How a new species of ancestors is changing our theory of human evolution | Juliet Brophy

Translator: Leslie Gauthier Reviewer: Krystian Aparta

翻译人员: Doris Zhang 校对人员: Yolanda Zhang

Human origins.

人类是如何起源的？

Who are we?

我们是谁？

Where do we come from,

我们从哪里来？

and how do we know?

又是怎么知道的呢？

In my field, paleoanthropology,

在我们古人类研究领域，

we explore human origins --

我们通过分析几千年前， 甚至百万年前的化石，

the "who" and "where" questions --

来探索人类的起源——

by analyzing fossils that date back thousands and even millions of years.

回答“是谁”和“在哪里”的问题。

In 2015, a team of colleagues and I named a new species in the genus Homo --

2015年，我和一个考察小组 命名了一个新发现的人类物种——

our genus --

我们的人属——

Homo naledi.

奈勒迪人。

Let's take a step back and put that into context.

来回顾一下这个过程， 就会更容易理解。

The last common ancestors between humans and chimps

最晚发现的猿和人的共同祖先，

可以追溯到600到800万年前。

date somewhere between six and eight million years.

The earliest hominins,

最早的人类，

或者说人类最远的祖先，

or earliest human ancestors,

evolved into a group known as the australopithecines.

进化为我们所说的南方古猿。

The australopithecines evolved into the genus Homo

这些南方古猿进化为人属，

and eventually modern humans -- us.

并最终进化成现代人类——我们。

With each new fossil discovery,

随着每种新化石的发现，

we get a little bit closer to better understanding who we are

我们都会更接近那个答案， 更能理解我们是谁，

and where we came from.

我们从哪里来。

With these new fossil finds,

基于这次新的化石发现，

we realize we now have to make changes to this tree.

我们意识到必须改变这个树形图。

Until this discovery,

在这次的发现之前，

we thought we had a pretty good idea about the patterns of evolutionary change.

我们以为自己对进化的 模式有个很好的概念，

Current fossil evidence suggests

现有的化石证据显示，

that the earliest populations of the genus Homo evolved in Africa

大概200-300万年前，

somewhere between two and three million years.

最早的人属在非洲进化而成。

Fast-forward to approximately 300,000 years to where we see the origins

快进一下，从大概30万年前，到第一批

of the first modern humans.

现代人类的出现。

While the fossil record between these time frames in Africa

虽然在这个时间框架中的化石记录

is relatively sparse,

相对稀少，

the fossils nonetheless demonstrated certain trends

这些化石还是展示出了 从我们最远的祖先到

from our earliest ancestors to modern humans.

现代人类的特定的演变趋势。

For example, our brains were becoming larger

比方说，相对于身体的其他部位

relative the rest of our body.

我们的大脑变得越来越大。

Our pelves were becoming more bowl-shaped,

我们的骨盆更呈现为盆状，

and our hand-wrist morphology, or form,

并且我们的手腕形态，或者说样子，

suggested a change in our grip as we began to make and use stone tools

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，

and spend less time in the trees.

同时也更少地待在树上。

These new fossils disrupt everything we thought we knew about these trends

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，

and force us to change the way that we think about human evolution.

并迫使我们改变对人类进化的认识。

South Africa in general,

南非这片土地，

but the Cradle of Humankind in particular,

是人类发展的摇篮。

contains numerous sites where hundreds of thousands of fossils have been found.

那里无数的遗址中， 数以万计的化石还未曾被发现。

As an undergraduate student, I fell in love with one of them ...

在读本科的时候，我爱上了其中一个

Mrs. Ples.

普莱斯先生。

The skull of a 2.1-million-year-old early human ancestor.

这是我们在210万年前 一个早期远祖的头骨。

From that point on,

从那时起，

I was determined to go to South Africa and study human evolution.

我决定去南非，研究人类进化。

I first traveled there in 2003,

2003年，我第一次去那里，

and I did get to see my beloved Mrs. Ples.

并有机会看望了我深爱的普莱斯先生。

(Laughter)

（笑声）

But words can hardly convey my excitement

语言根本无法形容我当时的激动心情。

when I was chosen as an early career scientist

当时我被世界著名的古人类学家李·博格

by Lee Berger,

选为青年科技人员，

a world-renowned paleoanthropologist,

并在一个最近发掘

to be one of the primary analysts of recently excavated unpublished fossils.

但尚未公布的化石遗址，担任分析组成员。

This treasure trove of fossils was being recovered from a new site

这个化石宝藏是在一个叫 Dinaledi Chamber的新遗址里发现的

called the Dinaledi Chamber in the Rising Star cave system.

属于瑞星洞系。

Species are often named based on a skull, a lower jaw,

我们以往常常根据头颅骨，下颚，

or, very rarely,

或者，极少见的情况下，

a handful of postcranial, or below-the-neck, elements.

一把颅后骨或者颈下骨的特点命名标本。

The fossils from Dinaledi were another story altogether.

在Dinaledi发现的化石却是不同的情况。

An unprecedented approximately 1800 specimens --

在瑞星系列洞穴出土了 大概1800件的标本——

so far --

到目前为止——

have been excavated from the Rising Star system,

这是一个史无前例的数目，

representing at least 15 individual skeletons.

它至少可以拼成15具独立的骨架。

The research team that I was invited to join

我参加的那个研究小组收到一项任务，

was tasked with describing, comparing and analyzing the fossils,

对这些难以分辨哪一块 属于哪一具骨架的化石

with the difficult goal of identifying to what species the fossils belonged.

进行描述，比较和分析。

We were divided up into our different areas of expertise.

我们被分成了不同领域的专项组。

We were divided up in different areas of the lab, too.

还被分配到了不同领域的实验室。

So there was "Hand Land," for the fossil hand people,

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...

"Hip Heaven" for the pelvis ...

I was in the "Tooth Booth."

我是研究牙齿的，在 "Tooth Booth"组。

(Laughter)

（笑声）

And after long, intense days in the lab,

尽管在实验室里劳碌了一整天，

the different teams would meet up at night and discuss our findings,

晚上，不同小组成员 还要开会，讨论新的发现，

still consumed by questions from our analyses.

我们仍然能对分析过程中 产生的问题兴致勃勃。

It was incredible how different the interpretations were.

你难以相信有多少种不同的解释。

Each body part seemed to come from a different species,

根据我们已知的化石记录，

based on what we knew from the fossil record.

每一个身体部位都好像是 来自一个不同的物种。

The suite of characteristics we were seeing didn't match any known species.

我们眼前的这些化石特点不能和 任何已知物种相匹配。

And if we had only recovered the skull, we might have called it one thing;

如果只发现了这个颅骨， 我们也许会称做它是一种东西；

if we had only recovered the pelvis, we might have called it another.

如果只发现了这个骨盆， 我们也许会称它为另一个东西。

The anatomy of the skeletons didn't make sense

当我们用自以为正确的 人类进化论模式思考时，

with the framework of what we thought we knew of human evolution.

对这些骨骼的刨析就站不住脚。

Did it belong in the genus Homo?

它属于人属吗？

Should it be an australopithecine?

它会是一种南方古猿吗？

Those bipedal, more apelike ancestors?

这些两足动物，更像我们的类猿祖先吗？

Or perhaps it should be its own species.

或许它应该自成一个物种。

Ultimately, after much deliberation,

最终，在反复商议之后，

we decided the Rising Star specimens did indeed warrant a new species,

我们决定把这种瑞星标本 列为一个新的物种，

which we called "Homo naledi."

就叫奈勒迪人。

From the head to the feet,

这些化石从头至脚

the fossils present a mosaic of primitive, or ancestral,

呈现出两种特征的混合：

and derived or more modern-like features.

原始的，或者说先祖的特征 和衍生的，更像现代人的特征。

The skull is quite derived,

这个头骨是衍生的。

appearing most similar to early representatives of the genus Homo,

它和早期人类的特征最相似，

like Homo habilis and Homo erectus.

就像巧人和直立人一样。

However, the brain is scarcely half the size of a modern human one.

然而，它的大脑仅仅是 现代人类的一半大小。

One that is smaller than any other early Homo that has ever been found.

它比任何一个已发现的 早期人类的头骨都要小。

As someone who studies teeth,

做为一个研究牙齿的成员，

I might argue these are the coolest fossils found at the site.

我得说，这是在这个遗址 发现的最酷的化石。

(Laughter)

（笑声）

The assemblage consists of 190 whole or fragmentary teeth

这组化石包括190颗整牙和牙齿碎片,

that range in age from very old to very young.

它们的年龄跨度从高龄到低龄。

Like the skeletons,

就像这具骨骼，

the teeth present a mix of primitive and derived traits.

它的牙齿呈现出原始和演化的特征。

In modern humans,

现代人的牙齿中，

the third molar is typically the smallest, while the first molar is the biggest,

第三颗磨牙的特征就是 最小的，而第一颗却是最大的，

but Homo naledi has the primitive condition

但是奈勒迪人牙齿的基本特征是：

where the third molar is the biggest and the first molar is the smallest.

第三颗磨牙是最大的，而第一颗是最小的。

The anterior teeth,

人类前面的牙齿，

or the incisors and canines,

也叫门齿和犬齿，

are small for the genus Homo,

是很小的，

and the lower canine has a cuspulid on it --

并且下犬齿有齿尖——

an extra cuspule that gives it a distinct mitten-like shape

那是一个明显像手套一样的额外的牙尖。

that it shares with some specimens of the early human, Homo erectus.

一些早期人类和直立人的 标本上都有这个特点。

The overall shape of the teeth looked odd to me,

我觉得这些牙齿形状看起来很奇怪，

so I performed crown-shape analysis

所以我在这个

on the occlusal surfaces of deciduous teeth, or baby teeth --

乳牙的咬合表面分析了牙冠-形状——

on your left --

左侧的-——

and the permanent premolars and molars on your right.

还有右侧的恒牙前齿和磨牙。

The deciduous teeth are especially narrow,

这些乳牙的轮廓格外狭窄。

和其他人种相比，

and the premolars are unique in their outline shape

compared to other hominids.

这些前齿的轮廓非常特别。

In fact, when I compare the outlines,

事实上，当我比较它们的轮廓时，

when I lay them on top of each other,

当我把一副牙骨放在另一副上，

they look very similar.

它们看上去非常相似。

We say they have "low intraspecific variations,"

我们说它们具有“低物种内多样性”

so the variation within the species is low.

也就是说，在同一物种内，变化较少。

When I compare this to groups like the australopithecines,

当我们把它们和一些类似 南方古猿的群体进行对比时，

the intraspecific variation is much larger.

物种内的多样性就大得多。

Postcranially, the team concluded

关于颅下结构，小组得出的结论是，

that the position of the shoulders suggesting naledi was a climber;

肩部的位置说明奈勒迪人擅长攀爬；

the flared pelvis and curved fingers are all primitive for the genus Homo.

宽阔的骨盆和弯曲的手指 都属于远古人的特征。

On the other hand,

另一方面，

和人类相似的腰部和足部，修长的双腿

the humanlike wrist, long slender legs and modern feet

are all consistent with other members of the genus.

都和其他人种类似。

In 2017, we announced more specimens of Homo naledi

2017年，我们公布了更多的奈勒迪人样本。

from the nearby Lesedi Chamber,

它们是在Lesedi Chamber旁边发现的，

also in the Rising Star cave system.

这个地方也属于瑞星洞系。

In addition, our geology team managed to produce an age estimate.

另外，我们的地质小组 设法做出了一个年代估算。

The date's a big deal because, up until now,

数据非常重要，因为目前为止，

we had based our analysis solely on the morphology of the specimens,

我们的分析仅仅是基于人类标本。

without previous knowledge of how old something is --

没有对年代判断的基本知识，

something which could unconsciously bias our interpretations.

也许有意无意中，我们的理解会有失偏颇。

With its small brain and flared pelvis,

看这个小小的头骨和宽阔的骨盆，

we would not have been surprised

如果早知道它们原来

if the fossils turned out to be two million years old.

已经有200万年历史了， 我们就不会如此惊讶了。

Instead, the fossils dated

其实，这些化石可以追溯到

to 235 to 336 thousand years,

23.5-33.6万年前。

an incredibly young date for such a small-brained individual.

对这么小的头骨来说， 这个年代太新，令人难以置信。

So think back to what I said earlier:

想一想我刚才说过的：

we thought that our brains were becoming larger relative to the rest of our body.

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。

Now we have a small-brained, young individual complicating this idea.

现在这个大脑体积小，年代很新的 标本让这件事复杂起来。

What does all this mean?

这都意味着什么呢？

Homo naledi has taught us

奈勒迪人给了我们一个启示，

that we need to reassess what it means to be in the genus Homo.

我们需要重新测评什么是人属。

We need to rethink what it means to be human.

我们需要重新思考什么是人类。

In fact, most of the characteristics that we use to define the genus Homo,

实际上，大多数我们 用来定义人属的那些特征，

such as brain size and hip morphology,

比如大脑尺寸和臀部形态，

are no longer valid.

都已经不再有效了。

No other species exists with this mix of primitive and derived traits.

没有哪个物种混合着 既原始又衍生的特点。

Why is there so much morphological variation in the genus Homo?

为什么会有这么多形态各异的人属？

And what force is driving that variation?

又是什么促进了这种多样性的呢？

Another implication for these fossils is that for the first time,

这些化石的另外一些影响是，它第一次

we have concrete evidence of a species coexisting in Africa,

提供了确凿的证据说明了

at 300,000 years,

30万年前非洲的物种和

现代人类的共生关系。

with modern humans.

Until this discovery,

这次发现之前，

we only had large-brained modern humans that existed in Africa.

我们以为只有大脑体积较大的 现代人在非洲存在过。

Did they interbreed with each other?

他们之间是否杂交过？

Did they compete with each other?

他们是否相互竞争？

Another implication that these fossils have

另外一个意义是，这些化石

is for the archaeologists studying stone tools in South Africa.

给考古学家提供了 研究非洲石器时代的机会。

Keep in mind that neither the Dinaledi nor the Lesedi Chambers

别忘了既不是Dinaledi， 也不是Lesedi Chambers

have any artifacts in them.

才拥有史前古器物。

However, they do overlap in time with several stone-tool industries,

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，

the makers of which are considered to be either modern humans

or direct human ancestors.

要么是人类祖先的。

This begs the question:

这就引出了一个问题：

Who made the stone tools of South Africa?

谁制造了南非的史前石器？

Brain size has historically played a key role

历史上，大脑的体积在界定物种的时候

in identifying a species as a tool user.

起到了重要作用。

The idea is that you need to have a large brain

这个概念说明，只有拥有较大的大脑，

to have even the capacity to make stone tools.

你才具备制造石器的能力。

但是我们开始怀疑这个概念了。

But that notion has been questioned.

Furthermore, Homo naledi, even with its small brain size,

进一步说，奈勒迪人虽然大脑体积小，

has a hand-wrist morphology similar to other species

手腕形状却和

that did make and use stone tools,

其他制造工具的物种类似，

suggesting it had the capability.

说明它也具备同样的能力。

With two species coexisting in Africa at 300,000 years,

考虑到这两种物种在非洲共生了30万年，

we can no longer assume we know the maker of tools

我们不能再假定我们知道，在遗址上的

at sites with no associated species.

工具制造者和别的物种没有关联。

So where does Homo naledi fit in our human evolutionary lineage?

那么，奈勒迪人应该在 人类进化线上哪个位置上呢？

Who is it most closely related to?

它最接近谁呢？

Who did it evolve from?

它从什么物种进化而来？

We're still trying to figure all that out.

我们仍然在寻找答案。

It's ironic, because paleoanthropologists are renowned

这很讽刺，因为古人类学家

for having small sample sizes.

以拥有少量的标本著称。

We now have a large sample size,

我们现在有大量的标本，

and more questions than answers.

问题却比答案更多了。

Homo naledi has taught us,

奈勒迪人给了我们启示，

has brought us a little bit closer

带我们更进一步

to better understanding our evolutionary past.

理解我们的进化史。

So while Mrs. Ples will always hold a special place in my heart,

因此我心中将会一直留有 普勒斯太太的角色，

she now shares that space with several thousand others.

她现在正在和成千上万的 人分享这个角色。

(Laughter)

（笑声）

谢谢。

Thank you.

（掌声）

(Applause)