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Author Topic: New Work May Complicate History Of Neandertals and H. sapiens  (Read 3504 times)
Charlie Hatchett
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Posts: 101

« on: October 25, 2009, 08:31:57 PM »

"...Recent sequencing of
ancient Neandertal DNA suggests that their
common ancestor with modern humans lived
a bit less than 500,000 years ago, quite likely
in Africa (Science, 13 February, p. 870).
Some researchers call this common ancestor
H. heidelbergensis, although they disagree
about which fossils to group in that species.
In his talk at Gibraltar, Tattersall argued that
the real evolutionary picture might be much
more complicated..."

"...Tattersall agreed that some fossils—
including the 225,000-year-old Steinheim
skull found near Stuttgart, Germany, and a
400,000-year-old skull from Swanscombe,
England—might fit Hublin’s “accretion
model.” But others, he said, emphatically do
not. The big stumbling block is one of the
most spectacular fossil finds in the history of
paleoanthropology: the discovery since the
mid-1990s of thousands of bones from some
28 hominin individuals at the cave site
of Sima de los Huesos in northern Spain
(Science, 2 March 2001, p. 1722). The published
finds include four hominin skulls with
both Neandertal-like and non-Neandertal features.
And the team working at the site, co-led
by anthropologist Juan Luis Arsuaga of the
Complutense University of Madrid, has
assigned its fossils to H. heidelbergensis.
The Sima fossils were f irst dated to
about 350,000 years ago. But more recent
uranium-series dating, led by geochronologist
James Bischoff of the U.S. Geological
Survey in Menlo Park, California, suggests
that they are at least 530,000 years old. That
would make them as old as or older than
“classic” H. heidelbergensis fossils from
southern France, Greece, and other places—
fossils that the Sima skulls don’t much resemble,
Tattersall insisted. Tattersall concludes
that two or more hominin lineages must have
existed side by side in Europe for several hundred
thousand years before H. sapiens arrived
from Africa. One line led to the Neandertals
and may have included the Sima fossils;
another, rightly called H. heidelbergensis,
went extinct while the Neandertals lived on
until at least 30,000 years ago..."

Jim Bischoff is having a heyday recently!


"...Tattersall then looked at Arsuaga, who
was sitting in the audience waiting to speak
next: “My central plea is to the colleagues
who assigned the Sima de los Huesos fossils
to H. heidelbergensis. They are clearly not
Neandertals, but not being a Neandertal does
not make them H. heidelbergensis. They need
another name.” A hush fell over the room as Tattersall sat
down and Arsuaga got up to speak. To nearly
everyone’s surprise, Arsuaga agreed that the
Sima de los Huesos skulls looked nothing
like other H. heidelbergensis specimens. Nor,
he said, do 13 other skulls his team had
recently excavated there. “We have always
said that we put the Sima hominins under the
H. heidelbergensis umbrella for convenience,
for practical reasons,” Arsuaga said, adding
that his team agrees with Tattersall that the
accretion scenario is not likely. But he resisted
Tattersall’s call to rename the Sima fossils,
at least until the remaining 13 skulls are published
in coming months..."

"...Chris Stringer, a paleoanthropologist at the
Natural History Museum in London whose
early research led to the recognition of H. heidelbergensis
as a formal species, says a lot is
riding on the new 530,000-year minimum date
for the Sima fossils. If the dating is right,
Stringer says, “it would be evident that an early
form of Neandertal was [in Europe] alongside
of H. heidelbergensis.” But he argues that the
dating is at the limit of the uranium-series technique
and also contradicts other molecular and
fossil evidence suggesting that the Neandertal
line split off somewhat after 500,000 years ago.
Bischoff defends his methodology, however,
saying that the date is a “conservative” estimate
and that the Sima hominins could be even older
than 530,000 years but not younger..."

New Work May Complicate History
Of Neandertals and H. sapiens

Charlie Hatchett
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Posts: 101

« Reply #1 on: October 25, 2009, 08:33:14 PM »

High-resolution U-series dates from the Sima de los Huesos
hominids yields 600+infinity/-66 kyrs: implications for the
evolution of the early Neanderthal lineage
James L. Bischoff a,*, Ross W. Williams b, Robert J. Rosenbauer c,
Arantza Aramburu d, Juan Luis Arsuaga e,f, Nuria Garcı´a e,f, Gloria Cuenca-Besco´s g
Journal of Archaeological Science 34 (2007) 763e770

The Sima de los Huesos site of the Atapuerca complex near Burgos, Spain contains the skeletal remains of at least 28 individuals in a mudbreccia underlying an accumulation of the Middle Pleistocene cave bear (Ursus deningeri). We report here on new high-precision dates on the recently discovered speleothem SRA-3 overlaying human bones within the Sima de los Huesos. Earlier analyses of this speleothem by TIMS
(thermal-ionization mass-spectrometry) showed the lower part to be indistinguishable from internal isotopic equilibrium at the precision of the TIMS instrumentation used, yielding minimum age of 350 kyr (kyr¼ 103 yr before present). Reanalysis of six samples of SRA-3 by inductivelycoupled plasma-multicollector mass-spectrometry (ICP-MS) produced high-precision analytical results allowing calculation of finite dates. The
new dates cluster around 600 kyr. A conservative conclusion takes the lower error limit ages as the minimum age of the speleothem, or 530 kyr. This places the SH hominids at the very beginnings of the Neandertal evolutionary lineage.

“…The SH collection now comprises more than 80% of the Middle Pleistocene record world-wide for the genus Homo and provides
for an unprecedented study of within-population variations
(Arsuaga et al., 1997c; Lorenzo et al., 1998). The SH hominids
are the evolutionary ancestors to the Neandertals (Arsuaga
et al., 1991, 1993; Arsuaga et al., 1997a,b) and thus, dating
of the deposit is clearly of great importance…”

“…Since 2003, over 55 human fossils have been recovered from below
a recently discovered speleothem at SRA while only a few human
bones have been recovered at SRB, and SRM. A jaw fragment
(AT 75) with two teeth (left M2eM3), designated as Individual 6 from the site, was originally recovered in the Sima proper from area A (square Q 10), together with an isolated tooth (AT-1760 ¼ left P3) from the same individual (also found in Q 10). Another tooth from this individual
(AT-1763 ¼ left P4) was subsequently found at SRB, and yet
another (AT-1759 ¼ left M1) from area B (square T-13)
(Bermu´dez de Castro et al., 2004). One tooth from SRA
(AT-4328 ¼ right P3) has also been assigned to Individual 6,
based on the compatibility of the wear stages and anatomical
similarity in the morphology of the cusps. Thus, Individual 6 is
represented in SRA, SRB, area B and area A of the Sima; a distribution
which covers the entire extent of the Sima deposits
(Figs. 3 and 4). This distribution suggests that the date for
the deposit established in SRA also applies to the rest of the
Rampa and SH proper…”

“…The entire sequence of human remains is capped by a sheet of
speleothem flowstone (Colada), generally earthy and impure. U series
and radiocarbon dating indicates the Colada formed from
about 68 kyr to about 25 kyr. The range of U-series nominal
dates for 25 bear bones (88-220 kyr) and for 16 human bones
(114-182 kyr) that underlie the Colada are similar and rather
broad, but are clearly affected by irregular post-depositional
uranium cycling. Nine additional bear bones were analyzed by
the combined ESR and U-series method (Bischoff et al.,
1997). Dates for six of these yielded 200 +/- 4 kyr whereas the
other three yielded dates of 320 +/-4 kyr. Thus, the earlier results
seemed to provide a firm minimum age of about 200 kyr for the
human entry; and suggestive evidence of possible entry prior to
320 kyr…”

“…a 14-cm thick in situ speleothem (SRA 3, Figs. 4 and 5) lying
stratigraphically beneath the Colada speleothem and, therefore,
older than the Colada. Immediately below the SRA 3
speleothem, bones belonging to at least two individuals of
the bear species, U. deningeri, were recovered, and among
the bear bones two human phalanges were found. Subsequent
excavations have recovered over 55 additional human fossils
from below the SRA 3 speleothem. The newly exposed speleothem
was examined carefully to establish that it is, indeed, in
situ, that it formed in place covering the bones. The lowermost
1 cm contains fragments of the underlying sediment and small
fragments of bone. Therefore SRA-3 is clearly younger than
the human bones. The speleothem is of high purity and crystallinity
and, therefore, excellent material for U-series dating
to provide a minimum age for the human bones. The speleothem
is laminated (ca. 1 cm laminae, Fig. 6), is pure calcite,
containing less than 0$3 wt% organic carbon and containing
exceptionally low amounts of detrital contamination. The laminae
truncate at about 4 cm below the top, representing a hiatus
in speleothem growth…”

“…U-series analyses by thermal-ionization mass-spectrometry
(TIMS) of 14 samples reported in 2003 (Bischoff et al., 2003)
were taken about every centimeter spanning the entire 14 cm
thickness. Results indicated that the uranium contents are relatively
high averaging 0.6 ppm, and the 230Th/232Th ratios are
all well in excess of 20, the limiting value below which extraneous
(detrital) Th significantly affects the date (Bischoff and
Fitzpatrick, 1991). Three samples above the hiatus yielded finite
dates in stratigraphic order from 153 to 281 kyr. Those below
the hiatus were indistinguishable from internal isotopic
equilibrium at the precision we were able to obtain from the
TIMS the instrumentation used at the time, yielding minimum
age of 350 kyr…”

“…All the samples yielded finite dates
ranging from 563 to 668 kyr (average 600 kyr). Two of the samples,
at _5 cm and at 10.5 cm, had upper limits of equilibrium
(infinite age). All the others had finite ages for their upper limit.
A conservative approach is to consider the lower limit ages as
the minimum age of the speleothem, a range from 513 to
571 kyr (average 530 kyr). We show in Table 2 the analytical
results of our analyses of solutions of equilibrium standards.
The results show that we obtain equilibrium values within analytical
error. Therefore, in as-much as the composition of the
SRA-3 samples are very close to equilibrium, they are finite,
and we deem the calculated dates to be real because of internal
consistency and reproducibility, and because of our results on
the equilibrium standards. Results of the two groups are shown
on an evolution diagram (Ludwig, 2000) in Fig. 7.…”

“…radiometric results should be considered conclusive for a minimum
age of 530 kyr (MIS 14) for the SH sediments. In addition,
the presence of several skeletal parts representing the
same individual (Individual 6) in different sectors of the
Sima complex, including below the SRA-3 speleothem, suggests
that the age of the speleothem can be applied to the entire
hominid sample from the site…”

E.P. Grondine
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Posts: 107

« Reply #2 on: October 26, 2009, 10:54:20 PM »

Thanks for the news. 

It's good to see a frank discussion of taxa, and I expect that more will be held as more data is recovered.

In my opinion, one of the big problems the palaeoanthropology community is facing is exactly how to name a robust Erectus, as "Robustus" is already taken for a separate and extinct line. I went with Heidelbergensis at the time of my book, and took a lot of heat for it, even though I explained why in a footnote.

Once again, I'd suggest looking at the Zamanshin impact, 1 Mya,  as being the event which separated the common ancestral neanderthal/sapien.

If the data finally suggests a different date, then I'd suggest looking for another major comet or asteroid impact.

But then I've been wrong before, and I reserve the right to be wrong both now and in the future.

(Two major examples: one, never stumbling across the shiva impact when refuting Keller; two, ascribing the die off at 8,350 BCE to comet impact, when the impacts occurred ca. 10,900 BCE. And there were more...)

E.P. Grondine
Man and Impact in the Americas
(a pretty good book, really)
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