Neandertals built a circle out of stalagmites deep underground. What does it mean?

I want to reflect for a moment on the first passage in the recent paper by Jacques Jaubert and colleagues (2016). The paper describes a series of circular structures, made like stone fencerows out of portions of stalagmites, that ancient Neandertals constructed deep within the Bruniquel Cave some 176,000 years ago.

Here are those first two sentences (the rest of the first paragraph introduces the stone structures):

Very little is known about Neanderthal cultures, particularly early ones. Other than lithic implements and exceptional bone tools, very few artefacts have been preserved. While those that do remain include red and black pigments and burial sites, these indications of modernity are extremely sparse and few have been precisely dated, thus greatly limiting our knowledge of these predecessors of modern humans.

This short summary of the state of our knowledge about Neandertal cultures is entirely correct. But at the same time, I think it summarizes only half the problem.

Archaeologists know well that the record of material culture that they can study is biased in various ways, sometimes extreme. They know that material artifacts have multiple uses and purposes within human social systems, and that testing hypotheses about some of the functions of artifacts requires evidence of patterning that can come only from recovering thousands of them across space and time. Even when the archaeological record approaches numbers of many thousands of each type of artifact, as in southwestern France after some 50,000 years ago, the patterns left on the landscape by ancient social systems may blend and mix because the people moved and cultures changed. The cultural patterning that archaeologists find in this later Middle Paleolithic record therefore reflects aspects of human behavior that lie at a larger scale than cultures as we recognize them in the ethnographic present.

For this reason, archaeologists who are interested in cognitive evolution and the cultural potential of ancient humans by and large cannot rely upon spatial and temporal patterning of artifacts. Or, to the extent that they rely on patterning for evidence about such cultural abilities, they interpret the evidence as entirely negative. What archaeologists call “the” Acheulean is spread across a million years of time and three continents of space. Linking recognized by the “type” artifact, the handaxe. Some archaeologists construe this distribution as powerful negative evidence about the cognitive and cultural abilities of ancient people. After all, if they were clever, wouldn’t they have done something more interesting? Wouldn’t they have cultural patterning on the scale of recent people? The mere existence of some spatial patterning is one of the more powerful arguments for a shift in the Middle Stone Age of Africa toward a more sophisticated array of cultural abilities. It remains unclear, however, whether the appearance of a change is merely a result of the increased intensity of investigation and density of evidence from Middle Stone Age sites.

And so, archaeologists of a cognitive bent tend to focus on another category of evidence: artifacts that require a complex series of steps to manufacture, or that are themselves inexplicable without reference to social phenomena. These are the “black swans” of Paleolithic archaeology. They are intrinsically rare in the record, but it hardly matters. The mere fact that a Neandertal might produce birch pitch, with its complex series of manufacturing steps, speaks more about the cognitive abilities of these ancient people than fifty thousand side scrapers.

Going deep into a cave and building stone circles from stalagmites is clearly one such activity. The mere existence of the structures speaks by itself of a level of social and cognitive abilities in the hominins who built them. That is why the report of such a thing is newsworthy, and why it is worthwhile to document so intensively the timeline of their manufacture.

But adding rare things to the numerator of Neandertal abilities is itself a bias, because the denominator is unknown and large.

Across the entire timespan of existence of Neandertals and the branch that gave rise to them, probably fewer than 50,000 of them existed at any time. I would not be much surprised if the true number was much smaller. If the average lifespan of a Neandertal was 20 years, maintaining a population of 50,000 individuals would require around 7 births per day. For the more than half million years this population and its ancestors existed, back past Sima de los Huesos to their common ancestors with Denisovans and African peoples, we can say there were as many as 1.3 billion Neandertals.

Weigh that against how little we know of them, how few pieces of their cultures they left for us. We do not know what the cultural production of an average Neandertal could have been, this is why the denominator is unknown. But it is evident that the fraction represented by the archaeological record is tiny.

The accompanying opinion essay by Marie Soressi is well worth reading, in it she reminds archaeologists of the limits of preservation:

These structures are among the best-preserved constructions known for the whole of the Pleistocene epoch, probably because they were sealed by calcite very soon after they were erected. When the best evidence is found in the best-preserved context, it serves as a reminder for archaeologists of how much we depend on preservation. The fact that some of the art of the period is also often found deep inside caves has been alternatively interpreted as a testimony of the preservation provided by the cave environment or as a result of spiritual preoccupations — the underground being a special place. Perhaps we need to further consider the idea that the fuzziness of the Neanderthal record is due to a lack of preservation.

One might argue that the fact that we only find a tiny number of uniquely informative Neandertal-associated artifact is itself information. Surely, if the Neandertals had been more culturally productive, more modern, they would have left more of a record? Soressi’s essay addresses that argument to some extent, but I want to examine a slightly different point of view. The fact is, it’s hardly just Neandertals. We know very little about the ancient cultures of modern humans.

As recently as the mid-twentieth century, the world’s peoples spoke more than 6000 languages, each representing a culture with some time depth, some antiquity. Yet the vast majority of these languages could be grouped into a much smaller number of families of languages, most of which had their own origins within the last several thousand years. The number of branches leading to extant languages that existed more than 10,000 years ago is today tiny. Ten thousand years ago, the world was full of modern humans. Their languages, their cultures, which must themselves have numbered in the thousands, are mostly today extinct. As we know increasingly from ancient DNA, today’s people derive most of their genetic heritage from only a very small subset of the people who existed 10,000 years ago. That is, early modern humans around the world have left very few cultural traces and many of them have left no genetic traces in today’s peoples. They are gone, almost without a trace.

How surprising is this absence of information from these earlier modern humans? Surely the situation is not so bad as for Neandertals, after all, we have the fairly dense Upper Paleolithic record of Europe, the Maghreb, the Natufian, there are real areas where we have lots of archaeological information from these people between 30,000 and 10,000 years ago. But Southeast Asia and large parts of Africa–home to the majority of the world’s population at the time–have a very sparse archaeological record with many blank spaces. As we are increasingly becoming aware, the first third of human occupation of the Americas is documented by only a handful of archaeological sites. Who knows how many millions of people lived without leaving any record that archaeologists have yet found?

Worldwide, they were not nearly so sparse as Neandertals. Of these early modern humans, by the time they inhabited Australia and entered the Americas, there were tens of millions. If the lifespan of these modern humans averaged 25 years, it would take on the order of 1000 births a day to maintain a population of 10 million humans. From 30,000 years ago to 10,000, a mere 20,000 years of time, some 7.3 billion modern humans would have existed, under this set of assumptions. The true number of course was probably more. This is not the same space as Neandertals; these modern humans lived around much of the world, not just western Eurasia. But without question their population was an order of magnitude larger.

Arguably, our archaeological knowledge of these vast multitudes of people is much greater than what we know so far of Neandertals. As Soressi points out, the archaeological record is biased by time, by the better chance of preserving evidence from these recent time periods, by the kind of artifacts that some of these modern humans made. What is clear is that even for modern humans within the last 30,000 years, vast spans of time and space are complete unknowns.

Again, we do not know the true size of the denominator, but it is large enough to know that the fraction archaeologists see is tiny.

We know so little about the past. As long as this is true, our view of the past will disproportionately be based on the greatest achievements we have found so far. Water crossings imply maritime abilities, technology for sailing and navigating. Regular use of deep underground spaces implies controlled fire, dominance over other fauna that use caves, social systems capable of escape if the light should be lost.

This logic does not apply only to Neandertals, of course. I really like the methodology applied by Jaubert and colleagues, and the paper is basically straightforward. Still I do have a bone to pick with the paper’s review of the use of cave environments by hominins:

Deep karst occupation does not appear to have occurred in Africa in any period, whether the Early or Middle Stone Age, or even the Late Stone Age if we exclude shelters and cave entrances with evidence for human presence in South Africa, Ethiopia and Maghreb (Extended Data Fig. 8). The oldest evidence for the appropriation of this difficult environment is found in Europe, Southeast Asia/Sunda, Wallacea and Australia/Sahul. The accumulation of human bodies by Acheuleans at Sima de los Huesos, Spain (0.35 Ma) is very different from the Bruniquel structures, however. In other examples, the human frequentation of caves is linked to engraving, painting or sculpting activities. These sites are thus younger than 42,000 calibrated years before present and are always associated with Homo s. sapiens. Symbolic, cultural or funerary activities were the main reasons for these cave visits. Until now no evidence has been found for regular Neanderthal incursions into caves, except for a possible case of footprints, and Neanderthal constructions inside caves, at least at a distance that is no longer exposed to daylight, were totally unknown. Moreover, Upper Palaeolithic constructions in caves are limited to fireplaces, simple hearths, and some rock or speleothem displacements. Even in caves regularly visited since the Aurignacian, constructions are non-existent or anecdotal.

This quote refers to extended figure 8, which is a timeline of archaeological evidence for various behaviors that archaeologists have included within the concept of “behavioral modernity”.

I am very familiar with one African site in which a primitive non-modern hominin species is clearly in a deep cave environment. Homo naledi is there deep in the Rising Star cave with no direct surface access. It’s not quite as far as Bruniquel, but it’s not peanuts, either. That is good evidence for some degree of deep cave access by that species.

Notes: This post on the Bruniquel evidence was written on the release of that research in 2016. In subsequent research, the evidence for deep cave use by Homo naledi grew stronger with the publication of fossil material from the Lesedi Chamber, showing access into multiple areas of the deep cave setting.

References

Jaubert, J., Verheyden, S., Genty, D., Soulier, M., Cheng, H., Blamart, D., Burlet, C., Camus, H., Delaby, S., Deldicque, D., Edwards, R. L., Ferrier, C., Lacrampe-Cuyaubère, F., Lévêque, F., Maksud, F., Mora, P., Muth, X., Régnier, É., Rouzaud, J.-N., & Santos, F. (2016). Early Neanderthal constructions deep in Bruniquel Cave in southwestern France. Nature, 534(7605), Article 7605. https://doi.org/10.1038/nature18291

Soressi, M. (2016). Neanderthals built underground. Nature, 534(7605), Article 7605. https://doi.org/10.1038/nature18440