Technical Research Bulletin
Technical Research Bulletin
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VOLUME 2 2008
Archetype
Publications
VOLUME 2 2008
11/10/2008 13:24:12
Conservation assessment of the Neanderthal
human remains from Krapina, Croatia and its
implications for the debate on the display and
loan of human fossils
Jill Cook and Clare Ward
Summary In 2005, the Ethiopian government’s decision to offer the fossilized remains of a three million-year
old human ancestor for an exhibition tour of the United States provoked condemnation from many palaeoanthropologists. In response, the council of the International Association for the Study of Human Palaeontology
passed a resolution stating that such remains should not be endangered by loan and exhibition but preserved
for qualified scientific access only. This report summarizes the findings of a detailed conservation assessment
of the collection of Neanderthal remains from Krapina Cave, Croatia. Examination showed that damage
had occurred due to the incorrect application of resins as preservatives and adhesives, and the moulding of
specimens for casting. Resin coatings had discoloured and contracted making it difficult to study surface
features as well as resulting in surface loss. Adhesive joins were often inaccurate and join edges had not been
strengthened by consolidation prior to adhesion, leaving them vulnerable to damage and further breakage.
The use of casting materials such as plaster, wax and rubber had resulted in loss of the fragile surface and new
breaks, or further breaks along old joins. The report concludes that human fossils may be as much at risk from
researchers as when on loan to exhibitions.
INTRODUCTION
THE SURVEY
The discovery of human remains more than 10000 years
old is always a cause for scientific celebration. Such finds
are rare and valuable, as each new sample or technique may
reveal threads of evidence in our understanding of human
evolution. Consequently, there is a persistent requirement to
measure, cast and sample from existing and newly discovered human bones. As a result many palaeoanthropologists, among them the curator of the Neanderthal human
remains from Krapina Cave, Croatia, Dr Jakov Radovčić,
have noted regrettable damage and distortion to specimens. In response to these concerns, and at the request of
Dr Radovčić and American colleagues Professor Milford
Wolpoff of Ann Arbor University, Michigan and Professor
Alan Mann of Princeton University, New Jersey, the British
Museum agreed to support a conservation survey of the
Krapina material.
The survey examined the largest known sample of Neanderthal human remains from Krapina Cave, north of Zagreb
in Croatia. Excavated between 1899 and 1906 by palaeontologist Dragutin Gorjanović-Kramberger, the collection,
curated at the Croatian Natural History Museum in Zagreb,
consists of approximately 830 bones or fragments, including
cranial and postcranial elements of individuals who lived
between about 120000 and 60000 years ago. The bibliography of over 3000 papers in 20 languages written on these
remains over the last century is a mark of their considerable
importance to international research and debate on human
evolution [1]. It also reflects the intense pressure placed on
the collection by four generations of scientists, each seeking
to answer new questions using the latest techniques.
39
JILL COOK & CLARE WARD
Method
In May 2007 the authors examined every bone and bone
fragment in the Krapina collection in Zagreb with the
exception of the phalanges and separate teeth. In the case
of the phalanges and teeth, representative samples of about
10% of each were examined so that an estimate of the condition and conservation requirements could be determined
for all the specimens. Each specimen was checked against
the collection catalogue [2]. This ensured the correct identification of the specimens and their numbers, as well as
showing up changes in their condition that have occurred
over the last 20 years. Dr Radovčić was on hand throughout
the work and provided the invaluable guidance and information that can only be acquired by long acquaintance with
a collection.
Following identification, every item was examined by eye
and using a ×2.75 Optivisor headband magnifier. As each
specimen was inspected, notes on its condition and conservation requirements were recorded in an Excel spreadsheet.
Photographs were taken to record the deterioration noted
on particular specimens, or types of alteration affecting the
collection generally. Additional, higher-resolution, digital
images of surfaces made during previous research by one of
the authors (JC) were also utilized. As the work progressed,
some basic solvent tests were carried out on the resins and
glues that have been used on the remains over the last
century in order to determine their composition, state of
degradation and potential ease of removal. Samples of these
resins were also taken for further analysis in the laboratory
at the British Museum.
As the specimens were examined, each was categorized
based on the approach developed by the British Museum
for regular auditing of the conservation requirements of its
own collections. Each piece was placed in one of the condition categories listed in Table 1.
By the end of the survey, even before the data collected
had been analysed, the method already indicated the conservation requirements. Around a third of the collection is a
high or medium priority and the rest requires attention in
the near future. The remainder of this contribution summarizes the data, outlines the conservation requirements and
suggests the actions required.
in many instances has been applied over sediment. This
was usual practice at the turn of the twentieth century;
in 1905 Rathgen recommended the application of natural
resins such as dammar, shellac, isinglass or/and animal
glues in appropriate solvents as a method of preservation
for fossil bone [3]. These coatings have embrittled and
discoloured with time, covering and damaging signifi-
table 1. Condition categories used to assess the Krapina collection
following the procedure used in the British Museum to indicate and
prioritize conservation requirements
Condition
category Condition
A
Good
B
C
D
Priority Requirement
No conservation
required
Stable but at risk of
Low
Conservation required
degrading within 10 years
within 10 years
Unstable
Medium Conservation essential
as soon as possible
Actively deteriorating
High Conservation urgent
figure 1. Photomicrograph of incised lines on Krapina skull 6.
Evidence of post-mortem modification of the skull is obscured by the
deteriorating resin coating, which is flaking off with fragments of the
periosteum
Present condition of the fossils
Most of the collection consists of fragments of bone that
have been rejoined since excavation. Many of the joins
were made years apart, so a single specimen may have
been reconstructed by various researchers using a number
of different techniques and adhesives. There is no documentation recording these reconstructions or the materials applied. Whether the specimens are complete bones,
rejoined or fragmentary, all but a few have been covered
with a thick coat of resin. In most cases this would appear
to have been applied soon after the initial excavation and
40
figure 2. Photomicrograph of cut marks in the area of the mylohyoid
line on the interior of juvenile mandible Krapina 53. The resin coating
has a crazed surface and is flaking away
CONSERVATION ASSESSMENT OF THE NEANDERTHAL HUMAN REMAINS FROM KRAPINA, CROATIA
cant post-mortem markings on the bone surfaces, Figures
1 and 2. The internal structure of the bone is fragile and
usually unconsolidated, causing a difference between the
hard outer surface and fragile interior that sets up longterm stresses within the bones and may eventually result
in surface loss. This is already visible on some fragments,
particularly where moulding for replication has taken
place. Tests on the coatings using acetone (propanone),
ethanol, isopropanol (propan-2-ol) and water were inconclusive, although in some cases there appeared to be a slight
softening with hot water, suggesting the presence of animal
glue. Recent DNA tests have revealed the presence of bovine
DNA, which could have resulted from the use of animal
figure 3. Interior view of the partial skull of a juvenile, Krapina 1
rejoined from several fragments. The old joins and the wooden stick
supports are unstable. The resin coating on the surface has become
brittle, discoloured and is flaking away removing fragments of periosteum. This is particularly evident where sticks have detached. Residues of Blu-Tack, plasticine and moulding materials also adhere to
the surface
glue [4]. Samples of these resins were also taken for laboratory analysis at the British Museum, where subsequent
testing revealed the presence of polyvinyl acetate, cellulose
nitrate, proteinaceous material and components derived
from conifer resin [5].
Figures 3 and 4 show some of the criteria that put a
number of specimens on the critical list of pieces requiring
urgent attention. Both illustrations show how newly discovered joins have been stuck together using a variety of adhesives over the years. As the ‘preservatives’ that have been used
only coat and harden the surface, without consolidating the
bone, the interior remains soft and fragile. When two such
pieces are joined, any adhesive will form a hard line along the
join. This will eventually result in further breakage and loss of
bone. A succession of repairs to such separated joins repeats
the problem, causing further damage with worse and ever
more inaccurate reconstructions. In many cases adhesive has
spilled out onto the surface of the joins. This excess adhesive
may contract as it degrades resulting in surface damage and
even loss. Tests on the adhesive suggest that there may be
cellulose nitrate present. Recent joins have been made with
an acrylic, Paraloid B48N, dissolved in acetone [4].
The use of small wooden sticks glued in place to hold
fragments in position was undoubtedly intended to support
and strengthen some joins, Figure 3. Unfortunately, this
has compounded the problems of excess adhesive and poor
joins. The sticks do not give adequate support to the fragments and in several cases they have detached, removing
the bone surface, leaving the bone unsupported and the join
unstable. Dimensional changes in the wooden sticks due
to environmental variations may also have contributed to
this movement. The distortion in form that may be caused
could result in the collection of misleading measurements
and provide poor bases for the comparison of specimens.
figure 4. Rejoined juvenile cranial fragments Krapina 31.10 and
Krapina 33.32 showing inaccurate, unstable joins
figure 5. Femur fragment Krapina 257.4 with resin coating on the
cancellous bone
Figure 6. Rejoined fragments of adult left parietal Krapina 16 showing
casting residues
41
JILL COOK & CLARE WARD
On fragments of limb bones there is often a hard fill
or consolidant material present on the exposed cancellous tissue, Figure 5. This appears to be stable, but is thick
and obscures the surface of the tissue. The few bones that
are uncoated are fragile but otherwise well preserved. The
Figure 7. Rejoined fragments of adult parietal Krapina 32.2 showing
a discoloured brittle resin coating and Blu-Tack used as an adhesive,
resulting in wide, inaccurate joins
Figure 8. Archive photograph of the Krapina fossils temporarily
displayed on a black cloth
teeth are in relatively good condition and in general do not
appear to have been coated with resin.
During a century of research the Krapina bones and teeth
have been extensively moulded for the production of casts.
Surfaces and joins bear the traces of this process, which
consist of remnants of casting materials such as plaster, wax
and rubber, all of which adhere to the surface. Damage to
the surfaces and joins, as well as significant distortion, is
also evident, Figure 6. The deleterious effects of these processes have also been detailed by Monge and Mann [6]. The
remnants of moulding materials need to be removed from
the Krapina bones with great care otherwise they will pull off
more fragments of periosteum, tooth enamel or dentine.
The use of plasticine (a putty composed of petroleum
jelly, fatty acids, and calcium carbonate) or ‘Blu-Tack’ (a
blue putty composed of hydrocarbon polymers, mineral oil,
fillers and pigment) to make temporary joins or to support
specimens during measurement or photography has also
resulted in damage to the specimens, Figure 7. There is a
large amount of Blu-Tack adhering to the surfaces. Blu-Tack
and plasticine are difficult to remove from porous surfaces
and also cause oily stains.
Other extraneous debris noted on specimens included
black fibres from fabrics used as back cloths for displays
or photography, and patches of adhesive that would seem
to be the result of attaching specimens to black fabric for
display, Figure 8.
The surfaces of the specimens are dirty and often show
numerous superficial nicks, scratches and indentations that
have accrued since excavation as a result of that process
and subsequent handling, including the use of metal
measuring implements and dental tools, Figure 9. They
also show copious pencil marks, which have been made
to locate joins, mark measuring points or left as residues
when tracing the edges of fragments. In addition, the specimens bear numbers in ink indicating their place in various
cataloguing sequences. These numbers are wearing away or
have partly disappeared as a consequence of surface loss and
are becoming difficult to read. The resin used in conjunction with the red ink is beginning to degrade, resulting in
shrinkage and cracking that will eventually cause the loss of
the number and damage to the bone.
ASSESSMENT
figure 9. Photomicrograph of recent marks made by metal instruments on parietal fragment Krapina 36. These have penetrated the
resin and periosteum to expose fresh bone
42
Examination of the Krapina collection indicates that much
of the damage that it has suffered is due to handling, the
incorrect application of resins as preservatives and adhesives, as well as the moulding of specimens for casting. There
are no records of which materials have been used or of how,
when and by whom they have been applied. The pressure
to allow the collection to be researched has resulted in the
requirements of these uses having priority over conservation considerations, despite the best efforts of the curator to
monitor and restrict any unnecessary activity.
CONSERVATION ASSESSMENT OF THE NEANDERTHAL HUMAN REMAINS FROM KRAPINA, CROATIA
Table 2 provides a summary of the observations and
sample data from the 833 hominid specimens. It shows
that the entire collection requires some conservation work
and about a third is in need of urgent or essential work due
to active deterioration. The urgent category (D) includes
all the cranial specimens, which are of considerable international scientific importance. It is vital that conservation of this material should begin soon to avoid further,
possibly irreversible, deterioration. The coatings present on
the specimens will become increasingly difficult to remove
over time as they age and degrade. This will cause edges
and surfaces to crumble or flake and irreparably damage
the bones, reducing their scientific value.
The time required for conservation of all the specimens is
estimated to be just over 1700 hours. The estimate includes
time for treatment of the object together with proper conservation documentation (an assessment of condition, results
of analyses, technical observations and a record of treatment) and conservation photography where necessary. The
estimate is based on the assumption that it will be possible
to remove the resin coatings from the bone surfaces, take
down old joins and rejoin fragments relatively easily using
appropriate solvents and application techniques. However
this depends on the nature of the resins that are found on
the specimens’ surfaces. Some may be more difficult, or
even impossible, to remove and this would increase the
conservation time required.
Consideration of the data collected during examination
of the bones has provided the basis for recommendations
about how the conservation work can best be achieved
together with improvements in storage. The latter adds
both to the timescale and cost of the conservation, but also
adds value and will help to ensure the future survival of
this collection. The next stage will be for those concerned
to cost these conservation proposals and to find funding
for an appropriate plan of action to implement the recommendations, most of which could be taken to apply to other
collections of human fossil remains which are in a similarly
deteriorating condition.
DISCUSSION
In 2005 the Ethiopian government offered to loan the
remains of a 3.2 million-year old skeleton of Australopithecus afarensis (popularly known as Lucy), an early human
ancestor, to museums in the United States. In response,
the council of the International Association for the Study
of Human Palaeontology passed a resolution against the
loan of human fossil remains for the purpose of display.
This international body of scientists involved in research
on human evolution feared that the risks of packing, transporting and displaying human fossils were too great to
allow, because of the immense value of the specimens to
the history of humanity. Instead, the Association wishes
to restrict access to scientists and only move specimens to
table 2. Summary of observational data
Condition
category
A
B
C
D
Total
Number of
specimens
0
671
120
42
833
Time in
hours
0
596.5
565.5
528
1704
their laboratories for scientific reasons. As this report on
the Krapina collection shows, concern for these fossils is
legitimate and this is not an isolated case [6, 7]. However, in
this case the cause of deterioration is not the exhibition of
the fossils but handling during scientific investigations and
lack of professional conservation. The curation and conservation care that such specimens receive in museum exhibitions is protectively benign by comparison with the way in
which specimens are sometimes handled during research.
Thanks to the informed concerns of Dr Radovčić, it is
not too late to reverse some of the damage and halt further
deterioration of the Krapina specimens if immediate action
is taken. This is a case which should be a wake-up call to
the palaeoanthropological community. Work on the reconstruction of fossils should not take place without the participation of professional conservators. Instead of preventing
the display of the common origins of humanity, the Association for the Study of Human Palaeontology should be
setting internationally accepted guidelines for the handling,
reproduction and sampling of fossil human remains. These
should focus on record keeping, storage, handling and
conservation, and should monitor research requirements to
ensure they can be met without detriment to the specimen.
The following suggestions made for the Krapina specimens
might form a starting point.
Recording
Curatorial and conservation records whether manual or
electronic should be kept for every specimen. These should
include curatorial data such as catalogue numbers, as well
as information about specimen condition and details of any
actions taken with specimens such as conservation treatment or scientific sampling. These details should include by
whom, when, how and with what materials or equipment
any work was done.
Storage
Specimens should be placed in storage in supportive, inert
materials. The storage areas should provide suitable environmental conditions. The past environmental conditions
in which the objects have been stored should be taken
into account, but for collections that have not previously
been kept in very dry conditions, the recommended environmental conditions for archaeological bone are 40–55%
43
JILL COOK & CLARE WARD
relative humidity with daily fluctuation of ±5% or less and a
temperature of 16–20°C with daily fluctuations of less than
±2°C [8]. These conditions should be monitored to provide
a constant check on their stability and conditions maintained by appropriate equipment if necessary.
Handling and conservation
Cautious, conservation-conscious handling regulations
should be drawn up to which researchers must sign up
before they are allowed access to the material. These regulations should prevent any further moulding of the specimens and any activities that involve handling or applying
materials to the surfaces or joins. Reconstruction of specimens and new joins should always be made in collaboration with professional conservators experienced in dealing
with organic materials. Institutions should have clear policies on the sampling of the specimens for dating, DNA or
isotope analyses, and such other techniques as may develop.
Where possible, institutions should look to the future and
try to adopt techniques such as computerized axial tomography (CAT scanning), magnetic resonance imaging (MRI)
or three-dimensional (3D) laser scanning to avoid casting
and to reduce the need for direct access to the fossils by
making high-resolution 3D images available electronically.
If casting is essential then rapid prototyping using scanned
data should be considered as an alternative to traditional
techniques [9].
These guidelines should not restrict scientific work,
but they could raise standards, improve the techniques of
enquiry and ensure the preservation of the fossils. Most of
these points will already be accepted and implemented as
best practice in many museums. The recording, storage and
handling requirements can be simply and cheaply achieved
almost anywhere, but access to professional conservation
skills and suitable laboratories is not so easy. Where internationally important specimens are concerned, the sharing
of knowledge and skills between collaborating institutions
should ensure the involvement and training of conservators
and access to techniques that may not be available in the
place of discovery; loan programmes may facilitate this.
CONCLUSIONS
It is important that museums be allowed to display and
borrow human fossils for exhibition if they are in a suitable condition [7]. At a time when globalization goes hand
in hand with social fragmentation and intolerance, such
44
fossils have the extraordinary power to remind us of our
common origins as we search for new identities in a world
of complexity and difference. In this role their significance
extends beyond science to the diplomatic, provoking questions that may enlighten our attitudes to one another and
providing opportunities to raise crucial funding for scientific and museum projects in the country of origin. Human
fossils are rare and precious archives of human ancestry that
need to be shared. To protect and preserve them we need to
build up standards of care and presentation that will enable
this, rather than restrict access to the few.
ACKNOWLEDGEMENTS
The authors would like to thank Dr Jakov Radovčić who requested and
supported the work on the Krapina specimens. Without his knowledge
of the collection and concern for the specimens, this project would not
have been possible. Thanks are also due to our colleagues Marei Hacke
and Rebecca Stacey for analysis of the resin samples.
AUTHORS
Jill Cook ([email protected]) is a curator in the
Department of Prehistory and Europe and Clare Ward (cward@
thebritishmuseum.ac.uk) a conservator in the Department of Conservation and Scientific Research at the British Museum.
REFERENCES
1. Frayer, D., ‘The Krapina neanderthals: a comprehensive, centennial illustrated bibliography’, www.paleoanthro.org/dissertations/
krapina-bibliography.pdf (accessed 21 March 2008).
2. Radovčić, J., Smith, F.H., Trinkhaus, E. and Wolpoff, M.H., The
Krapina hominids: an illustrated catalog of skeletal collection,
Zagreb, Mladost Press and the Croatian Natural History Museum
(1988).
3. Rathgen, F. (translators G.A. Auden and H.A. Auden), The preservation of antiquities: a handbook for curators, Cambridge University Press, Cambridge (1905) 151–152.
4. Radovčić, J., Croatian Natural History Museum, personal communication (May 2007).
5. Hacke, M. and Stacey, R., Identification of adhesives and resins used
for the restoration of hominid remains from Krapina, Croatia, CDS
report no. AR2007/79, British Museum (2007) (unpublished).
6. Monge, J. and Mann, A., ‘Ethical issues in the moulding and
casting of fossil specimens’, in Biological anthropology and ethics:
from repatriation to genetic identity, ed. T. Turner, State University
of New York Press, New York (2005) 91–110.
7. Cook, J., ‘Let Lucy sparkle’, British Archaeology 96 (2007) 15.
8. Saunders, D., Lighting and climatic criteria for the British Museum
collections, British Museum (2006) (unpublished).
9. France, D., ‘General considerations in casting’, in Human remains:
guide for museums and academic institutions, ed. V. Cassman,
N. Odegaard and J. Powell, Altamira Press, Lanham (2007) 67.