Today I’ve got one of the all-time greatest scientific mysteries for you.
It’s a cold case that goes back hundreds of thousands of years; involves at least 19 dead
bodies all found in a barely accessible chamber in a cave that was being explored for decades. Oh
and these humans don’t look like what we’d expect for their time period. I hope you’re in for a wild
ride because this is the story of Homo Naledi. My name is Riley Harnett and this is The HEAP.
Okay so like any suspicious death documentary, you need to know the potential victims first.
In this case we’re looking at Homo Naledi. We are homo sapiens so as you can guess by the name,
Naledi is another form of human, just like Neandertals or Homo erectus. This species is
a pretty recent find. It was first announced in 2015 , and as far as early humans go, Naledi is
equal parts familiar and strange. The skull, limb proportions, legs and feet are generally pretty
similar to most species of homo. But they share a number of features with Australopithecines too.
If homo was a movie, australopithecines would be the prequel. You can think of
them as being the first apes who came down from the trees to walk routinely on two legs,
but not quite as gracefully as we do. The large brains that humans have today also weren’t
around back then either. Australopithecines generally have a brain size a little larger
than chimpanzees. Turns out, they also have a brain size comparable to Homo naledi.
Their brains are very small as far as humans go, a little more than a third the size of
ours. Naledi’s also got curved fingerbones, a long thumb and shoulders very similar to those
australopithecines. These traits together tell us that Naledi probably spent time
climbing just like they did when they still lived part of their lives in the trees. We
don’t see these sorts of adaptations for climbing in most species of homo except for Homo habilis.
Homo habilis are the oldest humans we’ve given a name to, and the oldest individual clocks in
at around 2.3 million years old. To put this in perspective, the oldest Neandertals are about
5 times closer to us landing on the moon than they are to Homo habilis . Habilis is old, so we see a
higher frequency of those australopithecine traits in it simply because it’s time on the earth was
far less removed to them than later humans such as the Neandertals or us. So seeing a similar suite
of weird australopithecine traits in Naledi sure does make it seem like they’re also very old.
This idea is even more favorable when you look at Naledi’s skull. Like I said, It’s
got a really small brain. So small, in fact, that it fits in among the smallest Homo habilis . Brain
size in our lineage has, generally-speaking, gradually increased since that time too,
so the thinking goes that if you’ve got a small brain, chances are you’re as old as
those with comparable brain size. Now when Naledi was announced,
we hadn’t been able to date the site. Based on its body, it wouldn’t be surprising to have it
fall around the 2 million year old mark . But eventually, it got dated, and well,
Homo Naledi is 230-330 thousand years old . To put that into context, Neandertals had been in
Europe for at least 100 thousand years . Even the modern Homo sapiens body existed at least
230,000 years ago . Homo Naledi represents a group of people who aren’t out of place.
They’re a people who are out of time. So either they retained this suite of more primitive
traits for longer than could be reasonably assumed, or through some evolutionary left-turn
they evolved into a body that more closely resembles and performs like that of the past.
The body of Homo Naledi is incredibly interesting. Our relatively recent
ancestors and these people would have coexisted in Africa for hundreds of thousands of years,
and we’ve only known about it for less than 10. But if that’s not enough, it gets better.
Let’s talk about the scene of the crime. Okay well it might not be a crime, more on that later.
Homo Naledi have been discovered in one location and one location only, the rising star cave in
South Africa. As I understand it, this cave is a bit of a hotspot for cavers in South Africa. But
Homo Naledi wasn’t found in the highly trafficked areas. The only light you’ve
got for this is what you bring with you, and this sort of adventure is not for the claustrophobic.
To get to the Chamber where the discovery was made, you need to be committed. First you’ve
got to crawl through a narrow shaft. So narrow in fact, that some people can only fit with
one arm above their head. So they called it the “Superman Crawl.” After that, you’ve got to climb
a precarious 15 meters up the “The Dragon’s Back,” pretty much a cliff face inside the cave. Finally
you climb straight down a 12 meter long chute that narrows to only 8 inches wide. After you
make it down that shaft, you will find yourself in the Dinaledi Chamber. And there, on the ground,
was where cavers Rick Hunter and Steven Tucker found what they recognized as humanesque bones .
They reported this to Dr. Lee Berger, the top guy when it comes to South African Paleoanthropology.
Dr. Berger has a responsibility to excavate and study these remains,
but there’s a problem. He can’t get down there. Now I’m not judging, I’m pretty certain I can’t
get down there either. I doubt most people can. So he posts on facebook that he’s looking for
archaeologists with caving experience who can traverse this nearly impossible cave to excavate.
And he finds them, 6 women with the perfect skillset for the job. These 6 archaeologists
are known as the underground astronauts. There were cameras installed at the excavation site
so that the less gracile members of research team could communicate with those doing the excavation.
Really reminiscent of Nasa’s mission control. But the level of danger for this sort of work also
can’t be understated. If you hurt yourself, sure they would send a medical team down.
But there’s no getting out until you actually heal enough to do it on your own.
Luckily this never needed to happen. Anyway, most of the time when you find bones in a
cave, it’s not much. A partial skeleton if you’re lucky, and few people ever get that lucky. The
Dinaledi chamber is almost unprecedented in this regard, and so far its yielded 1550 bone fragments
from at least 15 individuals . We’ve found at least 4 other individuals in the nearby areas
of the cave . We’ve got a ton of fossil material with many bones being represented more than once
and an assortment of remains in different life stages from infants to adults.
The only thing like it that I’m aware of is half a world away in Spain. There we’ve got at least
28 Neandertals in a place known as Sima de los Huesos, or in English, the pit of bones . But
let’s put the Naledi find into some context. We now have more material for Naledi, this one
species, than all of the other species that speak to human evolution in Africa combined. It’s a big
deal. And don’t forget: Naledi is a new species. We went from not even knowing it existed to having
more information about it than we have for most of the species in our lineage. It’s an archaeological
dream-come-true if there ever was one. But all this begs the question, how did they get there?
First thing you need to know about caves back in the day is that they’re generally not the most
highly trafficked places. It’s a common idea in popular culture that our ancestors were cavemen.
This thought comes from the fact that we often find remains in caves, so we tend to think of
caves as being a common place to be. This probably isn’t true. Caves excel at preserving bodies
long enough that they stand a very good chance of being fossilized. Conditions in a cave are fairly
stable, temperature and humidity-wise, and you’re less likely to be found by scavengers. There’s
more science behind it than that, but you get the idea: There’s an abundance of remains in caves.
Not because humans spent a lot of time there, but because the few who ventured in,
only to find their demise, did so under conditions that often lead to fossilization.
That being said, the mouth of a cave is a fine shelter. It’s not too dark,
you can start a fire without worrying about suffocating. There’s utility in that.
But with Homo naledi, we’ve got at least 19 individuals in the most pitch black,
unreachable area of the cave. It’s very difficult to imagine them living in those conditions
where even other parts of the cave would have been a better option.
What if a carnivore brought them in? This happens all the time,
imagine a big cat, trying to find some shelter to have its snack.
but there are problems with this idea. First, carnivores don’t just eat one specific animal for
a snack. You’d expect to see other kinds too. Now we do find some other animal remains down there,
a few rodents, an owl, and a young baboon. But all of these are known to enter caves willingly,
so they don’t speak to carnivore activity . We’d also expect to see bite or gnaw marks on bones.
No evidence of that, but many of the bones are missing the thick outer layer of bone,
probably because of snail and insect activity or weathering. So teeth marks might have been lost.
Even considering that, it’s difficult to imagine a scenario where an incredibly picky carnivore went
to such lengths to have a stress-free meal. Unless it made it to the chamber through some other,
currently unknown route. Now this is an idea that is being looked into, caves change over
time like any other geological thing. But the team has been looking at this for 6 years now,
and so far there’s no evidence of another entrance ever being open .
Water activity might also explain how these bodies got to where they did. If the cave had
moving water at some point, these people could have died elsewhere and had their bones moved
into the cave by natural processes. We’d expect to be able to see evidence of this, but we don’t.
We do get one important hint that is likely crucial to understanding what actually
did happen though. The Homo naledi remains aren’t the result of a single event in time.
These bodies found their way to this deep dark chamber over a span of time, likely decades.
So is the Dinaledi Chamber some sort of death trap? Did Homo Naledi try to explore this cave
repeatedly only to have at least 19 people get trapped and find their end here? Well maybe.
It’s incredibly difficult to prove either way. But there’s one tiny piece of evidence here that makes
me a little bit more skeptical. They discovered infants down there. It’s very difficult to imagine
a scenario in which someone would bring their infant down there with them. One small child
was found more than 13 meters away from the chute, on a shelf in an extremely narrow passageway, so
it certainly didn’t end up there by falling to its death . It seems very likely that an infant would
have needed assistance to reach that part of the cave. Does that rule out the death trap idea? Not
at all. It’s a potential explanation for what we see here . But there’s one more thought that might
be the best fit for the evidence here. Since none of the more natural ideas are very convincing,
the researchers themselves favor a more human explanation. What if Homo naledi was deliberately
disposing of its dead in this specific place? At some point after we diverged from our common
ancestor with Chimpanzees, humans began disposing of their dead. I can’t tell you why. Dead bodies
smell terrible, they attract scavengers, and can potentially spread disease, but so
too can the bodies of butchered animals, and those are pretty common in our prehistory.
It’s possible that these sorts of behaviours are a result of concern for members of your group,
a concern that doesn’t end when they’ve died. Nonetheless, we see this behaviour in our species,
Homo sapiens, all the time, and there’s a lot of evidence to suggest that Neandertals buried their
dead too. See, depending on how you dispose of a dead body, you might be unintentionally
improving its chance at fossilization, remember caves are excellent for this sort of thing.
So back to Homo naledi, the idea that they were disposing of dead bodies in the Rising Star cave
is incredibly interesting. It’s possible that some of these bodies were simply dropped down
the chute, but some of the remains would need to be brought to their final resting location
such as that infant’s skull on a cave shelf. That’s a significant undertaking for whoever
would have done so, they’d have to carry that infant through this natural obstacle course
possibly in the dark. We don’t know if Naledi had the capacity for fire. If this is the case,
then this place isn’t a potential crime scene at all, it’s a tomb.
Now I’m not saying this explanation is guaranteed to stand the test of time, Naledi have incredibly
small brains after all, and very qualified people have cast doubt that these humans
would have had the ability to conceptualize such an undertaking . But brain size isn’t the be-all
end-all of determining intelligence , and we don’t know how efficient Homo naledi’s brain is.
Ultimately, the alternatives don’t look great at explaining all the details of this find,
especially how an infant’s skull found its way to that ledge.
This is a find that will be worked on for many years to come
and our understanding is likely to grow. If the deliberate disposal hypothesis is correct then an
evolutionary side branch has exhibited behaviours we thought too complex for it. That changes how
we view the capabilities of early humans. And this is just our first glimpse into Homo
naledi, our small brained, climbing cousin. We’ve come out of it with a remarkable amount
of information about a new species that lived during the time of the Neandertals.
Naledi’s body is full of primitive features but it may have been behaving in relatively modern ways.
That’s it for now, I hope you’ve enjoyed this look at one of the oddest discoveries of our
generation. I’ve posted social media links in the description if you’d like to follow me.
Otherwise, if you’ve got the time, I’d love it if you threw on another video. Thanks for watching.