Imagine

Abstract

Imagine that a human group is discovered that had not previously been contacted. A tribe, as they said before, lost and isolated that no one had news of, on some remote island or in some isolated place in the thickest of the jungles.

Our curiosity would be enormous. We would like to know everything about this unknown humanity. For a start, their way of life, their economy, their diet. We would assume that they would have fire because all people on Earth have it and no modern human culture has ever been known to lack it.

We would certainly be interested in their technology, and no less in their language and customs. We would like to know everything about their social organization and their family life: Monogamous or non-monogamous? Assuming that they would have art, or at least personal decoration, we would want to know their cultural codes.

And as soon as we could understand each other, we would question them about their illnesses, which they might attribute to spirits, and other more obvious causes of death, such as predators, parasites, hunger, cold, and violence. Do many attacks occur in your society? We would ask them. Is infanticide often practiced?

We would imagine that their lives would be dangerous, with a lot of child mortality, but that some lucky ones would reach the age of reproduction, have children, and raise them until they became adults, because otherwise those people would have gone extinct a long time ago.

But how many years would the elderly live? 50, 60, and 70 years? Surely no less than 50 years because some chimpanzees reach that age, and they belong to a species with a shorter life history than ours. But we would not expect that the elderly inhabitants of Atapuerca exceed 70 years of age, because there are very few individuals who live longer among modern societies of hunters and gatherers.

And finally we would ask them: are funeral rituals practiced? What is done with the dead?

Imagine now that this meeting has taken place, but not in a remote place on our planet, but in Western Europe, in Spain, specifically, just a few kilometers from the historic and important city of Burgos. And this is the story told in this special issue of Anatomical Record.

But this is not a population of our own species and our time, rather we are talking about a population of another species and another time.

Because exactly that is what has happened in the Sima de los Huesos of the Cueva Mayor de la Sierra de Atapuerca, near Burgos, in the Spanish region of Castilla y León. There, the skeletons of about 30 complete individuals are being recovered, and little by little they are being reconstructed. The species is not ours, nor is the time ours, but the questions we ask the human beings whose skeletons we are rescuing are not very different from those we would ask them if they were alive.

This is assuming they could talk, of course, that is, assuming they had a symbolic mind. And that would be the first thing we would try to find out if we had them before our eyes.

The Sima de los Huesos is the largest accumulation in history of fossil remains belonging to a species different from ours. It had never happened before, although now there is another comparable site in a place very far from Spain: the Rising Star cave in the Cradle of Humanity, South Africa (Berger et al., 2023). The chronologies are similar and the sites too, but the species are very different.

The Rising Star human fossils belong to the species Homo naledi and the Sima de los Huesos contains an archaic form of Neanderthals. In fact, it represents the deepest root known to date for Neanderthals.

But it would be a mistake to simply say that the Sima de los Huesos fossils are Neanderthals and stop there, because we would lose a lot of information. When compared with the so-called “classic” Neanderthals, which are the Neanderthals that Homo sapiens met when it left Africa, great differences can be seen.

In other words, thanks to the fossils from the Sima de los Huesos, we know how the “neanderthalization” process and the “sapienization” process occurred, that is, how two evolutionary branches separated from common ancestors: on the one hand, the branch that would lead to the living human population, and on the other hand, that which would give rise to the Neanderthals and the Denisovans, who, although they have contributed genetically to some current human populations, can be considered extinct. There are no longer Neanderthals and Denisovans recognizable as such.

The Neanderthals of the Late Pleistocene were well known before the Sima de los Huesos findings (Trinkaus & Shipman, 1993), but what was not so well known was how the evolution of Neanderthals had occurred in the Middle Pleistocene.

It is time to say something about the chronology, because this is still an issue to be clarified. The dating carried out on the sediment using luminescence techniques gives an age of around 400,000 years (Arnold et al., 2014), but the direct dating on the fossils using the combined method of ESR and uranium series points to 300,000 years, more or less (Bischoff et al., 1997).

In this prologue, I did not want to ignore the problem of the origin of the human accumulation of the Sima de los Huesos and their geological age, but these topics will not be discussed in depth in this monographic issue of AR journal. Other important topics are also not included in this collection of articles, such as studies of ancient DNA, which have confirmed the conclusion that paleontologists had reached before: these are archaic Neanderthals (Arsuaga et al., 2014; Meyer et al., 2014, 2016).

Given the abundance of fossils in the Sima de los Huesos, there is a lot of work for paleoanthropologists. All parts of the skeleton are represented, as well as both sexes, and as well as the different stages of life. In this way, it is possible to study development and sexual dimorphism for each region of the body. And that is what is done in this series of articles, along with the taphonomy and associated fauna at the site. It can certainly be said that we now have very complete information on the paleobiology of an extinct species.

The rest is history.

A history that began with the discovery of the first human fossils at the Sima de los Hueses site in 1976. Then history stopped until 1983, when systematic excavations began and have not stopped until now. We must remember 1992 as a particularly important year, in which three human skulls were brought to light (Arsuaga et al., 1993). As well as 1994, when a pelvis was found, which is the only truly well-preserved pelvis of an extinct human species (Arsuaga et al., 1999; Bonmatí et al., 2010). And many more field seasons are memorable, in fact all the 42 campaigns since 1983.

Now you can see those fossils and more specimens from the Sima de los Huesos in the facilities of the Museum of Human Evolution of Burgos.

We have stuff for many generations of researchers with everything unearthed. But there is still a large part of the site to be excavated. It has not been due to lack of time, nor desire to know more. But techniques advance at a glorious pace and we have to assume that they will continue to do so. Who knew that the Sima de los Huesos was going to provide the oldest human DNA in the world?

It was decided, therefore, to excavate more slowly if possible, although there must not have been many excavations as slow and meticulous in the field of prehistory as that of the Sima de los Huesos.

There remains, in short, a lot of room for hope for new and great discoveries, and for achieving a better understanding of what happened when human corpses accumulated there.

And what is better. There are still reasons to expect the unexpected, the unimaginable.