ONE of the oddest things about Homo sapiens is that he is alone. Though storytellers have filled the world with imaginary hominids-from woodland pixies to mountain giants-no sign of the real thing has ever been seen. But that was not true in the past. As recently as 40,000 years ago there were three other species of human on Earth: Neanderthals in Europe, the "hobbits" of Flores, in Indonesia, and a recently discovered and still mysterious group of creatures called the Denisovans, who lived in Central Asia. And now there is evidence that similar diversity existed earlier in human history, a little under 2m years ago, in Africa.
有关智人的最奇怪的事情之一就是他们在人类的进化史上十分孤独。尽管故事家们想象出了许多人种来丰富这个世界，从森林里的小精灵到山上的巨人等等，但人们却从未找到能证明这些人种真实存在的迹象。但从过去来看，这样的说法并不正确。早在4万年前，地球上还存在另外三个人种：欧洲的尼安德塔人，印度尼西亚佛洛里斯岛上的"霍比特人"，以及最近才发现的一个叫丹尼索瓦人的神秘人种，该人种曾居住在亚洲中部。而现在，人们在非洲又找到了另一个人种存在的证据，该人种在人类进化史上出现的时间更早，距今约不到200万年。
This evidence, just published in Nature, has been provided by a team led by Meave Leakey of the Turkana Basin Institute in Nairobi, Kenya. Dr Leakey is a member of an illustrious palaeontological clan. Her husband, Richard, discovered in 1967 that the area around Lake Turkana is a good place to look for human fossils and made many important finds there; Richard's parents, Louis and Mary, had earlier been responsible for showing the same was true of Olduvai Gorge in Tanzania; and in 1999 Dr Leakey herself found a new species of hominid, called Kenyanthropus platyops. At 3.5m years old Kenyanthropus predates Homo, the genus to which modern humans belong. Her latest discoveries, however, add to that genus, too.
这些发表在《自然》杂志上的证据是由肯尼亚首都内罗毕的图尔卡纳盆地研究所的一个研究小组提供的。该研究小组的领导人米芙•利基来自一个著名的古生物学研究家族，1967年，她的丈夫理查德发现图尔卡纳湖附近区域是一块寻找人类化石的好地方，并在那里取得了许多重要发现。理查德的父母路易斯和玛丽曾在早些时候负责坦桑尼亚奥杜瓦伊峡谷的人类化石发掘工作。米芙•利基博士本人曾在1999年发现了一个叫肯尼亚平脸人的新人种，该人种距今已有350万年，其出现时间比现代人所属的智人还早。而她最新取得的发现成果又给这一人种增添了新成员。
The problem with studying humanity's fossil record is that it is so sparse: a jawbone here; a braincase there. Often, it is difficult to know if different bones have come from the same species or not. Even multiple examples of the same type of bone can mislead. What looks like two species might actually be the male and the female of one.
研究人类化石记录最大的问题是资源稀缺，总是这儿一块颚骨，那儿一块头骨。而且研究者通常很难分辨它们是否来自同一人种。即便是同一人种，不同样本也会给人带来误导，两块看起来像是来自不同人种的骨头实际上可能分属于同一人种的男性和女性。
Such confusion has bedevilled the interpretation of the human fossils found near Lake Turkana. Some palaeontologists see a single, variable species called Homo habilis. Others add a second, Homo rudolfensis. The new fossils found by Dr Leakey and her team (which includes a third Leakey generation in the form of her daughter, Louise) may, however, help clear up what is going on.
这种极易混淆的情况一直困扰着那些想要解读图尔卡纳湖附近人类化石的研究者们。有一些古生物学家认为人种是单一的，即只有能人一种，其他人种都是能人的变异体。而另外一些古生物学家则认为除能人之外还有第二个人种，即卢尔多夫人。而利基博士与她的团队（该团队成员还包括利基家族的第三代人，即利基的女儿路易斯）最新发现的人类化石或许可以帮忙理清这些人种之间的关系。
One of the new specimens, known as KMN-ER 62000, has a face like the type specimen of Homo rudolfensis (the fossil that defines the species, if species it turns out to be), though it seems to be from an adolescent, whereas the type specimen is an adult. Crucially, 62000 has a reasonably well-preserved upper jaw, which the type specimen lacks. A computer reconstruction (see diagram) suggests this upper jaw meshes well with the second of Dr Leakey's discoveries, a lower jaw (KMN-ER 60000). She is not suggesting they are from the same individual, since they are of different ages, but they seem to come from the same species, namely Homo rudolfensis.
这些新发现的样本中有一个被标为KMN-ER 62000的新样本，其脸型与卢尔多夫人样本（该化石是用来鉴别卢尔多夫人人种的一个样本，如果研究者能用此种方式辨认出样本属于卢尔多夫人种）的脸型相似，尽管62000样本看起来像是来自一个青少年，而卢尔多夫人化石样本则属于一个成年人。关键是，62000样本拥有一个保存相当完好的上颌，而这正是这一类型的样本所缺少的。一张电脑重建图（见上图）显示这一上颌与利基博士发现的第二个人种的一个下颌样本（KMN-ER 60000）十分吻合。由于两块骨头分属两个年龄不同的人，因此利基博士并不认为这两块骨头是来自同一个人的，但看起来这两块骨头的主人属于同一人种，即卢尔多夫人。
Equally significantly, a different computer reconstruction shows that the upper jaw of 62000 does not match another famous fossil from the area, known as KMN-ER 1802. This was found in 1973 and had previously been thought likely to be the lower jaw of rudolfensis.
同样重要的是，另一张电脑重建图显示，62000样本的上颌与KMN-ER 1802样本并不吻合。KMN-ER 1802这块有名的样本化石同样来自这个地区，1973年人们发现它时曾认为这块下颌骨可能属于卢尔多夫人种。
What 1802 actually is, is now obscure. It is too different from what this chain of reasoning suggests was the shape of Homo rudolfensis to be explained by sexual dimorphism, unless the sexes differed in this species in ways not seen in any other primate. But its previous attribution was made because it does not look much like Homo habilis either.
现在人们仍旧无法弄清1802样本到底属于哪个人种。这一推理链认为它是卢尔多夫人，并以人种的两性差异来解释其外形差异；但这一差异实在太大，除非这一人种的两性差异在其他灵长类动物中见所未见方能自圆其说。但之前人们之所以将其归为卢尔多夫人种是因为它看起来也并不像是能人的下颌。
It seems then that at least two, and possibly three species of Homo were stalking the east-African savannah a little under 2m years ago: habilis, rudolfensis and something as yet unnamed. The intertwining history of the human family and the Leakey family has just become even more complicated.
这样看起，在距今不到200万年前，曾有三个人种在东非大草原上生活过：能人，卢尔多夫人，以及一个尚未被命名的人种。利基家族一直都致力于研究人类大家族的历史，现在二者之间的关系交织在一起，使历史更加复杂了。