Beaver exploitation, 400,000 years ago, testifies to prey choice diversity of Middle Pleistocene hominins

Data regarding the subsistence base of early hominins are heavily biased in favor of the animal component of their diets, in particular the remains of large mammals, which are generally much better preserved at archaeological sites than the bones of smaller animals, let alone the remains of plant food. Exploitation of smaller game is very rarely documented before the latest phases of the Pleistocene, which is often taken to imply narrow diets of archaic Homo and interpreted as a striking economic difference between Late Pleistocene and earlier hominins. We present new data that contradict this view of Middle Pleistocene Lower Palaeolithic hominins: cut mark evidence demonstrating systematic exploitation of beavers, identified in the large faunal assemblage from the c. 400,000 years old hominin site Bilzingsleben, in central Germany. In combination with a prime-age dominated mortality profile, this cut mark record shows that the rich beaver assemblage resulted from repetitive human hunting activities, with a focus on young adult individuals. The Bilzingsleben beaver exploitation evidence demonstrates a greater diversity of prey choice by Middle Pleistocene hominins than commonly acknowledged, and a much deeper history of broad-spectrum subsistence than commonly assumed, already visible in prey choices 400,000 years ago.


SUPPLEMENTARY TEXT 1: THE BILZINGSLEBEN SITE
The Bilzingsleben archaeological site is situated in the Wipper Valley, a tributary of the Saale river in central Germany.The site was embedded in sand and lake carbonates of a travertine spring, which subsequently covered the archaeology yielding deposits with a 3-4 m thick sequence of solid travertines, exploited for building material.Extensive excavations took place between 1969 and 2002 by Dietrich Mania, over a total area of about 1800 m 2 ; smallscale excavations by Clemens Pasda followed from 2004 to 2007 [1][2][3][4] .More than three decades of excavations yielded large numbers (> 100,000) of stone artifacts, tons of vertebrate bones and bone fragments, famously including hominin remains (NISP 28, MNI 3) assigned to H. erectus bilzingslebensis 5 , the fragmentary nature of which makes them difficult to assess 6 .
The vertebrate fauna comprises 54 species, including rhinos, elephant, bear, wolf, cervids, bovids, horse, primates (besides Homo: Macaca florentina), a wide range of small mammals as well as Castor fiber and Trogontherium cuvieri.The site also yielded large amounts of molluscs, wood fragments, pollen and a wide range of leaf imprints.Floral remains and the rich fauna are indicative of a warm-temperate climate, which on the basis of biostratigraphy and some chronometric (U-series and ESR) data is younger than the Cromerian and Elsterian complexes but older than the Saalian glaciation, and correlative to Marine Isotope Stage 11,   with an estimated age of 374 to 424 ka (see e.g. 3,7for further discussion of the age range estimates for the site).In Mania's interpretation of the Bilzingsleben evidence 2 , the archaeological finds come from a small peninsula-like shore terrace edge (Uferplatte), of an approximately 200 by 300 m large lake, with primary context traces of hominin occupation).This edge is bordered by an alluvial fan close to the travertine spring, made up of friable travertine sands (Schwemmfächer) that contained material reworked from occupations on the Uferplatte.The finds come from both the shore and the alluvial fan facies.There is debate on the specifics of the site formation processes and the interpretation of the spatial patterns at the Uferplatte: according to Mania and his team the archaeological material there is preserved in primary context, including in situ remains of a number of dwelling structures, whereas Pasda and colleagues have suggested that the site contains reworked and redeposited cultural and natural materials formerly scattered in the surrounding landscape (see discussion in 3,8 ).However, there is little doubt about the homogeneity of the rich fauna in terms of it belonging to one warm-temperate phase.
A recent study by Brasser 4 focused on the megaherbivores from the site as well as its bear remains, investigating a possible anthropogenic impact through the analysis of > 8200 skeletal According to Brasser, the faunal assemblage formed over a relatively short period and contains a mixture of animals that died of natural processes, including carnivore kills, and as a result of human hunting, with the bones of bears and rhinos showing traces of human interference in the form of cut marks.The general paucity of cut marks identified in Brasser's study may be due to abrasion which altered bone surfaces and erased cut marks on bones from larger taxa faster than on bones from smaller taxa, as suggested by taphonomic experiments 9,10 and underlined by the good cut mark evidence from the beaver assemblage presented in this study.

Spatial distribution of beaver remains
The excavations at Bilzingsleben were carried out using a 1.5 by 1.5 m grid system (Planquadrate) and extended over an area of approximately 1,800m 2 .As mentioned above, Mania separated two distinct depositional areas, in the northern partthe alluvial fan (Schwemmfächer) and the terrace edge (Uferplatte).All archaeological finds, including the beaver bones, are labeled according to their square of origin and find number.In a previous study, Heinrich 11 reported two main areas of deposition for beaver teeth, at the transition from the alluvial fan to the terrace edge, and in the area of the "working zones" identified by Mania in the terrace edge area.In Heinrichs interpretation, the spatial distribution in these two areas points to areas where hominins exploited beavers.
We plotted the spatial distribution of the 2496 beaver specimens (bones and teeth) within the excavated area (Supplementary Figure 1).Interestingly, almost all cut marked specimens hail from either the terrace edge/Uferplatte or the area of transition to the alluvial fan/Schwemmfächer.In general, the spatial distribution of the beaver remains follows the distribution of larger mammals analysed by Brasser 4 .

SUPPLEMENTARY TEXT 2: BEAVER EXPLOITATION IN THE EUROPEAN LOWER AND MIDDLE PALAEOLITHIC
There exists some scattered evidence for exploitation of beaver in the later phases of the Middle Palaeolithic, from a small number of sites in Germany, France, Spain, Italy and Croatia.Most data come from a relatively short period, the Last Interglacial, when the temperate climate and forested conditions in major parts of Eurasia provided ideal habitats for beavers.The Eemian "spear site" Lehringen (Germany) yielded one cut marked beaver pelvis fragment 12 .Bratlund 13 , studying the faunal material from the Last Interglacial travertine site Taubach (Germany), identified 10 cut marked beaver bone fragments from an assemblage with an MNI of 17 13 , twice the amount of cut marked bones recovered from contemporaneous deposits in the Grand Abri aux Puces in France 14 .The Last Interglacial Layer 1 at Krapina (Croatia) (beaver MNI 19, NISP 353) also yielded some cut marked Castor fiber remains 15 .At other Middle Palaeolithic sites evidence consists of very small numbers in MNI for beaver as well as for cut marked bones.Examples come from Pech de l'Azé IV, France with one cut marked bone 16 , two cut marked bones at Pech de l'Azé I (level 7) 17 , and rare occurrences of cut marked beaver bones in two final Middle Palaeolithic sites in northeast Italy 18 .For the Lower Palaeolithic, data are virtually absent: some beaver remains from Gruta Aroeira and Gruta da Oliveira (Portugal), from archaeological deposits found in association with remains of hunted game and stone tools, may have entered the site through human activities, but there are no cut marks to testify to human interference 19 .Anthropogenic modifications of Lower Palaeolithic beaver remains are in fact limited to in total seven cut marked bones from two levels in the Caune de l'Arago (France), thought to attest to occasional procurement and exploitation of Castor around 350-400,000 years ago 20 .
Bilzingsleben beaver material.NISP: Number of Identified Specimens, MNE: Minimum Number of Elements, MNI: Minimum Number of Individuals, NISPcut: Number of Identified Specimens with cut marks, MNEcut: Minimum Number of Elements with cut marks, MNIcut: Minimum Number of Individuals with cut marks, dex: skeletal elements from the right side of the body, sin: skeletal elements from the left side of the body, indet: body side indeterminate.