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Australopithecus afarensis lived between3.85 and 2.95 million years ago.

(圖解:阿法南方古猿生活在385至295萬年前)

New evidence suggests hominins firstdeveloped outsized brains by scavenging fatty animal marrow, rather thanactively hunting for meat.

副標題:新的證據表明,古人類能第一個演化出特大號的大腦靠的是食用動物脂髓,而不是積極地獵取肉食。

NORTHERN ETHIOPIA WAS once home to a vast,ancient lake. Saber-toothed cats prowled around it, giant crocodiles swamwithin. The streams and rivers that fed it — over 3 million years ago, duringthe Pliocene — left behind trails of sediment that have now hardened intosandstone.

埃塞俄比亞北部曾經是一個巨大古湖泊的故鄉。劍齒虎在它周邊潛行,巨大的鱷魚在其中游曳。三百多萬年前上新世的溪水河流為其蓄積水源,留下的沉積物痕跡如今已經變硬,成為了砂巖。

Deposited within these layers are fossils:some of early hominins, along with the bones of hippos, antelope, andelephants. Anthropologist Jessica Thompson encountered two of these specimens,from an area named Dikika, in 2010.

沉積在這些地層中的是化石:一些早期人類、連同河馬、羚羊和大象的骨頭。2010年時,人類學家杰西卡·湯普森在一個叫迪奇卡的地區偶然發現了其中兩具標本。



Humans are the only primate to regularlyconsume animals larger than themselves. This nutritional exploitation,something Thompson and her colleagues call the “human predatory pattern,” haslong been synonymous with the flesh-eating, man-the-hunter view of humanorigins.

人類是唯一一種習慣性食用體型比自己更大的動物的靈長類動物。這種對營養物質的利用,被湯普森和她的同事們稱為“人類掠食模式”,長久以來,這和人類起源中吃生肉、狩獵者的觀點是同義詞。

Because large animals such as antelope packa serious micro-and-macro-nutrient punch, scientists have thought their meatcontributed to humanity’s outsized brains. A consensus arose in the 1950s thatour ancestors first hunted small animals before moving on to larger beastsaround 2.6 million years ago. Flaked tool use and meat eating became definingcharacteristics of the Homo genus.

由于羚羊這樣的大型動物在微觀和宏觀層面上都富有營養效力,科學家們已經認為它們的肉對人類特大號的大腦是有所貢獻的。五十年代的時候出現過一個共識,即我們的祖先一開始捕獵的是小型動物,直到約260萬年前才轉換到捕獵大型野獸。薄片狀工具的使用和吃肉成了人屬的本質特征。

“It’s a very appealing story,” says Thompson. “Right around that timethere appeared to be the first stone tools and butchery marks. You have theorigins of our Homo genus. A lot of people like to associate that with what itmeans to be human.”

“這是一個非常有吸引力的故事”,湯普森說?!熬驮谀莻€時期,似乎出現了第一件石器和宰割痕跡。這就找到了我們這個人屬的起源。有很多人喜歡把這一點和它對人類的意義聯系在一起?!?br />
Then, starting in the mid-1980s, anopposing theory arose in which Homo’s emergence wasn’t so tightly coupled withthe origins of hunting and predatory dominance. Rather, early hominins firstaccessed brain-feeding nutrients through scavenging large animal carcasses. Thedebate has rolled on through the decades, with evidence for the scavengingtheory gradually building.

然后,從八十年代中期開始出現了一種相反的理論,認為人屬的出現,和狩獵與吃肉為主的起源之間的關系沒有那么緊密。相反,早期的古人類是靠以大型動物的尸體為食來獲取補腦的營養物質。這場爭論已經一路持續了幾十年,食腐理論的證據也逐漸建立起來。

The new paper goes further: Harvestingouter-bone meat would have come at significant costs, the authors argue. Thechance of encountering predators is high when scraping raw flesh from acarcass. Chewing raw meat without specialized teeth doesn’t give much energeticbenefit, studies have shown. In addition, meat exposed to the elements willquickly rot.

這篇新的論文又進了一步:那些作者的主張是,獲取外部骨骼上的肉會付出巨大代價。從尸體上搜刮生肉時,遭遇掠食者的可能性會很高。研究已經顯示,在沒有特化牙齒的情況下去咀嚼生肉,從精力方面考慮并不會帶來太多益處。此外,暴露在自然環境中的肉很快就會腐爛。

Marrow and brains, meanwhile, are lockedinside bones and stay fresh longer. These highly nutritional parts are also aprecursor to the fatty acids involved with brain and eye development. And moreeasily than flesh-meat, bones could be carried away from carcass sites, safefrom predators.

與此同時,骨髓和大腦被鎖在骨頭內部,保持新鮮的時間會更久。這些營養價值很高的部分也是負責大腦和眼睛發育的脂肪酸的一種前體。而且比取肉更容易的是,骨頭是可以從尸骸所在地拿走的,如此就能保證安全,不會受到掠食者的威脅。

(譯注:前體物質,是指能直接被微生物在生物合成過程中結合到產物分子,而自身結構不發生過多變化,但產物的產量可以獲得較大提高的一類化合物)

Conventional thinking has been that thebehavioral package of early hominins was to go after meat and marrow together,explains Briana Pobiner, a paleoanthropologist at the Smithsonian Institution,who did not contribute to the new paper. But in the new paper, she says, “Thisteam has shown that marrow may have in fact been more important. It’s a nuance,but an important nuance.”

沒有參與這篇新論文的史密森學會古人類學家布里安娜·波賓納解釋到,在傳統的想法中,早期人類的行為包模式就是同時獵取肉和骨髓。但在這篇新論文中,她說,“該團隊已經展示出,可能骨髓一直都是更重要的目標。這是一個微妙的差別,但卻是一個很重要的微妙差別?!?br />


As to who wielded these percussiveinstruments, the timeline presents a puzzle. The earliest Homo specimen is nowdated to 2.8 million years. The Dikika fossils suggest butchery behaviors at3.4 million years ago. Homo may have emerged earlier than scientists suspected— a theory that would need more fossil evidence to support it — or anotherhominin, such as Australopithecus, may have created tools before Homo.

至于是誰在揮舞這些敲打工具,在時間軸上呈現為一個謎團?,F今最早的古人類標本可以追溯到280萬年前。出土于迪奇卡的化石表明,宰割行為出現在340萬年前。古人類的出現也許比科學家們猜想的更早(該理論需要更多的化石證據來支持),另一種古人類,比如南方古猿,也許在人屬出現之前就創造出了工具。

Some scholars aren’t convinced by thestudy’s arguments, however. For example, Craig Stanford, an anthropologist atthe University of Southern California, questions the emphasis on homininscavenging behavior appearing before hunting. “We have no examples today ofanimals that scavenge but don’t hunt,” he adds.

然而,有些學者并不信服該研究的論證。比如克雷格·斯坦福,他是南加州大學的人類學家,他所質疑的是:研究強調了古人類在狩獵行為之前就出現了食腐行為?!拔覀冋也坏饺魏维F存動物食腐而不狩獵的例子”,他補充說。

To test the new theory, the review authorssuggest seeking out further evidence of percussive tools that predate flakedtools. Researchers could, they note, broaden the search for the signatures ofsuch instruments within both the existing fossil record and at dig sites.Thompson’s graduate students, for example, are using 3D scanning and artificialintelligence techniques to improve the identification of marks on fossils —whether they were created by early hominins, saber-toothed cats, hyenas, orother types of creatures.

為了驗證這個新理論,這篇評論的作者提議,找出敲打工具在時間上早于切削器的進一步證據。他們提到,研究者可以在現存的化石記錄以及遺址挖掘中,同時擴大對這類工具蛛絲馬跡的搜索。比如說,湯普森的畢業生們正在使用3D掃描和人工智能技術來改善對化石上痕跡的鑒識水平,即它們是由早期人類,還是由劍齒虎、鬣狗或其他類型生物留下的。

What they uncover could deal a blow totheir theory, but it will also, undoubtedly, enrich our understanding of howour ancestors evolved.

他們所揭示的可能會打擊到他們的理論,但毫無疑問也會豐富我們對我們祖先進化方式的理解。