Some Prehumans Feasted on Bark Instead of Grasses
Almost two million years after their last meals, two members of a prehuman species in southern Africa left traces in their teeth of what they had eaten then, as well as over a lifetime of foraging. Scientists were surprised to find that these hominins apparently lived almost exclusively on a diet of leaves, fruits, wood and bark.
If you are what you eat, the new research and other recent studies suggest there was more diversity in the diets of early prehumans, both within and between species, than previously understood. And this could in part account for the recently recognized physical diversity among the long intermediate line of hominins belonging to the genus Australopithecus.
如果说吃什么就变什么的话，最新的调查和近期的研究都表明，不管是在同一物种内部，还是不同物种之间，早期原人的食物结构，都比人们先前所知的更多样化。而这可能在一定程度上解释了最近发现的南方古猿属 (Australopithecus) 各原人种之间物理特征的多样性。
The dietary pattern of the enigmatic species, Australopithecus sediba, discovered four years ago in the Malapa caves northwest of Johannesburg, was unexpected for several reasons. It contrasted sharply with available data for other hominins in the region and elsewhere in Africa; they mainly consumed grasses and sedges from the savanna.
四年前在约翰内斯堡 (Johannesburg) 西北的玛拉帕 (Malapa) 山洞里发现的南方古猿源泉种 (Australopithecus sediba) 是一个非常神秘的物种。从好几个方面来看，它们的饮食结构都有些出乎意料。 首先，它和在同一地区以及非洲其他地方得到的关于其他原人的数据明显不同;后者主要的食物是热带草原上的青草和莎草。
The Au. sediba diet also appeared to be a matter of choice, not necessity. Other evidence from animal fossils and sediments in the area indicated the presence at the time of vast grasslands in the vicinity. Yet these hominins, their skeletons adapted for tree climbing as well as upright walking, chose to feed themselves in adjacent woodlands. In this, scientists said, their behavior was more like that of modern chimpanzees, which tend to ignore savanna grasses, or perhaps the more apelike hominin Ardipithecus ramidus, which lived largely on hard foods some 4.4 million years ago.
此外，南方古猿源泉种的饮食结构看起来更像是基于选择，而不是必然。从动物化石和当地沉积物中得到的其他证据表明，当时周围出现了辽阔的草原。然而，尽管它们的骨骼既能爬树也适应直立行走，但这些原人却选择去附近的林地觅食。科学家们认为，在这一点上，它们的行为更接近现代黑猩猩——因为黑猩猩就不吃草原上的草——或是一种叫做地猿始祖种 (Ardipithecus ramidus) 的古类人猿。地猿始祖种生活在约440万年以前，基本上以坚硬的食物为生。
An international team of scientists led by Amanda G. Henry of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reported on Wednesday the research that supported their findings. Their paper was published online by the journal Nature and will appear later in a printed edition.
由德国莱比锡马普研究所人类进化学协会 (Max Planck Institute for Evolutionary Anthropology) 的阿曼达·G·亨利 (Amanda G. Henry) 领导的一个国际科学家小组周三发表了支持他们结论的研究报告。他们的文章被《自然》(Nature) 杂志发表在网上，随后会出现在杂志的印刷版上。
“If these individuals are representative of the species,” the scientists wrote, “Au. sediba had a diet that was different from those of most early African hominins studied so far.”
They also concluded that the “inferred consumption” of woodland products “increased the known variety of early hominin foods.” But there is still much that is unknown or unclear about the newfound species: how or if it is related to modern humans and just where it fits on the hominin family tree.
The discovery, by Lee Berger of the University of Witwatersrand in Johannesburg, of two partial skeletons — one an adult female, the other a juvenile male — was the basis for the announcement two years ago of the new hominin species. These and at least one other adult specimen indicate that these hominins stood little more than four feet tall and had small brains and a mix of primitive and more modern anatomies. Dr. Berger was an author of the new journal report.
这两具不完整骨骸是由约翰内斯堡金山大学 (University of Witwatersrand) 的李·伯杰 (Lee Berger) 发现的，其中一具属于成年女性，另外一具属于未成年男性。两年前，依据这两具化石，科学家确定了这个新的类人物种。这两具化石以及另外至少一具成年人化石标本表明，这些类人生物直立身高略高于四英尺，大脑较小，解剖学特征有的依然原始，但有的已经比较现代。伯杰博士是这篇报告的作者之一。
Few other paleoanthropologists agree with Dr. Berger’s contention that the new species is the most plausible known ancestor of archaic and modern humans. Dr. Henry’s group said that studies of additional fossils from the Malapa caves “will provide a better understanding of the dietary ecology of Au. sediba.”
Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York, who was not involved in the research, called the findings “intriguing” and the research “an imaginative and multisided approach that makes you want to know more about this morphologically unusual species.”
伊恩·塔特索尔 (Ian Tattersall) 是纽约美国自然历史博物馆 (American Museum of Natural History) 的一名古人类学家，他没有参与研究。他认为，研究结论“很有趣”，并表示这项研究“是一次富有想象力的尝试，有很多方面的意义，让人们想要更多地了解这个从形态学上来看很不同寻常的物种。”
“Fortunately,” Dr. Tattersall added, “rumor has it that more specimens are on the way.”
Dr. Henry’s team followed three lines of research. One was an analysis of carbon isotopes extracted by laser from tooth enamel, one of the most durable and least contaminated body parts, and one that preserves chemical signatures of what was eaten in one’s youth. The type and amount of isotopes left from a diet of tree leaves, fruit and bark were well outside the range of those seen in all previously tested hominins — at least 95 percent forest food.
A second approach was an examination of dental microwear, which can reveal pits, scratches and cracks left by hard foods consumed shortly before death. Dr. Tattersall said that this “doesn’t help much to clarify the situation, since it appears to differ significantly between the two individuals.”
Finally, microscopic plant particles, called phytoliths, were recovered from dental tartar for the first time from a very ancient hominin (but from only one of the two individuals). Scientists said this apparently confirmed the carbon isotopic evidence for woodland diets.
Benjamin H. Passey, a geochemist at Johns Hopkins University, who conducted the tests determining the high ratio of carbon isotopes indicating a diet mostly of forest foods, explained why the research was important to an understanding of human evolution.
本杰明·H·帕西 (Benjamin H. Passey) 是约翰·霍普金斯大学 (Johns Hopkins University) 的一名地球化学家。他主持进行了碳同位素检测的实验，就是他的实验检出了高比例碳同位素，说明该物种的饮食主要是森林植物。关于这个研究对了解人类进化的重要意义，他说：
“One thing people probably don’t realize is that humans are basically grass eaters,” Dr. Passey said in a statement. “We eat grass in the form of the grains we use to make breads, noodles, cereals and beers, and we eat animals that eat grass. So when did our addiction to grass begin? At what point in our evolutionary history did we start making use of grasses? We are simply trying to find out where in the human chain that begins.”