine immature and six adult individuals. These fossils included
various anatomical elements, such as parts of the skull, jaw, ribs, teeth,
limbs, and inner ear bones. Some elements were articulated or nearly
articulated, including a nearly complete skull with the jawbone and nearly
complete hands and feet. This collection represents a diverse range of
individuals of both sexes and various age groups, making it the most extensive
assemblage of associated fossil hominins found in Africa.
The
holotype specimen, DH1, includes a partial male calvaria, a partial maxilla,
and a nearly complete jawbone. In 2015, Berger and colleagues officially named
this new species Homo naledi, with "naledi" meaning "star"
in the Sotho language, referring to the Rising Star Cave where the remains were
found.
In 2017,
additional hominin remains, including two adults and a child, were reported in
the Lesedi Chamber of the same cave by John Hawks and colleagues, expanding our
understanding of this ancient hominin population.
Homo
naledi, displays a combination of characteristics resembling both contemporary
Homo species and ancestral Australopithecus, indicating a form of mosaic evolution.
Notably, they had a small cranial capacity ranging from 465 to 610 cm3, in
stark contrast to modern humans with capacities of more than 1200. On average, Homo
naledi individuals stood at about 4 ft 9 inches tall and weighed approximately
39.7 kg resulting in a low encephalization quotient of 4.5. Despite their small
brains, their brain anatomy appeared similar to contemporary Homo, suggesting
potential cognitive complexity.
Interestingly,
Homo naledi's physical characteristics and brain size challenge the previous
assumption that a larger brain size necessarily confers an evolutionary
advantage. Furthermore, their unique anatomical features significantly expand
the known range of variation within the Homo genus.
In terms
of locomotion, HOMOnaledi exhibited human-like long-distance travel
capabilities with a bipedal stride and gait. However, they displayed a greater
degree of arboreality compared to other Homo species, suggesting better
adaptation for climbing and suspensory behavior in trees rather than endurance
running. Analysis of their tooth anatomy indicates a diet that included gritty
foods covered in particulates like dust or dirt.
The
phylogenetic position of Homo naledi is a topic of ongoing debate in
paleoanthropology. Hawks & Lee Berger (2016) have mentioned three different
scenarios
1. Pliocene Age Scenario
2. Early Pleistocene Age Scenario
3. Late Pleistocene Age Scenario
One Idea
Is That naledi fossils have originated from the late Pliocene period, roughly
before three million years ago. Homo naledi's anatomical features place it
within the Homo family tree. An earlier date for the fossils suggests that key
branching points in this family tree occurred earlier. Homo naledi shares
distinctive traits with Homo erectus, implying a closer relationship between
these two species than either has with Homo habilis. This raises the
possibility that Homo habilis may have descended from a point on the family
tree predating the common ancestor of Homo naledi and Homo erectus.
Homo naledi's
lack of advanced features found in other Homo species suggests that its lineage
existed before the appearance of Homo erectus around 1.8 million years ago.
After
about 2.1 million years ago, there is clear evidence of various early Homo
species coexisting in different regions. However, before this time, we have
only fragmentary Homo specimens, making it challenging to assign them to
specific species. The prevailing idea is that Homo likely originated after 3
millio n years ago as the environment became drier. Early Homo adapted to a
more selective diet, including meat, and began using stone tools. These Homo
species eventually spread across eastern and southern Africa, with different
body sizes and brain sizes, all larger than australopiths. Later, Homo erectus
ventured beyond Africa into Eurasia.
If the
Dinaledi fossils are indeed from the Early Pleistocene, this aligns with
existing ideas that HOMO naledi might have been one of several early Homo
species in Africa. Its unique characteristics leave open the possibility that HOMO
naledi could be an ancestor or sister species to HOMO erectus, coexisting
alongside it in southern Africa, similar to how HOMO habilis and HOMO erectus
coexisted in other regions.
If the
Dinaledi fossils are relatively young, possibly less than a million years old,
it doesn't change their phylogenetic relationship with other species. If the
Dinaledi fossils are from the Late Pleistocene, it means that Human species
existed in Africa with competition from other hominin forms. Homo naledi's
dental features suggest a generalist diet. They show abilities to make complex
tools and navigate landscapes similar to more advanced Homo species.
Furthermore,
if Homo naledi existed in the Late Pleistocene, it raises the possibility that
archaeological finds attributed to archaic Homo sapiens may actually be the
work of Homo naledi. Distinguishing their contributions to archaeological
assemblages may be challenging without direct associations between hominin
remains and artifacts.
Complex
behaviors such as funerary caching, creating engravings on cave walls, and
using fire have been observed in Homo naledi, challenging traditional notions
of human evolution and cognitive abilities. These behaviors were traditionally
believed to be exclusive to Homo sapiens.
Throughout
history, humans have honored their deceased through various burial practices,
including digging pits and placing bodies inside.
Burial
methods have cultural significance and can vary widely.
Determining
whether ancient remains were part of a deliberate burial can be challenging due
to changes in burial sites over time and cultural variations.
One of
the earliest example of an ancient burial includes a nearly 80,000-year-old
child's partial skeleton intentionally buried in a pit in Kenya. The question
of whether Homo naledi engaged in deliberate burial, which involves
deliberately placing bodies or body parts in an inaccessible location, has
sparked debate. While it's challenging to explain why at least 15 individuals
of Homo naledi would repeatedly venture deep into a cave system and die there,
proponents of funerary caching argue that this behavior could reflect a
deliberate practice.
Three
important conditions been laid down for supporting the funerary behaviour:
1.
Presence of artificial lights
2.
Possibility of fluvial transport.
3.
Articulation of skeltons
Scientists
are searching for evidence of artificial light, such as charcoal fragments or
torch residue, in the cave. Light would have been crucial for Homo naledi to
navigate the cave system. The researchers claim that the mortuary and engraving
activities in Rising Star Cave involved strategic use of fire for illumination.
The
Rising Star Cave system is complex, with interlinked passages and chambers
offering multiple potential routes to the Dinaledi Chamber. The cave contains
vertical fissures with distinct sedimentary fills, which may have acted as
alternative routes to the Dinaledi Chamber.
Characteristics
of the cave system and analysis of the cave sediments indicate that it is highly
unlikely for bones to have spontaneously flowed into the Dinaledi Chamber.
The
position of parts such as limb elements and hands, indicated they are
articulated body parts, however this does not exclude the role of natural
processes like mummification which could explain the articulation of these
remains.
These
evidences more or less support that deliberate mortuary and funerary practices,
marking one of the earliest examples of such behaviors in hominins.
The
relationships between Homo naledi and other Homo populations in terms of their
mortuary and funerary behaviors are unclear. There are three possible
explanations:
a) HOMO naledi's
behaviors are the result of parallel evolution independent of human lineage.
b) These
behaviors date back to early Pleistocene or even Pliocene hominins and then
diverged between homo naledi and homo sapiens.
c) HOMOsapiens
or HOMOnaledi borrowed these behaviors as cultural practices from each other
due to sympatry.
The cave
environment likely induced strong emotional reactions and bonding among Homo
naledi community members. The repetition of these behaviors over time indicates
valued social and cultural traditions, implying a capacity for meaning-making
similar to other Homo populations of the same period.
This
emotional awareness allowed them to share beliefs and take intentional actions
together, such as deliberate burials. Engravings in the same area suggest
shared remembrance or attention to these locations.
Similar
demonstrations of emotional self-awareness in other hominins, like Neanderthals
through their use of caves and stone tools, challenge the notion that only
modern humans possess such creative abilities.
Small-brained
hominins played key roles in human evolution, such as developing stone tools
and expanding out of Africa. The use of fire might have also emerged with
small-brained hominins.
Homo
naledi's religio-artistic behavior challenges the notion that increased brain
size alone drives complex cultural actions. Instead, it implies that a cultural
and empathetic niche, involving complex social relationships, played a
significant role in the development of these behaviors.