Every year, the Penn Museum provides support to Penn undergraduates and graduate students as they deepen their understanding of the human experience outside the Museum’s walls. Follow these blog posts from our intrepid young scholars as they report on the sights and sites that they encounter throughout their travels in the field.
Although Neanderthal specimens were known in Spain, Belgium, and Germany decades before Darwin’s publication of the Origin of Species in 1859, these single specimens from each site were dismissed as mere diseased modern humans. Without an evolutionary perspective, and with physicians primarily studying the specimens, the pathological interpretation was the most parsimonious and sensible. For example, the specimen for which the species was later named, found by quarry workers in the Neander Valley in Germany in 1856, was diagnosed by prominent medical anatomists as a Cossack horseman riddled with rickets and arthritis who crawled into a cave to die. For over 40 years this strain of argument persisted and was applied to the whole human fossil record, until the Krapina Neanderthals were unearthed.
Excavated in 1899 by Croatian (then Austro-Hungarian) paleontologist and geologist Dragutin Gorjanović Kramberger, the Krapina site, about 55 hilly kilometers north of Zagreb, includes the remains of numerous Neanderthals, over nine hundred bones of at least a few dozen individuals, and among them many youngsters. So sizeable a sample of adults and juveniles with similar anatomy among themselves and as a group so different from modern humans put paid to the notion that these strange humanoid fossils were just medical oddities, firmly establishing Neanderthals as a once-living population.
Gorjanović Kramberger’s meticulous documentation of the Krapina site’s excavation over six years (1899-1905) was unparalleled and unprecedented in its time. While earlier Neanderthal specimens were collected with at best cursory attention to details of context and location, Gorjanović Kramberger supervised a careful excavation of the site, arranged the hundreds of skeletal fragments by layer and collected stone tools and the fossilized remains of extinct animals, proving the antiquity of the remains.
The fauna of the site are markedly different than those of other Neanderthal sites in Europe, including such critters as rhinos, cave bears, turtles, beavers, and land snails. Only using the animal remains, Gorjanović Kramberger was able to determine that the site represented a warm period assemblage, and more recent methods have corroborated his prescience in detecting an interglacial period of provenience. This last interglacial period (sometimes called the Eemian, Riss-Würm, or Marine Isotope Stage 5e) lasted from about 130,000 to 115,000 years ago and preceded a glacial period (the last so-called “Ice Age”) that engulfed much of Europe for the following 100,000 years, ending only after the last Neanderthals disappear from the fossil record. Electron spin resonance dating and uranium series dating independently show a date of approximately 130,000 years before present for the Krapina site.
Concisely, the Krapina Neanderthals are considerably older than most other European specimens, include a much larger sample size, and represent a population living in a drastically different environment than later Neanderthals on the continent. Since their discovery, the material evidence of stones and bones at Krapina have proved that prehistoric hominid populations of great antiquity inhabited Central Europe. Moreover, Gorjanović Kramberger’s efforts in unearthing, studying, and curating this collection changed the face of paleoanthropology.
Just as Gorjanović Kramberger’s careful excavation was decisive in generating perhaps the richest single sample for insight into Pleistocene hominid life, the careful curation of this collection has been decisive not only for preserving this remarkable slice of prehistory but also for ensuring that new discoveries and interpretations in and of this material sprout faithfully every year despite decades of study by scores of paleoanthropologists. Ongoing research on the Krapina collection over more than the last 100 years, curated at the Croatian Museum of Natural History in Zagreb, has revealed unrivaled and continuing insight into Neanderthal lifeways, ecology, health, behavior, growth, and morphological variation: the earliest apparent amputation occurred at Krapina (on an ulna, as Gorjanović Kramberger himself noted), the world’s oldest bone tumor (a fibrous dysplasia) was identified on a rib from the site (identified by Penn’s Janet Monge, Alan Mann, and Morrie Kricun), patterned scratch marks around bone trauma suggest evidence of some sort of “paleo-surgery,” and eagle talons with scratch marks from Krapina suggest some kind of non-nutritional processing, perhaps use in ornamentation (see Davorka Radovčić’s 2015 publication in PLoS). The simple but essential practice of approaching a collection with new questions and fresh eyes as a solid means to further interpretations has proven outrageously successful at Krapina. If the past is any guide, the traces of prehistoric life, death, and evolution at Krapina are not yet fully disclosed.
And now for something completely different! Growth and Human Evolution
A long, sometimes silly and sometimes sordid, preoccupation of philosophers has been the definition of the human in relation to the rest of the living world. When Plato conveyed Socrates’ definition of the human being as a featherless biped, Diogenes the Cynic plucked a chicken, went to Plato’s academy and declared: “Behold, I have brought a man!” (Such yarns are cute and all, but we shouldn’t forget that the distinctions and classifications inherent in the exercise of defining humanity have given excuse to acts that make manifestly true the Latin proverb “Homo homini lupus est” or “A man is a wolf to another man.”)
In any case, one of the most interesting differences between humans and the rest of the living world isn’t bipedality or big brains or tool use—the usual short list of special characteristics—although it has rather a lot to do with all that. As far as I can tell, the first person to define a prolonged period of growth (and dependency) as a defining feature of our species was Anaximander, the Greek Presocratic philosopher. Plutarch reports him as writing as follows: “Further, he [Anaximander] says that in the beginning man was born from animals of a different species. His reason is, that, while other animals quickly find food for themselves, man alone requires a prolonged period of suckling. Hence, had man been originally such as he is now, he could never have survived.”
Fascinatingly, Anaximander suggests a kind of evolutionary (albeit of course not Darwinian) scenario and uses the strange pattern of human growth as a fact in his favor. Although he is, arguably, one of the first evolutionists (sensu lato), Anaximander wasn’t quite right on the details: (ethnographic evidence shows that) humans actually nurse for less time than our closest ape relatives. But, it is true that humans are incredibly underdeveloped at birth—extrauteral parasite blobs, really—and that we are dependent on adults for far longer portions of our lives than most other species. The squishiness of the human skull at birth (to allow for the postnatal growth of the brain), the periods of accelerated growth that we call “growth spurts” (contrasted with so-called “quiescent periods” which are the probable actual evolutionary innovation, slowing the more continuous ancestral pattern of growth) are just a couple of uniquely human signatures of this process.
Indeed, the human pattern and timing of growth and dependence is unique in the animal world, and its prolongation relative to the faster ancestral model, a workable approximation of which exists in contemporary apes, is what allows us the time to marinate in the social transmission which is the stuff of culture and the real source of our strange position between the them and the angels. And, of course, this human pattern of growth evolved. Darwin wrote about it in his essential The Descent of Man in 1871, but, thanks to Gorjanović Kramberger’s efforts, and those of many others, we have something now that Darwin didn’t have and which could shed light on this problem: a human fossil record.
Paul shows the baby and developing adult teeth in the mandible of a Neanderthal, died around 130,000 years ago at about four years of age, from Krapina at the Croatian Natural History Museum. Photo by Davorka Radovčić
So, why have I visited the historic Krapina collection? Here the grand sweep of history narrows to the breadth of incisor tooth: I am among the storied remains from Krapina to study teeth, baby teeth particularly. Although it rings at least slightly perverse, I’ll admit to a deep fascination with teeth. It wasn’t love at first bite for me, but after knowing something about what teeth can reveal about growth, death, and life, they’re hard not to fall for.
As enamel is the hardest material in the body, teeth preserve well and are the most abundant osteological element in the fossil and archaeological record. Teeth, unlike bones, do not remodel or change shape after they are formed, which is to say that they only wear down, and they often wear down contingent upon the details of diet, oral hygiene, and tooth use apart from food consumption, such as for securing objects while the hands are busy. Conversely, in their formation, because they don’t remodel or change shape like bone, they preserve a record of the timing and chemical environment of growth in the child and can, through histological analyses, even reveal the age of birth, weaning, and death.
Paul marvels at the Neanderthal teeth from Krapina with Davorka Radovčić of the Croatian Natural History Museum. Photo by Zeko Radovčić
It is this feature of teeth, that they reveal something important about early development, that makes them especially intriguing. Teeth form from the tip of the crown, the part that’s in your mouth and which you bite down on, to the apex of the root in the alveolar bone of the maxilla or mandible. Teeth grow incrementally, with each micron-thick line of layered enamel on the crown representing about one week of growth (the exact number varies slightly between human populations and fossil species but is determinable with histological investigation). External manifestations of these minute minutes on teeth are called perikymata and can be counted to determine a time of formation for the tooth, and, if the tooth is incomplete the time of death of the individual who bore it. Although the perikymata of permanent—that is, adult—teeth have been counted and studied in humans and Neanderthals, these structures have not been investigated on the deciduous dentition (baby teeth).
What makes these teeth relevant to studies of development, and the big grand problems so sketchily outlined above, is that tooth growth is linked to other kinds of growth in the body (for example, with the brain), and that we know that our close relatives grow their teeth more quickly than we do. Thus, we expect that faster rates of tooth development indicate faster development generally. This assumption appears a safe one based on what we know. What is contentious, or really an open question, is when the human pattern of growth evolved. Obviously, a change happened between ourselves and our ancestors—our common ancestor with chimpanzees, for example, didn’t take 17 years to erupt its third molars—but we don’t know when this happened. Recent research demonstrating genetic admixture between “modern humans” and Neanderthals (see the recent work from the spring of 2015 on the Oase 1 mandible from Romania) shows the arbitrariness of these labels—insofar as the term has meaning in biology, we are the same species.
But, this finding is apparently at odds with research on Neanderthal permanent teeth which purports to show a significantly faster period of growth for Neanderthals than modern humans. Did we have different patterns of growth, despite being the same species? We may have, or we may have not, but much more work is needed to fully address this question.
Approaching this question from two directions is what motivates my visit to the Krapina collection: First, can we see what the deciduous teeth say about the earliest periods of development? Do Neanderthal babies grow quickly immediately postnatally like modern humans? Permanent teeth, which start to form latter, are not sufficient to answer this question. Second, what variation is present in rate of growth and development in a Neanderthal population, and how does this compare to variation in growth and development in populations of modern humans? The brute fact of variation in biology means that we have to think statistically, not typologically, if we are to define changes in populations through time and space. So far, studies on Neanderthal tooth growth and development are effectively case studies. Krapina, as the largest Neanderthal sample in the world, contains many juveniles. For this reason, Krapina is the ideal collection to investigate these questions of growth, death, and evolution in recent hominid history, and I have spent an appreciable chunk of the last two weeks, sometimes laboriously, with a microscope between me and these Neanderthal baby teeth. Of course, research is frequently unpredictable, and a completely happenstance examination of faunal bones from Krapina and a very curious accidental discovery has meant that I’ve also spent a lot more time looking at cave bear penis bones (the os baculum for those who care or would like to “google” it) than I planned to. (I didn’t plan to at all.) This story, though, is for another time…
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Well, anyway, the answers aren’t here yet, and now I’m off to dig up skeletons in Israel, with every intention to return again to Zagreb to continue this work after getting more data on modern humans in the fall in Philadelphia. The details of hundreds of thousands of years of evolution are revealed divinely in a day, and Zagreb is a place to which I truly look forward to returning. I must here acknowledge the curator at the Croatian Natural History Museum, Davorka Radovčić, and her father Jakov and mother Danka, for their almost fanatical hospitality. It’s been an honor to work with Davorka and this collection, and I thank her and the Croatian Natural History Museum for this fantastic opportunity.
We hypothesize that Neanderphiles are getting nosy based on the nasal polishing on this 50 year old bronze statue at the Krapina excavation site. Photo by author.
 Even today, only one site among all those in the fossil record of human evolution contains remains from more individuals than Krapina, the much more recently excavated but geologically older “Sima de los Huesos,” “Cave of the Bones,” in Atapuerca, Spain.
 Arguably, Gorjanović Kramberger’s discoveries at Krapina as well as Dutch physician-turned-paleoanthropologist Eugene Dubois’s finds of Anthropopithecus erectus (later Pithecanthropus erectus and now Homo erectus) in Java at the close of the 19th century marked the end of any serious scientific objection to the fact of human evolution and the genesis of paleoanthropology.
 See Dave Frayer’s 2006 centennial bibliography of all the research published on Krapina.
Radovčić D, Sršen AO, Radovčić J, Frayer DW (2015) Evidence for Neandertal Jewelry: Modified White-Tailed Eagle Claws at Krapina. PLoS ONE 10(3): e0119802. doi:10.1371/journal.pone.0119802.
Ewen Callaway, “Early European may have had Neanderthal great-great-grandparent” Nature. 13 May 2015, http://www.nature.com/news/early-european-may-have-had-neanderthal-great-great-grandparent-1.17534 Accessed 10 August 2015.