ゆっくりと成長していた - Living, Loving, Thinking, Again

Agence France-Presse “Neanderthal boy's skull reveals they grew like modern boys” https://www.theguardian.com/science/2017/sep/22/neanderthal-boys-skull-reveals-they-grew-like-modern-boys

西班牙のEl Sidron遺跡*1で発見された４万9000年前に亡くなった７歳のネアンデルタール人 *2の男の子を巡る西班牙国立自然科学博物館*3の研究ティームの分析について。記事のタイトルはちょっとミスリーディングかも知れない。問題は寧ろネアンデルタール人と私たちホモ・サピエンスとの微妙な差異であるので。

He was still growing when he died, and his brain was about 87.5% the size of an average adult Neanderthal brain, said the report.
A modern human boy would be expected to have a brain weight about 95% of an adult’s by that age, it added.
An analysis of his vertebrae showed some had not yet fused. These same bones tend to fuse in contemporary people at a younger age, between four and six.

Adam Van Arsdale氏（人類学者、ウェスレイ・カレッジ）*4のコメント；

The study is “an important contribution to our understanding of human evolution,” and “consistent with a now vast and growing body of research that demonstrates the similarities between Neanderthals and living humans,” he said.
It also sheds new light on the history of human development. Neanderthals evolved separately – in western Eurasia – from humans who emerged from Africa, but they had plenty in common.

何故ネアンデルタール人の脳は大きいのか問題。時間をかけた（ゆっくりとした）成長；

Neanderthals are known to have had much larger skulls than people do today, and possibly larger brains, although this did not necessarily make them smarter.
But little is known about how Neanderthals became this way. One theory is that they grew up faster – that Neanderthal children reached adult size more quickly than we do.
Previous studies suggesting this path have relied mainly on dental clues.
The latest study is based on a more complete specimen. The Neanderthal child’s skeleton included 36% of his left side and parts of his skull along with baby and adult teeth.
After studying his remains, researchers believe that instead of simply outpacing contemporary people in brain growth, Neanderthals may have grown up over a longer period of time.
“One mechanism of growing a larger brain would be expanding the period of growth,” Rios*5 told reporters.

また、この子どもの死因の謎。カニバリズム疑惑；

Just how the Neanderthal child died is a mystery.
Scientists have found no evidence of disease, and described him as “sturdy,” weighing 57 pounds (26 kilograms) and standing just over three and a half feet tall.
But his bones also contained marks similar to other remains at the cave, where other studies have suggested cannibalism may have been rampant*6.
“The bones have some marks, but we do not know the cause of death,” co-author Antonio Rosas, chairman of the Paleoanthropology Group at Museo Nacional de Ciencias Naturales, said.

そもそも子どもの年齢を「7歳」と断定したことなどへの疑問；

Milford Wolpoff*7, professor of anthropology at the University of Michigan, agreed “that Neandertals may have had extended period of brain growth.”
But he questioned the authors’ attempt to age the child so precisely.
“Age determination for dead people is at best an estimate, and giving an age estimate to two decimal places (they say 7.69 years of age) really overstates the accuracy that is possible,” said Wolpoff, who was not involved in the study.
He also questioned the comparison to modern humans, since different rates of brain growth are common across various people and time periods.
Furthermore, assessments of Neanderthal brain size could be skewed high, because most of the specimens paleoanthropologists have belonged to males, who were physically larger than females. This may lead us to believe Neanderthals were bigger on average than they actually were, he added.
Therefore, trying to derive much meaning from small skull size differences might be a fruitless endeavour when the bigger picture is clear.
“Neanderthal brain growth may or may not be like any human population, but surely seems to fit within the normal human range,” Wolpoff said.

See also

Jen Viegas “Neanderthal Boy Found in Spanish Cave Was Human-Like, but With a Larger Brain” https://www.seeker.com/culture/archaeology/neanderthal-boy-found-in-spanish-cave-was-human-like-but-with-a-larger-brain

*1:See eg. “El Sidrón Site” http://www.biology-online.org/articles/paleobiology_comparative_morphology_late/el_sidrn_site.html https://en.wikipedia.org/wiki/Sidr%C3%B3n_Cave

*3:http://www.mncn.csic.es/ See eg. https://en.wikipedia.org/wiki/Museo_Nacional_de_Ciencias_Naturales

*4:https://blogs.wellesley.edu/vanarsdale/

*5:Luis Rios 西班牙国立自然科学博物館。

*6:See eg. K. Kris Hirst “El Sidrón - Evidence for Neanderthal Cannibalism in Spain” https://www.thoughtco.com/el-sidron-evidence-for-neanderthal-cannibalism-172640

*7:See eg. http://www-personal.umich.edu/~wolpoff/ https://en.wikipedia.org/wiki/Milford_H._Wolpoff