Pre-prehistoric man——人们对美洲文明史的认识

The dating of a Californian fossil site suggests Homo sapiens may not have been the original species of human to reach the New World

在加利福利亚发现的化石表明，智人可能不是最早出现在新大陆的物种。

When did the first human beings arrive in the Americas? Though there are arguments about the details, the consensus is that it was around 15,000 years ago, when retreating glaciers at the end of the last ice age permitted travellers from Asia to cross what is now the Bering strait but was then dry land.

人类第一次出现在美洲是什么时候？尽管人们对此存在细节上的争议，但普遍认为是在15000以前。那是在最后一个冰河时期，冰川退缩，从而允许来自亚洲的旅行者穿越今日的白令海峡，当时还是一片干燥的陆地。

This makes sense. The evidence suggests that, recent migrants from Africa and their progeny aside, people now alive in Asia, Australia, Europe and the Americas are descended from a handful of Africans who left the continent of their birth about 70,000 years ago. This fits nicely with the conventional date for America’s colonisation, by giving time for the heirs of these African émigrés to make it to eastern Asia, ready for the hop to the New World when conditions permitted.

这样说有一定的道理。有证据表明，现在居住在亚洲、澳大利亚、欧洲、美洲的人都是70000年前非洲人的后代，这和美洲殖民时期的时间相吻合，让这些非洲移民者的后裔有时间迁移到东亚，为在条件允许的情况下开发新大陆做好准备。

What, then, to make of a discovery, reported in this week’s Nature, by Thomas Deméré of the San Diego Natural History Museum and his colleagues? They have just dated an archaeological site found in California in 1992, which seems to be a place where human beings used stone tools to dismember a mastodon, a now-extinct type of elephant. Unfortunately for existing theories, the age Dr Deméré and his associates have come up with for this site is 130,000 years—a time when Homo sapiens was confined to Africa.

在本周《自然》报道中，圣迭戈自然历史博物馆工作人员托马斯·德梅雷（Thomas Deméré）及其同事会有什么发现呢？他们刚刚确定了一个在1992年加利福利亚发现的考古遗址的年代，即130000年前，当智人仅在非洲的时候。而且他们还发现人类似乎在这个考古地点用石头肢解过已灭绝乳齿象。

The Cerutti mastodon site, as the place is known, is near San Diego. It is named after its discoverer, Richard Cerutti, who is one of Dr Deméré’s co-authors on the paper. It contained a lone mastodon skeleton and five large cobblestones. The whole area appears to have been buried more or less intact by sediment from a stream. The cobbles are far larger than any other stones in the sediment. Marks they bear, and fragments found nearby that seem to have flaked off them, suggest they have been used as tools.

切鲁迪乳齿象遗址在圣迭戈附近，它是以其发现者理查德·切鲁迪（Richard Cerutti）——德梅雷博士的合著者之一命名的。在这遗址上发现了一个长长的乳齿象骨头和五块巨大的鹅卵石。整个地区因被河流的沉积物埋藏而几乎完好无损。鹅卵石也比其它任何埋藏在沉积物的石头大，这些鹅卵石上的标记，以及附近发现的脱落的碎片，表明它们当做工具来捶打乳齿象。

Two of the tools seem to have been anvils, and three hammerstones. Their purpose, judging from the condition of many of the mastodon’s bones, which have been shattered in ways that suggest they have been hit hard and deliberately, and fragments of which are clustered around the putative anvils, was to break those bones. This might have been done to extract the nutritious marrow inside, or to use the bone-fragments themselves to make further tools. Indeed, Dr Deméré and his colleagues have conducted experiments on a modern elephant skeleton that help confirm this interpretation.

五块鹅卵石中，似乎有两块是充当铁砧，三块充当石锤。从许多已破碎的乳齿象骨头的痕迹来看，它们用来用力敲打过，并且它们的碎片集中分布在铁砧周围，这说明它们的目的是用来捶打骨头。这么做的原因可能是为了汲取骨髓，或者是利用骨头制造新的工具。德梅雷博士和他的同事还用当今的大象骨头做研究以证实这一推论。

All of this was interesting 15 years ago, when the site was discovered. The stone tools found are similar to those used over 1m years ago in Africa, by Homo erectus, an ancestor of Homo sapiens, and dissimilar to the precisely crafted tools of the Clovis culture typical of other early-human discoveries in North America, a fact which has long been a source of speculation about the true nature of the Cerutti mastodon site. Unfortunately, no organic material remains in the bones, so they cannot be radiocarbon-dated.

15年前，当这个遗址被发现的时候，很多人对比很感兴趣。1百万年前的非洲智人和直立人也曾用石头充当这种类似的工具，而北美洲的克洛维斯人却不是这样，这些是推测切鲁迪乳齿象遗址的年代的重要资料。不幸的是，没有原始物质存在于骨头里，所以无法使用放射性碳定年法确定具体时间。