科學家發現的證據顯示人類早期的革新行為在人類演化史中出現的時間可以更往前推
根據三篇新研究，這類演化革新出現的證據可以追溯至某個時期，當時人類身處的環境動盪不安而難以預料
美國史密森尼國家自然歷史博物館的人類學家和國際團隊合作之下，發現大約320,000年前東非的早期人類已經開始會和遠方的人類族群進行貿易，還會使用顏料並運用比舊石器時代還要精密的工具。這些新發現的人類活動所在年代跟已知最早的智人化石大約同期，比之前在東非找到的類似證據還早了數萬年。上述這些行為是生活於中石器時代的人類具備的特徵，取代了之前數萬年來人類遵循的生活方式與技術。
這些證據標明了人類演化歷程上的里程碑，它們來自肯亞南部的歐羅結撒依立耶(Olorgesailie)盆地，早期人類生活方式的考古紀錄在此延續了一百多萬年之久。在3月15日發表於《自然》(Science)期刊的三篇新論文公佈了最新發現，指出這些人類行為出現的時候該區域的環境變化相當劇烈。科學家表示當時地震活動使得地形改變，而氣候狀況也在乾燥和濕潤之間來回變動，技術創新、群體間的交易網路和原始符象溝通方式或許能幫助早期人類存活，同時在難以預測的環境下仍能獲得所需資源。
美國國家自然史博物館人類起源計畫的主持人Rick
Potts表示：「這一連串十分先進的行為變化牽涉到更加高端的心智能力以及更為複雜的社會活動，或許就是這些優勢使我們祖先得以從其他早期人類之中脫穎而出。」
30年多以來，Potts在肯亞國立博物館的協助下於歐羅結撒依立耶領導人類起源計畫的研究。在發表於《自然》的三篇論文中，以Potts為主要作者的論文描述了早期人類在此演化階段適應環境時面臨的挑戰。另一篇論文的主要作者為喬治華盛頓大學人類古生物學高等研究中心的人類學教授Alison
Brooks，她也是人類起源計畫的副主持人；此論文著重於表述歐羅結撒依立耶的早期人類曾彼此交換資源並使用顏料的證據。第三篇論文的主要作者為共同進行此計畫，柏克萊地質年代中心的Alan
Deino；此論文詳述了定年這些中石器時代發現所用的方法。
歐羅結撒依立耶盆地最早有人類活動的證據來自於距今120萬年前。之後數十萬年間，居住在此的人們製作並使用一種由石頭切割而成的大型工具，稱作手斧(handaxe)。從2002年起，Potts、Brooks和團隊開始在歐羅結撒依立耶發現許多作工更加仔細的小型工具。Deino和同事的同位素定年結果顯示這些工具的年代早得驚人――它們製造於距今320,000至305,000年前。這些工具的作工相當仔細，且跟體積較大、可以用在各方面的手斧相比，它們的用途更為專一。其中許多相當尖銳，設計成可以綁在棍棒上的工具或許是拿來當作投擲性武器，而其他工具的形狀則像是刮刀或錐子。
早些年代的手斧是用當地的石頭打造而成，但史密森尼團隊發現在中石器時代場址中，用來做成小型石製利器的黑曜岩並非產於當地。黑曜岩是一種邊緣鋒利的火山岩，在歐羅結撒依立耶沒有一處能開採這種岩石，但團隊卻在此處發現大塊且尚未加工的黑曜岩碎片。距離此處15至55英里的各個方向都有黑曜岩的產地，此處工藝品多樣的化學成分符合這些黑曜岩的化學成分範圍，代表當時已經有交易網路出現使得這種貴重的岩石能在這個古老大地上四處流通。
團隊也在考古場址發現黑色和紅色的岩石――錳和赭石，同時有證據顯示這些岩石曾經過處理以當作顏料使用。「我們不知道這些顏料的用途是什麼，但是考古學家通常把顏料的使用視為複雜符象溝通方式的基礎。」Potts表示，「就像今日我們會用服裝或者旗幟的顏色來表達身分，這些顏料或許有助於當時的人們傳達彼此之間的同盟關係，並讓相距遙遠的族群之間維繫連結。」
研究團隊希望能找出是什麼因素驅使人類行為的基本層面出現如此變化，他們彙整從各種來源得到的數據，評估並重建這些器物的使用者生活當時的古代環境樣貌。他們發現這些行為出現的時候是地形和氣候處於變動狀態的其中一段時期，此時資源的取得狀況較不穩固。
地質學、地球化學、古植物學和動物學證據顯示從360,000年前左右開始，此區就一直受到長時間的不穩定氣候影響，同時頻繁的地震活動也持續改變地形。雖然之前有些研究人員提出早期人類是為了應付乾燥環境而逐漸演化，Potts表示他們團隊的發現支持了另一種說法：環境波動可能帶給歐羅結撒依立耶盆地的居民相當重大的挑戰，促使他們的科技和社會結構發生改變，使他們更有機會在資源匱乏的時刻獲取資源。
發表在《科學》的三篇論文的研究團隊包括來自以下機構的合作研究人員：史密森尼學會、肯亞國家博物館、喬治華盛頓大學、柏克萊地質定年中心、美國國家科學基金會、伊利諾大學厄巴納―香檳分校、波爾多大學(法國國家科學研究中心)、猶他大學、哈佛大學、聖塔莫妮卡大學、密西根大學、康乃狄克大學、埃默里大學、卑爾根大學、香港浸會大學和薩克其萬大學。
研究經費來自史密森尼學會、美國國家科學基金會和喬治華盛頓大學。
Scientists discover evidence of early human
innovation, pushing back evolutionary timeline
Evidence of
innovation dates to a period when humans faced an unpredictable and uncertain
environment, according to three new studies
Anthropologists at the Smithsonian’s
National Museum of Natural History and an international team of collaborators
have discovered that early humans in East Africa had—by about 320,000 years
ago—begun trading with distant groups, using color pigments and manufacturing
more sophisticated tools than those of the Early Stone Age. These newly
discovered activities approximately date to the oldest known fossil record of
Homo sapiens and occur tens of thousands of years earlier than previous
evidence has shown in eastern Africa. These behaviors, which are characteristic
of humans who lived during the Middle Stone Age, replaced technologies and ways
of life that had been in place for hundreds of thousands of years.
Evidence for these milestones in humans’ evolutionary
past comes from the Olorgesailie Basin in southern Kenya, which holds an
archeological record of early human life spanning more than a million years.
The new discoveries, reported in three studies published March 15 in the
journal Science, indicate that these
behaviors emerged during a period of tremendous environmental variability in
the region. As earthquakes remodeled the landscape and climate fluctuated
between wet and dry conditions, technological innovation, social exchange
networks and early symbolic communication would have helped early humans
survive and obtain the resources they needed despite unpredictable conditions,
the scientists say.
“This change to a very sophisticated set of behaviors
that involved greater mental abilities and more complex social lives may have
been the leading edge that distinguished our lineage from other early humans,”
said Rick Potts, director of the National Museum of Natural History’s Human
Origins Program.
Potts has been leading the Human Origin Program’s
research in Olorgesailie for more than 30 years in collaboration with the
National Museums of Kenya. He is the lead author on one of the three Science publications that describe the
adaptive challenges that early humans faced during this phase of evolution.
Alison Brooks, a professor of anthropology at George Washington University’s
Center for the Advanced Study of Human Paleobiology and an associate of the
museum’s Human Origins Program, is lead author on the paper that focuses on the
evidence of early resource exchange and use of coloring materials in the
Olorgesailie Basin. A third paper, by Alan Deino at the Berkeley Geochronology
Center and colleagues, details the chronology of the Middle Stone Age
discoveries.
The first evidence of human life in the Olorgesailie
Basin comes from about 1.2 million years ago. For hundreds of the thousands of
years, people living there made and used large stone-cutting tools called
handaxes. Beginning in 2002, Potts, Brooks and their team discovered a variety
of smaller, more carefully shaped tools in the Olorgesailie Basin. Isotopic
dating by Deino and collaborators revealed that the tools were surprisingly
old—made between 320,000 and 305,000 years ago. These tools were carefully crafted
and more specialized than the large, all-purpose handaxes. Many were points
designed to be attached to a shaft and potentially used as projectile weapons,
while others were shaped as scrapers or awls.
While the handaxes of the earlier era were manufactured
using local stones, the Smithsonian team found small stone points made of
non-local obsidian at their Middle Stone Age sites. The team also found larger,
unshaped pieces of the sharp-edged volcanic stone at Olorgesailie, which has no
obsidian source of its own. The diverse chemical composition of the artifacts
matches that of a wide range of obsidian sources in multiple directions 15 to
55 miles away, suggesting exchange networks were in place to move the valuable
stone across the ancient landscape.
The team also discovered black and red
rocks—manganese and ocher—at the sites, along with evidence that the rocks had
been processed for use as coloring material. “We don’t know what the coloring
was used on, but coloring is often taken by archeologists as the root of
complex symbolic communication,” Potts said. “Just as color is used today in
clothing or flags to express identity, these pigments may have helped people
communicate membership in alliances and maintain ties with distant groups.”
Hoping to understand what might have driven such
fundamental changes in human behavior, the research team integrated data from a
variety of sources to assess and reconstruct the ancient environment in which
the users of these artifacts lived. Their findings suggest that the period when
these behaviors emerged was one of changing landscapes and climate, in which
the availability of resources would have been unreliable.
Geological, geochemical, paleobotanical and faunal
evidence indicates that an extended period of climate instability affected the
region beginning around 360,000 years ago, at the same time earthquakes were
continually altering the landscape. Although some researchers have proposed
that early humans evolved gradually in response to an arid environment, Potts
says his team’s findings support an alternative idea. Environmental
fluctuations would have presented significant challenges to inhabitants of the
Olorgesailie Basin, prompting changes in technology and social structures that
improved the likelihood of securing resources during times of scarcity.
The research teams for the three studies published in
Science include collaborators from the following institutions: the Smithsonian
Institution, the National Museums of Kenya, George Washington University, the
Berkeley Geochronology Center, the National Science Foundation, the University
of Illinois at Urbana-Champaign, the University of Missouri, the University of
Bordeaux (Centre National de la Recherche Scientifique), the University of
Utah, Harvard University, Santa Monica College, the University of Michigan, the
University of Connecticut, Emory University, the University of Bergen, Hong
Kong Baptist University and the University of Saskatchewan.
Funding for this research was provided by the
Smithsonian, the National Science Foundation and George Washington University.
原始論文：Richard
Potts, Anna K. Behrensmeyer, J. Tyler Faith, Christian A. Tryon, Alison S.
Brooks, John E. Yellen, Alan L. Deino, Rahab Kinyanjui, Jennifer B. Clark,
Catherine Haradon, Naomi E. Levin, Hanneke J. M. Meijer, Elizabeth G. Veatch,
R. Bernhart Owen, Robin W. Renaut. Environmental
dynamics during the onset of the Middle Stone Age in eastern Africa. Science, 2018 DOI:
10.1126/science.aao2200
引用自：Smithsonian.
"Scientists discover evidence of early human innovation, pushing back
evolutionary timeline: Evidence of innovation dates to a period when humans
faced an unpredictable and uncertain environment, according to three new
studies."
沒有留言:
張貼留言