原始人：在台灣發現新化石, 與北京和爪哇系統不同

A few weeks ago the Mainichi News on-line reported the following:

原人:台湾で新たな化石発見　北京やジャワと別系統

毎日新聞　2015年01月28日　01時05分（最終更新　01月28日　01時23分）

　台湾沖の海底で新たな原人の化石が見つかったと、国立科学博物館などの国際チームが２７日付の英科学誌ネイチャー・コミュニケーションズ（電子版）に発表した。北京原人などアジアの他の原人とは異なる特徴を持つ「第４の原人」と考えられ、古代の人類が各地で多様に進化していたことを示す発見として注目される。【大場あい】

　チームによると、発見されたのは下あごの骨の右半分の化石。時期は不明だが、台湾本島と澎湖（ほうこ）諸島の間の海域で底引き網に引っかかり、地元収集家が保管していた。この海域では、台湾が大陸と陸続きだったころに生息していたゾウなどの化石が大量に見つかっている。

　２００９年に高井正成・京都大霊長類研究所教授が人類の化石と確認した。

　化石に含まれるフッ素などの分析から、アジア東南部に２０万年前以降に現れるハイエナの一種と同時代と推定。陸続きだった時期を考慮すると、１９万年前より新しい可能性が高いという。

　今回見つかったあごの骨の幅は、７５万〜４０万年前の北京原人の化石の平均よりも４ミリ以上厚く、親知らずの一つ手前の第２大臼歯も一回り大きかった。８０万年前のジャワ原人よりも大きい。

　進化に伴って歯やあごは小さくなるため、ジャワ原人、北京原人の子孫ではないと結論づけた。

　アジアではこれまで、ジャワ原人（１２０万〜５万年前）▽北京原人（７５万〜４０万年前）▽０３年にインドネシアでみつかった小型のフロレス原人（１００万〜数万年前）−−の三つの原人グループが知られている。

　海部陽介・国立科学博物館人類史研究グループ長は「台湾での原人発見は予想もしていなかった。今後アジアの人類の化石の空白地帯を埋めていくことで、人類の過去がもっと詳しく分かっていくだろう」と話す。

(試譯文)

  A British science magazine the Nature Communications dated the 27^th (January) (electronic edition) announced that an international team in the National Science Museum found primitive man's new fossil at the sea bottom off the coast of Taiwan. It was regarded as the "4th primitive man" with features different from the Peking Man and other primitive men in Asia; this discovery attracted attention because it showed that ancient mankind evolved differently in different regions.

 According to the team the fossil found was half of the lower right jaw bone. The timing was unknown. It was picked up by a dragnet at the sea area between Taiwan Island and Penghu Islands, and a local collector was keeping it. At this sea area large quantity of elephant fossils were found. They lived here at the time when Taiwan was connected with the continent by land.

 Professor Masashige Takai of the Kyoto University Primate Research Institute in 2009 confirmed it was a human fossil.

 From an analysis of the fluorine inside this fossil, it was presumed to belong to the same period's one kind of hyenas which appeared since 200,000 years ago at the south-eastern part of Asia. Yet when the period of land bridge was taken into consideration, it might be said that there was a new high possibility that the fossil was more 190,000 years ago.

 The width of the bone of the jaw found this time was more than 4 millimeters, thicker than the average of Peking Man's fossil remains that was 750,000 - 400,000 years ago. The 2nd molar just before one of the wisdom teeth was also slightly bigger. It was bigger than the Java Man of 800,000 years ago.

Because in evolution the tooth and jaw would become smaller, it was concluded that the fossil was not the descendant of Java Man and Peking Man.

 Up to now, the Java Man (1,200,000-50,000 years ago) ▽ the Peking Man (750,000-400,000 years ago) ▽the Small Flores primitive man (1,000,000- tens of thousands years ago) found in the year 2003 in Indonesia were the three known primitive man groups in Asia.

 Yousuke Kaifu the study group chief of the National Science Museum human history said that "the discovery of primitive man in Taiwan was not expected. From now on more Asian human fossil blank areas could be filled up. Mankind’s past would be known more in detail".

It is an interesting scientific discovery. It shows that ancient mankind may evolve differently in different regions.