演讲MP3+双语文稿:一个新的祖先物种是如何改变我们的人类进化理论的？
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【演讲者及介绍】Juliet Brophy
古人类学家朱丽叶-布罗菲（Juliet Brophy）探讨了南部非洲的人类进化。
【演讲主题】一个新的祖先物种是如何改变我们的人类进化理论的？
【中英文字幕】
翻译者Doris Zhang 校对者Yolanda Zhang
00:13
Human origins. Who are we? Where do we come from, and how do we know? In my field, paleoanthropology, we explore human origins -- the "who" and "where" questions -- by analyzing fossils that date back thousands and even millions of years. In 2015, a team of colleagues and I named a new species in the genus Homo -- our genus -- Homo naledi. Let's take a step back and put that into context.
人类是如何起源的？ 我们是谁？ 我们从哪里来？ 又是怎么知道的呢？ 在我们古人类研究领域， 我们通过分析几千年前， 甚至百万年前的化石， 来探索人类的起源—— 回答“是谁”和“在哪里”的问题。 2015年，我和一个考察小组 命名了一个新发现的人类物种—— 我们的人属—— 奈勒迪人。 来回顾一下这个过程， 就会更容易理解。
00:47
The last common ancestors between humans and chimps date somewhere between six and eight million years. The earliest hominins, or earliest human ancestors, evolved into a group known as the australopithecines. The australopithecines evolved into the genus Homo and eventually modern humans -- us.
最晚发现的猿和人的共同祖先， 可以追溯到600到800万年前。 最早的人类， 或者说人类最远的祖先， 进化为我们所说的南方古猿。 这些南方古猿进化为人属， 并最终进化成现代人类——我们。
01:09
With each new fossil discovery, we get a little bit closer to better understanding who we are and where we came from. With these new fossil finds, we realize we now have to make changes to this tree. Until this discovery, we thought we had a pretty good idea about the patterns of evolutionary change. Current fossil evidence suggests that the earliest populations of the genus Homo evolved in Africa somewhere between two and three million years. Fast-forward to approximately 300,000 years to where we see the origins of the first modern humans. While the fossil record between these time frames in Africa is relatively sparse, the fossils nonetheless demonstrated certain trends from our earliest ancestors to modern humans. For example, our brains were becoming larger relative the rest of our body. Our pelves were becoming more bowl-shaped, and our hand-wrist morphology, or form, suggested a change in our grip as we began to make and use stone tools and spend less time in the trees. These new fossils disrupt everything we thought we knew about these trends and force us to change the way that we think about human evolution.
随着每种新化石的发现， 我们都会更接近那个答案， 更能理解我们是谁， 我们从哪里来。 基于这次新的化石发现， 我们意识到必须改变这个树形图。 在这次的发现之前， 我们以为自己对进化的 模式有个很好的概念， 现有的化石证据显示， 大概200-300万年前， 最早的人属在非洲进化而成。 快进一下，从大概30万年前，到第一批 现代人类的出现。 虽然在这个时间框架中的化石记录 相对稀少， 这些化石还是展示出了 从我们最远的祖先到 现代人类的特定的演变趋势。 比方说，相对于身体的其他部位 我们的大脑变得越来越大。 我们的骨盆更呈现为盆状， 并且我们的手腕形态，或者说样子， 这些表明当我们开始制造和使用石器时， 用手抓握的方式产生了变化， 同时也更少地待在树上。 这些新发现的化石打乱了 我们对这些演变趋势的一切认知， 并迫使我们改变对人类进化的认识。
02:28
South Africa in general, but the Cradle of Humankind in particular, contains numerous sites where hundreds of thousands of fossils have been found. As an undergraduate student, I fell in love with one of them ... Mrs. Ples. The skull of a 2.1-million-year-old early human ancestor. From that point on, I was determined to go to South Africa and study human evolution. I first traveled there in 2003, and I did get to see my beloved Mrs. Ples.
南非这片土地， 是人类发展的摇篮。 那里无数的遗址中， 数以万计的化石还未曾被发现。 在读本科的时候，我爱上了其中一个 普莱斯先生。 这是我们在210万年前 一个早期远祖的头骨。 从那时起， 我决定去南非，研究人类进化。 2003年，我第一次去那里， 并有机会看望了我深爱的普莱斯先生。
02:55
(Laughter)
（笑声）
02:56
But words can hardly convey my excitement when I was chosen as an early career scientist by Lee Berger, a world-renowned paleoanthropologist, to be one of the primary analysts of recently excavated unpublished fossils.
语言根本无法形容我当时的激动心情。 当时我被世界著名的古人类学家李·博格 选为青年科技人员， 并在一个最近发掘 但尚未公布的化石遗址，担任分析组成员。
03:13
This treasure trove of fossils was being recovered from a new site called the Dinaledi Chamber in the Rising Star cave system. Species are often named based on a skull, a lower jaw, or, very rarely, a handful of postcranial, or below-the-neck, elements. The fossils from Dinaledi were another story altogether. An unprecedented approximately 1800 specimens -- so far -- have been excavated from the Rising Star system, representing at least 15 individual skeletons. The research team that I was invited to join was tasked with describing, comparing and analyzing the fossils, with the difficult goal of identifying to what species the fossils belonged. We were divided up into our different areas of expertise. We were divided up in different areas of the lab, too. So there was "Hand Land," for the fossil hand people, "Hip Heaven" for the pelvis ... I was in the "Tooth Booth."
这个化石宝藏是在一个叫 Dinaledi Chamber的新遗址里发现的 属于瑞星洞系。 我们以往常常根据头颅骨，下颚， 或者，极少见的情况下， 一把颅后骨或者颈下骨的特点命名标本。 在Dinaledi发现的化石却是不同的情况。 在瑞星系列洞穴出土了 大概1800件的标本—— 到目前为止—— 这是一个史无前例的数目， 它至少可以拼成15具独立的骨架。 我参加的那个研究小组收到一项任务， 对这些难以分辨哪一块 属于哪一具骨架的化石 进行描述，比较和分析。 我们被分成了不同领域的专项组。 还被分配到了不同领域的实验室。 因此，这里有"Hand Land," 一个专门研究手的小组， "Hip Heaven" 是骨盆专家们... 我是研究牙齿的，在 "Tooth Booth"组。
04:15
(Laughter)
（笑声）
04:16
And after long, intense days in the lab, the different teams would meet up at night and discuss our findings, still consumed by questions from our analyses. It was incredible how different the interpretations were. Each body part seemed to come from a different species, based on what we knew from the fossil record. The suite of characteristics we were seeing didn't match any known species. And if we had only recovered the skull, we might have called it one thing; if we had only recovered the pelvis, we might have called it another. The anatomy of the skeletons didn't make sense with the framework of what we thought we knew of human evolution. Did it belong in the genus Homo? Should it be an australopithecine? Those bipedal, more apelike ancestors? Or perhaps it should be its own species.
尽管在实验室里劳碌了一整天， 晚上，不同小组成员 还要开会，讨论新的发现， 我们仍然能对分析过程中 产生的问题兴致勃勃。 你难以相信有多少种不同的解释。 根据我们已知的化石记录， 每一个身体部位都好像是 来自一个不同的物种。 我们眼前的这些化石特点不能和 任何已知物种相匹配。 如果只发现了这个颅骨， 我们也许会称做它是一种东西； 如果只发现了这个骨盆， 我们也许会称它为另一个东西。 当我们用自以为正确的 人类进化论模式思考时， 对这些骨骼的刨析就站不住脚。 它属于人属吗？ 它会是一种南方古猿吗？ 这些两足动物，更像我们的类猿祖先吗？ 或许它应该自成一个物种。
05:06
Ultimately, after much deliberation, we decided the Rising Star specimens did indeed warrant a new species, which we called "Homo naledi." From the head to the feet, the fossils present a mosaic of primitive, or ancestral, and derived or more modern-like features. The skull is quite derived, appearing most similar to early representatives of the genus Homo, like Homo habilis and Homo erectus. However, the brain is scarcely half the size of a modern human one. One that is smaller than any other early Homo that has ever been found.
最终，在反复商议之后， 我们决定把这种瑞星标本 列为一个新的物种， 就叫奈勒迪人。 这些化石从头至脚 呈现出两种特征的混合： 原始的，或者说先祖的特征 和衍生的，更像现代人的特征。 这个头骨是衍生的。 它和早期人类的特征最相似， 就像巧人和直立人一样。 然而，它的大脑仅仅是 现代人类的一半大小。 它比任何一个已发现的 早期人类的头骨都要小。
05:45
As someone who studies teeth, I might argue these are the coolest fossils found at the site.
做为一个研究牙齿的成员， 我得说，这是在这个遗址 发现的最酷的化石。
05:50
(Laughter)
（笑声）
05:51
The assemblage consists of 190 whole or fragmentary teeth that range in age from very old to very young. Like the skeletons, the teeth present a mix of primitive and derived traits. In modern humans, the third molar is typically the smallest, while the first molar is the biggest, but Homo naledi has the primitive condition where the third molar is the biggest and the first molar is the smallest. The anterior teeth, or the incisors and canines, are small for the genus Homo, and the lower canine has a cuspulid on it -- an extra cuspule that gives it a distinct mitten-like shape that it shares with some specimens of the early human, Homo erectus. The overall shape of the teeth looked odd to me, so I performed crown-shape analysis on the occlusal surfaces of deciduous teeth, or baby teeth -- on your left -- and the permanent premolars and molars on your right. The deciduous teeth are especially narrow, and the premolars are unique in their outline shape compared to other hominids.
这组化石包括190颗整牙和牙齿碎片, 它们的年龄跨度从高龄到低龄。 就像这具骨骼， 它的牙齿呈现出原始和演化的特征。 现代人的牙齿中， 第三颗磨牙的特征就是 最小的，而第一颗却是最大的， 但是奈勒迪人牙齿的基本特征是： 第三颗磨牙是最大的，而第一颗是最小的。 人类前面的牙齿， 也叫门齿和犬齿， 是很小的， 并且下犬齿有齿尖—— 那是一个明显像手套一样的额外的牙尖。 一些早期人类和直立人的 标本上都有这个特点。 我觉得这些牙齿形状看起来很奇怪， 所以我在这个 乳牙的咬合表面分析了牙冠-形状—— 左侧的-—— 还有右侧的恒牙前齿和磨牙。 这些乳牙的轮廓格外狭窄。 和其他人种相比， 这些前齿的轮廓非常特别。
07:00
In fact, when I compare the outlines, when I lay them on top of each other, they look very similar. We say they have "low intraspecific variations," so the variation within the species is low. When I compare this to groups like the australopithecines, the intraspecific variation is much larger.
事实上，当我比较它们的轮廓时， 当我把一副牙骨放在另一副上， 它们看上去非常相似。 我们说它们具有“低物种内多样性” 也就是说，在同一物种内，变化较少。 当我们把它们和一些类似 南方古猿的群体进行对比时， 物种内的多样性就大得多。
07:20
Postcranially, the team concluded that the position of the shoulders suggesting naledi was a climber; the flared pelvis and curved fingers are all primitive for the genus Homo. On the other hand, the humanlike wrist, long slender legs and modern feet are all consistent with other members of the genus.
关于颅下结构，小组得出的结论是， 肩部的位置说明奈勒迪人擅长攀爬； 宽阔的骨盆和弯曲的手指 都属于远古人的特征。 另一方面， 和人类相似的腰部和足部，修长的双腿 都和其他人种类似。
07:42
In 2017, we announced more specimens of Homo naledi from the nearby Lesedi Chamber, also in the Rising Star cave system. In addition, our geology team managed to produce an age estimate. The date's a big deal because, up until now, we had based our analysis solely on the morphology of the specimens, without previous knowledge of how old something is -- something which could unconsciously bias our interpretations. With its small brain and flared pelvis, we would not have been surprised if the fossils turned out to be two million years old. Instead, the fossils dated to 235 to 336 thousand years, an incredibly young date for such a small-brained individual.
2017年，我们公布了更多的奈勒迪人样本。 它们是在Lesedi Chamber旁边发现的， 这个地方也属于瑞星洞系。 另外，我们的地质小组 设法做出了一个年代估算。 数据非常重要，因为目前为止， 我们的分析仅仅是基于人类标本。 没有对年代判断的基本知识， 也许有意无意中，我们的理解会有失偏颇。 看这个小小的头骨和宽阔的骨盆， 如果早知道它们原来 已经有200万年历史了， 我们就不会如此惊讶了。 其实，这些化石可以追溯到 23.5-33.6万年前。 对这么小的头骨来说， 这个年代太新，令人难以置信。
08:29
So think back to what I said earlier: we thought that our brains were becoming larger relative to the rest of our body. Now we have a small-brained, young individual complicating this idea. What does all this mean?
想一想我刚才说过的： 我们以为相对于身体的其他部位 而言，我们的大脑正在变大。 现在这个大脑体积小，年代很新的 标本让这件事复杂起来。 这都意味着什么呢？
08:44
Homo naledi has taught us that we need to reassess what it means to be in the genus Homo. We need to rethink what it means to be human. In fact, most of the characteristics that we use to define the genus Homo, such as brain size and hip morphology, are no longer valid. No other species exists with this mix of primitive and derived traits. Why is there so much morphological variation in the genus Homo? And what force is driving that variation?
奈勒迪人给了我们一个启示， 我们需要重新测评什么是人属。 我们需要重新思考什么是人类。 实际上，大多数我们 用来定义人属的那些特征， 比如大脑尺寸和臀部形态， 都已经不再有效了。 没有哪个物种混合着 既原始又衍生的特点。 为什么会有这么多形态各异的人属？ 又是什么促进了这种多样性的呢？
09:14
Another implication for these fossils is that for the first time, we have concrete evidence of a species coexisting in Africa, at 300,000 years, with modern humans. Until this discovery, we only had large-brained modern humans that existed in Africa. Did they interbreed with each other? Did they compete with each other?
这些化石的另外一些影响是，它第一次 提供了确凿的证据说明了 30万年前非洲的物种和 现代人类的共生关系。 这次发现之前， 我们以为只有大脑体积较大的 现代人在非洲存在过。 他们之间是否杂交过？ 他们是否相互竞争？
09:38
Another implication that these fossils have is for the archaeologists studying stone tools in South Africa. Keep in mind that neither the Dinaledi nor the Lesedi Chambers have any artifacts in them. However, they do overlap in time with several stone-tool industries, the makers of which are considered to be either modern humans or direct human ancestors. This begs the question: Who made the stone tools of South Africa? Brain size has historically played a key role in identifying a species as a tool user. The idea is that you need to have a large brain to have even the capacity to make stone tools. But that notion has been questioned. Furthermore, Homo naledi, even with its small brain size, has a hand-wrist morphology similar to other species that did make and use stone tools, suggesting it had the capability. With two species coexisting in Africa at 300,000 years, we can no longer assume we know the maker of tools at sites with no associated species.
另外一个意义是，这些化石 给考古学家提供了 研究非洲石器时代的机会。 别忘了既不是Dinaledi， 也不是Lesedi Chambers 才拥有史前古器物。 然而，他们的几个石器工业时代 在某些时候是重合的， 它们上面的标记被认为要么是现代人的， 要么是人类祖先的。 这就引出了一个问题： 谁制造了南非的史前石器？ 历史上，大脑的体积在界定物种的时候 起到了重要作用。 这个概念说明，只有拥有较大的大脑， 你才具备制造石器的能力。 但是我们开始怀疑这个概念了。 进一步说，奈勒迪人虽然大脑体积小， 手腕形状却和 其他制造工具的物种类似， 说明它也具备同样的能力。 考虑到这两种物种在非洲共生了30万年， 我们不能再假定我们知道，在遗址上的 工具制造者和别的物种没有关联。
10:43
So where does Homo naledi fit in our human evolutionary lineage? Who is it most closely related to? Who did it evolve from? We're still trying to figure all that out. It's ironic, because paleoanthropologists are renowned for having small sample sizes. We now have a large sample size, and more questions than answers. Homo naledi has taught us, has brought us a little bit closer to better understanding our evolutionary past. So while Mrs. Ples will always hold a special place in my heart, she now shares that space with several thousand others.
那么，奈勒迪人应该在 人类进化线上哪个位置上呢？ 它最接近谁呢？ 它从什么物种进化而来？ 我们仍然在寻找答案。 这很讽刺，因为古人类学家 以拥有少量的标本著称。 我们现在有大量的标本， 问题却比答案更多了。 奈勒迪人给了我们启示， 带我们更进一步 理解我们的进化史。 因此我心中将会一直留有 普勒斯太太的角色， 她现在正在和成千上万的 人分享这个角色。
11:16
(Laughter)
（笑声）
11:18
Thank you.
谢谢。
11:19
(Applause)
（掌声）
