REPORTS
15. P. Mansky, C. K. Harrison, P. M. Chaikin, R. A. Register,
N. Yao, Appl. Phys. Lett. 68, 2586 (1996).
16. K. Shin et al., Nano Lett. 2, 933 (2002).
17. E. Huang, L. Rockford, T. P. Russell, C. J. Hawker, Nature
395, 757 (1998).
18. This work was supported by NSF Grant Opportunities for Academic Liaison with Industry award
(DMI-0217816), the U.S. Department of Energy under
contract DE-FG03-88ER45375 and the Materials
Research Science and Engineering Centers at the
University of Massachusetts (DMR-0213695) and
Santa Barbara (DMR-0080034). D.Y.R. thanks the
support by the Postdoctoral Fellowship program of
Korea Science and Engineering Foundation in Korea. We
thank C. Silvas of Dow Chemical for providing the
brominated BCB.
Estimating Duration and Intensity
of Neoproterozoic Snowball
Glaciations from Ir Anomalies
Bernd Bodiselitsch,1 Christian Koeberl,1* Sharad Master,2
Wolf U. Reimold2
The Neoproterozoic glaciations supposedly ended in a supergreenhouse
environment, which led to rapid melting of the ice cover and precipitation
of the so-called cap carbonates. If Earth was covered with ice, then extraterrestrial material would have accumulated on and within the ice and
precipitated during rapid melting at the end of the glaciation. We found
iridium (Ir) anomalies at the base of cap carbonates in three drill cores from
the Eastern Congo craton. Our data confirm the presence of extended global
Neoproterozoic glaciations and indicate that the duration of the Marinoan
glacial episode was at least 3 million, and most likely 12 million, years.
The Snowball Earth hypothesis (1–3) states
that the Sturtian Eabout 710 million years ago
(Ma)^ and Marinoan glaciations (about 635
Ma) were of global extent and lasted for
several million years each. A variation of
this hypothesis, called the Slushball Earth,
requires milder conditions without substantial equatorial sea ice (4, 5). The Snowball
Earth glaciations would have ended abruptly
in a greenhouse environment, whereas the
Slushball would have experienced a slower
deglaciation. Silicate weathering and photosynthesis, which are the major sinks for CO2
at present, would have been inhibited by the
ice that covered both continents and oceans,
and huge amounts of CO2 could have accumulated in the atmosphere. Greenhouse
gases, particularly large amounts of CO2 (up
to È0.12 bar), would have been needed to
overcome the high albedo caused by the
glaciation and would have caused rapid
melting (6). This scenario has led to an
estimate for the duration of a Snowball
glaciation of È4 million to 30 million years
(My), under the assumption of a modern rate
for CO2 outgassing from subaerial volcanism, with no air-sea gas exchange, lower
solar luminosity in the Neoproterozoic, and
reduced pelagic deposition of carbonate to
reduce the release of volcanic CO2 at con1
Department of Geological Sciences, University of
Vienna, Althanstrasse 14, A-1090 Vienna, Austria.
2
Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private
Bag 3, Johannesburg 2050, South Africa.
*To whom correspondence should be addressed.
E-mail: [email protected]
vergent margins (7). This estimate is in broad
agreement with a 96- to 910-My duration derived from the d13C isotopic excursion in the
Otavi (North Namibia) cap carbonates (2).
Multiple magnetic polarity reversals within the
Elatina Formation (South Australia) suggest
a minimum time duration of several hundred
thousand to 1 million years for the Marinoan
glacial epoch (8).
If Earth was indeed covered by ice for long
periods, extraterrestrial material would have
accumulated on and within the ice and would
have been precipitated at the base of the cap
carbonates when the ice melted. To determine
whether such an extraterrestrial signal is
present at the base of the cap carbonates, we
studied three drill cores that intersected
diamictite/cap carbonate boundaries from
the Lufilian tectonic arc in the Democratic
Republic of the Congo and Zambia of the
Eastern Congo craton (Fig. 1) (9).
We measured the concentrations of 43 elements by neutron activation analysis and x-ray
fluorescence spectrometry, and we measured
the Ir content by multiparameter coincidence
spectrometry after neutron activation (10). Ir
anomalies were found at the base of all cap
carbonates after the Marinoan and Sturtian glaciations in the Nguba and Kundelungu Groups
at Kipushi, as well as after the Sturtian glacial
deposits in the Nguba Group at Chambishi. Ir
and other platinum-group elements are typical
proxies for extraterrestrial material, in which
they are much more abundant than in Earth_s
upper mantle and crust. The average Ir concentration in cosmic matter is about 4.6 105
parts per trillion (ppt) (11), which is greater
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Fig. S1
21 October 2004; accepted 22 February 2005
10.1126/science.1106604
by a factor of about 104 than in crustal terrestrial rocks.
The accretion of extraterrestrial material
during the Neoproterozoic is thought to have
been dominated by the delivery of interplanetary dust particles (IDPs) over a time
scale of millions of years (12). IDP accretion
rates vary over periods ranging from a few
thousand years (13) to millions of years (14).
During glaciations, IDPs, as well as extraterrestrial matter from asteroids and comets
that struck the Earth during that time (9),
would have accumulated on the ice sheet.
Substantial Ir anomalies up to almost 2
parts per billion (ppb) mark the base of the cap
carbonate deposits (Fig. 2) (9). Before ascribing an extraterrestrial origin to the Ir, possible
terrestrial sources, including reduced sedimentation rates, increased meteor ablation rates,
accretion of extraterrestrial material or of terrestrial dust (such as volcanic airborne particles), and anoxic conditions connected with
sulfide precipitation in seawater need to be considered. Our geochemical data clearly indicate
that the (substantial) Ir anomalies at the base
of the cap carbonates are derived from extraterrestrial sources, whereas the other (smaller) Ir
anomalies disappear or are greatly diminished
when ratios with other elements are used Esee
(9) for detailed considerations^. Thus, these variations can be attributed to changing deposition
rates or to the dissolution of an extraterrestrial
signal caused by the addition of sediment.
Further confirmation that the Ir anomaly at
the Kipushi Petit Conglomerat/cap carbonate
transition (KPCCT) is of extraterrestrial origin
comes from Cr/Ir and Au/Ir ratios of 2.9 103
and 0.11, respectively. These values are similar to those of C1 chondrites (carbonaceous
chondrites type 1) (5.5 103 and 0.29,
respectively) (15). Cr/Ir and Au/Ir ratios
from other samples show higher values
ranging from 8.4 104 to 1.8 106 and
1.1 to 80, respectively (Fig. 2).
In contrast to the sharp Ir anomaly at the
KPCCT, the Nguba Group Ir anomaly extends
over a broader interval, between 236.91 and
237.93 m, with a maximum of 648 ppt of Ir at
237.93 m. The integrated Ir concentrations are,
however, as high as those at the other location.
This Ir anomaly does not occur exactly at the
Kipushi Grand Conglomerat/cap carbonate
transition (KGCCT), but 0.63 m above, at
238.56 m in the cap carbonate succession (Fig.
2). Ir/element ratios with Fe, Cs, and Al,
compared with the Grand Conglomerat and
cap carbonate succession, are much higher in
8 APRIL 2005
239
REPORTS
B
EL
T
K
IB
A
R
A
N
100km
n,
ia nt
b r me
am di
ec se d
Pr lly vere
ca o
lo c
T
EL
B
240
N
IA
D
EN
B
U
BANGWEULU
BLOCK
LUFILIAN
ARC
10°
Archaean to lower
Proterozoic
I
Katanga Supergroup
II III
CHAMBISHI
to
R
ec
en
t
BAROTSE
BASIN
c
oz
oi
Sinda
Batholith
IV
Chipata
Granite
Hook
Granite
Complex
ZAMBEZI BELT
Zambezi Belt
ae
Z
MS
Zambezi Belt
Archaean to lower
Proterozoic
CHOMA-KALOMO
BLOCK
100km
15°
MOZAMBIQUE BELT
L
N
0
IR
U
M
ID
E
B
EL
T
Lu
an
gw
aV
all
ey
KIPUSHI
Pa
l
the Ir-enriched interval. Ni/Ir ratios of 1.1 104 at 236.91 m and 2.6 104 at 237.93 m,
respectively, are similar to the C1 chondritic
value of 2.3 104 and are distinctly lower
than the values throughout the cap carbonate
succession. Also, Au/Ir and Cr/Ir ratios of
0.46 and 1.05 104, respectively, at 237.93
m are also similar to the corresponding
chondritic values of 0.29 and 0.55 104
(15), whereas ratios below and above the Ir
anomaly are comparatively much higher. No
indicators exist for hydrothermal, hydrogenous, or volcanic influences or for strong
anoxic or reducing conditions that could
produce an Ir anomaly. Thus, this enrichment
was also likely caused by admixture of extraterrestrial material. The fact that the Ir anomaly after the Sturtian glaciation is characterized
by a broader peak of high Ir, Co, Cr, and Ni
values near the base of the cap carbonates
could be the result of a transgression and
slightly delayed deposition of the cap carbonates (3).
In the Chambishi core, the Ir anomaly is
located closer to the top of the Sturtian glacial
deposits (only 9 cm above the top of the Grand
Conglomerat) at 147.72 m than in the
Kundelungu succession. The Ir anomaly at
the Chambishi Grand Conglomerat/cap carbonate transition (CGCCT) is distinguished
from the other Ir anomalies by an Ir/Fe ratio
that is twice as high (Fig. 2). Changes in debris
rainout during the glaciation caused by basal
melting of ice sheets, floating glacier tongues,
or episodic migration of calved icebergs into
regions of warmer water (16) would affect the
relative abundances of Fe and Ir but not their
ratio. Thus, the occurrence of new source
material in the glacial deposits may indicate
warming periods during the glacial episode.
The Ir/Al ratio and element/Cs ratios for Ce,
Co, Cr, Eu, Fe, Hf, Sc, Ta, and Th at all Ir
anomalies in this succession show values that
are similar to the background values, except
the Ir/Cs ratio at the Ir anomaly at 170.70 m,
which is twice as high as that at the other Ir
anomalies. However, the carbonate succession
over the CGCCT Ir anomaly shows very high
Ir/Fe, Ir/Al, and Ir/Cs ratios and low Co/Ir
and Cr/Ir ratios, as well as Ir abundances of
45 to 60 ppt. This is very high, if we assume
that cap carbonates precipitated very rapidly
(17–19). Furthermore, at 144.96 m, strong
evidence for the input of volcanogenic material is signaled by the very high element/Al
ratios of Th, Ta, Hf, K, and Ti, which indicate
the inclusion of a silicic volcanic component
and/or a Hawaiian-like volcanic component
(20, 21) (Fig. 2). However, it does seem that
the deposited material was mostly extraterrestrial. It was probably not deposited at once
but rather swept into the sea from uplands
after a long glaciation, which was recorded
for the Sturtian period in the Nguba Group
succession from Kipushi.
ZIMBABWE
CRATON
30°
25°
Basement inliers in
Lufilian Arc
I - External fold-thrust belt
Strike-slip fault
II - Domes Region
Thrust
III - Synclinorial belt
International
boundary
IV - Katanga High
L - Lusaka
Borehole
MSZ - Mwembeshi Shear Zone
Fig. 1. Geological map of the Lufilian Arc in Congo and Zambia and part of the Zambezi belt,
showing location of drill holes [modified after (29, 30)].
Extraterrestrial influx rates (total mass)
estimated from ocean sediment studies based
on Ir and Os measurements from mid–Pacific
Ocean sediment samples range from 78 109 T 26 109 g yearj1 in the time interval
between 33 and 67 Ma (14) to 30 109 T
15 109 g yearj1 between 0 and 80 Ma (22).
This agrees well with other flux estimations
from different time intervals from today to
700,000 years ago equal to È40 109 g
yearj1, derived from 3He analyses in Pacific,
Atlantic, and Indian Ocean sediments (23–25).
If we assume an Ir concentration of 500 ng
per g of extraterrestrial material and an Earth
surface area of 5.1 1018 cm2, Ir influx rates
of 8 T 3 ng cmj2 Myj1 to 3 T 1.5 ng cmj2
Myj1 are implied. However, the Ir flux
estimated by (26), which was calculated
from fossil meteorites in Lower Ordovician
marine limestones from Kinnekulle, Sweden, at È30 ng cmj2 Myj1, indicates that
accretion rates of extraterrestrial material were
an order of magnitude higher during the Early
Ordovician than at present.
We made the conservative assumption that
all Ir at the KPCCT is extraterrestrial (thus,
no background needs to be calculated and
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removed) and that no extraterrestrial material
was deposited by major impact events. Then
we integrated the elevated Ir abundances that
represent the peak and took a rock density of
2.5 g cmj3 into account, to obtain an Ir concentration of 93 ng cmj2 at the KPCCT. If
the Ir influx rates discussed above are used, a
maximum duration of the Marinoan glaciation
of 41 T 20 My and a minimum of 12 T 4 My
are obtained for the Ir flux during 0 to 80 Ma,
and a duration of È3 My if we assume the Ir
input flux determined for the Early Ordovician. Nevertheless, because there probably was
an unusually enhanced flux of extraterrestrial
material in the Early Ordovician, we view the
normal (0 to 80 Ma) values as the most representative, leading to a most likely duration
of the Marinoan glaciation of 12 My.
A problem in Neoproterozoic geology is
the lack of reliable radiometric dates. For the
Marinoan glaciation, age limits between 610
and 575 Ma are based on assumed relationships of Marinoan-to-Varanger glacial intervals from different locations (27), as well
as estimations of sedimentation rate for the
time between glacial deposition and for the
Precambrian/Cambrian boundary (28). Recent
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REPORTS
Co/Ir
[x10 -3 ]
Cr/Ir
[x10 -3 ]
Ni/Ir
[x10 -3 ]
Au/Ir
Ti/Al
Middle Kundelungu
Group
Ir/Al
[x10 -9 ]
Upper Nguba
Group
Limestone
Calcaire Rose
Limestone
Kakontwe
50 150
50 150 500 1500 300 900
20 50
0.06 0.10
Dolomitc
Shale
Middle Nguba Group
Diamictite
Petit Conglomerat
Diamictite
Grand Conglomerat
40 100
100
400 200 700
100 300
20
70
0.07 0.13
Finely Laminated
Limestone
(mm Scale)
Mwashya Subgroup
Laminated
Shale
Breccia
Laminated
AnhydriteDolomite
Upper Roan Subgroup
Nguba Group
Roan Group
Sturtian Glaciation - Chambishi MJZC9
Sturtian Glaciation - Kipushi KHI 115034HZ-S
Marinoan Glaciation - Kipushi KHI 1150PVSSW
Core
Fig. 2. Stratigraphic A
columns showing Ir
Ir/Cs
Depth
Strat.
Ir
Ir/Fe
Gr.
Lith.
abundances and se[x10 -6 ]
[m]
unit
[ppt]
[x10 -9 ]
lected element ratio
0
Ku 1.2.3
profiles. (A) The middle
part of the Kundelungu
Ku 1.2.2
Group to the top of the
30
Nguba Group, Kipushi,
Ku 1.2.1
Congo, showing Petit
60
Conglomerat from the
Ku 1.1
Marinoan glaciation
overlain by the Calcaire
90
Rose cap carbonates.
Ng 1.2.3
(B) The middle of the
120
Nguba Group, Kipushi,
Congo, showing Grand
600 1800 100 300 1000 4500
Conglomerat from the
Sturtian glaciation over- B
lain by the Calcaire de
Kakontwe cap carbon180
ates. (C) The Sturtian
Ng 1.2.1
Grand Conglomerat
210
overlain by the Calcaire
de Kakontwe cap car240
bonates from the mid270
dle of the Nguba Group,
further to the Mwashya
Ng 1.1
300
Subgroup at the base
of the Nguba Group,
and the Upper Roan
100 450
10 40 1000 5000
Subgroup at the top
of the Roan Group, C
Chambishi, Zambia.
100
For tables of elemental
Ng 1.2.1
concentrations, see (9).
Analytical uncertainty
150
for Ir is 95 relative %
Ng 1.1
(rel%) for values 9500
ppt and 5 to 15 rel%
for lower values. Ana200
lytical uncertainties for
elemental ratios are
between 5 and 15 rel%.
250
Ku 1.2.3, dolomitic shale;
Ku 1.2.2, dolomitic shale;
Ku 1.2.1, Calcaire Rose;
Ku 1.1, Petit Conglom300
erat; Ng 1.2.3, dolomitic
shale; Ng 1.2.1, Calcaire
de Kakontwe; Ng 1.1,
350
Grand Conglomerat;
Strat. Unit, stratigraphic unit; Lith., lithology.
400
The dip of the beds at
Kipushi is not vertical
100 400 30 90 100 500
but is about 70-. Thus,
borehole depths do not
represent true stratigraphic thickness.
U-Pb dating indicates that the Marinoan glaciation took place at 635.5 T 1.2 Ma (9). The
duration of glaciation in the Neoproterozoic is
difficult to quantify because of uncertain age
limits and nonuniform, noncontinuous sedimentary records. Previous methods used to
estimate the duration of Neoproterozoic glaciation are as follows: magnetic polarity intervals (8), calculation of CO2 amounts needed
to overcome a totally frozen Earth (6), and
thermal subsidence modeling (2). The use of
Ir anomalies located immediately at the transition from glacial deposits to cap carbonates
is an another possible way to estimate the du-
Laminated
Dolomitic
Shale
100
400 200 600 600 2000 500 1500 50 200
ration of long glacial epochs. The advantage
of this method is that samples from only the
transition region of an undisturbed stratum are
needed, otherwise a permanent ice sheet must
have existed during the glaciation. We calculated a minimum duration for the Marinoan
glacial epoch of È3 My, assuming the same
Ir flux as obtained for the Lower Ordovician,
and a most likely duration of about 12 My,
based on the average accretion rate.
For the Sturtian event, no Ir anomaly was
found directly at the transition from the
Sturtian glacial deposits to cap carbonates in
the Chambishi and Kipushi successions, but it
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5
was found 9 and 63 cm above, respectively.
Furthermore, the extraterrestrial Ir is distributed
over a wider interval in the cap carbonate succession. This distribution implies that extraterrestrial material was accumulated in upland
areas over thousands or millions of years and
was then washed into the sea after deglaciation. Unlike the Marinoan cap carbonates,
Sturtian cap carbonates lack a transgressive
stage, which implies that seawater did not reach
critical oversaturation with respect to carbonate
until after the postglacial marine transgression
(3). Therefore, the extraterrestrial Ir in a global
ice cover would have been partly dispersed
8 APRIL 2005
241
REPORTS
before the cap carbonate precipitated. This may
explain the lack of a sharp Ir spike at the base
of the Sturtian cap carbonate. Alternatively,
during the Sturtian glacial epoch, Earth_s
surface may not have been fully covered with
ice on which extraterrestrial material could
accumulate for a long time; however, the presence of banded iron formations in and below
Sturtian glacials suggests that the ocean was
ice-covered at that time (3).
References and Notes
1. J. L. Kirschvink, in The Proterozoic Biosphere, J. W.
Schopf, C. Klein, Eds. (Cambridge Univ. Press,
Cambridge, 1992), pp. 51–52.
2. P. F. Hoffman, A. J. Kaufman, G. P. Halverson, D. P.
Schrag, Science 281, 1342 (1998).
3. P. E. Hoffman, D. P. Schrag, Terra Nova 14, 129 (2002).
4. W. T. Hyde, T. J. Crowley, S. K. Baum, W. R. Peltier,
Nature 405, 425 (2000).
5. T. J. Crowley, W. T. Hyde, W. R. Peltier, Geophys. Res.
Lett. 28, 283 (2001).
6. K. Caldeira, J. F. Kasting, Nature 359, 226 (1992).
7. K. Caldeira, Geology 19, 204 (1991).
8. L. E. Sohl, N. Christie-Blick, D. V. Kent, Geol. Soc. Am.
Bull. 111, 1120 (1999).
9. Materials and methods are available as supporting
material on Science Online.
10. C. Koeberl, H. Huber, J. Radioanal. Nucl. Chem. 244,
655 (2000).
11. J. T. Wasson, in Meteorites: Their Record of Solar
System History (Freeman, New York, 1985), p. 267.
12. Z. Ceplecha, Astron. Astrophys. 263, 361 (1992).
13. K. A. Parley, D. B. Patterson, Nature 378, 600 (1995).
14. F. T. Kyte, J. T. Wasson, Science 232, 1225 (1986).
15. E. Anders, N. Grevesse, Geochim. Cosmochim. Acta
53, 197 (1989).
16. H. Heinrich, Quat. Res. 29, 142 (1988).
17. J. D. Roberts, J. Geol. 84, 47 (1974).
18. I. J. Fairchild, in Sedimentology Review, V. P. Wright,
Ed. (Blackwell, Oxford, 1993), pp. 1–16.
19. M. J. Kennedy, J. Sediment. Res. 66, 1050 (1996).
20. D. C. Noble, W. L. Rigot, H. R. Bowman, GSA Spec.
Pap. 180, 77 (1979).
21. Basaltic Volcanism Study Project, in Basaltic Volcanism
on the Terrestrial Planets (Pergamon, New York, 1981),
p. 1286.
22. B. Peucker-Ehrenbrink, Geochim. Cosmochim. Acta 60,
3192 (1996).
23. F. Marcantonio et al., Nature 383, 705 (1996).
The Brain of LB1,
Homo floresiensis
Dean Falk,1* Charles Hildebolt,2 Kirk Smith,2 M. J. Morwood,3
Thomas Sutikna,4 Peter Brown,3 Jatmiko,4 E. Wayhu Saptomo,4
Barry Brunsden,2 Fred Prior2
24. F. Marcantonio et al., Geochim. Cosmochim. Acta. 62,
1535 (1998).
25. F. Marcantonio et al., Earth Planet. Sci. Lett. 170, 157
(1999).
26. B. Schmitz, B. Peucker-Ehrenbrink, M. Lindström, M.
Tassinari, Science 278, 88 (1997).
27. A. H. Knoll, M. R. Walter, Nature 356, 673 (1992).
28. J. P. Grotzinger, S. A. Bowring, B. Z. Saylor, A. J.
Kaufman, Science 270, 598 (1995).
29. H. Porada, Precambrian Res. 44, 103 (1989).
30. R. M. Key et al., J. Afr. Earth Sci. 33, 503 (2001).
31. We thank H. Rice and F. Popp from the University of
Vienna for discussions and comments. This work was
supported by the Austrian Science Foundation. This
is University of the Witwatersrand Impact Cratering
Research Group publication no. 93.
Supporting Online Material
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DC1
Materials and Methods
Fig. S1
Tables S1 to S3
References and Notes
30 August 2004; accepted 18 January 2005
10.1126/science.1104657
tate shape comparisons (Fig. 1 and fig. S2).
LB1_s shape most resembles that of ZKD XI,
which is typical of classic H. erectus from
China and Java (Trinil) (fig. S3). Both endocasts
are noticeably wider caudally than rostrally
(Fig. 1A), wider ventrally than dorsally (fig.
S2), and relatively long and low in lateral
profile (Fig. 1B). However, LB1 lacks the de-
The brain of Homo floresiensis was assessed by comparing a virtual endocast
from the type specimen (LB1) with endocasts from great apes, Homo erectus,
Homo sapiens, a human pygmy, a human microcephalic, specimen number Sts 5
(Australopithecus africanus), and specimen number WT 17000 (Paranthropus
aethiopicus). Morphometric, allometric, and shape data indicate that LB1 is not
a microcephalic or pygmy. LB1’s brain/body size ratio scales like that of an
australopithecine, but its endocast shape resembles that of Homo erectus. LB1
has derived frontal and temporal lobes and a lunate sulcus in a derived position,
which are consistent with capabilities for higher cognitive processing.
The type specimen of Homo floresiensis (LB1,
female) (1) has a brain size of È400 cm3,
which is similar to that of Australopithecus
afarensis specimen AL 288-1 (Lucy) (2), who
lived approximately 3.0 million years ago. Yet
LB1_s species was associated with big-game
stone technology, remains of Stegodon, and
charred animal bones that hint at the use of fire
and cooking. Its ancestors also had to cross the
sea to reach the Indonesian island of Flores (3).
Could a tiny hominin with an ape-sized brain
really have engaged in such advanced behaviors? Some workers reject the notion that LB1
1
Department of Anthropology, Florida State University, Tallahassee, FL 32306, USA. 2Mallinckrodt Institute of Radiology, Washington University School of
Medicine, St. Louis, MO 63110, USA. 3Archaeology
and Palaeoanthropology, University of New England,
Armidale, New South Wales 2351, Australia. 4Indonesian Centre for Archaeology, JI. Raya Condet
Pejaten No. 4, Jakarta 12001, Indonesia.
*To whom correspondence should be addressed.
E-mail: [email protected]
242
represents a new species that was closely tied
to H. erectus (1) and suggest instead that it was
a pathological human microcephalic (4). To
help address this debate, we compared threedimensional computed tomographic (3DCT)
reconstructions of the internal braincase (virtual endocasts) that reproduce details of external brain morphology, including sulci, vessels,
sinuses, cranial capacity, and shape (5–8),
from LB1, an adult female chimpanzee, an
adult female H. erectus (specimen ZKD XI), a
contemporary woman, and a European microcephalic. To broaden taxonomic comparisons
and supplement limited sample size, our analysis also included endocasts of the skulls of
specimen Sts 5 (A. africanus), specimen
KNM-WT 17000 (Paranthropus aethiopicus),
10 humans, 10 gorillas, 18 chimpanzees (9), an
adult female pygmy, and five H. erectus.
Our virtual cranial capacity estimate for
LB1 is 417 cm3 (10). Virtual endocasts of the
microcephalic, modern woman, H. erectus, and
chimpanzee were scaled to 417 cm3 to facili-
8 APRIL 2005
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Fig. 1. Comparisons of virtual endocasts of LB1
(center). (A) Dorsal views. (B) Right lateral
views. Hs, H. sapiens; Pt, Pan troglodytes; mcHs,
a human microcephalic; He, H. erectus.
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