The more we learn about our evolutionary
tree, the more complicated it has become, for sure! and there's one recently discovered
branch which raises a lot of questions. Not only about the trajectory of human evolution but
also about behavior that we pretty much consider unique to us as a species. I'm of course talking
about Homo Naledi so let's take a look at the archaeological evidence and see what questions
are raised by this distant cousin of ours. One Friday night in 2013 two cavers
were exploring a cave called rising star within the Cradle of Humankind in
South Africa, a region full of caves containing hominin remains. The cavers
squeezed through dark and narrow turns, at times having to crawl on their stomachs just to
fit through spaces only several centimetres wide. Rather them, than me let me tell you. They eventually arrived at a small enclosed
space known as the Dinaledi chamber filled with what appeared to be human bones. It ended
up being a cache of over 1550 bones and teeth belonging to at least 15 individuals. What was
equally as shocking as finding over 15 hominid individuals in the single cave chamber was what
researchers didn't find. No evidence of fire, even though the chamber was in the dark zone
where light can't reach, no tools of any kind, in fact other than the bones no archaeological
traces of any kind, nothing, and no evidence of any other animals except for six bones belonging
to a single bird. Additionally most of the individuals were articulated meaning that their
bones hadn't separated from each other that much. This suggests that they arrived in the Dinlaedi
chamber alive or shortly after they died. Either way, before they started to decompose. Plus
they found individuals from every age group, infants, elderly, males, females, this
naturally raises a ton of questions. Who were these people? When did they get in there? How did they get in there? And
what were they doing in there? When the local University in Johannesburg got a
look at these specimens the team knew right away this was something they had never seen before.
These individuals had primitive skeletons yet at the same time had a unique combination of some
modern features which were all highly consistent across individuals, all the same. There was barely
any anatomical variation between them. Their skeletons were overwhelmingly archaic. In terms
of body size, estimates for one individual range from approximately 144 to 148 cm. With weights
of eight individuals ranging from approximately 40 to 56 kilograms. This is about the same
as the largest australopithecines and small bodied Homo sapiens. Their brains also
overlap in size with Australopithecus and Paranthropus (which I also made a video
on. Shout out to those STI riddled guys). Their brains are about the third to half
the size of our modern brains now. While their brains were certainly smaller than more
recent members of our family tree of Homo, their skulls were similarly shaped. They were much
rounder and taller compared to Australopithecus and Paranthropus. What's really cool is that some
of the homo Naledi skulls preserve an imprint of the brain called an endocast. These endocasts
show that their brains might have been organized in a similar way to later species of Homo even
though they were much smaller, and it makes you wonder if they were shaped the same way, did they
work the same way, did they think the same way? They also had features that are thought to be
adaptations to climbing which are seen in earlier hominins. These include long arms and fingers
and a flared rib cage and pelvis. On the other hand they had very modern-looking wrists ankles
hands feet and teeth which are much more similar to Homo sapiens and other more recent hominins
like Homo erectus and Neanderthals. All these modern features are so important because animals
use their teeth and hands and feet to directly interact with their environments. This means that
homo Naledi was probably eating, manipulating objects, and walking upright in ways similar to us
and was therefore perhaps also capable of similar behaviors. Without any concrete evidence at the
moment though we we still can't say for sure. So where does homo Naledi fit on our evolutionary
tree? Basically no one knows. Based on the sort of archaic anatomy that they had it was hypothesized
that they had evolved around two million years ago, still definitely homo but at the base of
our lineage. But that was really complicated by a 2017 discovery. Anthropologists were able to
obtain dates from one of the teeth of the homo Naledi specimens and it turned out that they
had lived around 300,000 years ago roughly. That was quite the shock. Anthropologists still
kind of feel that the anatomy of Homo Naledi is just too archaic for them to have evolved
around 300,000 years ago. So basically, the current thinking is we're still looking at a
relative of perhaps Homo erectus a species that evolved 2 ish million years ago, but that
homo Naledi somehow got geographically or reproductively isolated and sort of just went
on its own path basically. You could sort of compare it perhaps to another small hominin on
the other side of the world Homo floresiensis. What's really interesting about that young
date, that 300,000 ish year date, is that it forces us to question the trajectory of human
evolution. Before the discovery of homo Naledi anthropologists had basically thought that once
bigger framed, bigger brained hominins had evolved that smaller more archaic species were basically
out competed and would have disappeared from the archaeological record. Homo Naledi basically
shows that we were wrong about that or at least it's more complicated. That in some areas,
for whatever reason, smaller framed hominins we're able to survive and perhaps thrive for
hundreds of thousands of years.. so...uhh... yeah. How and why they entered the Dinaledi chamber
are still burning questions. One clue is that according to the team's geologists the
deposition of these individuals occurred over an extended period of time. Vague but it
can help us narrow things down and eliminate situations that involved a single event. I
know everyone always wants to say massacre but doesn't look like it. There have been a number
of hypotheses proposed. So far, one pretty obvious one is that they lived in there. I mean, first
of all the small chamber is incredibly hard to access. Perhaps it had a different entry back
then but it is a narrow chamber and like I said earlier there's no archaeological evidence of
anything at all especially not occupational debris so this one's been eliminated for the time
being. Another was that the cave had flooded, carrying these individuals inside of the Dinlaedi
chamber but there's no geological evidence that the cave was ever majorly flooded nor that the
bones themselves were ever submerged in water and if the geologists are correct that the deposition
occurred over an extended period of time this cave would have had to have been continually flooded to
keep bringing them in there. Could they have been dragged in or chased by predators? Or could they
have been the predators? If this was the case we'd expect to see a few remains of these predators and
prey or at least some bite marks on some of the naledi bones as the predators consumed them, but
we don't. There are no other animals found in the chamber except for that partial bird skeleton
and basically who knows how and when that got in there. What if they just fell in? Well the
geologists found that there wasn't a vertical entrance to the chamber 300 thousand years ago
and none of the individuals had injuries or broken bones that had occurred when they died.
The only hypothesis that the team thinks holds any water is that the bodies were deliberately
disposed of in the Dinaledi chamber. It's even possible that the bodies were put there by
other hominins, like modern humans perhaps. As you can imagine this is highly debated, highly
controversial. Remember these Homo Naledi hominins had brains about the size of a chimps not much
bigger. Is it possible that a hominin species with such a small brain could be capable of these more
advanced social and cognitive abilities? I mean, I have made a video on how early hominins
disposed of the dead. Chimpanzees do seem to go through a process of mourning but two hundred
thousand, three hundred thousand years ago, structured deposition of individuals is still
pretty highly debated even amongst hominins with much larger brains. So it really makes us
ponder. To make things even more complicated in 2017 a completely separate chamber within rising
star called the lesedi chamber was found to also have homo Naledi remains. They were found
with other animals too including rodents and mammals but again no archaeological
traces of any kind no tools or anything. So what can we say with some degree of certainty
about homo Naledi? well they were certainly a hominin, certainly a new species that we didn't
know about before. They probably descended from homo erectus or a similar style of hominin and
that's about it really. As for what they were doing in that cave we can only speculate
at the moment but isn't it fascinating how 200-300 thousand years ago, how varied life was
for our family tree on this earth. You had us, Neanderthals, Denisovans, homo Naledi, homo
erectus, Luzonensis, homo floresiensis, just thinking about that and how, whether we could have
communicated with them and what our interactions were like with these different species, that
were in some ways so similar to us and yet so different. Thinking about that kind of stuff
keeps me up all night, I don't know about you. Anyway thanks for joining me on this walk
through the woods, next time on the channel we're going to be going even further back
in time to talk about miocene hominins, so thanks very much for my patrons
for supporting me. Thanks to Amanda Rosillo for helping me with script
and research that's about it. See ya!
