Evolutionary Anthropology
169
Radiocarbon Dating: The Continuing Revolution
R. E. TAYLOR
Radiocarbon (I4C) dating, now in its fifth decade of general use, continues to be
the most widely employed method of inferringchronometricage for late Pleistocene
and Holocene age materials recovered from archeological contexts. Over the last
decade, several technical advances in I4C studies have provided contexts for a
number of significant applications in archeology that were previously either not
possible or not practical.These includethe extension of the calibrated 14C time scale
into the late Pleistocene and the development of accelerator mass spectrometry
(AMS). The contribution of AMS-based I4C values to the critical evaluation of archeological data is illustrated by considering the problems of dating early plant
domestication in the Near East and Mesoamerica, New World Paleoindian human
skeletal materials, and European Upper Paleolithic and Mesolithic materials.
RADIOCARBON DATING MODEL
The natural production of radiocarbon (14C) is a continuous process,
traceable to the production of neutrons from the interaction of high-energy cosmic rays with gas molecules
high in the earths atmosphere. After
its production from neutron reactions
with I4N, I4C is rapidly oxidizedwithin, at most, several days-to form
14C02.Although there is significant
variation in the atmospheric production rate of I4Cwith latitude, of critical
importance to the usefulness of the
technique is that I4C is rapidly mixed
by stratospheric winds. Because of
this, with fortunately few exceptions,
atmospheric 14C concentrations are
R E Taylor is aprofessor in the Department
of Anthropology, a research anthropologist
in the Institute of Geophysics and
Planetary Physics, and director of the
radiocarbon laboratory at the University of
California, Riverside. His research focuses
on the application of dating and analytical
techniques in archeology (archeometry)
with emphasis on radiocarbon and amino
acid racemization dating. He received his
Ph.D. in anthropology at UCLA in the
isotope laboratory of the late Willard F.
Libby.
retaylor@ucracl .ucr.edu
Key words: dating, accelerator mass
spectrometry, calibration, de Vries effect,
geochronology
approximately uniform by the time a
I4C-tagged CO, molecule reaches the
planetary surface. About 85% of I4Cis
absorbed in the oceans by several
mechanisms, while about 1 % becomes part of the terrestrial biosphere, primarily by means of
photosynthetic processes and the dist r i b u t i o n of c a r b o n c o m p o u n d s
through the chemically complex pathways of the carbon cycle (Fig. 1).
Metabolic processes in most living
terrestrial organisms maintain I4C
content in approximate equilibrium
with atmospheric 14C concentrations;
i.e., while I4C decays in living tissue, it
is replaced through the ingestion of
plant or animal tissue. However, when
a plant or an animal dies and its metabolic processes cease, the amount of
I4Cbegins to decrease by beta decay to
I4N at a rate measured by the I4C half1ife.l
The radiocarbon age of a sample is
based on measurement of its residual
I4Ccontent. For a 14Cage to be equivalent, with a reasonable level of precision, to the actual age of a sample, a
set of primary assumptions must be
met. The most important of these assumptions are that the concentration
of I4Cin each carbon reservoir has remained essentially constant over the
14C time scale, that there has been
complete and rapid mixing of I4C
throughout the various carbon reservoirs on a worldwide basis, and that
the carbon isotope ratios in samples
have not been altered since the death
of an organism except by I4C decay.
Much of the history of the more
than four decades of the application of
the 14C dating method in archeology
and paleoanthropology has focused
on two types of efforts: first, investigations designed to examine and compensate for the effects of violations of
the assumptions as applied to specific
sample types or sample types from
specific carbon reservoirs, and second, documentation of the physical
relationship between a sample on
which a 14C age estimate is obtained
and the archeological object, feature,
and stratigraphic or geomorphological context for which an age deteimination is desired.
FIRST THREE DECADES AND TWO
REVOLUTIONS
The development of I4C dating, especially as it has been applied to archeological samples, can perhaps be
most clearly appreciated if it is divided
into three generations of research focus. The first generation of studies,
which Colin Renfrew later called the
“First Radiocarbon Revolution,” began in 1950 with the appearance of the
first I4C “date list.”l Again using the
phraseology advanced by Renfi-ew,the
“Second Radiocarbon Revolution”
was initiated with the recognition that
there were systematic offsets or secular variations between 14C and “real”
or solar time. Because of this, 14Ctime
needed to be calibrated to allow it to be
compared with solar or calendar time.
The “Third Radiocarbon Revolution”
in I4C studies was ushered in by the
advent of accelerator mass spectrometry (AMS) technology in the late
1970s.4
ARTICLES
170 Evolutionary Anthropology
P
R
0
D
U
C
T
I
0
N
FC
European archeologists, particularly
in central and eastern Europe, regarding the chronological relationship between their local sequences and the
historically known chronologies in the
Near East. As a result, a few archeologists working in these regions questioned the general validity of the 14C
method.’ However, the rapidly mounting evidence of the overall correctness
of the I4C dating model redirected
questions of validity to questions of
the accuracy of I4C values from specific archeological or geological contexts, geochemical environments, or
sample types.8
The first empirical test of the validity of a primary assumption of the I4C
method-the equilibrium between E4C
production and decay-was the analysis of the 14C activity of a suite of as-
PROTON
+
\
SPALLATION
PRODUCTS
I4c
I
0x1DAT ION
D
I
S
T
R
I
B
U
T
I
0
N
4
w
D
E
C
A
Y
-
-
-
D
I4C
-
D
0
-
0
/3-
CARBON ATE
BICARBONATE
I4N
t,,2
= ca. 5700 Y E A R S
Figure 1, Radiocarbon dating model: production,distribution, and decay of I4C.’
The First Radiocarbon Revolution
In several later historical retrospections, the initial impact of I4C dating
on the conduct of archeology was
characterized as having been truly
revolutionary. For example, the late
Glyn Daniel equated the importance of
the development of the I4C method in
the twentieth century with that of the
discovery, in the nineteenth century, of
the antiquity of the human specie^.^
Without the I4C time scale, prehistorians would still be, in the words of J.
Desmond Clark, “foundering in a sea
of imprecisions sometimes bred of inspired guesswork but more often of
imaginative speculation.” In providing a common temporal framework
for the late Pleistocene and Holocene,
I4C data made a world prehistory pos-
sible by contributing a time scale that
transcends local, regional, and continental boundaries.
Several suites of archeologically
relevant 14C dates obtained during the
first decade of I4C studies were responsible for initiating major revisions in
widely held views concerning several
important archeological topics. For
example, early I4C values pointed to
the impressive antiquity of agriculture
and sedentary village societies in
southwestern Asia from the ninth
through the seventh millennia B.C.
and, as well, suggested the same features in at least one core area of
Mesoamerica several millennia later.
Also, an increasing corpus of I4C data
contained age estimates that were at
odds with long-held views of some
The late Glyn Daniel
equated the
importance of the
development of the 14C
method in the twentieth
century with that of the
discovery, in the
nineteenth century, of
the antiquity of the
human species.
sumed known-age samples ranging in
age from about 1,400 to 4,600 years.
The results of these measurements
were presented as the first 14C“Curve
of K n o ~ n s . The
” ~ reasonable agreement of the measured I4C values with
the expected values to about +lo%
supported the initial assumption of
constant I4C concentration in living
organisms over the recent past. However, increases in measurement precision resulting from developments in
technology began to identify apparent
discrepancies between some thirdmillennium B.C. (mostly Egyptian)
“known-age’’and 14C-basedage estimates. These samples were dating several centuries too young. This
ARTICLES
Evolutionary Anthropology 171
nal American Antiquity adopted the practice of Radiocarbon
except for punctuation (B.P. rather than BP). In the early
Standard I4C-basedage estimates are expressed in terms
of a set of parametersthat define a conventionalradiocarbon 1970s, the journal Antiquity adopted a nomenclature which
age. These parameters, introduced in the mid-1970s by distinguished conventional (uncalibrated)and calibrated I4C
Stuiver and P o l a ~ hand
, ~ ~now widely employed, include values whereby “bp” and “ad / bc” are employedto designate
1) using 5,568 (5,570)years as the I4Chalf-life,even though conventional I4C values, whereas “BP” and “AD/BC” are
the actual value is probably closer to 5,730 (k 40) years, used to designate calibrated I4Cvalues.
The I4C time scale now extends from about 300 years to
2) using A.D. 1950 as the zero point from which to count I4C
between
40,000 and 75,000 years. The limitations on the
time, 3) the normalizationof the measured I4Cconcentration
to a common I3C/l2C(6’3C) value to correct for natural frac- young end of the I4Ctime scale are a consequence of three
tionation effects, and 4) an assumption that I4Cin all reser- factors: first, recent significant variability in I4C production
rates associated with modulations in I4Cproduction, primarvoirs has remained constant over the I4Ctime scale.
ily
due to rapid changes in solar magnetic intensity in the
In addition, each I4C determination is expected to be acseventeenth
century; second, the effect of the combustion of
companied by an expressionthat provides an estimate of the
experimental uncertainty.Because statistical constraints as- large quantities of fossil fuels beginningin the late nineteenth
sociatedwith the measurementof I4Cconcentrationsin sam- century (the Suess or industrial effect); and third, the proples are usually the dominant component of this uncertainty, duction of artificial I4C (“bomb” I4C) as a result of the detothis value is informally referred to as the statistical error. This nation of nuclear and thermonuclear devices in the
“f”term is added as a suffix to all appropriately documented atmosphere, particularlybetween 1955 and 1963 (the atomic
I4Cage estimates and is typically expressed as L one stand- bomb, nuclear or Libby effect). As a result of the complex
arddeviation(k10).
In most cases, this value underestimates interplay of these factors, it is not currently possible, except
the actual total analytical or measurement uncertainty.I5A under very special circumstances, to use the I4Cmethod to
reference that cites the laboratory number assigned to the assign unambiguous ages to materials living within the last
sample is also necessary to permit a researcher, if neces- 300 years.
sary, to query investigators about technical aspects of a I4C
One of these special circumstancesis associated with the
analysis.
presence of “bomb” I4C activity. The concentration of this
For samples from some carbon reservoirs, conventional artificial I4C peaked in 1963 at slightly in excess of 100°/o
contemporary standards may not define a zero I4Cage. A above the prebomb contemporary I4C reference level. An
reservoir corrected radiocarbon age can sometimes be cal- international agreement in that year halted atmospheric riuculated by documentingthe apparent age exhibited in control clear testing, thus allowing I4Cto begin the process of reessamples and correctingforthe observeddeviation. Reservoir tablishing a new atmosphericI4Cequilibrium. Because of the
effects are most often observed in shell samples from fresh- rapid change of I4C in such a short period, it is possible to
water lakes and marine environments.A calibrated radiocarassign an “age” with a 95% confidence intervalo f f 3-5 years
bon age takes into consideration the fact that I4Cactivity in
for materials growing in 1963-64 and two possible ages for
living organisms has not remainedconstant over the I4Ctime
materials growing during the several decades of rapid rise
scale because of changes in I4Cproduction rates, exchange
and
slower decay.
rates, or other parameters of the carbon cycle. The study of
The
maximum I4C ages that can be inferred depend on
the various factors responsible for the variability in 14C procharacteristics
of different laboratory instrumentationand exduction rates and changes in the worldwide distribution of
perimental
configurations
(e.g., counter size, length of countI4C in various carbon reservoirs has occupied the attention
ing, and background values) as well as, to some degree, the
of researchers for more than two decades.
In the current nomenclature of the journal Radiocarbon, amount of sample availablefor analysis. Employing relatively
“I4C years BP” is indicated only as “BP,” with the “I4C years” large samples typically not availablefrom archeological conimplied (e.g. 2,510+50 BP). Calibrated ages are expressed texts, several laboratories have the capability to obtain finite
with only the “cal” designation attached (e.g., cal AD 1,520, ages up to about 70,000 years.73With isotopic enrichment,
3,720 cal BC) with the “years” implied. As M. Stuiver has again using relatively large ( > I 5 grams of carbon) amounts
noted, calibrated years are, within counting errors, solar of samples, ages up to 75,000 years have been reported on
years. If one wishes to use a strictly defined terminology, a small number of samples.74Efforts are now underway to
calibrated years are not calendar years, for the length of a exploit AMS technology to extend the I4C time scale to as
calendar year varies in different calendar systems. The jour- much as 90,000 years.
Radiocarbon Time
stimulated interest in a more systematic investigation of the apparent
anomalies.
By the early 1960s, it had become
clear that the suggestion of the pioneering Dutch researcher Hessel de
Vries, that “radiocarbon years” and solar (“real”) years should not be assumed to be equivalent values, was
correct.’O For the next 10 years and
beyond, the pursuit of a more accurate
and detailed understanding of the
character of the various components
of what came to be known as secular
variation in natural 14C concentrations
occupied the attention of an increasing number of researchers. In 14Cstudies, secular variation refers to any
172 Evolutionary Anthropology
systematic variability in 14Ctime other mined that this value, used to calcuthan that caused by I4C decay. The late conventional 14C dates, is about
transformation of “14C time” to “real” 3% too low. The most widely quoted
or solar time required a calibration I4C half-life value-the so-called Camprocess in which I4C values were bridge half-life-is 5,730k40 years.
paired with assumed known-age values to quantify an age offset. The im- The Second Radiocarbon
plications of the I4C age deviations Revolution
In the early 1970s, Colin Renfrew in
became important in geophysics, solar physics, atmospheric chemistry, Before Civilization: The Radiocarbon
and climatology, as well as in histori- Revolution and Prehistoric Europe
pointed to the role of calibration of the
cal and archeological studies.
Throughout the 196Os, using primarily dendrochronologically (treering) dated wood to provide
known-age controls, the I4C secular
variation phenomena were docu- The principal detailed
mented further and further back into documentation of the
the middle and early Holocene. By the
various types of
end of the decade, I4C and tree-ring
4
C time
data had a time depth of 7,000years.I’ variations in the 1
By that time, the 14Cdata appeared, at scale was initially
least to some investigators, to exhibit
derived from 14C
two types of periodicity: a major trend,
with what initially appeared to be a determinations carried
long-term “sine wave” characteristic, out on tree ring-dated
and a series of medium- and shortterm, higher frequency components of wood, including
various durations and apparent peri- samples obtained from
odicities. Over the years, these short- the giant California
term variations have been informallyreferred to as “wriggles,” “wiggles,” sequoia (Sequoia
“kinks,”“windings,”and “warps.”Since gigantea),the
the late 196Os, they have come to be European oaks
more formally known as de Vries effects.
The principal detailed documenta- (Quercusspp.), and, for
tion of the various types of variations the oldest portions of
in the I4C time scale was initially de- the time series, the
rived from I4C determinations carried
out on tree ring-dated wood, includ- bristlecone pine (Pinus
ing samples obtained from the giant longaeva).
California sequoia (Sequoia gigantea),
the European oaks (Quercus spp.),
and, for the oldest portions of the time
series, the bristlecone pine (Pinus lon- I4C time scale as the basis of the “Secgaeva, originally known as r! avistata). ond Radiocarbon Revolution.”12For
By the early 1970s, using this dendrohim, this revolution involved a rechronological and I4C data base, the
evaluation of traditional underamount of correction required to
standings by European archeologists
bring middle and late Holocene 14C
values into approximate alignment of the timing of the introduction of imwith solar time varied from a mini- portant innovations in prehistoric
mum of about -250 years in the mid- Europe. In his view, calibrated 14Cage
dle of the first millennium A.D. to a estimates played a major role in revismaximum of about +800 years in the ing views of the factors involved in the
fifth millennium B.C.I2 A small por- origins of several important archeotion of the solar and I4C time offset logical features of “European barbareflected the use of the Libby half-life r i sm ,” i nc 1ud i ng the mega 1it h i c
of 5,568 +30years for conventional I4C chamber tombs, European metalage calculations. It had been deter- lurgy and Stonehenge in England.
ARTICLES
Since the mid-l930s, due in large
part t o the influence of Gordon
Childe, the first two developments had
been seen as having their ultimate origins in the Near East, whereas Stonehenge was considered to reflect the
inspiration of Mycenaean Greece. According to this perspective, European
advances in areas such as monumental architecture and metallurgy were
initiated or stimulated by diffusion of
knowledge, initially from Egypt
through the eastern Mediterranean
and Aegean and hence to southeastern, east central, and then western
Europe. Renfrew insisted that diffusionist views were seriously undermined by the calibrated I4C values,
which appeared to place the megalithic tomb structures earlier than the
Egyptian pyramids and to place copper metallurgy in the Balkans earlier
than in Greece. Also, he noted that
Stonehenge appeared to have been essentially completed before Mycenean
civilization in Greece began.
In place of diffusionist explanations
for these cultural innovations, Renfrew and those influenced by him emphasized local factors such a s
increasing population pressures,
trade and exchange systems, and the
manner in which social organization
interrelatedwith developingindigenous
economies and technologies. Another
British archeologist characterized the
“revolutionary” impact of both conventional and calibrated I4C data on
British prehistory as “radical . . . therapy” for the “progressivedisease of ‘invasionism.’”’3
THE THIRD RADIOCARBON
REVOLUTION: CURRENT
RESEARCH ISSUES
During the last decade, several major technical and methodological advances have provided contexts for a
series of significant applications of the
I4C method in archeological studies.
These include the extension of the
calibrated I4C time scale into the late
Pleistocene, further detailing of the
Holocene “time warps,” and the development of accelerator mass spectrometry ( A M S ) technology. The
development of AMS technology has
been appropriately labeled as revolutionary in its impact on the conduct of
14C~ t u d i e sThe
. ~ extension of the cali-
ARTICLES
- 5000
Evolutionary Anthropology 173
c a l BP
30000 25000 20000 15000 10000 5000
0
L
4500
u
2
'
4000
3500
L
3000
d
rn 2500
0
v
2000
[u
1500
?
1000
[u
500
-4
0
0
'
' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
%-500
' ' '
a
30000 25000 20000 15000 10000 5000
I'
c a l BC
' ' ' '
[o]
c a l AD
Figure 2. Characterization of Late Pleistocene and Holocene deviation of 14Cfrom dendrochronologially based and uranium-series-basedages: 0 to 30,000 years. Solid-line curve in excess of
11,390 cal BP taken from splined U/Th and 14C dates (triangles) on coral, assuming a 400-year
resewoir age offset. Dotted-line curve for period before 23,000 cal BP based o n assumed atmospheric equilibrium or steady-state value 50% above the contemporary standard at 30,000 cal
BC.2122
interlinking of the German oak and
pine dendrochronological seq u e n c e ~ This
. ~ ~component
~~~
of the
calibration data base is provisional because it currently includes a "floating"
tree-ring segment. Future revisions in
Extending the Calibration of the the overlap correlations are possible.
Thus, for the period from 9,840 to
14CTime Scale
11,440 cal BP-in I4C time, back to
Comparisons of 14C and dendroabout 10,050 BP-calibrated values
chronological data based on Irish and are not, as yet, confidently fixed in
German oaks, Douglas fir, sequoia, time. For the pre-10,OSO-BP late Pleisand bristlecone pine currently docu- tocene period, paired uranium and
ment about 9,800 years of dendro- thorium (234U/230Th)
and 14C samples
chronological time with bidecadal(20 from cores drilled into coral formayear) time-ring segments.I4 The 14C tions provide the data on which a late
measurements comprising these data Pleistocene 14C calibration curve has
sets are characterized as "high-preci- been extended to 21,950 cal BP (as exsion," referring to counting uncertain- pressed in 14C time, to 18,400 BP) in
ties at the f 1 o level of <20 years for 50-year increments. 18-20 A half -1 i fethe 14Cvalues used to provide the Cali- based offset is built into most I4C
bration data. Laboratories where the timekalibrated time comparisons becalibration data were produced have cause conventionally expressed I4C
undertaken extensive and detailed in- values are calculated on the Libby
terlaboratory comparisons to exam- half-life of 5,568f30 years, which is
ine the validity of the stated about 3% below the most likely I4C
uncertainties. l 5
half-life value.
The dendrochronologically based
With the extension of the I4C Calicalibration record has been provision- bration framework achieved through
ally extended to 1 1,390 cal BP by the use of the uranium-series data on cor-
bration of the I4C time scale beyond
that provided by tree-ring data was accomplished primarily by the use of
AMS-based I4C and U-series measurements on marine coral samples.
als, it now appears that the original
inferred "sine-wave"-like characterization of the various I4C secular
variation plots was an artifact of the
limited time frame documented by the
tree-ringP4C data. Figure 2, a plot of
the suggested relationship between
14Cand "real" time for the last 30,000
years, is, in large measure, based on
the current combined dendrochron~logical/*~C
and coral uranium .series/I4C data. These data suggest that
at about 20,000 cal BP, I4C values are
about 3,500 years too young.!' 22
Based on these data, it appears that
the long-term secular variation 14C
anomaly over about the last 30,000
years can be characterized as representing a slow-decay function on
which middle- and short-term perturbations have been superimposed.
Unfortunately, inferences about the
14C anomalies based on estimates of
temporal variations in the earth's dipole magnetic field, the assumed principal cause of the major I4C secular
variation anomaly, suggest a somewhat different pattern for the age offsets for the late Pleistocene. A5
illustrated in Figure 3, one interpretation of the geomagnetic data models a
14C/solartime offset up to about 2,500
years to about 15,000 cal BP, followed
by a downward tendency to about
25,000 cal BP, and then a second upward tendency until about 40,000 cal
BP. This model also predicts thai at
about 45,000-50,000 years there will
be good agreement between 1% and
solar time.23A somewhat different interpretation of the I4C secular variation trend before 15,000 BP also
emerges if a short-term geomagnetic
reversal or major excursus, termed the
Laschamp event, is assumed to have
occurred at about 45,000 BP.24Comelations between I4C and other Quaternary dating methods (e.g., WAr) for
this period also are not consistent with
the current coral uranium-seriesP4C
data.25The possibility that a relatively
close supernova occurred about at
35,000 BP, resulting in a brief, sharp
rise in 14Catmospheric content at that
time, also has been considered. 26
Like the I4C method itself, anyaccurately measured calibration data base
is applicable to all regions of the world
with some suggested caveats. For example, I4C measurements on two den-
ARTICLES
174 Evolutionary Anthropology
4L
1
500
3
A
G
v
S
0
.c
8 2
i
Q)
8
1
0
0
10
20
30
40
50
True Age (Ky)
Figure 3. Suggested magnetic calibration of the 14C time scale: 0-50,000 years. Age corrections
based on 14C production rate calculations taken from geomagnetic dipole strength data based
on natural remanent magnetization measurements on sediments recovered in a series of marine
cores.Ages of sediments based on oxygen isotopes time scale.77Shaded portion indicates uncertainties in the measurementof the geomagneticdipole strength data. Modifiedfrom originalfigure
with perrni~sion.~~
drochronologically dated matched
ring series from trees growing at the
same time during the nineteenth centurj-an oak in the Netherlands and a
pine in Cape Town, South Africahave been used to argue that there is
an offset in calibration data of up to
0.5%, or about 40 years, between the
Northern and Southern Hemis p h e r e ~ .However,
*~
the interpretation
of these data has been questioned.
Other dendrochr~logical/~~C
comparisons from sites in the Southern Hemisphere, such as Tasmania, agree well
with Northern Hemisphere data2*
Clearly, additional studies are required to establish firmly whether or
not there is any consistent, systematic
14C offset effect in the two hemispheres.
Detailing Holocene de Vries
Effects
A fuller rendering of the entire
Holocene I4C time scale permits researchers to review more precisely the
timing and characteristics of the de
Vries “wiggles”over the last 10 millennia. Figure 4 plots a series of Holocene
“time warps“ reflecting the time
ranges of the de Vries effect perturbations in the calibration curve.22 The
inherent uncertainties and fluctua-
tions in the calibration curve cause
discrete cal ages t o broaden into
ranges, even when, as in Figure 4, the
1% ages are plotted with a hypothetical zero variance. Thus, I4C age determinations deriving from time periods
with large calibration-range values
will be inherently less precise than determinations from periods with small
calibration-range values. For example, calibrated age equivalences for
8,000-10,000 BP are, on the average,
inherently much less precise than
those for @2,500 BP because the time
warps in this period are of a significantly larger magnitude than are time
warps in earlier millennia.
A means of circumventing the inherent uncertainties in de Vries perturbations is to employ “wiggle-matching’’
strategies. This involves matching the
pattern of de Vries “wiggles”exhibited
by a set of continuous rings in a wood
sample of unknown age against the
known pattern in I4C age exhibited by
wood samples making up a high-precision calibration curve. This approach recently has been used, for
example, to assign a 14Cage of A.D. 320
+5 years to a wood sample from a site
in Japan.29
In Figure 4, 12 major and five intermediate de Vries effect perturbations
are identified. Major de Vries effects
have been defined as warps exceeding
250 cal years; intermediate de Vries effects exhibit ranges in excess of 140cal
years; and minor de Vries effects have
ranges of less than 140 cal years. The
17 major and intermediate de Vries
perturbations have been assigned Roman numeral and letter combinations. The Roman numerals identify
the I4C millennium (i.e., I = 0 to 1,000
BP, I1 = 1,000 to 2,000 BP), while
lower-case letters identify the perturbation in chronological order within
each 14Cmillennial period. It has been
noted that a major de Vries effect
anomaly (Xa) centered on 9,600 BP
and spanning almost five centuries
complicates the interpretation of 14C
determinations from Star
Another major perturbation (IIIa) in the
first millennium B.C. complicates
comparisons of I4C values with some
historically based chronologies in
Near Eastern archeology.
Accelerator Mass Spectrometry
Technology
From the initiation of 14C studies
until the late 1970s, the means of inferring 14C concentrations and, therefore, the I4C age of samples exclusively
employed decay counting technology.
In decay counting, isotopic concentrations are measured by counting decay
events in an ionization or scintillation
detector and comparing the count rate
in a sample of unknown age to that
exhibited by appropriate standards
under a common set of experimental
conditions. For 14C, this involves
counting beta particles, or negatively
charged electrons emitted from the
I4C nucleus. In decay counting, a relatively small fraction of the 14C atoms
present in a carbon sample are actually measured.
As early as 1970, Oeschger and his
co-workers noted the great increase in
sensitivity that could be obtained using mass spectrometric methods, especially if they were combined with
isotopic e n r i ~ h m e n t . ~Mass
’
spectrometers, as their name implies, take
advantage of the differences in mass
of different isotopes to detect and directly measure their relative concentrations. Unfortunately, throughout
the 1970s, experiments using a conventional low-energy (several thou-
ARTICLES
Evolutionary Anthropology 175
w
In the late 1970s, this problem was
overcome by accelerating sample atoms, in the form of ions, to much
400
higher energies (several million elecIIIb
tron volt acceleration) in particle accelerators. This technology, initially
cn
I
called
high-energy mass spectrometry,
300
Ia
is now referred to as accelerator mass
_I
spectrometry. Both terms emphasize
Q
u
the linkage of particle accelerator and
mass
spectrometry methodologies for
200
U
the detection of rare cosmogenic isoc3
topes such as I4C.
z
4
Two types of AMS systems, cycloa
trons and tandem accelerators, have
100
been used for direct or ion-counting
I4Cmeasurements. Luis Alvarez, a Nobel laureate, briefly explored the basic
concept behind the cyclotron-based
n
AMS
approach in experiments he conU
5000
4000
3000
2000
1000
0 ducted just before World War I[ in
which he used the 60-inch cyclotron at
RADIOCARBON AGE (YRS BPI
the University of California a t
Berkeley. In the late 1970s, Richard
M ~ l l e took
r ~ ~up this work again and,
in 1977, wrote the first published report of an AMS-based I4C determ ina400
tion on a n archeologically related
VlIIa
Xb
sample.35For this determination he
xc
I
used an 88-inch (224-cm) cyclotron.
Throughout the 198Os, Muller’s
3CO
group attempted to develop the potential capabilities of a cyclotron-based
system. Their studies focused on the
development of a smaller, relatively
low energy (40-keV) “cyclotrino” 1hat
200
used an external ion source. Unfortunately, several major difficulties fi-ustrated the use of that technology for
routine work in I4Cdating.36However,
100
another laboratory has now reported
more encouraging results.37
The second type of AMS system employs an electrostatic tandem accel0
erator. Typically, this type of AMS
10000
9000
8000
7000
6000
5000 system is called tandem accelerator
RADIOCARBON AGE (YRS BP)
mass spectrometry (TAMS). In 1977,
two accelerator groups simultaneFigure 4. Holocene ’%2 ranges in cal yr obtained from the calibration of conventional I4C ages:
ously published suggestions about
Top: 0-5000 BP; Bottom: 5.000-10,000 BP. Ranges produced for an ideal hypotheticalcase with zero
I4C sample standard deviation.The youngest cal age obtained for each I4C was set to zero. The
how a tandem accelerator could be
sample was assumed to have been formed during a 20 year or shorter interval.22
employed to measure 14C at natural
concentrations using milligram
amounts of carb0n.~8,39
One great advantage of the TAMS system is that the
sand electron volt acceleration) mass ties similar to that of l4c(e.g.,I3CHOr acceleration process destroys molecuspectrometer were frustrated, in part I2CH2)could not be sufficiently elimi- lar species (e.g., 1 3 or 12CH2)
~
~ in the
because of the extremely low natural nated from the mass spectra. Come- beam. This significantly reduces the
14C concentrations (14C/l*C=ca10-12) quently, relatively high backgrounds relatively high backgrounds that had
and partly because I4N and stable mo- could not be sufficientlysuppressed to occurred with conventional mass
lecular ions with charge-to-mass ra- permit natural I4C mea~urements.3~J3spectrometers. TAMS proved to be a
4
v
1 I1II
t
-1i
ARTICLE5
176 EvolutionaryAnthropology
HIGH ENERGY
MASS SPECTROMETRY
ARCHEOLOGICAL
APPLICATIONS OF AMS
TECHNOLOGY
Thin carbon
foil stripper
Cl+...&
I
1 c-
7
I I I I I I I I I I r;ti I. I I I I I I I I I I
FN-TANDEM ELECTROSTATIC
ACCELERATOR
b . JI I
LOW ENERGY
MASS
SPECTROMETRY
VELOCITY (Wien)
ANALYZING
MAGNETS
IONIZATION
DETECTOR
Slits
figure 5. Schematic representation of major elements of a TAMS-typeAMS system at the University
of California Lawrence Livermore National Laboratory (LLNL). Figure prepared with the generous
assistance of John R. Southon, LLNL.40
practical AMS technology for a whole
range of isotopes, including 14C. To
date, almost all routine AMS I4C determinations have used this approach.
Figure 5 is a schematic representation
of the TAMS-type AMS system operating at the University of California
Lawrence Livermore National Laborat0ry.4~~~
Three advantages of AMS technology in the measurement of 14C were
anticipated as a result of the greatly
enhanced detection efficiency. First,
major reductions in sample sizes
would be possible, from gram
amounts of carbon to milligram
amounts and, with additional efforts,
to less than 100 micrograms. Second,
major reductions in counting times
would be possible. Mini- and microcounting systems require months or
weeks, and even conventional systems
require several days for counting.
However,only minutes of counting are
necessary for AMS systems to achieve
f l %counting statistics. Finally, it was
anticipated that the applicable dating
time frame could be inreased from the
currently routine 40,000-70,000 years
to as much as 100,000years.34
The first two of these anticipated
benefits of AMS technology have been
fully realized during the last decade.
Order-of-magnitude reductions in
both sample sizes and counting times
have been made possible on a routine
basis. However, the third projected advance has not yet occurred, because of
the current inability to exclude microcontamination of samples, primarily
During the last decade, the expanding use of A M S technology for I4C
analysis has continued to open new
and diverse areas of research. Indeed,
I4C data have yielded important new
understandings that would not have
been possible or practical with decay
counting. In archeology, a variety of
issues and topics have been significantly affected by the new ability to
obtain I4C measurements on milligram amounts of sample.
Early Plant Domestication
The impact of AMS technology on
issues of major archeological interest
by modern carbon introduced during is well illustrated by the results of sevsample preparation.
eral studies that have examined the
The source of a significant portion accuracy of 14Cage estimates assigned
of sample contamination is the cur- to domesticated plant species in sevrent requirement in almost all AMS eral regions of the world. The critical
laboratories that samples be con- question, of course, is the timing of
verted to some type of graphitic carb- the earliest appearance of cultivated
on for use in the ion source of an AMS or domesticated plants that later besystem. The I4C contained in micro- came the basis of a horticultural or aggram amounts of modern carbon con- ricultural subsistence regimen i n
tamination
translates
into these regions.
background levels in the 40,000 to
In the early 1970s, conventional I4C
50,000 BP range. For example, an av- measurements had been obtained on
erage ( N = 1 9 ) apparent age of New World charcoal samples as52,140f450 BP was obtained for dupli- sumed to be stratigraphically associcate 1-milligram samples of carefully ated with specimens of Zeu mays from
pretreated wood with a purported age several caves and rock shelters in the
of ; 100,000 years. These samples had Tehuacan Valley of central Mexico. On
been combusted to CO, and converted the basis of an age assignment to the
to graphitic carbon by catalytic reduc- fifth or sixth millennium B.C. protion on cobalt. The lowest background vided by the associated charcoal I4C
value obtained was 56,150 +S40 BP.42In- values, the maize samples from Tevestigators in another laboratory have huacan had been viewed as the earlireported a background value on Mi@ est examples of cultivated maize in the
cene-age coal of about 55,000 BP for New World. Table 1 compares the I4C
graphite samples of ;200 mi~rograms.4~values previously obtained on purTo eliminate the need to convert portedly associated charcoal with the
C 0 2 to graphitic carbon, researchers AMS I4C values directly obtained from
at the Oxford AMS laboratory have de- the maize samples. In contrast to the
veloped a CO, gas source as part of 5,350 to 7,000 BP values on associated
their TAMS system. They report that charcoal, the range in I4C values diages up to 50,000 years can be deter- rectly obtained from the maize fragmined with background s~btraction.4~ments is 1,560 to 4,700 BP for the
For example, a n Oxford CO, gas- samples from San Marcos Cave and 450
source AMS determination of ;44,800 to 4,090BP for the specimensfrom CoxBP was obtained on charcoal from a catlan C a ~ e . ~ ~significantly
The
later ocMiddle Paleolithic level at Kebara Cave currence of maize at Tehuacan raises
that had yielded an average thermolu- anew questions about where the center
minescence date of 5 1,900 (f3,500) BP (or centers) of maize domestication in
on burned flints.45
Mesoamerica may have been.
ARTICLES
Evolutionary Anthropology 177
TABLE 1. Comparison of 14Cdetermination on samples of charcoal and maize
from Tehuacan Valley, Mexico46
Decay counting on associated charcoal
AMS direct counting on maize
specimens
I4Cage BP (range) Calibrated AD/BC
(range)
14Cage BP
CalibratedAD/BC
(range)
Son Marcos Cave
5350-7000
1560f45
4150 f 50
4600 f 60
4680 f 50
4700 f 60
4700f 110
AD 440-620
288C-2660 BC
3380-3360 BC
3500-3380 BC
3500-3380 BC
3640-3360 BC
Coxcatalan Cave
450 f 40
1860 f 45
1900k60
3740 f 60
4040 f 100
4090 f 50
AD 1400-1460
AD 80-220
AD 20-220
228C-2040 BC
2580-2500 BC
2870-2580 BC
4 150-5800 BC
In the Old World, six-rowbarley and
several other plant domesticates from
the Late Palaeolithic site of Wadi Kubbaniya in southern Egypt had been assigned ages of 17,000 and 18,500 BP
based on conventional I4C measurements of wood presumably associated
with them. Although AMS I4C values
on wood supported the Late Paleolithic age of the site, a date obtained
directly from a barley seed at the Arizona AMS laboratory yielded an age of
4,850 BP, indicating the intrusive nature of the plant domesticates at this
site.47
At the Oxford AMS facility, 14Cvalues were obtained from two seeds of
domesticated wheat (Triticum dicoccum) recovered from Kebaran levels
at the cave site of Nahal Oren in Palestine. Although I4Cvalues on presumably associated bone are in the range
of 16,000-17,000 BP, AMS values on
the seeds indicated ages of 2,940 and
3,100 BP. AMS determinations were
also obtained on grains of domestic
wheat initially thought to be associated with Natufian levels at the site
of ’Ain Mallaha in Palestine. An essentially modern age (330 BP) was
obtained, again pointing to the potential of small seeds having been introduced far down a stratigraphic
profile.48
Peopling of the New World
AMS 14C technology has also been
used to address one of most acrimonious debates in New World archeology,
the nature and timing of the peopling
of the Western Hemisphere. Historically, this debate has centered on two
issues: the scientific validity of data offered as evidence of human presence
and the accuracy of the age estimates
associated with these
A number of discussiocs have centered on questions concerning the validity of Paleoindian materials with
assigned ages in excess of the welldocumented Clovis-period occupation of North America.soOf the more
than 100 sites in North America that
have been reported during the last
century to contain evidence of “preClovis” occupation, only a small number, including the Meadowcroft Rock
Shelter in Penn~ylvania,~’
remain under active consideration. Of these remaining alleged pre-Clovis sites in
North52 and South53,54America, either
the cultural nature of the material or
the adequacy of the geochronological
data associated with the remains (or
both) are questioned. In the case of
Meadowcroft, for example, it has been
suggested that charcoal samples from
the site are contaminated with a form
of coal, thus rendering the 14Cages too
01d.55.56 The current body of I4C age
determinations associated with sites in
northeastern Siberia57 and interior
Alaska58 also currently pose major problems for those seeking evidence of human migration between northeastern
Asia and northwestern North America
before 1 1,500BF!
The ability of AMS technology to
permit routine measurement of 14C
values using milligram amounts of
carbon provided the technical capability for direct examination of a series of
human skeletons from North American sites that, on various grounds, had
been declared t o date to before
11,000-12,000 BP-i.e., to be of preClovis age.59AMS technology permitted detailed analysis of the validity of
14C age estimates on a range of organic
extracts including individual amino
acids and other highly specific organic
constituents contained in bone. Such
analyses are necessary because of the
well-documented problems in obtaining accurate I4C determinations on
b~ne.~O-~~
Table 2 summarizes AMS 14Cvalues
obtained on various organic fractions
extracted from human skeletal samples and, in one case, an artifact fabricated from a nonhuman bone from a
North American site, all of which had
been assigned a pre-Clovis age. The
basis of the initial age assignment of
these samples included other Quaternary dating methods such as amino
acid racemization, uranium-series
testing and, in a small number of
cases, prior decay-counting 14Cdeterminations. The corpus of the AMSbased I4C values on these human
skeletal samples indicate that all are
younger than 11,000 BP. These data
are the basis of the current conclusion
that all currently known 14C-dated human skeletons from the Western
Hemisphere a r e of Clovis age o r
younger. The only exceptions are two
14Cvalues obtained in connection with
experiments to determine the validity
of 14C determinations on a noncollagen component of bone, osteocalcin.64 These two values are interpreted
as representing fractions that have
been contaminated in the process of
their chemical extraction, the reason
being that a significant number of I4C
dates, along with other evidence,
points to the age of the Haverty (Ange-
ARTICLES
178 Evolutionary Anthropology
TABLE 2. Revisions of age estimates on human bone (except Old Crow) from North American sites of purported Pleistocene
age based on AMS I4Cdeterminations.Sources for these data may be found in the caption of Table 25.5 in reference 60
Original Estimate
Skelton(s)/Artifact
Basis
Revised Estimate
14CAge (BP)
Age
Sunnyvale
AAR
U-series
70,000
a300/900o
360~4850
6300
Haverty (Angeles Mesa)
AAR
>50.000
Del Mar
AAR
U-series
4 1,000-48,000
1 1 .OOO/1 1,300
4050-5350
5200
7900-10.500
2730-4630
4600-13.500
5250
15,900
5320
Los Angeles (Baldwin Hills)
Taber
Yuha
4c
AAR
Geologic
4c
AAR
Old Crow
Laguna
Natchez
Anzick
Tepexpan
Calaveras
' 4c
14
C
Geologic
Clovis
Geologic
Geologic
les Mesa) skeletons as being in the
range of 4,000 to 5,000 BP.65
The experimental osteocalcin I4C determinations reflect current efforts to
deal with the problem of the accuracy of
such determinations on bone samples
of modern levels)
containing low (4%
or trace ( < I % of modern levels)
amounts of residual collagen, the principal organic constituent of bone, since
it has been observed that such samples,
in some cases, exhibit anomalous I4C
values. Typicdy, bone characterized by
low or trace amounts of collagen exhibit
14Cages that are too young, indicating
that chemical pretreatment methods
have not totally removed modem carbon
contamination. In the case of the
Haverty skeletons, the ages of the osteocalcin fractions are interpreted as being
too old, which suggests contamination
with 14C-"deadreagents (i.e., reagents
exhibiting no detectable I4C) during
chemical pretreatment.
>23.000
26,000
22,00060,000
22,000
23,000
19,000
23,000
7100
17,150
> 14,800
"Pleistocene"
10,000-1 1,000
"Pleistocene"
"Pliocene"
Laboratories
4830
1 150-5060
3560
UCR/Arizona AMS
UCSD (Scripps)/
Oxford AMS
UCR
GX (Geochron)
UCLA
UCR/LLNL-CAMSAMS
UCR/LLNL-CAMSAMS
DSIR, New Zealand AMS
DSIR, New Zealand AMS
UCSD (Scripps)/
Oxford AMS
Arizona AMS
Arizona AMS
UCR/Arizona AMS
3550
1650-3850
Chalk River AMS
Arizona AMS
1350
Simon hazer/
Mc MAster AMS
UCSD (Scripps)/
Oxford AMS
5100
5580
86 10- 10.680
920-1980
740
Dating the European Upper
Paleolithic and Mesolithic
The initial promise of AMS technology to extend the I4C time frame to as
much as 100,000 years offered the
prospect of obtaining direct age estimates on Upper Pleistocene hominids.
This would have permitted the use of
14Cto study the temporal relationship
between populations of modern
Homo sapiens and their relationship
to the Neanderthals. As already noted,
current background levels limit the
routine usefulness of AMS-based I4C
measurements to the last 40,00050,000 years. In addition, I4C values
obtained from collagen-depleted bone
samples often yield anomalous results. Unfortunately, it is likely that a
significant number of Upper Pleistocene bone samples from Europe and
the Near East would be characterized
by low or trace amounts of collagen.
Arizona AMS
Arizona AMS
Arizona AMS
UCR/Arizona AMS
Despite current limitations, AMS
values have played a significantrole in
the study of the later portions of the
Upper Paleolithic and Mesolithic in
Europe. As illustrated by the results
presented in Table 3, AMS values have
been particularly important in distinguishing the age of human skeletal
materials in contexts where there was
the possibility of stratigraphic mixing
of later human bone samples with earlier Pleistocene sediments. At Kent's
Cavern and Paviland Cave in England,
for example, I4C values have distinguished Pleistocene-age material
from later intrusions. In another instance, the Badger Hole hominids,
once thought to be of late Pleistocene
age on the basis of comparison of their
fluorine, nitrogen, and uranium content with that of associated extinct
fauna,66were found to include material of post-Pleistocene age. On the
other hand, the assignment of an early
ARTICLES
Evolutionary Anthropology 179
TABLE 3. Selected AMS I4C analysis on human bone by the Oxford AMS laboratory from European Mesolithic and Paleolithic
contexts in Western Europe. Numbers in parenthesesfollowing age of specimens indicate number of bone samples analyzed
Oxford AMS
Site
Issue/Context Association
Results (14Cyrs BP)
Interpretation
Date list No.
Kent‘s Cavern, England
Paviland Cave, England
Pleistocene (Kc 4)
30,900 (1)
Early Upper Paleolithic
Pleistocene (Kc 1, Kc 3)
3560-8870 (2)
Mesolithic
Pleistocene (Paviland 1,
“Red Lady”)
Pleistocene(Paviland 2)
26,350 (1)
Early Upper Paleolithic
7190 (1)
Mesolithic
9
4,9
Sun Hole, England
Late glacial
12,210(1)
Late glacial
3
Gough’s Cave, England
Late Pleistocene
1 1,480-1 2,380 (2)
Late Pleistocene
13
Grotte Margaux. Belgium
Group burial
9330-9350 (2)
Badger Hole, England
Late Pleistocene
1380-9360 (3)
Gough’s New Cave,
England
Vasil’evka. Ukraine
“Cheddar Man“ late glacial 9100 (1)
or early postglacial
7620-8020 (3)
Phase II
One of the oldest group
burials in Europe
Mixed post-Pleistocene
deposit
Early postglacial
Aveline’s Hole, England
Mesolithic/Neolithictransition
Phase 111
9980-10,080 (3)
Mesolithic
8740-91 00 (3)
Mesolithic
19
4,9, 13
4
19
4.6
Berlin-Schmockwitz,
Germany
Gross Frendenwald,
Germany
Ogof-yr-ychen, Wales
Mesolithic
6900-8200 (2)
Mesolithic
Neolithic or Mesolithic?
7360-7660 (2)
Mesolithic
Mesolithic lithics
7020 (1)
Mesolithic cave burials
18
Grosse Ofnet-Hohle.
Germany
Rees. Germany
Late Pleistocene
7360-7560 (5)
Mesolithic
9
Mesolithic
5160 (1)
Mesolithic
5
Asteback, Abri, Luxembourg Mesolithic
5010 (1)
19
Loccum. Germany
Late glacial faunal remains
3030 (1)
Mesolithic-Middle
Neolithic
Holocene
MacArthur Cave, Scotland
Mesolithic
2 170-2460 (4)
Neolithic
19
1265 (1)
Saxon period
18
HunstantonWoman, Norfolk Pleistocene (c. 18,000)
post-Pleistocene or Mesolithic age to a
number of human skeletal samples
has been confirmed. AMS-based I4C
measurements on two marine shell
samples excavated from Mousterian
levels at Grotte du Prince, Monaco,
were undertaken to evaluate their age
because the species of shell apparently
could have derived only from the Indian Ocean. Archeological studies
were spared creative inferences concerning a Mousterian shell trade network when the average age of the
shells was determined to be 670+50
The Upper Paleolithic rock-shelter
site of Abri Pataud at Les Eyzies in the
Dordogne region of southern France
provided the opportunity to compare
a series of AMS 14Canalyses of animal
bone samples from a long stratigraphic series with conventional I4C
values obtained using much larger
amounts of bone or antler. Figure 6
summarizes the results of the Oxford
AMS I4C analysis (open squares) on
bone as compared with the earlier
measurements obtained by the Groningen laboratory by means of conventional decay counting (solid circles).68
In at least four instances (designated
in the figure by asterisks), the AMS I4C
determinations were younger than expected. In each case, the Oxford laboratory reported that the amount of
collagen present was less than 5% of
that typically found in modern bone.
The interpretation of these results is
that younger contamination was not
totally removed by the pretreatment
5
19
19
methods employed. If the collagen
content of the sample is not at a sufficiently high level, the effect of a few
percent modern contamination could
explain the anomalous 14C ~ a l u e s . 6 ~
CONCLUSION
The impact of I4Cdating on the conduct of archeological research has
been, in some aspects, clear and explicit and, in others, more subtle and
indirect. Most obvious is the fact that
I4Cdata provide a common worldwide
chronometric time scale for the entire
late Quaternary, the foundation on
which a majority of the prehistoric
chronologies for the last 40,00050,000 years in many regions of the
world are, directly or indirectly, constructed.
ARTICLES
180 Evolutionary Anthropology
'rota-MaydJlen~an
LEVEL 2
19
-
20
-
21
-
23
25
LEVEL 3
-
22
21
PerlgardlJ" VI
-
-
26
-
27
-
28
29
-
3031
32
-
3334-
Figure6.Radiocarbon dates from Abri Pataud,Les Eyzies. France.Cornparision of AMS-baseddates
produced by the Oxford Laboratory (OxA). Decay counting dates determined at the Groningen
Laboratory (GrN). The Oxford Determinationsobtained on the bone total amino acid fraction. The
Groningen values obtained on the total acid-insoluble organics treated with base to remove humic
acids. Figure used with permi~sion.~~
For archeology, the 14Cmethod provides a means of deriving chronometric relationships that are completely
independent of any assumptions
about cultural processes and totally
unrelated to any manipulation of artifact data. Beyond this, it has been
noted that I4C dating led to a noticeable improvement in archeological
field methods in that it pointed to the
need for more rigor in recording the
details of stratigraphic context and
geomorphological relationship^.^^ It
has also been suggested that the nature of 14C age expressions-i.e., the
presence of a mathematically explicit
error term-was responsible, at least
in part, for the increasing attention
given to statistical formulations in the
evaluation of archeological data.71
While sometimes not currently
stressed or appreciated, more than
forty years after its introduction, the
role of I4C data on the conduct and
outcome of archeological researchat least for those concerned with empirically documenting the validity of
their assertions about the past-continues to be both pervasive and persuasive.
ACKNOWLEDGMENTS
The UCR Radiocarbon Laboratory
is supported by the Gabrielle 0.Vierra
Memorial Fund, the Accelerator Mass
Spectrometry Laboratory of the University of California, Lawrence Livermore National Laboratory (LLNL),
and the Intramural Research Fund,
University of California, Riverside. I
appreciate the helpful comments of
Sylvia Broadbent, David A. Burney,
and an anonymous reviewer of an earlier draft of this article. I also thank
John Southon (LLNL) for his help in
preparing Figure 5 a s well as A.
Mazaud and Springer-Verlag for permission to use Figure 3 and Paul Mellars
and the Wenner-Gren FoundatiodUniversity of Chicago Press for permission
to use Figure 6. The author would prefer to use the spelling "archaeology"
where that word appears in this article, but understands that Evolutionary
Anthropology prefers "archeology."
This is contribution 95-23 of the Institute of Geophysics and Planetary
Physics, University of California, Riverside.
REFERENCES
1 Taylor RE (1987) Radiocarbon Dating: An
Archaeological Perspective,Orlando: Academic
Press.
2 Renfrew C (1974)Before Civilization; The Rudiocarbon Revolution and Prehistoric Europe.
New York: Alfred A Knopf.
3 Arnold JR, Libby WF (1950) Radiocarbon
dates (September 1, 1950). Chicago, University of Chicago: Institute for Nuclear Studies.
4 Linick TW, Damon PE, Donahue DJ, Jull AJT
(1989) Accelerator mass spectrometry: The
new revolution in radiocarbon dating. Quaternary Int I: 1-6.
5 Daniel G (1967) The Origins and Growth of'
Archeology. New York: Crowell.
6 Clark JD (1979) Radiocarbon dating and African archeology. In Berger R, Suess HE (eds),
Radiocarbon Dating. Berkeley: University of
California Press, pp 7-31
7 Neustupny E (1970) The accuracy of radiocarbon dating. In Olsson IU (ed),Radiocarbon
Variations and Absolute Chronology. Stockholm: Almqvist and Wiksell, pp 23-34
8 Forenbaher S (1 993) Radiocarbon dates and
absolute chronology of the central European
Early Bronze Age. Antiquity 67:218-220,235256.
9 Arnold JR, Libby WF (1949) Age determinations by radiocarbon content: Checks with
samples of known age. Science 110:678-680.
10 de Vries H (1958) Variations in concentration of radiocarbon with time and location on
earth. Proceedings, Ned Akad Wetenschappen, Series B61:l.
11 Suess HE ( I 970) Bristlecone-pine calibration of radiocarbon time 5200 B.C. to present.
In Olsson IU (ed),Radiocarbon Variations and
Absolute CI?rotzology . Stockholm : A1mqvis t
and Wiksell, pp 303-3 12
12 Ralph EK, Michael HN, Han MC (1973)
Radiocarbon dates and reality. MASCA Newsletter 9:l-20.
13 Atkinson RJC (1975)Britishprehistoryand
the radiocarbon revolution. Antiquity 49: 173177.
14 Stuiver M, Long A and Kra RS (eds) (1993)
Calibration 1993.Radiocarbon 35:t -244.
15 Scott EM, Long A , Kra R (eds) (1990) Proceedings of the International Workshop on Intercomparison of Radiocarbon Laboratories.
Radiocarbon 32:253-397.
16 Kromer B, Becker B (1993) German oak
and pine 14c calibration, 7200-9439 BC. Radiocarbon 35: 125-135.
17 Becker B (1993) An 11.000-year German
oak and pine dendrochronology for radiocarbon calibration. Radiocarbon 35:201-2 13.
18 Bard E, Arnold M, Fairbanks RG, Hamelin
B (1993) 23qh-234U and 1% ages obtained by
mass spectrometry on corals. Radiocarbon
35:19 1-1 99.
19 Bard E, Stuiver M, Shackleton NJ (1993)
How accurate are our chronologies of the
past? In Eddy JA, Oeschger H (eds), Global
Changes in h e Perspective of the Past. New
York John Wiley & Sons.
20 Edwards RL (1993) A large drop in atmospheric 14C/12C and reduced melting in the
Younger Dryas, documented with 23Wh ages
of corak. Science 260: 962-968.
21 Stuiver M, Braziunas TG (1 993) Modeling
atmospheric 1% influences and 1% ages of
marine samples to 10,000 BC. Radiocarbon
35: 137-189.
22 Taylor RE, Stuiver M , Reimer PJ (n.d.) Development and extension of the calibration of
the radiocarbon time sca1e:Archaeological applications. Manuscript in preparation.
23 Mazaud A, Laj C, Bard E, Arnold M, Tric E
(1992) A geomagnctic calibration of the radiocarbon time-scale. In Bard E, Broecker WS
ARTICLES
(eds), The Last Degluciation: Absolute and Radiocarbon Chronologies. Berlin: Springer-Verlag, pp 163-1 69.
2 4 Sternberg RS, Damon PE (1992) Implications of dipole moment secular variation from
50,000-10,000 years for the radiocarbon record. Radiocarbon 34: 189-1 98.
25 Southon JR, Deino AL, Orsi G, Terrasi R,
Campajola L (1995) Calibration of the radiocarbon time scale at 37KA BP. Abstracts of Papers, 209th American Chemical Society
National Meeting, Part 2, p. 10.
26 Sonett CP (1992) A supernova shock ensemble model using Vostok 1OBe radioactivity.
Radiocarbon 34:239-245.
27 Vogel JC (1993) Pretoria calibration curve
for short-lived samples, 1930-3340BC. Radiocarbon 35: 73-85.
28 Barbetti M, Bird T, Doleal G, Taylor G,
Francey R, Cook E, Peterson M (1992) Radiocarbon variations from Tasmanian conifers:
First results from Late Pleistocene and Holocene logs. Radiocarbon 3430-817. (Also A.
Long, pers. comm.)
29 Kojo Y, Kalin RM, Long A (1994) High-precision “wiggle-matching” in radiocarbon dating. J Archaeol Sci 21:475479.
30 Mellars P (1990) A major “plateau” in the
radiocarbon time-scale at c. 9650 b.p.: The evidence from Star Carr (North Yorkshire). Antiquity 64:836-841.
31 Oeschger H, Houtermans J, Loosli H, Wahlen M (1970) The constancy of cosmic radiation from isotope studies in meteorites and on
the earth. In Olsson IU (ed), Radiocarbon
Variations and Absolute Chronology. Stockholm: Almqvist and Wiksell, pp 471496.
32 Anbar M (1978) The limitations of mass
spectrometric radiocarbon dating using CNions. in Gove HE (ed), ProceedingsoftheFirst
Conference on Radiocarbon Duting with Accelera
tors.Rochester: UniversityofRochester,pp 152155.
33 Wilson HW (1979) Possibility of measurement of 1% by mass spectrometer techniques.
In Berger R, Suess HE (eds), Radiocarbon Dating. Berkeley: University of California Press,
pp 238-245.
34 Muller RA (1977) Radioisotope dating with
a cyclotron. Science 196:489494.
35 Muller RA, Stephenson EJ, Mast TS (1978)
Radioisotope dating with an accelerator: A
blind measurement. Science 201 :347-348.
36 Bertsche KJ (1989) A small low energy cyclotron for radioisotope measurements. Unpublished Ph.D. thesis, University of
California, Berkeley.
37 Chen M-B (1994) Breakthrough of the mini
cyclotron AMS for 1% analysis. Presented at
the 15th International Radiocarbon Conference, Glascow, Scotland, August 13-19. 1994.
38 Nelson DE, Korteling RG, Scott WR (1977)
Carbon-14: Direct detection at natural concentrations. Science 198507-508.
39 Bennett CL, Beukens RP, Clover MR, Gove
HE, Liebert RB, Litherland AE, Purser KK,
Sondheim WE (1977) Radiocarbon dating using accelerators: Negative ions provide the
key. Science 198508-509.
40 Taylor RE (n.d.) Radiocarbon dating. In
Taylor RE, and Aitken M (eds) Chronometric
dating in Archaeology. New York: Plenum
Press, in press.
41 Davis JC, Proctor ID, Southon JR, Caffee
MW, Heikkinen DW, Roberts ML, Moore TL,
Turteltaub KW, Nelson DE, Lloyd DH, Vogel
JS (1990) LLNL/UC AMS facility and research
program. Nucl. Instrum. Methods in Phy Res
B52:269-272.
42 Kirner D, Taylor RE, Southon JR (n.d.) Re-
Evolutionary Anthropology 181
duction in backgrounds in microsamples for
AMS radiocarbon dating. Radiocarbon, in
press.
4 3 Kitagawa H, Masuzawa T, Makamura T,
Matsumoto E (1993) A batch preparation
method for graphite targets with low background for AMS 14C measurements. Radiocarbon 35:295-300.
44 Hedges REM, Humm MJ, Foreman J, Van
Klinken GJ, Bronk CR (1992) Developments
in sample combustion to carbon dioxide, and
in the Oxford AMS carbon dioxide ion source
system. Radiocarbon 34:306-311.
45 Hedges REM, Housley RA, Ramsey CB,
Van Klinken GJ (1994) Radiocarbon dates
from the Oxford AMS system: Archaeometry
Datelist 18. Archaeometry 36:337-374.
46 Long A, Benz BF, Donahue DJ, Jull AJT,
Toolin LJ (1989) First direct AMS dates on
early Maize from Tehuacin, Mexico. Radiocarbon 3 I : 1035-1040.
47 Wendorf F, Schild R, Close AE, Donahue
DJ, Jull AJT, Zabel TH, Wieckowska H,
Kobusiewicz M, Issawi B, el Haddidi N (1984)
New radiocarbon dates on the cereals from
Wadi Kubbaniya. Science 225:645-646.
4 8 Legge AJ (1986) Seeds of discontent: accelerator dates on some charred plant remains
from the Kebaran and Natufian cultures. In
Gowlett JAJ, Hedges REM (eds) Archaeological Results from Accelerator Dating. Oxford: Alden Press, pp. 13-2 l .
49 Dillehay TD, Meltzer DJ (1991) The First
Americans: Search and Research. Boca Raton:
CRC Press.
50 Haynes CV Jr ( 1 992) Contributions of radiocarbon dating to the geochronology of the
peoplingoftheNew World. InTaylorRE, Long
A, Kra RS (eds), Radiocarbon After Four Decades: An Interdisciplinary Perspective. New
York Springer-Verlag, pp 355-374.
51 Adovasio JM, Donahue J, Stuckenrath, R
(1990) The Meadowcroft radiocarbon chronology 1975-1990.Am. Antiquity 55:348-354.
5 2 Payen LA (1982) The pre-Clovis of North
America: Temporal and artifactual evidence.
Unpublished PhD dissertation, University of
California, Riverside.
5 3 Lynch TF (1990) Glacial-age man in South
America: A critical review. Am. Antiquity
55:12-36.
54 Meltzer DJ, Adovasio JM, Dillehay TD
(1994) On a Pleistocene human occupation at
Pedra Furada, Brazil. Antiquity 68:695-714.
55 Haynes CV Jr (1980) Paleoindian charcoal
from Meadowcroft Rockshelter: Is contamination a Problem? Am. Antiquity 45:582-587.
56 Tankersley KB, and Munson CA (1992)
Comments on the Meadowcroft Rockshelter
radiocarbon chronology and the recognition
of coal contaminants. Am. Antiquity 57321326.
57 Kuzmin YV (1994) Prehistoric colonization of northeastern Siberia and migration to
America: Radiocarbon evidence. Radiocarbon 361367-376.
58 Erlandson J, Walser R, Maxwell H, Bigelow
N, CookJ, Lively R, Adkins C, Dodson D, Higgs
C, Wilber J (1991) Two early sites of eastern
Beringia: Context and chronology in Alaskan
interior archaeology. Radiocarbon 33:35-50.
59 Waters MR (1985) Early man in the New
World: An evaluation of the radiocarbon dated
pre-Clovis sites in the Americas. In Mead JI,
Meltzer DJ (eds) Environments and Extinctions: Man in Late Glacial Norrh America.
Oronto: Center for the Study of Early Man. pp
125-1 43.
6 0 Taylor RE (1992) Radiocarbon dating of
bone: To collagen and beyond. In Taylor RE,
Long A, Kra RS (eds) Radiocarbon After Four
Decades: An Interdisciplinary Perspective. New
York: Springer-Verlag. pp 375402.
61 Hedges REM, Klinken GJ (1992) A review
of current approaches in the pretreatment of
bone for radiocarbon dating by AMS. Radiocarbon 34:279-291.
62 Stafford TW, Hare PE, Currie L, Jull AJT,
Donahue DJ (1990) Accuracy of North American human skeleton ages. Quaterary Res
4:lll-120.
63 Stafford TW, Hare PE, Currie L., Jull .4JT,
Donahue DJ (1991) Accelerator radiocarbon
dating at the molecular level. J Archaeol Sci
18:35-72.
64 Ajie HO, Kaplan IR, Hauschka PV, Kii-ner
D, Slota PJ, Taylor RE (1992) Radiocarbon
dating of bone osteocalcin: isolating and characterizing a non-collagen protein. Radiocarbon 34:296-305.
65 Brooks S, Brooks RH, Kennedy GE, Austin
J, Kirby JR, Payen LA, Slota PJ, Prior C, Taylor
RE (1991) The Haverty human skeletons:
Morphological, depositional, and geochronological characteristics. J California Great
Basin Anthropol 12:60-83.
6 6 Oakley KP (1980) Relative dating of the
fossil hominids of Europe. Bull. Br. Museum
Nat. Hist. (Geology) 34:l-63.
67 Hayden B, Nelson DE, Cataliotti-Valdina J
(1993) Dating the Cassis rufa shell from the
Mousterian levels of the Grotte du Prince,
Monaco. Antiquity 67609-612.
68 Gowlett JA, Hedges REM, Law iA, Perry C
(1987) Radiocarbon dates from the Oxford
AMS system: Archaeometry datelist 5. Archaeometry 29:125-155.
69 Mellars PA, Bricker HM, Gowlett JAF,
Hedges REM (1987) Radiocarbon accelerator
dating of French Upper Paleolithic Sites. Curr
Anthropol28:128-133.
70 Johnson F (1965) The impact of radiocarbon dating upon archaeology. in Chatters RM
and Olson EA (eds) Proceedings of tke Slxrh
International Conference Radiocarbon crnd
Tritium Dating. Springfield: Clearinghouse for
Federal Scientific and Technical Information,
pp 762-780.
71 Thomas DH (1978) The awful truth about
statistics in archaeology. Am Antiquity 43:
23 1-244.
72 Stuiver M, Polach H (1977) Discussion: Reporting of 1% data. Radiocarbon 19:355-363.
73 Long A, Kalin RM (1992) High-sensitivity
radiocarbon dating in the 50,000 to 70,000 BP
range without isotopic enrichment. Radiocarbon 34:351-359.
74 Erlenkeuser H (1979) A thermal diffusion
plant for radiocarbon isotope enrichment
from natural samples. In Berger R, Suess HE
(eds), Radiocarbon Dating. Berkeley: Uniiiersity of California Press, pp 216-237.
75 Hedges REM, Housley RA, Ramsey CB, van
Klinken GJ (1995) Radiocarbon dates from
the AMS system: Datelist 20. Archaeometry
37:429. Contains a complete list of the references for the Oxford AMS datelists 1 through
19, (1984 to 1995).
76 Stuiver M, Reimer PJ (1993) Extended 1%
data base and revised Calib 3.0 1% age calibration program. Radiocarbon 35:2 15-230.
77 Tric E, Valet J, Tucholka P, Paterne M, Labeyrie L, Guichard F, Tauxe L, Fontugne N
(1992) Paleointensity of the geomagnetic field
during the last 80,000 years. J Geophys Res
97:9337-935 I .
01996 Wiley-Liss, Inc.