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May 9, 2017 10:06 PM

"[T]he scientists who uncovered Homo naledi have announced two new findings: They have determined a shockingly young age for the original remains, and they found a second cavern full of skeletons. The bones are as recent as 236,000 years [academic article], meaning Homo naledi roamed Africa at about the time our own species was evolving." The claims are, of course, disputed. Previously
posted by Eyebrows McGee (27 comments total)

Mmmm more potential simultaneous hominids. My crops are watered, my face is clear, the sun is shining. Everything is good.
posted by Homo neanderthalensis at 10:41 PM on May 9, 2017 [14 favorites]

I love how both the Naledi discovery and the - maybe equally important 47,000 year old Neanderthal cave structure at Bruniquel - were both only made possible by getting hold of sufficiently svelte spelunkers. It raises the idea of just how many discoveries might await in cave chambers that we are just a little too chubby to fit into.

I also think that, over time, we may become more cautious about describing other hominids as "primitive". The implication is that they lacked the kind of behavioural or physiological sophistication of homo sapiens.. But these were species that either possibly, or certainly, seem to have shown the adaptability to last much longer on the planet than we have, so far.
posted by rongorongo at 12:12 AM on May 10, 2017 [14 favorites]

how many discoveries might await

Indeed. We probably don't know the half of it.

(btw, Wasn't there a move to drop 'hominid' in favour of 'hominin' in these contexts a while ago?)
posted by Segundus at 2:22 AM on May 10, 2017 [1 favorite]

Speciation in the history of human evolution is a really interesting topic because of the implications of where and how you ultimately draw the line between human and animal (even in the sense of modern vs. archaic human). Or even just how you draw the line between different species vs. examples of natural variation within a species. Not surprisingly, the history of forensic anthropology is pretty closely linked to the foundations of scientific racism.
posted by shapes that haunt the dusk at 3:16 AM on May 10, 2017 [7 favorites]

(I once took a class with a forensic anthropologist who would ask the class if we would refer to Neanderthals as humans, or if Lucy was a person, and what it implied if we wanted to say no. It's interesting to note the vocabulary people use in news stories about these kinds of findings when they refer to the remains.)
posted by shapes that haunt the dusk at 3:32 AM on May 10, 2017 [3 favorites]

I once took a class with a forensic anthropologist who would ask the class if we would refer to Neanderthals as humans, or if Lucy was a person, and what it implied if we wanted to say no.

Huh, thinking about it, I'm not sure what I would say myself. My first instinct is to say that at least for neanderthals, they weren't human (humans are homo sapiens), but they were people.

What did he say? And what did a class full of actual students in the subject say?
posted by Kutsuwamushi at 4:54 AM on May 10, 2017 [3 favorites]

(btw, Wasn't there a move to drop 'hominid' in favour of 'hominin' in these contexts a while ago?)

This was part of the campaign for recognition of "ad hominid" attacks, right?

I am enjoying these discoveries that complicate simplistic pathways of evolution and survival. Interbreeding and cannibalism are not how most people think of their ancestry, but evidently both were a factor, and now there is another branch of the family tree hanging out in the neighborhood for a long time.
posted by Dip Flash at 6:21 AM on May 10, 2017

Some Humans Ain't Human
posted by Slarty Bartfast at 7:20 AM on May 10, 2017

As a primatologist, all this excites me because I've been arguing since I was applying for grad school that understanding primate communities and community ecology and coexistence of closely-related species was really very relevant for human evolution research, and faculty kept sort of rolling their eyes at me. In fact, when I interviewed at Prestigious University for grad school (I did not get in), the chair of the department told me that primate community ecology and the questions I was interested in weren't really the sort of evolutionarily relevant, intellectually rigorous questions that students at Prestigious University's department of anthropology were asking. Well, clearly they should have been asking questions along those lines!
posted by ChuraChura at 8:43 AM on May 10, 2017 [13 favorites]

Mmmm more potential simultaneous hominids. 

well...considering how heartless/selfish/warmongering/racist/homophobic/insensitive/cruel the various 'right wings' of the world are, I'd say we're probably living with more than one species now.

Interbreeding and cannibalism are not how most people think of their ancestry, but evidently both were a factor

Well, also factor in that (according to modern computerized genetic analysis) the biggest mover in genetics isn't evolution (slow, random changes) or natural selection (can be super-fast, but is mostly a removal process where genes are lost), but sideways genetic transfer (where genes are swapped between species, mostly by viruses), and having other hominids/ins around becomes a much bigger deal, as we could very well have been sharing genes with them, even if we never interacted with them at all.
posted by sexyrobot at 8:47 AM on May 10, 2017 [4 favorites]

Interbreeding and cannibalism are not how most people think of their ancestry, but evidently both were a factor,

This is fascinating stuff, but denial about those origins is more a new world phenomenon than a universal human condition I suspect. Europeans have always seemed to be keenly aware of their murky cultural past with its periods of darkness and brutality. They still joke about cannibalism and inbreeding among populations in more remote, isolated village settings, to the extent those still exist post-globalization.
posted by saulgoodman at 8:47 AM on May 10, 2017

Maybe it comes from watching too much Star Trek, but I'd have no problem accepting a non-human (e.g., a Neandertaler) as a person. For that matter, there are a lot of humans around who barely seem to qualify as people.
posted by Faint of Butt at 9:44 AM on May 10, 2017

This is a pretty good, accessible review of the issues around who belongs in genus Homo, and why.

I would argue pretty strongly that all genus Homo are "humans" by definition and to be consistent with other animal genera. Whether any given fossil belongs in genus Homo is waaaay outside my expertise though. There have been suggestions to collapse everyone from Home erectus onwards into Homo sapiens, as well as to extend the concept of "human" to at least before the split with Chimpanzees, hence "Homo troglodytes". From the outside this just highlights how difficult it is to make the concept "species" work in fossil settings. And "personhood" is a whole new ball of wax as many examples show recently, e.g.

It's fairly striking that brain size is still such an issue for so many. Homo floresiensis have very small brains and yet complex (or complex enough) stone tools; and in all likelihood they are responsible for a recently discovered site on Sulawesi dating to 120,000 years ago, which would have required a substantial water crossing. Some of the criticism around the Homo naledi claims is that they were too old (now maybe not) and too small-brained (WTF) to have what amounts to a fairly simple funerary practice of tossing their dead deep into caves. One interesting aspect of the new chamber is there is a baboon tooth in there as well, suggesting either a different route into the chamber in the past (Chris Stringer suggests a sinkhole, but then why only one baboon tooth and so many H. naledi?) or maybe the H. naledi took a baboon tooth in with them.

Anyway, I was grumbling to anyone who would listen when the first, undated H. naledi find came to light that they just needed to apply Electron Spin Resonance dating to the teeth, so ya know I am going to take the credit for this one.
posted by Rumple at 10:17 AM on May 10, 2017 [5 favorites]

"What did he say? And what did a class full of actual students in the subject say?"

I taught philosophy 101 for five years and we had a unit on "what is a person?" and we did very similar thought experiments. We'd go through dogs, elephants, gorillas, dolphins, Koko the sign language gorilla; other hominids; intelligent aliens; AI; hypothetically genetically engineered/evolved animals that can speak to us ("dolphins swim up to Florida and say, "Hey, so, we want the right to vote, we're going to pay taxes by running a water park where people pay to swim with us""); various eldrich genetic experiments (half-corn, half-man); and then the varieties of actual humans like fetuses and babies and children and people with senility or traumatic brain injuries and so on.

People's intuitions are different and it's interesting to examine and push on them with different examples. The most common form I saw was people who were 100% positive fetuses were "people" but Koko the sign language gorilla was absolutely not. "It's genetics! Only genetically distinct humans are people, that's why fetuses are but Koko isn't!" So then I'd be all, "Clones? Twins?" And we'd also talk about the ways genetics and race and "species" have been used in the past to define out "undesirable" humans from being people -- like historical claims that Africans, or the Irish, or whomever, were actually more closely related to monkeys than men.

After we bickered for a couple hours they'd be like, "Fine, so what IS the right answer?" and I'd be like, "I don't know, I keep hoping if I teach this unit enough times someone will come up with something really brilliant." I think the best student definition I ever got was that a person is EITHER an individual who can communicate with us in something we understand to be similar to human language (such as Koko the gorilla) OR a member of a species the majority of whose members can communicate with us using language (which prevents you from defining babies or a profoundly disabled human out of personhood because they can't talk). I'm relatively comfortable with that definition although it's still not perfect. And then we'd watch ST:TNG The Measure of a Man, because it highlights some of the stakes of the discussion (I liked coming up with ways to show why philosophical debates matter in the real world) without it being about abortion, which is boring and also makes them all turn their brains off.
posted by Eyebrows McGee at 10:31 AM on May 10, 2017 [9 favorites]

as well as to extend the concept of "human" to at least before the split with Chimpanzees, hence "Homo troglodytes".


I'm partial to Pan narrans.
posted by the man of twists and turns at 11:02 AM on May 10, 2017

a person is EITHER an individual who can communicate with us in something we understand to be similar to human language (such as Koko the gorilla) OR a member of a species the majority of whose members can communicate with us

Is this similar to the "genetics!" argument? In that genes determine which species you are a member of? (only referring to the second part of course)
posted by dmh at 11:54 AM on May 10, 2017

I think the best student definition I ever got was that a person is EITHER an individual who can communicate with us in something we understand to be similar to human language (such as Koko the gorilla) OR a member of a species the majority of whose members can communicate with us using language (which prevents you from defining babies or a profoundly disabled human out of personhood because they can't talk).

Does this mean we already have AIs that qualify as persons? Would digital assistants such Siri, Alexa, Cortana, and Google Now be considered persons? It's true, they're not yet at a level sufficient to pass the Turing Test; but neither is Koko, I would argue. If we grant that Koko is a person based on her rudimentary language skills, does that mean Alexa is too?
posted by DevilsAdvocate at 12:51 PM on May 10, 2017

"Is this similar to the "genetics!" argument?"

I think it's a little more sophisticated because "member of a species" is defined in a more sophisticated, slightly fuzzier way than just plain "genetics!" But you probably could go to just plain "genetics!" if you wanted to. I think the student really did identify a central problem with defining personhood, which is that we want both an individual definition and a group definition, because most of us are horrified by the idea that grandma-with-senility "loses" her personhood, and it's sort-of tricky to reconcile those two things in a coherent way.

When my students said "genetically human," though, it was typically reflexive appeal to the authority of science to support unexamined religious (or other) beliefs -- as were claims about the inferior humanity of subject races during slavery, as were claims about eugenics in the 1920s. What I wanted to push back on was the idea that "human" is easy to define or value-neutral or unchanging in definition. By the end of the unit, where they had to propose and defend a definition of "person," some of them would go with "genetically human" and defend it reasonably and that was okay with me. But as a starting point it was literally always code for "yes fetuses but no monkeys, because I am anti-abortion and therefore think fetuses must be people so abortion can be murder, and I also think God created man as distinct from animals." After we knocked out a bunch of the lazy-ass non arguments and appears to authority, it is totally possible to make an argument restricting personhood to humans! I don't agree with that definition but I think you can make a reasonable argument for other people to take seriously. Just not, "But genetics! Because fetuses!"

(The argument is always "genetically distinct individuals" because that's what they've learned from the pro-life movement is what gives fetuses rights against their mothers -- they're "genetically distinct" from the mother, so not just "like an organ" (which is genetically identical to "you") and the fetus is therefore entitled to live to express its genetic distinctness. They are REALLY EASY TO FLUMMOX with questions about whether you can kill your identical twin, or what if you're pregnant with your own clone, or what if
you have a heart transplant so your heart is genetically distinct from you, does that imply your heart has a right to live outside of you? "But a heart can't survive if it's not hooked up to you!" "Well, neither can a 12-week-old fetus ..." It's a weaksauce moral argument as well, it's an appeal to the authority of science without really understanding the science, because they're not able to articulate a strong moral claim or defend it against objections. Fake-ass appeals to science are almost always the sign of muddled morality and an attempt to railroad your opponent with a "factual" claim they can't dispute because you can't defend your actual moral claim. I'm loosely pro-life and that whole line of argumentation is just maddeningly stupid.)
posted by Eyebrows McGee at 12:53 PM on May 10, 2017 [6 favorites]

"If we grant that Koko is a person based on her rudimentary language skills, does that mean Alexa is too?"

Generally my students would argue that there was some component of self-awareness, consciousness, or desire in there (not JUST ability to communicate), which rules out very sophisticated computers but rules in "true" AIs like Data in Star Trek. But, yes, I bet some of them would argue Alexa and Siri are people and I'm sure I'd enjoy reading the papers they wrote. I always told them philosophy is not about being right, but about being wrong in interesting ways. I think that idea's wrong, but in a very interesting way that would be very worthwhile to explore. :)
posted by Eyebrows McGee at 12:58 PM on May 10, 2017 [1 favorite]

Here's Chris Stringer's updated phylogenetic tree.

An explainer by John Hawks, one of the key researchers.

Review in SciAm by Kate Wong.

The dates were not the only new H. naledi paper out yesterday: roundup here.

One underappreciated aspect of this whole discovery is that the researchers have been putting up the three-d scan/print files as open access simultaneously with publication, so you can already download and print your own copies of the new chamber finds. Compare to traditional paleoanthropology, where some researchers (cough Tim White cough*) might hold on to their specimens for up to 10 years without independent examination
posted by Rumple at 1:27 PM on May 10, 2017 [4 favorites]

And if you'd showed me that Chris Stringer phylogeny 10 years ago I would have said you were on crack. Interesting times in PaleoAnth.
posted by Rumple at 1:29 PM on May 10, 2017

Looking at the Chris Stringer tweets, while I understand why some of the paleontology community commentators find it doubtful that naledi could have manipulated fire to take the bodies into the dark, none of them have answered the question of how, if it was a somehow accidental deposit or redeposit by water... why only naledi bones? If the researches somehow missed an easy opening, and it was just naledi tossing their dead down a pit to stop predators from being attracted, why wouldn't they do the same with prey remains? If it was a gathering of accidental deaths from a sinkhole/redeposit, surely other animals would fall into the pit/be washed into the gathering. If it was a predator's stash, surely they would eat something other than just naledi, and yet both caves are apparently almost purely naledi.

It's really hard to conceive of these gatherings as anything other than an indication that naledi regarded the bodies of their dead as something special, worth taking considerable effort and risk to place them somewhere important to them. Whether it was to protect them from predators or because the cave had some deeper meaning to them.

And that in turn suggests some pretty complicated stuff was going on in their heads, small brain or not. So I'm a little frustrated by the 'they can't have had fire! they can't have buried their dead! their brains were too small'. When the evidence so strongly suggests the opposite, I'd really like something other than a kneejerk 'brains are too small' for evidence on the other side.
posted by tavella at 2:23 PM on May 10, 2017 [2 favorites]

Tavella, I completely agree. Something is missing in that argument. I strongly suspect people are underestimating the capacities of these ancient humans based on their brain size. H. floresiensis has a cranial capacity of about 400cc, H. naledi about 500cc. The former are almost certain to have had controlled use of fire based on fire broken rock and burnt stegodon bones, not to mention that they made perfectly respectable stone tools and hunted these small elephants, with more-or-less chimp-sized brains. Since the brain is a metabolically hungry organ, there may well be times when it is under selective pressure to become more efficient, while not necessarily becoming much or any stupider.

I mean, there is a long history of denying real human intelligence to everything before Homo sapiens sapiens. Neanderthals were long characterized as complete brutish idiots, but the reality is more subtle than that. Anything pre-Neanderthal is widely seen as being just lacking the spark. I think until proven otherwise there should be a default understanding that anything placed in genus Homo may well have at least considerable mental horsepower, even if it is indeed lesser than our own.

And yes, that's the interesting thing about the baboon tooth. As far as I could see that's the only non-H. naledi taxon in the cave, and it is just one element. I've worked in (much more recent) cave settings which include former holes in the ceiling where crtters dropped in. Under these holes there is a huge variety of local fauna. Further away there is only the fauna which entered the cave deliberately (e.g., hibernating bears)

And, something allowed them to use optical dating at this new chamber, which depends on the time elapsed since quartz or feldspar is exposed to sunlight. So in this new chamber one assumes the dated sediments came in from the outside at relevant times to bracket the fossils. However, it also seems they place much more emphasis on the ESR dates on teeth. This whole site is so far from my field I hate to comment, but the pieces don't make perfect sense yet.

It's also worth noting that in the first chamber, they have only excavated one square meter of the cave floor. A single 1 X 1 and they have, I think, about 1,300 elements from 15 individuals? That's extraordinary in its own right.

Anyway, all in all, I think a combination of conservative or even out-dated assumptions about brain size and intelligence, and the fairly revolutionary implications of both naledi and floresiensis are acting together to produce resistance to the most parsimonious explanation: these hominins were pretty smart and cared at least a little about their dead.

Which, since all kinds of taxa like chimps (correct me if I'm wrong ChuraChura) and elephants share a certain suite of behaviours around their dead then that shouldn't really be a huge barrier to pass, but in some ways I suppose it is the barrier in our own heads as we unconsciously ring-fence and do boundary maintenance what it means to be a human person.
posted by Rumple at 3:09 PM on May 10, 2017 [6 favorites]

One glaring issue with "genetics" - what about people with congenital chromosomal abnormalities such as Downs Syndrome (trisomy 21) or Klinefelter Syndrome (X chromosome duplication)?
posted by porpoise at 4:12 PM on May 10, 2017

tavella: "while I understand why some of the paleontology community commentators find it doubtful that naledi could have manipulated fire to take the bodies into the dark, "

Is there some evidence to uphold the theory that Naledi were afraid of the dark of something? Exploring a tunnel complex is something that can be done by feel.
posted by Mitheral at 9:32 PM on May 10, 2017 [1 favorite]

I guess it's possible, though the cave diagrams look kind of unfriendly for it. And it seems you'd almost have to be more intelligent to have the drive to do that kind of dangerous exploration. It's not as if you are likely to find food, and if you were seeking water, I wouldn't think you'd go much beyond the first chamber -- the later ones aren't significantly deeper at least in Dinaledi.

I'm trying to think of ways they could have self-selected:

- Maybe naledi had a habit of retreated into the ground to avoid predators, some particular type of predator would pursue them that had the ability to get past the superman crawl squeeze but not the next, and hung out in the big chamber, trapping them there until they died (which seems really unlikely) or the naledi injured themselves badly enough they couldn't climb back up. Avenues of investigation: what's the max possible size of both squeezes in the past before sediment/flowstone shrank them, i.e. was there a time when the first of them could have admitted a larger predator than the other? What predators were in the area at the time, and are there any whose relatives/descendants ever practice underground pursuit like that? How steep or unclimbable could the chute have been in the past? Are there any signs of pre-mortem recent injury on the bones?

- What was the climate/vegetation at the time? Would it have been susceptible to the sort of regular grass/forest fire that would drive naledi into retreating into holes? Is there anything about the air circulation of the cave, or possible air circulation in the past, that could mean that smoke was drawn down, leading to them retreating further and further and eventually being suffocated? I'd rather expect to see a lot of other animals suffocated as well, mind you, but you could at least model the cave to see.

- The pursuit of water idea. Is there anything about the hydrology of the area that would indicate that the caves where they found the bones would be a reliable source of water in a severe drought, compared to the easier-to-get-to areas?

They all seem kind of doubtful to me, but they at least provide avenues of investigation, while smugly repeating the shibboleth 'brain too small' doesn't go anywhere.
posted by tavella at 2:08 PM on May 15, 2017

The one thing I could see pointing towards potential self-selection is that both groups of fossils come immediately below steep vertical shafts, but at least at Dinaledi it's very rough and doesn't look like the sort of shaft down which you could easily plunge in one drop or that a hominin with climbing specializations wouldn't be able to get back up.

And of course even if the shafts trapped them, you have to justify why they so regularly ended up in them when they would have had to gone so far in dark and difficult environments to get there. They found 15 individuals at Dinaledi and have only excavated something like a percent or two of the chamber, so it seems like there were hundreds of naledi that ended up there.
posted by tavella at 7:04 PM on May 15, 2017