Scientists on Thursday described an astonishing collection of 17
fossil skulls unearthed in the cave dating from about 430,000 years
ago of an extinct human species closely related to the Neanderthals
who later prospered across Europe and Asia from roughly 250,000 to
40,000 years ago.
The skulls, reassembled from jumbled fragments from a small chamber
deep within the cave, are the oldest known fossils to show clear
Neanderthal features in the skull, although the scientists stopped
short of calling them actual Neanderthals.
"Never before had such a tremendous collection of hominin (extinct
human) skulls been discovered at a single site. For the first time
in history we can study a fossil population, not isolated fossils,"
said paleontologist Juan Luis Arsuaga of the Universidad Complutense
de Madrid, who led the study published in the journal Science.
The site did not yield just skulls. The scientists have pieced
together skeletons of at least 28 individuals, Arsuaga said, mostly
young adults and teenagers but with a few older adults and children.
Researchers have been conducting excavations at the location -
designated a UNESCO world heritage site - over the past four decades
and previously described some of the skulls and other remains. There
has been a spirited debate about the age of the fossils and the
precise species they represent.
The researchers did not assign them to any specific species, noting
genetic differences from Neanderthals - formal name Homo
neanderthalensis - as evidenced by DNA recovered from one of the
Sima fossils. They also said the skulls were not representative of
another species that lived at the time, Homo heidelbergensis,
because of jawbone differences.
The scientists found Neanderthal-like characteristics in the skulls
as well as features associated with more primitive humans. This
backs the idea that Neanderthals developed their various defining
characteristics separately and at different times – a "mosaic
pattern" of evolution, they said.
The Sima individuals lived during the Middle Pleistocene, a span of
about half a million years for which scientists are seeking a better
understanding of human evolution.
"Phylogenetically, they are early members of the Neanderthal
lineage. The specific (species) name is still an open question. I am
not in favor of calling them just 'Neanderthals'," Arsuaga told
'GAME OF THRONES'
The skulls showed that the earliest changes in the Neanderthal
lineage occurred in the teeth, jaw and face, with those
characteristics related to a specialization in chewing, perhaps
related to meat eating. The skulls retained some primitive traits
like a smaller brain case. The Neanderthal trait of an elongated and
rounded brain case appeared later.
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Arsuaga said the fossils suggest that human evolution in Europe at
the time was not a slow, orderly process encompassing uniform
changes across the continent's various peoples, but rather something
more chaotic akin to the struggles between clans in the fantasy TV
series "Game of Thrones."
Neanderthals are the closest extinct relative to our species, Homo
sapiens, and disappeared after early modern humans first trekked
into Europe from Africa. Genetic evidence shows there was
inter-breeding between Neanderthals and Homo sapiens.
The researchers used six sophisticated techniques to establish the
age of the Sima fossils, which previously had been estimated as
being roughly 530,000 to 600,000 years old, dates that had
complicated the question as to the species involved.
"As a result of this study we are able to answer two of the most
important questions that surround the Sima de los Huesos fossil
assemblage: Who were these people? And when were they living on the
landscape?" said another of the researchers, geochronologist Lee
Arnold of the University of Adelaide in Australia.
"Both these findings are critical to better understanding the
complex patterns of human evolution across Europe during the Middle
Pleistocene, not least because the site contains more than 80
percent of the world's known Middle Pleistocene fossil record for
the genus Homo," Arnold added.
(Reporting by Will Dunham; Editing by James Dalgleish)
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