« To the past
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Dec 21, 2012
池谷 そして、もうひとつ味わい深い事実がありまして、ほぼ日刊イトイ新聞-脳の気持ちになって考えてみてください。 〜「やる気」と「脳」の話を、池谷裕二さんと。〜 (via highsea)
人類って遺伝子的にいうと、
大雑把に２種類いるんです。
つまり、黒人と、黒人以外なんですけど。糸井 そうなんですか。池谷 はい、かなり粗い分類ですが、
２種類に分けられるんですよ。
つまり、たぶん、こういうことです。
そもそも、私たちの祖先である人類は
アフリカで生活していました。
そして、10万年くらい前にアフリカを出て行くまで
ずっとアフリカで生活していたんです。
約10万年、アフリカを出て行った人類は、
ヨーロッパやアジア圏に移り住み、
それぞれ、白人と黄色人種になりました。
アフリカに残った人類は、アフリカ黒人になりました。糸井 ほう、ほう。池谷 一方、そのまえに誕生したネアンデルタール人は、
やはりアフリカで誕生したあと、50万年以上前に、
ヒトよりも先にアフリカを出て行ってるんです。
これがなにを意味するかというと、
つまり、その後、アフリカを出て行ったヒトが、
ヨーロッパやアジア圏で
ネアンデルタール人と出会った。
そして、交雑が起こったわけです。
だから、いまのアフリカの黒人たちには、
ネアンデルタール人の遺伝子は残ってないんですよ。糸井 はーーーー！池谷 ということは、種としての純粋性で見たら、
彼らのほうは純血の血統書付きで、
我々は雑種なんですよ。糸井 なるほど、なるほど。
いやー、そうか。池谷 そのあたりをね、考えていくと、
ものすごく味わい深くって。糸井 たしかに、たしかに。池谷 だって、ネアンデルタール人の
ゲノム解析した研究者たち自身が
驚いたと言っていますからね。
「うわー、自分たち、混血なんだ」って。糸井 いや、それは、語りたくなる話題ですね。
研究者ばかりじゃなく、一般人にとっても。池谷 ええ、ふだんは研究の話は
自宅ではほとんどしないんですけど、
この話題に関しては妻と盛り上がりました（笑）。
(via mitaimon)
Dec 10, 2012
Age estimation from teeth
Eruption of deciduous (baby or milk) teeth and permanent (adult) teeth occurs at fairly regular intervals during the subadult years of development (see the figure above, deciduous teeth are shaded). Therefore, age estimation of subadults based dental eruption is quite accurate.
While tooth wear and permanent tooth loss can occur in subadults, these degenerative changes are usually associated with adults. Loss of permanent teeth and accompanying bone resorption of the alveolar bone of the maxilla and/or mandible are often associated with old age. Tooth wear or dental attrition most often occurs in adults, but the age of onset depends on diet and other environmental factors. This process leads to loss of outer white tooth enamel and exposure of the yellowish dentine of the pulp cavity, especially on the cusps of the teeth. The older an individual is, the more dentine is exposed due to tooth wear.
Image is scanned from Tim D. White, Michael T. Black & Pieter A. Folkens: Human Osteology, Academic Press, 3 ed. (2011)
(via scientificillustration)
Nov 2, 2012
Previously Unknown Population Explosion of Human Species 40,000 Years Ago —Discovered
DNA sequencing of 36 complete Y chromosomes has uncovered a previously unknown population explosion that occurred 40 to 50 thousand years ago, between the first expansion of modern humans out of Africa 60 to 70 thousand years ago and the Neolithic expansions of people in several parts of the world starting 10 thousand years ago. This is the first time researchers have used the information from large-scale DNA sequencing to create an accurate family tree of the Y chromosome, from which the inferences about human population history could be made.
“We have always considered the expansion of humans out of Africa as being the largest population expansion of modern humans, but our research questions this theory,” says Ms Wei Wei, first author from the Wellcome Trust Sanger Institute and the West China University of Medical Sciences. “The out-of-Africa expansion, which happened approximately 60,000 years ago, was extremely large in geographical terms with humans spreading around the globe. Now we’ve found a second wave of expansion that is much larger in terms of human population growth and occurred over a very short period, somewhere between 40,000 to 50,000 years ago.”
(via gwebarchaeology)
Oct 19, 2012
Archaeological News: Core sample sends carbon clock farther back in time
The carbon clock is getting reset. Climate records from a Japanese lake are set to improve the accuracy of the dating technique, which could help to shed light on archaeological mysteries such as why Neanderthals became extinct.
Carbon dating is used to work out the age of organic material —…
Sep 26, 2012
Archaeological News: Oldest Ivory Workshop in the World Discovered in Saxony-Anhalt
Excavations at the mammoth hunting site of Breitenbach near Zeitz have uncovered a 35,000-year-old ivory workshop.
During this year’s campaign, site directors Dr. Olaf Jöris and Tim Matthies and their team found the oldest evidence for clearly distinct working areas which are interpreted as…
Sep 25, 2012
Did Neandertals Truly Bury Their Dead?
During excavations in the French Dordogne beginning more than 100 years ago, French archaeologists discovered the skeletons of seven Neandertals, including four children and infants, and the most complete adult Neandertal skull ever found. They concluded that all were deliberately buried, making this site pivotal to contentions that Neandertals had symbolic capacities. Until now, that is. New excavations at La Ferrassie are in part designed to reexamine this question, which many researchers had long thought was itself dead and buried.
(Source: xmorbidcuriosityx)
Aug 31, 2012
Archaeological News: Most Neanderthals Were Right-Handed Like Us
Right-handed humans vastly outnumber lefties by a ratio of about nine to one, and the same may have been true for Neanderthals. Researchers say right-hand dominance in the extinct species suggests that, like humans, they also had the capacity for language.
A new analysis of the skeleton of a…
Aug 31, 2012
Did Humans Mate With Neanderthals? (no, probably not)
by Megan Gannon
There has been a long-standing debate over whether humans had sex with Neanderthals and recent studies have pointed to shared genes as evidence of such interspecies dalliances.
But new research claims that common ancestry, not interbreeding, better explains why people of European and Asian descent share 1 to 4 percent of their DNA with Neanderthals. Some of us may not be part caveman after all.
The new version of events, as told by scientists at the University of Cambridge, looks like this: Neanderthals and modern humans once shared a common ancestor who is thought to have lived across Africa and Europe about half a million years ago. But then 350,000 to 300,000 years ago, the European range and the African range of this ancestral species became separated. The European range evolved into Neanderthals, while the African range became modern humans…
(read more: Live Science) (image: Mauro Cutrona)
(via scientificillustration)
Aug 20, 2012
Archaeological News: Excavation reveals ancient hair fashion
Archaeologists conducting excavations in the northwestern province of Çanakkale’s Ayvacık district have discovered hairpins thought to be over two millennia old, proving that ancient societies also had a pronounced desire to “look good,” according to researchers.
“The hairpins show us that there was a high demand for them in ancient times. Maybe their existence shows us that there was a small atelier for hair pin production here,” said Professor Nurettin Arslan of Çanakkale Onsekiz Mart University, the head of the excavations, adding that women of the age placed great importance in being well-groomed and stylish.
Arslan said the hairpins had been found in many places in the ancient city but that the most were in the agora, which has been the site of the school’s ongoing dig.
Noting the unique designs on the hairpins, Arslan said, “They date back to the second century B.C. They are nearly 2,200 year old.”
(via gwebarchaeology)
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