Human origins.

人類起源。

Who are we?

我們是誰？

Where do we come from,

我們來自何處？

and how do we know?

我們怎麼知道的？

In my field, paleoanthropology,

在我的領域，古人類學，

we explore human origins --

我們探究的是人類的起源——

the \"who\" and \"where\" questions --

「誰」以及「何處」的問題——

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

做法是分析數千年 甚至數百萬年的化石。

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

2015 年，我和同事組成的團隊

our genus --

為一個新物種命名， 它隸屬「人屬」——

Homo naledi.

和我們同屬——

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

納萊迪人（Homo naledi）。

The last common ancestors between humans and chimps

咱們先倒帶一下，把情境帶進來。

date somewhere between six and eight million years.

人類和黑猩猩的共同祖先 最後出現是在

The earliest hominins,

約六百萬年前到八百萬年前之間。

or earliest human ancestors,

最早的人族，

evolved into a group known as the australopithecines.

或說最早的人類祖先，

The australopithecines evolved into the genus Homo

演化成為一般所知的南方古猿。

and eventually modern humans -- us.

南方古猿演化成為人屬，

With each new fossil discovery,

最終演化成現代人——我們。

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

每發現一塊新化石，

and where we came from.

我們就稍微更進一步 了解我們是誰，

With these new fossil finds,

及我們來自何處。

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

因為這些化石的新發現，

Until this discovery,

我們了解到，我們得要 修改這個樹狀圖。

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

在這個發現之前，

Current fossil evidence suggests

我們以為我們很清楚知道 演化改變的模式。

that the earliest populations of the genus Homo evolved in Africa

目前的化石證據指出

somewhere between two and three million years.

最早的人屬是在非洲演化出來的，

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

大約在兩百萬到三百萬年間。

of the first modern humans.

快轉約三十萬年，

While the fossil record between these time frames in Africa

到我們看到最早的 現代人起源之處。

is relatively sparse,

雖然在非洲這些時間點 之間的化石記錄

the fossils nonetheless demonstrated certain trends

相對比較稀少，

from our earliest ancestors to modern humans.

但不論如何，化石仍然 顯示出了某些趨勢，

For example, our brains were becoming larger

從我們最早的祖先 到現代人的趨勢。

relative the rest of our body.

比如，相對於我們的身體， 我們的大腦越來越大。

Our pelves were becoming more bowl-shaped,

我們的骨盆越來越像碗形，

and our hand-wrist morphology, or form,

我們手腕的形態學，或者說形式，

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

顯示出我們的握法有所不同， 我們開始製造及使用石頭工具，

and spend less time in the trees.

花在爬樹上的時間變少。

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

這些新化石打斷了我們認為 我們對於這些趨勢所知的一切，

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

強迫我們改變我們對於 人類演化的看法。

South Africa in general,

南非大部分的地方， 但特別是「人類的搖籃」地區，

but the Cradle of Humankind in particular,

有許多地點都找出了數十萬件化石。

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

我還是大學生時， 就愛上了其中一件……

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

普雷斯太太。

Mrs. Ples.

這是 210 萬年前人類祖先的頭骨。

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

從那時起，

From that point on,

我就下決心要到南非 以及研究人類演化。

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

2003 年，我初次到那裡，

I first traveled there in 2003,

我的確得以見到 我摯愛的普雷斯太太。

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

（笑聲）

(Laughter)

但我的興奮無法言喻，

But words can hardly convey my excitement

因為我被選為青年科學家，

when I was chosen as an early career scientist

且是李貝加挑選的， 他是聞名世界的古人類學家，

by Lee Berger,

讓我擔任主要分析師之一，

a world-renowned paleoanthropologist,

分析近期挖出但尚未發佈的化石。

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

這些貴重的化石 是在一個新地點發現的，

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

這個地點叫做迪納萊迪洞穴， 屬於新星岩洞體系。

called the Dinaledi Chamber in the Rising Star cave system.

物種通常是根據頭骨、 下顎來命名，

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

或，非常罕見的狀況，

or, very rarely,

是用許多顱後或頸後元素來命名。

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

來自迪納萊迪的化石全部 加在一起又是另一回事了。

The fossils from Dinaledi were another story altogether.

前所未有，近一千八百個樣本——

An unprecedented approximately 1800 specimens --

只是截至目前為止——

so far --

已經從新星岩洞體系挖出來，

have been excavated from the Rising Star system,

代表至少十五個人的骸骨。

representing at least 15 individual skeletons.

我被邀請加入一個研究團隊，

The research team that I was invited to join

其工作任務是在描述、 比較、分析那些化石，

was tasked with describing, comparing and analyzing the fossils,

且有個很困難的目標： 辨識出那些化石屬於什麼物種。

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

我們被依據專長領域分開來。

We were divided up into our different areas of expertise.

我們也被分到實驗室的不同區域。

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

所以，研究化石手的人 在「手部大地」，

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

骨盆的人在「髖部天堂」……

\"Hip Heaven\" for the pelvis ...

我則是在「牙齒亭」。

I was in the \"Tooth Booth.\"

（笑聲）

(Laughter)

在實驗室中經過了漫長、 緊繃的白天之後，

And after long, intense days in the lab,

不同的團隊會在晚上見面， 討論我們的的發現，

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

仍然投注在我們的分析 所產生的問題上。

still consumed by questions from our analyses.

大家的詮釋差異大到不可思議。

It was incredible how different the interpretations were.

每個身體部位似乎 都來自不同的物種，

Each body part seemed to come from a different species,

詮釋根據是我們從化石 記錄習得的知識。

based on what we knew from the fossil record.

我們所看到的一系列特徵 並不符合任何已知物種。

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

如果我們只發現了頭骨， 我們可能會稱它是某樣東西；

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

如果只發現了骨盆， 可能又會稱它是另一樣東西。

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

這些骨骸的解剖學並不合理，

The anatomy of the skeletons didn't make sense

用我們對人類演化的既有 知識框架是說不通的。

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

它屬於人屬嗎？

Did it belong in the genus Homo?

它會不會是更新世靈長類動物？

Should it be an australopithecine?

那些兩足動物，更像人猿的祖先？

Those bipedal, more apelike ancestors?

或者，也許它自己另屬一種物種。

Or perhaps it should be its own species.

最終，經過許多的考量，

Ultimately, after much deliberation,

我們決定這些新星樣本 的確有理由成為一種新物種，

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

我們稱之為納萊迪人。

which we called \"Homo naledi.\"

從頭到腳，

From the head to the feet,

這些化石呈現出混合了 原始的，或祖先的特徵

the fossils present a mosaic of primitive, or ancestral,

以及衍生的，或更像現代的特徵。

and derived or more modern-like features.

頭骨就很明顯是衍生的，

The skull is quite derived,

外觀上很類似早起的人屬代表，

appearing most similar to early representatives of the genus Homo,

比如巧人和直立人。

like Homo habilis and Homo erectus.

然而，大腦幾乎不到 現代人大腦的一半。

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

比所有已發現的其他 早期人類的大腦都還要小。

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

身為研究牙齒的人，

As someone who studies teeth,

我可以主張從那個地點挖出的 化石中最酷的就是這些了。

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

（笑聲）

(Laughter)

這一組化石包含了 190 個 完整或部分牙齒，

The assemblage consists of 190 whole or fragmentary teeth

年齡從非常年輕到非常老都有。

that range in age from very old to very young.

和骨骸一樣，

Like the skeletons,

牙齒也呈現出遠古和衍生的特性。

the teeth present a mix of primitive and derived traits.

就現代人類來說，

In modern humans,

第三個臼齒通常 是最小的，第一個最大，

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

但納萊迪人具有原始的狀態，

but Homo naledi has the primitive condition

也就是第三個臼齒最大， 第一個最小。

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

前面的牙齒，也就是門牙和犬齒，

The anterior teeth,

對於人屬來說很小。

or the incisors and canines,

下犬齒上面有個尖處——

are small for the genus Homo,

額外的尖端讓它呈現 獨特的連指手套形狀，

and the lower canine has a cuspulid on it --

一些早期人類的樣本 也有這個特性，

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

如直立人。

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

在我看來，牙齒的 整體形狀很奇特。

The overall shape of the teeth looked odd to me,

所以我進行了冠形分析，

so I performed crown-shape analysis

分析乳牙的咬合表面——

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

在你們的左邊——

on your left --

還有你們右邊的 永久前臼齒及臼齒。

and the permanent premolars and molars on your right.

乳牙特別窄，

The deciduous teeth are especially narrow,

與其他人類祖先相比，

and the premolars are unique in their outline shape

前臼齒的輪廓形狀很獨特。

compared to other hominids.

事實上，我在比較輪廓時，

In fact, when I compare the outlines,

我把它們疊在一起時，

when I lay them on top of each other,

它們看起來非常相似。

they look very similar.

我們說，它們的「種內變異很低」。

We say they have \"low intraspecific variations,\"

也就是在這個物種中的變異很低。

so the variation within the species is low.

當我把它和南方古猿 等族群做比較時，

When I compare this to groups like the australopithecines,

種內變異就大很多。

the intraspecific variation is much larger.

顱後的部分，團隊的結論是

Postcranially, the team concluded

肩膀的位置，顯示出 納萊迪人會向上攀爬；

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

就人屬來說，喇叭形的骨盆 和彎曲的手指都是原始的特徵。

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

另一方面，

On the other hand,

像人的手腕、修長的腿， 以及現代的腳，

the humanlike wrist, long slender legs and modern feet

都和同屬的其他物種一致。

are all consistent with other members of the genus.

2017 年，我們公佈了 更多納萊迪人的樣本，

In 2017, we announced more specimens of Homo naledi

是從附近的雷沙迪洞穴挖出來的，

from the nearby Lesedi Chamber,

也是隸屬新星岩洞體系。

also in the Rising Star cave system.

此外，我們的地質學團隊 做出了時代估計。

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

年代是很重要的， 因為，到目前為止，

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

我們的分析全都立基在 樣本的形態學上，

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

事先完全不知道 什麼東西有多古老——

without previous knowledge of how old something is --

我們的詮釋有可能 在不知不覺中受到偏見影響。

something which could unconsciously bias our interpretations.

因為有很小的大腦 以及喇叭形的骨盆，

With its small brain and flared pelvis,

如果最後確認這些化石 是兩百萬年前的，

we would not have been surprised

我們也不會感到意外。

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

結果，這些化石的時間

Instead, the fossils dated

卻是 23 萬 5 千年 到 33 萬 6 千年之間，

to 235 to 336 thousand years,

就大腦這麼小的人來說， 年代這麼近是很不可思議的。

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

所以，回想一下我剛剛說的：

So think back to what I said earlier:

我們以為，相對於我們的身體， 我們的大腦變得越來越大。

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

現在，我們找到了年代更近、 大腦卻很小的人，

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

讓這個想法變複雜了。

What does all this mean?

這一切意味著什麼？

Homo naledi has taught us

納萊迪人教我們的是，

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

我們需要重新評估 身為人屬的意義。

We need to rethink what it means to be human.

我們需要重新思考 身為人類的意義。

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

事實上，我們用來 定義人屬的大部分特徵，