AN ENVIRONMENTAL TALE FROM PLEISTOCENE JAVA
Reconstructing Dietary Niche and Palaeoenvironment by Applying Stable Isotope Analysis to Selected Fossil Fauna From Trinil (Java, Indonesia)
Heather Blain
MA Palaeolithic Archaeology S1198912
Wil Roebroeks Josephine Joordens Palaeolithic Archaeology
University of Leiden, Faculty of Archaeology
Leiden, the Netherlands
2
heatherlblain@gmail.com
TABLE OF CONTENTS
List of Figures 5
List of Tables 6
List of Appendices 7
Preface 8
1. Introduction 9
2. Stable Isotopes 13
2.1 Basic Information 13
2.2 Stable Isotopes and Plants 15
2.3 Stable Isotopes and Teeth 16
2.4 Stable Isotopes and Aquatic Fauna 18
3. Trinil, Java, Indonesia 20
3.1 Early History of the Site 21
3.2 Chronology 22
3.3 Palaeoenvironment – Stratigraphy and Faunal Evidence 26
3.4 Modern Studies 28
3.4.1 Strontium Stable Isotopes – Trinil and Sangiran 29
3.4.2 Modern Wetland Bovid Descendants 29
4. Materials and Methods 31
4.1 Bovid Teeth 32
4.2 Cleaning Procedures 33
4.2.1 Ultrasound Bath 33
4.2.2 Acetic Acid Soak 34
4.2.2.1 Acetic acid 34
4.2.3 Drying 35
4.3 Drilling of Enamel 35
4.4 Aquatic Fauna 37
4.4.1 Preparing Aquatic Fauna 37
4.5 Weighing Material 38
4.6 Mass Spectrometry 38
5. Results 40
4
5.1 Initial Analyses for Fossil Terrestrial Fauna - Bovids 40
5.2 Initial Analyses for Fossil Aquatic Fauna 44
5.2.1 Trinil Fossil Aquatic Fauna 45
5.2.2 Sangiran Fossil Aquatic Fauna 46
6. Discussion and Conclusions 48
Abstract 53
Bibliography 54
Appendices 60
LIST OF FIGURES
2.1 Carbonate cycle in the biosphere 14
3.1 Regional map of western Indonesia 20
3.2 Homo erectus skull-cap, femur and molar from Trinil 22
3.3 Palaeogeographic model of Pleistocene Central Java 23
3.4 Idealized lithostratigraphic profile of Sangiran Dome 24
3.5 Palaeogeographic model of Pleistocene Central Java 26
3.6 Strontium stable isotope values at Pleistocene Trinil and Sangiran 29
4.1 Sample teeth T1-T3 31
4.2 Sample teeth T4-T6 32
4.3 Ultrasound bath 34
4.4 Ready for drying 35
4.5 Teeth after drilling 35
4.6 Schematic of mass spectrometer 39
4.7 Delta+ with Gasbench Mass Spectrometer 39
5.1 Stable Isotope Values of Carbonate Fraction – Bovids 41
5.2 Stable Isotope Values of Carbonate Fraction – Aquatic Fauna 45
6 LIST OF TABLES
4.1 Table of tooth attributes 33 4.2 Drill site locations and observation 36 4.3 Aquatic fauna 37 5.1 Laboratory results for the stable isotopes of the carbonate fraction of
fossil bovid teeth (Trinil). 40 5.2 Terrestrial Faunal Data Ranges, Means and Incidentals. 43 5.3 Laboratory results for the stable isotopes of the carbonate fraction of
the aquatic fauna (Trinil and Sangiran). 44
LIST OF APPENDICES
Appendix 1 Hrdlička’s Transcription of Dubois’ Report to the Royal Dublin
Society, 1891. 60
8 PREFACE
My academic career to this point had not prepared me for working with stable isotope technology, and very little preparation for working with the fossil remains of extinct terrestrial and aquatic fauna. So stepping out of my comfort zone to attempt to find viable stable isotopes of the carbonate fraction of select osteological remains from Trinil HK required many people being willing to share their vast knowledge in: stable isotopes and the protocols that go with them; Trinil HK and its terrestrial and aquatic fauna; bovid dentition;
and, of course, those who offered wise suggestions for improving this
manuscript. Most importantly this project could not be achieved without the
use of the stable isotope laboratory at VU Amsterdam. In alphabetical order, I
am greatly and humbly indebted to: John de Vos, José Joordens, Lisette
Kootker, Katherine MacDonald, Inge Van der Jagt, Suzan Verdegaal, and
Hubert Vonhof.
1. INTRODUCTION
Let me tell you a story about extinct terrestrial dental enamel and fossil aquatic osteological remains and the information they have retained through the millennia. Since no one has attempted to discover this story, mine is a pilot project, which if proved successful should lead to greater and more promising tales. These tales will help to establish the dietary resources (faunal and floral) available to Homo erectus. I am analyzing the stable isotopes of the carbonate fraction of selected bovid teeth and aquatic fauna from Trinil HK (Haupt Knochenschicht, the main bone layer) for dietary niche(s) and as proxies for reconstruction of the palaeoenvironment.
The type fossil for Homo erectus (Figure 3.2) was discovered at Trinil, Java in the late 19
thCentury. To date there has been inadequate analysis for the reconstruction of the palaeoenvironment reflecting the dietary niches of the terrestrial fauna (including Homo erectus) and vice versa. Many stable isotope studies in Africa, Europe and mainland Asia have been used for environmental and hominin dietary reconstruction (e.g. Bedaso et al. 2010;
Lee-Thorpe et al. 2010; Quade et al. 1994; Richards and Trinkaus 2009;
Wang et al. 2008; van der Merwe et al. 2008; Cerling et al. 2011; Henry et al.
2012), but none have been done in Java, Indonesia for the approximately 1 million year old (Ma) site of Trinil HK (for a discussion on dating see Chapter 3). Reconstruction of climate and environment is now an integral part of the analysis of an archaeological site (e.g. Parfitt et al. 2010). Reconstructing the dietary niche of fossil fauna from the Early Pleistocene site of Trinil will give us a broader understanding of the possible variations in local and regional environment and climate that Homo erectus coped with during their
existence. Present day Trinil lies in a tropical rainforest climatic zone on the bank of the modern Solo River (Figure 3.1). However, the expansion of
grasslands in Africa and across Asia (also known as ‘Savannahstan’) is linked
with the evolution and expansion of the genus Homo, both temporally and
geographically (Dennell and Roebroeks 2005; Dennell 2009). Considering
10
Trinil’s close proximity to the sea the question must be asked, what was the palaeoenvironment at Trinil?
Dietary niche can indicate a local or regional environment that further indicates a particular climate to support that environment. However,
assumptions regarding habitat, climate and environment cannot be made based on the species present alone as some species are known to adapt to changes in one or more aspects of their individual biotope (an
environmentally uniform region of a habitat, occupied by a particular biological community, OED 2012). Ergo, a species or genus may have occupied a different environment in the past. The adaptation to a new environment can lead to ‘speciation’ events (e.g. Ursus maritimus, Edwards et al. 2011; Ramsay and Hobson 1991; Lindqvist et al. 2010). To conclude this thought, multiple proxies (including stable isotope analysis) should be employed to analyze a palaeoenvironment.
The aim of this study is to reconstruct the palaeoenvironment in which Homo erectus existed with their fellow terrestrial and aquatic fossil faunal species. To achieve this, I will analyze the stable isotope values of the carbonate fraction of the dental enamel of six (6) bovid teeth and various fossil aquatic fauna. Due to the age of the fossil teeth of approximately 1 Ma the viability (usefulness) of the dental enamel for isotopic analysis is
unknown. The aquatic fauna has already been successfully used for stable isotope studies of strontium (Joordens et al. 2009). This aquatic fauna is from both Trinil HK and the nearby and associated Sangiran Dome, which will reflect a regional aspect to my research.
Some studies have been able to use osteological remains of
considerably older fossils (Lee-Thorp 2008; Henry et al. 2012), but diagenesis
(the dissolution and recombination of elements) must be considered as a
possible problem, although diagenesis can also be an indicator of climate. If
these values are not viable due to diagenesis then some inference can be
made about climatic conditions, and the project will not be entirely in vain.
Viable results will make it possible to define the dietary niche or niches of the bovids, and the terrestrial and aquatic environments of Trinil HK.
“You are what you eat” is never truer than in stable isotope analysis as the skeletal elements retain traces of the chemical elements that are ingested by the individual. Stable isotope values of the carbonate fraction of bovid dental enamel indicate the type of plant resources (i.e. carbon three C
3plants, carbon four C
4plants, or a mixture) and moisture or water sources (brackish water, plant source, freshwater, or a combination). Stable isotope value data from aquatic fauna enhances the interpretation of the results, particularly of the water source(s) available. As stable isotope technology is not, as yet, a well-understood method of research for all archaeologists I begin by
introducing my audience, in Chapter 2, to stable isotope technology as it pertains to my research.
No good story is complete without the background information that gives it relevance to the present. In Chapter 3 I provide an overview of Trinil HK, Java from its discovery by Dubois in 1891, fast-forward to the work of Joordens et al. (2009) with respect to the availability of aquatic fauna as a food resource for Homo erectus. The latter group analyzed the salinity of water resources at Trinil HK and Sangiran Dome by employing the stable isotope values of strontium of the fossil aquatic fauna as a proxy. Included in this chapter is information regarding the descendants or related species of the bovids that will give insight and direction for discussion.
Chapter 4, a major part of the paper, gives the details of the actual analysis from selection to running the material through the mass
spectrometer. Without the analysis there would be no results, good or bad, on which to base my discussion and conclusions.
The results are highlighted in Chapter 5, relating the particulars of
individual dietary and water source niches of individuals. All of which will give
an inkling of where the discussion on the palaeoenvironment will go. Which
brings us to Chapter 6 and my understanding of the palaeoenvironment and
where certain individuals belong in it.
12
And therefore, I reiterate, I am analyzing the stable isotopes of the carbonate fraction of selected bovid teeth and aquatic fauna from Trinil HK for dietary niche(s) as a proxy for reconstruction of the environment and as a pilot project for a palaeodietary study on Homo erectus, since this has never been done before.
2. STABLE ISOTOPES
All good stories have links that hold the tale together. In my story these links are stable isotopes, the analysis of which is now often a part of the analysis of an archaeological or palaeontological site along with the analysis of stratigraphy, faunal remains, palynology, palaeobotanical remains and artifact studies, amongst other disciplines (e.g. Bedaso et al. 2010; Lee-Thorp et al. 2010; Quade et al. 1994; Richards and Trinkaus 2009; Wang et al.
2008). Due to preservation bias some of the relevant evidence is often weak or non-existent. In some instances stable isotopes tend to have a better preservation rate than other material as they can survive in soil and often in osteological remains (e.g. Bettis III et al. 2009; Quade et al. 1993). Stable isotope analysis is but one of many environmental proxies, each providing its own data. For a truly convincing environmental reconstruction we should employ the data from as many of these proxies as possible. In this chapter I will present all the necessary information for understanding stable isotopes as they pertain to my research, linking terrestrial and aquatic fauna with their environment. Keeping in mind that Home erectus was one of the species of terrestrial fauna involved in this environment.
2.1 Basic Information
Stable isotopes are understood by scientists to have been primarily formed during the ‘big bang’ that began the universe, and also from the ongoing fusion and fission happening in stars. Once formed, they are eternal.
All atoms have isotopes, many of which are radioisotopes (e.g. uranium,
plutonium, carbon as
14C), which are not stable as each decays at its own
rate. Stable isotopes are atoms that have enough, or more than enough,
neutrons necessary to keep the protons in the nucleus. All atoms with extra
neutrons react normally combining with other atoms, to make molecules and
compounds. These atoms just weigh more due to the greater number of
neutrons (Fry 2006).
14
The basic chemical elements in all organic matter are referred to as the Light Elements HCNOS (i.e. hydrogen, carbon, nitrogen, oxygen, and sulphur). The stable isotopes of carbon and oxygen jointly compose the majority of stable isotopes in organic matter. The Light Elements are found in all areas of the biosphere. These areas are the atmosphere, fresh and salt water, plants, animals, and soil (as organic matter and carbonate nodules), and their stable isotopes cycle through the biosphere (Fry 2006) through such processes as illustrated in Figure 2.1 for the carbon cycle, below.
Figure 2.1 Carbon cycle in the biosphere (Windows 2012).
Of the 283 stable isotopes many are filial (more than one stable
isotope for a single element). We are interested in the stable isotopes of the
carbonate (CaCO
3) fraction of the fossilized terrestrial faunal dental remains,
and aquatic skeletal or exoskeletal remains, which includes all molecules that
incorporate carbonate ions in their formulae. Besides carbon’s radioisotope
(
14C) it has two stable isotopes,
12C and
13C. Oxygen actually has three stable isotopes,
16O,
17O (extremely rare), and
18O. In all cases the superscript denotes the quantity of neutrons in the element (Fry 2006).
Fry (2006, 22-24), Lee-Thorp (2008, 926), and Quade et al. (1994), among others, define the difference (δ) measurement (explanation below) relative to an international standard (in this paper I am using VPDB, Vienna PeeDee Belemnite, Fry 2006, 23), which due to the minuteness of the
differences are reported in “
0/
00” or per mill (also permil or per thousand). The accepted conventional equation is a ratio of ratios, where the differential value (δ) of the heavy isotope (
HX) of the element under study is equal to the ratio of the heavy isotope to the light isotope of the sample (R
sample) divided by the ratio of the heavy isotope to the light isotope of the standard (R
standard), minus 1, all multiplied by 1000.
δ
HX = [(R
sample/R
standard-1)] 1000
Where a negative value indicates less than the standard, a zero value indicates the standard, and a positive value indicates more than the standard.
2.2 Stable Isotopes and Plants
Three plant categories can be distinguished based on photosynthesis and transpiration (the processes by which plants take up, use and retain C and O), these are: the non-evaporative plants (C
3, the vast majority of plant species world wide), the evaporative plants (C
4, approximately 3% of plant species), and the CAM (Crassulacean acid metabolism) plants (xerophytic plants having adapted to extremely arid conditions) (Biology 2012; Kadereit et al. 2003). Because the photosynthetic pathways of C
3and C
4plants are different the values of their stable isotopes differ greatly (Cerling and Harris 1999), as recorded below.
As demonstrated (e.g. Bedaso et al. 2010, Cerling et al. 1988, Cerling
et al. 2011) individually and in combination δ
13C values and δ
18O values can
be used to infer dietary niche and environment. C
3and C
4plants are indicated
by which direction and how far from the VPDB standard of
13C the values of
16
the samples are. Aridity in the environment is indicated in the same way for the difference of the sample values from the VPDB standard of
18O. I will emphasize again that a 0 (zero) value for any stable isotope indicates that it is the same as the standard, not that it is not present in the sample (Fry 2006, 24; Lee-Thorp 2008, 926). In combination the two values indicate the types of vegetation (xerophytic or CAM, C
3, or C
4) that exist in a given environment.
And whether those C
3or C
4plants are hydrophytic or mesophytic. ‘To make a long story longer’ (as my father used to say), xerophytic plants retain moisture in extremely arid environments (e.g. cacti, succulents), hydrophytic plants (including the halophytes which exploit marine water) require a ready source of water from saturated ground or are rooted in a water source, and the mesophytic plants are the majority that grow between the two extremes.
Bedaso et al. (2010) state that those plants that are considered to be non-evaporative which includes most trees, and shrubs, and those herbs and grasses that have a cool and moist growing season are classed as C
3plants.
The δ
13C values for the C
3plants range between -35
0/
00to -22
0/
00with a mean of approximately -27
0/
00(Bedaso et al. 2010, Lee-Thorp 2008). They also state that the evaporative plants, C
4plants, which include many grasses, some sedges (which are hydrophytic) and herbs exist in climates with a dry or warm growing season, or both. Due to the evaporative character of their environment they have enriched δ
13C values (compared to C
3plants) ranging from -19
0/
00to -9
0/
00with a mean of approximately -13
0/
00(Bedaso et al.
2010, Lee-Thorp 2008). However, C
4herbaceous and shrub plants are also known to exist in cool temperate regions that have saline environments (Long 1999).
2.3 Stable Isotopes and Teeth
Factual stories (written and oral) are records of the past. In this pilot project the tooth enamel of the fossil bovids is the “faithful record of diet”
(Cerling and Harris 1999, 347) as its isotopic composition allows for
determining the fraction of C
3and C
4plants in the diet. This is due to a direct
relationship between the isotopic composition of mammalian tooth enamel and the mammals diet (Lee-Thorp and van der Merwe 1987).
Bone, in its various forms, contains 69-97% by weight of the inorganic mineral hydroxyapatite (Ca
10(PO
4)
6(OH)
2), which in itself contains small amounts of “structural” carbonate in carbonate ion form as a substitute for phosphate and hydroxyl ions (Wang and Cerling 1994, 282). These stable isotope ratios of the carbonate fraction are a reflection of the diet of the individual during the bone building and rebuilding process (Wang and Cerling 1994). Dental enamel is the densest and therefore hardest and most resilient of osteological forms as it contains >96% by weight of the inorganic material, while dentine contains approximately 75% (Wang and Cerling 1994; White and Folkens 2005). Cementum contains roughly 50% each organic and inorganic material (Wang and Cerling 1994; White and Folkens 2005). Teeth are formed in the jaw and erupt virtually complete as the crowns do not change after eruption except through the processes of “attrition (tooth wear), breakage, or demineralization” (White and Folkens 2005, 127), therefore the stable isotope ratios of the carbonate fraction in dental enamel reflects the diet of the individual when the teeth were being formed (Bedaso et al. 2010, White and Folkens 2005, Wang and Cerling 1994). Because dentine and cementum are not as crystalline as dental enamel they can be subject to change in their δ
13C values and δ
18O values if they should encounter a dietary shift (known as remodeling) (White and Folkens 2005). There can be slight variation of the stable isotope values at the mesial and distal surfaces of neighbouring teeth due do minute remodeling occurring where they rub against each other (Kootker personal communication).
Cerling and Harris (1999, 347), through experiment, have determined
that “the isotope enrichment of
13C between tooth enamel of large ruminant
mammals and their diet is 14.1 ± 0.5
0/
00”. Therefore, subtracting 14.1 from
the δ
13C value determined for a ruminant mammal (such as a bovid) will
result in the δ
13C value of the biomass the animal was consuming.
18
There is always a word of warning. Fossil teeth, like all fossilized bone, can be subject to diagenesis where the original chemical composition is gradually replaced by other chemicals in the surrounding environment
(Hedges 2002) and therefore this possibility must be taken into account when undertaking stable isotope analysis.
We have discussed the relationship between
13C, plants and ungulate mammal teeth. Now it is the turn of
18O. Oxygen isotopes for terrestrial faunal species give a more straightforward indication of the water source or sources exploited by the individual. These can include plant (giraffe) (Cerling et al.
2011, 2), standing stagnant or brackish water, or fresh water. Thus, the dietary and water source niches suggest the climate and ecosystem (a
biological system composed of all the organisms found in a particular physical environment, interacting with it and with each other, OED 2012). With more than one faunal species involved in the analysis there is a broader look at diet, environment and climate.
2.4 Stable Isotopes and Aquatic Fauna
As with teeth or bone of terrestrial mammals the stable isotopes of aquatic fauna are also a record of the environment in which they exist or the palaeoenvironment in which they existed. Changes in climate and hydrology over time can also be evaluated using the stable isotopes of aquatic fauna (Wang et al. 2008, 74; Yan et al. 2009, 379).
Yan et al. (2009) determined through experimentation that δ
18O values of the aragonite of bivalve shells were in equilibrium with the δ
18O of the water the growing season. Their source species the Corbicula fluminea, although indigenous to Asia has spread throughout much of the world,
ceases to grow during the cold winter months. These data are also consistent with the same phenomenon of equilibrium between δ
18O values of fish apatite and the δ
18O values of their habitat (Wang et al. 2008).
However, for this particular filter feeder (C. fluminea) this equilibrium
does not exist for δ
13C values of the shell aragonite and the δ
13C values of
the dissolved inorganic carbon, as these values were more negative (less enriched) than predicted. Yan et al. (2009) suggest that metabolic carbon incorporation is responsible for this result, especially as the negativity increased with increasing age.
As aquatic fauna are totally immersed in their watery environment no analysis of the stable isotopes of the carbonate fraction of aquatic fauna would be complete without the knowledge of the values of the stable isotopes of the carbonate fraction of ocean water and lake water. The dissolved
inorganic carbon in ocean water is related to photosynthesis of plankton with δ
13C values between -19
0/
00and -24
0/
00.There are many variables for the dissolved inorganic carbon in fresh water, (weathering of carbonic rock, mineral springs, atmospheric CO
2,organic matter respiration) any or all of which can be involved. Strong respiration inputs can result in δ
13C values near -20
0/
00,whereas, phytoplankton/algae uptake can cause the δ
13C value of the fresh water to reach -45
0/
00(Fry 2006). The stable isotope values of oxygen within the biosphere are more difficult to delineate as about a fifth is in the form of O
2, although there are predictable variations due to evaporation and condensation (Fry 2006, 49-50).
Bringing as many of these values of δ
13C and δ
18O in relation to each other and the sources of those values (in this case Pleistocene terrestrial mammalian dental enamel, plants, aquatic apatite and aragonite) can be used as proxies for the palaeoenvironment occupied by these organisms and other species (such as Homo erectus) that may have exploited more than one facet of this environment.
20 3. TRINIL, JAVA, INDONESIA
Trinil, Java, Indonesia, (7°22’0”S, 111°21’0”E)(Google 2012) on the shore of the modern Solo River is the flagship palaeontological site of Palaeolithic/stone age archaeology outside of the western world (Figure 3.1
Figure 3.1 Regional map of western Indonesia, Sumatra in the west, Borneo to the north and Java to the south. Inset: Central Java displaying modern river systems, hominin sites, and volcanoes. Gn = Gunung (volcano) (Joordens 2009, 658).
collection and on published accounts of fish fossils from the Dubois and Selenka collections (Boeseman, 1949; Dubois, 1907, 1908;
Hennig, 1911; Koumans, 1949). Ecological and size data of fish species were obtained from Fishbase (www.fishbase.org).
Both Dubois and Selenka also assembled extensive collections of fossil shells (Dubois, 1907, 1908; Dozy, 1911; Martin, 1911; Martin- Icke, 1911). Furthermore, fossil shells were excavated at Trinil by the Geological Survey of the Netherlands Indies, Bandung, in the 1930’s.
The non-marine shells from these collections were studied in detail byVan Benthem Jutting (1937). She mentioned that marine shells were found at Trinil, but they were not considered in her publication.
To obtain a more complete picture of paleoenvironmental conditions in Trinil, we identified both non-marine and marine molluscs in molluscan bulk samples (fossiliferous sediment samples) collected by Dubois from the sandstone and andesititic tuff layers at Trinil (Fig. 3b,c). These samples had not been studied before by malacol- ogists and provide new data on the mollusc fauna. They are curated as part of the Dubois Collection at Naturalis, Leiden (collection numbers 1543,1546, 6900, 8138, 9608, 9609, 9665, 9687, 9691, 9694, 9697, 9779, 9820). Three bulk samples (Trinil 9691, 1546, 9697) were analysed in detail by identifying and counting every recognizable shell larger than 2 mm from 1.5 kg of fossiliferous sediment. Data on Fig. 1. Map of the Indonesian region with islands Sumatra, Borneo, and Java. Inset rectangle: Central Java showing present-day river systems, hominin sites, and volcanoes.
Gn. ¼ Gunung (volcano).
J.C.A. Joordens et al. / Journal of Human Evolution 57 (2009) 656–671 658
and 3.2). A true flagship it was, for it was here, decades before discoveries in Africa, that the first fossil non-European evidence for a connection between Homo sapiens and the apes was discovered. This discovery strengthened the received wisdom of late 19
thCentury western thought that human origins were to be found in Asia (Dennell 2009, 3), although Darwin (1871, 161) had predicted that Africa was a more logical location due to it being the habitat of chimpanzees and gorillas (our closest primate relatives) (Dennell 2009, 4).
Not until 1921 had any fossil ‘human’ remains been found in Africa, which is when lead and zinc miners discovered Homo rhodesiensis (Broken Hill skull/Kabwe cranium) near the town of Broken Hill, Rhodesia (now Zambia) (Hrdlička 1930). This and subsequent finds in Africa led to the controversial
‘out of Africa’ hypothesis for the evolution and distribution of Homo erectus (Klein 2009; Dennell 2009; Wolpoff et al. 2000). The background story of my narrative is contained in this chapter, so read on my friends, read on.
3.1 Early History of the Site
It was at Trinil, from 1890 - 1897, that Eugène Dubois led the
excavation of Trinil HK (Hauptknochenschicht or main bone layer) from which the holotype (i.e. first description of a new species) fossil remains of
Pithecanthropus erectus (later renamed Homo erectus) were discovered.
They consisted of a skull-cap, femur, and molar (Figure 3.2), all found in different years in the same layer (according to Dubois) (Figure 3.3), and which were the first fossil evidence of an early bipedal individual with a brain case twice as large as a chimpanzee (Figure 3.3b) (Dennell 2009; Dubois 1898 as cited in Hrdlička 1930). Of greater importance for this pilot study is Dubois’ commitment to his palaeontological work whereby these hominin fossils were a small, but not insignificant, part of the total faunal collection.
Therefore to study and understand the biozone (the total stratigraphical range
in which fossil remains of a particular taxon are found, OED 2012) he
22
returned to Europe with all of the other fossil material of terrestrial, avian and aquatic fauna that were excavated.
Figure 3.2 Homo erectus (holotype fossil) skull-cap, femur and molar from Trinil (Dubois, 1894 in Joordens 2011,16).
3.2 Chronology
Palaeontological excavations in the 19
thCentury were ‘dated’ through the laws of superposition, the presence of extinct and extant species, or both.
Superposition is the understanding that if item or layer ‘A’ is below item or layer ‘B’ then it is older. Superposition takes into account neither bioturbation (the disturbance of sediment by burrowing or other activity of living
organisms; the disturbed state that results, OED 2012) nor secondary
deposition due to wind or water. Dubois did not have the advantages of
Figure 3.3 a: Stratigraphy of the Plio-Pleistocene Solo Basin. Larick et al.
(2001) determined the Grenzbank deposits (≈ Trinil HK) to be ~1.51 Ma, although others assume an age of ~0.9 Ma (e.g. Bouteaux et al., 2007). b:
Stratigraphy of Trinil HK from top down: modern soil, soft sandstone, lapillibed (~1 m deep) (main bone layer showing position of H. erectus skullcap and femur, Dubois, 1896), conglomerate(~0.5 m deep), mudstone, marine breccia. Rainy and dry season water levels are indicated. c: Grube II (Trench II) by the Selenka expedition at Trinil (landward side of Dubois’
excavation): 8 = bone bed, 9 = plant leaf bed, 10 = white-striped tuff, 11 = tuff with loam patches, 12 = volcanic mud tuff, sandstone,13 = light-coloured tuff, 17 = soil. Wedge lower left is conglomerate underlying the bone bed
(Carthaus 1911, Blanckenhorn 1911, de Vos and Aziz, 1989, all sited in Joordens et al. 2009).
modern dating methods and used his knowledge of the vertebrate fauna of India to assert that: “in no case … can it be younger than the oldest
Results
Faunal analysis: fish
In total, we have encountered nine fish species in the fossil fauna from Trinil (Table 1). The collections are numerically dominated by catfish remains: Clarias batrachus, Clarias leicanthus, Hemibagrus nemurus, and unidentified silurids (Table 2).
Two spine fragments (1639c) from the Dubois collection, identi- fied byKoumans (1949)as ‘‘Siluroidae fin spines,’’ were found to be tail spines (stings) of stingrays (Fig. 5). The spine characteristics (estimated total spine length, lack of dorsal groove) match with those of Pastinachus sephen and Himantura chaophraya (Schwartz, 2007; Cuny and Piyapong, 2007). The conspicuous robustness of the spine is similar to the robustness documented from an (incomplete) spine specimen of the Giant Freshwater Stingray Himantura Fig. 3. (a) Stratigraphy of the Plio-Pleistocene Solo Basin. The age of the Grenzbank deposits (zTrinil HK) was determined byLarick et al. (2001)to be w1.51 Ma, while others assumed a younger age of w0.9 Ma (e.g.,Bouteaux et al., 2007). The Sangiran Formation is also known as the Pucangan Formation, and the Bapang Formation also as the Kabuh Formation (Duyfjes, 1936). (b) Stratigraphy of Trinil HK, the type locality of Homo erectus, according toDubois (1896). Sequence from top down: modern soil layer, soft sandstone layer, lapillibed or main bone bed (with position of H. erectus skullcap and femur), conglomerate, mudstone, marine breccia. Two river water levels are indicated, the lower one is the level during the dry season and the higher one the level during the wet season. The thickness of the lapillibed is about 1 m, that of the conglomerate about 0.5 m. (c) Stra- tigraphy of the ‘‘Pithecanthropusschichten’’ (Trinil HK) according toCarthaus (1911)inSelenka and Blanckenhorn (1911). This excavation in Grube II (Trench II) by the Selenka expedition was situated at the same place as Dubois’ excavations but more landward (De Vos and Aziz, 1989). 8 ¼ Bone bed, 9 ¼ Plant leave bed, 10 ¼ Sandstone-like tuff (white- striped), 11 ¼ Tuff with loam patches, 12 ¼ Volcanic mud tuff, sandstone, 13 ¼ Sand-stone like tuff (light-coloured), 17 ¼ Soil. The wedge in the lower left of the drawing is a conglomerate underlying the bone bed.
J.C.A. Joordens et al. / Journal of Human Evolution 57 (2009) 656–671 660
24
Pleistocene. … the species surely belong almost exclusively to living genera – only the genus Leptobos and the sub-genera Stegodon and Hexaprotodon are extinct - …” (Dubois 1898 as cited in Hrdlička 1930, 29) (see Appendix 1
Figure 3.4 Idealized lithostratigraphic profile for the Sangiran dome (after Itihara et al. 1994) showing the magnetostratigraphy of Itihara et al. (1994) and of Sémah (1982) (after Langbroek and Roebroeks 2000, 596).
Geomagnetic polarity;
Normal Reversed
Volcanic sediments;
Lahar Tuff Lower Lahar
Puren (Kalibeng)Sangiran (Pucangan)Bapang (Kabuh)
Pohjajar (Notopuro)
Formation Schematic lithostratigraphy
Magnetostratigraphy Magnetostratigraphy
Sampling gapB/M B/M
Grenzbank Lower Tuff Middle TuffTEKTITES Upper Tuff Upper Lahar
HOMINIDS
Uppermost Lahar
(Sémah, 1982) (Itihara et al., 1994)
Figure 1. Idealized lithostratigraphic profile for the Sangiran dome (afterItihara et al., 1994), showing Formation names, tuff marker beds, the reconstructed stratigraphic range of the hominid fossils, the stratigraphical position of the tektites, and the magnetostratigraphy ofItihara et al. (1994)and ofSe´mah (1982).
596 . .
for Hrdlička’s transcription of Dubois’ report). Trinil HK lies near or on the base of the Bapang Formation (Figure 3.3 above) that overlies the Sangiran Formation. Both geological formations appear at the Sangiran Dome (Figure 3.3 and Figure 3.4). Sangiran is another archaeologically significant
palaeontological site (several H. erectus fossils have been discovered there during the 20
thCentury) (Bettis III et al. 2009, 12), from which some of my fossil aquatic faunal material comes. The cemented breccia that separates these two formations at the Sangiran Dome is conventionally called the Grenzbank Zone and has been radiometrically dated to ca. 1.5 million years old (Ma) (Itihara et al. 1994; Bettis III et al. 2009) or ca. 0.8 Ma (Sémah 1982;
Dennell 2009) Figure 3.4). Bettis III et al. (2009) favour the 1.5 Ma date for Trinil HK due to their stable isotopic studies of the carbonate fraction of palaeosols from the nearby and associated Sangiran Dome suggest that Trinil HK layer is associated with Cycle 1 of the Bapang Formation, while other sources suggest that the assemblages of Asian H. erectus are less than 1.0 million years old (e.g. Rightmire 1990, 12-14). Therefore, the fossils in Trinil HK cannot be older than 1.5 Ma. Since 2009 the dating of the beginning of the Early/Lower Pleistocene is set at ca. 2.6 Ma, however great debate had ensued for more than two decades to change the date from ca. 1.8 Ma (a date that Dubois would have been more familiar with as it dealt with
stratigraphic layers) (Lowe and Walker 1997; Johnson 2012). The boundary between the Early Pleistocene and the Middle Pleistocene is set at the Brunhes-Matuyama palaeomagnetic boundary (ca. 0.78 Ma) (Johnson 2012) but it’s placement in the Sangiran stratigraphy is debated (as shown in Figure 3.4 above). The 1.5 Ma date is enticing but there is always the possibility of a hiatus or other geological phenomenon between the Sangiran Formation and Trinil HK. There have also been difficulties with stratigraphic context within and between the Sangiran Dome and other palaeontological sites on Java due to tectonic and volcanic events (for discussions see Langbroek and Roebroeks 2000, Bettis et al. 2009, and Dennell 2009). Due to this
uncertainty and my personal preference for round numbers, I have chosen to
26
take the more cautious approach of an approximate date of 1 Ma (keeping in mind Dubois’ extinct fauna as mentioned above) for Trinil HK until a more precise absolute date can be achieved.
Figure 3.5 Palaeogeographic model of Pleistocene Central Java illustrating the many long-standing palaeogeographic features present during habitation by Homo erectus. It is not a ‘snapshot’ recording a moment in time. (Joordens et al. 2009; Huffman and Zaim 2003; after Huffman et al. 2000).
3.3 Palaeoenvironment – Stratigraphic and Faunal Evidence
Stop! Is not the determination of the palaeoenvironment at Trinil HK and associated Sangiran one of the objectives of this thesis? Yes, but others, (e.g. Dubois 1898; Joordens et al. 2009), have inferred the environment in the Trinil HK area from the evidence available to them. New evidence from stable isotopes can enhance or refute their findings.
Throughout the presence of hominins on Java there have been indications of habitat or environmental shifts suggested by changing faunal collections. Among the Ci Saat fauna were the oldest Homo erectus fossils (e.g. Sangiran 27, 4, 31) yet found on Java (Indriati and Antón 2008).
the mammalian, reptilian, and avian faunal composition from Trinil were obtained from published accounts (e.g.,De Vos and Sondaar, 1982; Weesie, 1982; Delfino and De Vos, 2006).
Geochemical analysis
Strontium isotope analyses were applied in order to determine water provenance and water salinities of the aquatic paleoenvir- onments at Trinil. In well-preserved shells, fish bones, stingray stings, and other aquatic fossils, Sr isotope ratios of the fossils are unaffected by biological or climatological fractionation processes and reflect the Sr isotope ratio of the host water in which they were growing (Faure, 1986). In the early Pleistocene there were two main sources of freshwater that determined the strontium isotope ratio (87Sr/86Sr) of waters in the Solo Basin: 1) run-off from the volcano Gunung Merapi on Central Java draining volcanics with Sr isotope values of w0.705–0.706 (Gertisser and Keller, 2003) and 2) run-off from Gunung Lawu on East Java draining volcanics with Sr isotope values of w0.7046–0.705 (Whitford, 1975; Carn and Pyle, 2001). In addition, episodic marginal marine influence of seawater with a Sr isotope ratio of ca. 0.7091 was also a possible contribution (McAr- thur et al., 2001). Due to the relatively high Sr concentration in seawater (100–1000 times higher than freshwater; Palmer and Edmond, 1989; Vonhof et al., 1998, 2003), even a minor seawater component in the aquatic system will strongly influence the
87Sr/86Sr of aquatic fossils.
Strontium isotope (87Sr/86Sr) analyses were carried out on a modern freshwater shell from the Solo river collected by Dubois near Trinil and on well-preserved fossil material (seven shells, three fish bones) from Trinil and the Sangiran Dome following the
approach and methods outlined inVonhof et al. (1998, 2003). We analyzed species that we expected to represent a variety of habitats in the Solo Basin. SEM inspection of the fossil shells revealed that the original lamellar aragonite structure was still present (Fig. 4a,b) with occasional evidence for minor aragonite dissolution (Fig. 4c).
Diagenetic overgrowth was absent. The absence of diagenetic aragonite leads us to believe that diagenetic alteration of the original Sr-isotope signal has not occurred.
For isotopic analysis of Sr in shell fossils, about 0.001 g of cleaned HCl-leached shell was dissolved in 1 ml 5 N HAc. After centrifuging the samples within 30 minutes from the start of the reaction, the supernatant was pipetted off and Sr was separated by use of an ion exchange resin. For Sr isotope analysis of fish bone and spine fossils, a small piece of cleaned bone was added to 1 ml 5 N HAc for 30 minutes to dissolve any carbonate present. After centrifuging, the supernatant was pipetted off and discarded, and about 0.001 g of the remaining leached bone was dissolved in 3 N HNO3for subsequent Sr separation with ‘Elchrom Sr spec’ ion exchange resin.87Sr/86Sr ratios were determined by standard mass spectrometric methods (Ther- mofinnigan MAT 261 and 262), and normalized to86Sr/88Sr ¼ 0.1194.
The average87Sr/86Sr ratio of the NBS 987 standard (n ¼ 14) was 0.710245 " 0.000009. Sr in the blanks was < 0.05% of the Sr measured. To obtain an approximate value of the Sr concentration of Central-East Javan freshwater, a water sample was taken from the modern Solo river at Waduk Ngablak (7#5103200 S, 110#2502600E) where living bivalve shells were present in the river. The sample remained unfiltered and unacidified prior to analysis. The Sr concentration of the sample was measured using ICP-MS (Thermo electron X-series II) and linear regression against a single element Sr standard (CPI).
Fig. 2. Paleogeographic model of Pleistocene Central Java (fromHuffman and Zaim, 2003; adapted fromHuffman et al., 2000). The geological reasoning behind this model is addressed inHuffman (2001). The model illustrates the close proximity of diverse long-standing paleogeographic features of the eastern Javan landscape during the period of Homo erectus habitation. It is diagrammatic, not intended to show paleogeography at any specific moment in time.
J.C.A. Joordens et al. / Journal of Human Evolution 57 (2009) 656–671 659
Belonging to the upper Sangiran Formation (Figure 3.3a) most of these fauna are considered to be ‘island hoppers’ with the ability to traverse water barriers (e.g. cervids, Hexaprotodon, Stegodon, and Panthera) (de Vos et al. 1994;
Huffman et al. 2006). The sediments they were found in suggest an
environment that was coastal deltaic, lacustrine-marsh, or both (Joordens et.
al. 2009).
The Bapang Formation brings a shift to aggrading (infilling) fluvial sediments from the lacustrine of the Sangiran Formation along with a fossil faunal change, indicating an environmental shift (Larick et al. 2001). For there are is a larger variety of fossil faunal species and a greater presence of Homo erectus than has been witnessed in the Ci Saat fauna. Among these new species are those considered as poor swimmers (de Vos et al. 1994), indicating a land link between the rising island of Java and the Asian mainland. This is how Dubois (1898 cited in Hrdlička 1930) describes the location of Trinil while also mentioning that several of the taxa discovered there are freshwater vertebrates (more about those later). Let us first look at the stratigraphy and the sedimentary evidence for both Trinil and Sangiran Dome. What Dubois found along the modern Solo River near Trinil was a bank of 12 to 15 meters deep near the base of which is a meter thick layer of lapilli “particularly rich in fossil bones” (the now famous HK layer) (Dubois 1898 cited in Hrdlička 1930). As shown in Figure 3.3 b, underlying this is a layer of conglomerate resting on a sedimentary layer of mudstone that in turn is resting on marine breccia. All of these layers are overlain by a thick layer of soft sandstone topped with a thin layer of modern soil (Dubois 1896). Not far away at the Sangiran Dome, where Huffman et al. (2000) (Figure 3.5) depict a palaeo- lake or lagoon, the sediments show a more volcanically and
tectonically active story with several defined layers of ash and lahar (Figure
3.3 a and Figure 3.4) (Bettis III et al. 2009). A lahar is a debris flow of water-
saturated pyroclastic elements (volcanic ash, lapilli, etc.), and anything that
gets in the way, as it moves down the side of the volcano, along existing
28
water courses and across flood plains. A severe lahar can destroy and cover buildings in its path (USGS 2010).
Fossil faunal vertebrate evidence from Trinil HK for a fluvial, lacustrine or swamp environment include the mammal Lutrogale sp. (otter), the reptiles Crocodylus siamensis (crocodile), Geomydidae and Trionychidae (taxonomic turtle families), and the waterfowl Branta cf. ruficollis (goose) and Tadorna tadornoides (goose-like), and the fish Himantura cf. chaophraya (also found at Sangiran) (Joordens et al. 2009). There are numerous species of molluscs found at Trinil and Sangiran that suggest a freshwater environment, a
brackish water environment or both (Joordens et al. 2009).
Wetland habitats connected to rivers (such as marshy grasslands) or open forests near bodies of water (fresh or brackish) are suggested by such fossil faunal vertebrate species as Rhinocerus sondaicus (rhinoceros), the bovids Bubalus palaeokerabau (water buffalo) and Duboisia santeng
(antelope) (see more on these two species below), Muntiacus muntjak (deer) and Leptoptilos cf. dubius (stork).
I assume that these habitats of these extinct species are based on the habitats of modern forms. As noted in Chapter 1, some species can and do adapt to changing habitats. Therefore, we cannot assume that these habitats are in fact those that existed when the Trinil HK fauna were extant, even though it is a good place to start. Which is why I am analyzing the carbonate fraction of dental enamel of two terrestrial fossil bovid species from Trinil HK, as well as the carbonate fraction from several fossil faunal aquatic species from Trinil HK and Sangiran.
3.4 Modern Studies
Today, the Dubois Collection is curated in a precisely controlled
environment at NCB (Nederlands Centrum voor Biodiversiteit) Naturalis,
Leiden. Because of Dubois’ insistence of keeping the entire fossil record from
Trinil HK, modern research has been and is being done (e.g. present work by
author) using both old and new technologies: various stable isotope studies of
29
fossil fauna for salinity, dietary niche, and climate reconstruction; and studies of the fossil aquatic fauna as possible hominin dietary resources (Joordens et al. 2009) and an attempt at greater precision in dating (dating in progress, Joordens personal communication) for the Trinil HK site.
3.4.1 Joordens et al.’s (2009) analysis of the fauna and geochemistry of the aquatic fossils from Trinil suggest that instead of assuming that hominins did not use aquatic resources (due to lack of
archaeological evidence) “the default assumption should be that omnivorous hominins in coastal habitats with catchable aquatic fauna could have
consumed aquatic resources” (Joordens et al. 2009, 656). They inferred from their research that at the time the Trinil HK layer was formed that the local habitat included “near-coastal rivers, lakes, swamp forests, lagoons and marshes with minor marine
Figure 3.6 Strontium stable isotope values at Trinil and Sangiran (Joordens et al. 2009, 668).
influence, laterally grading into grasslands” (Joordens et al. 2009, 656). Their results showed that some aquatic species preferred the brackish water (Figure 3.6). Brackish water can be a result of stagnant or very slow moving water that allows for greater evaporation and a build up of naturally occurring salts (alkaline), and/or ‘fresh’ water that has mixed to some degree with marine water (often tidal transgressions).
3.4.2 Back to those wetland bovids mentioned above. Duboisia santeng, although only found in Indonesia, is considered to be an
terrestrial mammals are met in the early Pleistocene on Java. The omnivorous terrestrial mammal Homo erectus was living in the wetland habitat of the Solo Basin (Sangiran and Trinil), as well as in the coastal delta habitat of Mojokerto (Huffman et al., 2006). Edible, nutritious aquatic fauna was available and catchable. Thus, it is valid to hypothesize that H. erectus on Java consumed aquatic resources.
The next step will be to test the hypothesis. As this concerns the early Pleistocene time period, we expect that it will be relatively difficult to find unequivocal, ‘‘smoking gun’’ evidence of aquatic exploitation, such as hominin tools or bones in a cave with cut- marked or burned aquatic fossils. However, because aquatic food sources contain constituents such as the fatty acid DHA (Kainz et al., 2004) with strong physiological effects on brain gene expression, development, and cognition (Calderon and Kim, 2004; Kitajka et al., 2004; Kawakita et al., 2006), it is important to actively search for subtle clues indicating early use of aquatic foods.
It would theoretically be possible to test the hypothesis of aquatic exploitation by measuring stable isotope ratios of nitrogen and carbon in dental collagen (Lee-Thorp and Sponheimer, 2006;
Richards et al., 2006; Richards, 2007) of fossil Homo erectus teeth.
However, the antiquity of Javan H. erectus teeth most likely precludes the extraction of well-preserved collagen and thus the study of N and C isotope ratios. A further drawback is that isotopic analyses involve destructive sampling of precious hominin fossil teeth. A non- destructive approach is to focus on anomalies in species composition and taphonomy of the aquatic fossil assemblages from hominin sites.
In hominin sites with possible signs of fish exploitation, the number of fish fossil elements is very high: for instanceStewart (1994)has documented recovery of thousands of fossils of the catfish Clarias batrachus from Bed I and Bed II at Olduvai Gorge. The total number of fish fossil elements recovered from Trinil is low, thus providing no indication of exploitation of this possible resource at Trinil.
The number of shells of most of the molluscan species is also low and on the same order of magnitude as the fish fossils, again showing no indication for possible exploitation. However, the presence of a relatively large number of only adult, large-size Pseudodon shells excavated from a very limited area (Hauptkno- chenschicht in Trinil), in both the Dubois and Bandung collections, is a discrepancy in the aquatic assemblage that merits further atten- tion for these shells. Collector’s bias (preferring large-size Pseudo- don shells) could have played a role. But then the Dubois and Bandung collectors (excavating about thirty years apart) would have had exactly the same bias, which seems unlikely. In addition, the fact that Pseudodon fragments were collected as well, indicates that
shells as smaller and fragile specimens of various other species are present. The fact that many of the Pseudodon valves are still paired and well-preserved would suggest that the molluscs were not dead and transported by water before fossilization but were buried in live position. However, the complete absence of small, juvenile shells as well as the mixed occurrence of two different (but equally large- sized) shell forms argues against interpretation of burial of a live population (Van Benthem Jutting, 1937). Instead, the discrepancies suggest that the Pseudodon shells could have been brought together, prior to fossilization, by a size-selective collecting agent who may have used them for consumption of molluscan flesh.
The Elongaria shell assemblage collected from Trinil is in these aspects comparable to the Pseudodon assemblage: a relatively large number of shells, no young individuals but only adults, two shell forms mixed in single field lots. It is striking that the posterior part of the Elongaria shells is often missing. In a Holocene kitchen midden from Sampung Cave on Java, many Pseudodon and Elongaria shells have been found among mammal, bird, and fish remains, together with human tools (Van Es, 1930). Two forms of Elongaria shells were present in the Sampung Cave kitchen midden (Van Benthem Jutting, 1937), just as in the Trinil collections.Van Ben- them Jutting (1932:105)writes: ‘‘In the Lamellibranchs (bivalves, JJ), as far as they have been shattered, invariably the siphonal region of of the valves is missing to a larger or a smaller extent. Apparantly the people duly recognized this posterior end as the most fragile part of the shell.’’ The Elongaria assemblage from Trinil, just like Pseudodon, appears to indicate collection by a selective agent for the purpose of mollusc consumption. The Pseudodon and Elongaria assemblages from Trinil have the characteristics of shell middens (e.g., Waselkov, 1987; Rosendahl et al., 2007): large adult shells only, many complete shells, no signs of damage due to water roll- ing, signs of damage due to being deliberately opened, presence of human (hominin) bones in the same layer. We conclude that they represent a subtle clue of possible aquatic predation by non-hom- inins or by hominins. A possible non-hominin predator could be the otter Lutrogale sp., although the extant Smooth-coated otter Lutrogale perspicillata is not known to produce shell middens. This otter preys on fish, crustacea, molluscs, frogs, turtles, and birds, using its molars to crush molluscs (Gurung and Singh, 1996). If Lutrogale was the non-hominin mollusc predator at Trinil, we would expect mainly shell fragments and shells with bite marks, instead of the many undamaged Pseudodon valves present in the collections.
If Homo erectus at Trinil collected Pseudodon and Elongaria molluscs for consumption, we predict that traces of handling and
87 Sr/
86 Sr
0.703 0.704 0.705 0.706 0.707 0.708 0.709 0.710
HimanturaPisces sp.
Pseudodon Tarebia
ElongariaTarebiaLucina Himantura
TarebiaLucina Physunio
Trinil Sangiran Solo
Brackish water
Freshwater
Brackish-fully marine water
Fig. 8. Sr isotope ratios of aquatic fossils from Trinil and Sangiran, and of a Physunio shell from the modern Solo River. The dotted rectangle indicates the Sr isotope ratios cor- responding to a brackish salinity range (oligohaline: 0.5–5 psu: practical salinity units), based on results of the mixing model using the ‘‘non-anthropogenic’’ freshwater Sr concentration (Fig. 7).
J.C.A. Joordens et al. / Journal of Human Evolution 57 (2009) 656–671 668
