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《科学秀》由Brilliant.org赞助播出。
Around 74,000 years ago, in what's now Sumatra, a volcano called Toba exploded.
约七万四千年前，在现今的苏门答腊岛，一座名为多巴的火山爆发了。
It was the largest known eruption in at least the past two million years,
这是至少在过去两百年来最大一次的已知火山爆发，
a whole order of magnitude bigger than the 19th-century eruption of Tambora,
整个数量级比19世纪坦博拉火山爆发还大，
which is the largest volcanic eruption in recorded history.
坦博拉火山是历史上记载的最大的一次火山爆发。
The Toba eruption produced 2800 cubic kilometers of magma, deposited meters-thick layers of ash,
多巴火山爆发产生了2800立方公里的岩浆，堆积了几米厚的灰烬，
and spewed thousands of tons of sulfuric acid and sulfur dioxide into the atmosphere.
向大气层中喷发出了数万吨硫酸和二氧化硫。
It may have caused global temperatures to dip by as much as 10 degrees Celsius for the next decade
在接下来十年，可能还造成了全球气温下降10摄氏度
— with some cooling lasting nearly a thousand years.
降温持续近一万年。
This was the Middle Paleolithic Period, when the height of human technology was stone tools and fire.
这是旧石器时代中期，当时人类的顶级技术还是石头工具和火。
So you get why scientists would think the giant explosion had a serious impact on the human population.
所以你该知道科学家为什么认为这次火山爆发对人类人口有着严重影响。
But the evidence seems to show that humanity was mostly fine. And we're not totally sure why.
但其证据似乎表明人类大部分都没受到影响。并且我们也不能够完全确定其中原因。
The main climate effects from volcanoes come from the ash and sulfurous gases they belch out.
火山爆发的主要气候影响来自火山喷发出的灰烬和含硫气体。
After a big eruption, this stuff can circulate in the atmosphere for years, reflecting sunlight
经历大型火山喷发后，这些物质会在大气层中流通多年，反射阳光
and causing global cooling — hence that possible decade-long volcanic winter caused by Toba.
并引发全球降温—因此多巴火山爆发引发了可能长达十年的火山冬天。
It makes sense that an endless global winter would be bad news for the planet's inhabitants.
无尽的全球冬季对地球居民而言是个坏消息，这一点是说得通的。
For comparison, the eruption of nearby Tambora turned 1816 into what became known as "the year without a summer"
比较来看，附近坦博拉火山的喷发造就了1816年—那个“没有夏季的年份”
and led to crop failure and famine around the world.
并且导致世界范围内的作物减产和饥荒。
And Tambora only put out 175 cubic kilometers of stuff, compared to Toba's thousands.
和多巴火山喷发产生的数千立方公里相比，坦博拉火山产生的物质仅为175 立方公里。
So in the 1990s a scientist named Stanley Ambrose proposed what's been called the Toba catastrophe theory.
因此，20世纪90年代，一位名为史坦尼·安布鲁士的科学家提出了多峇巨灾理论。
His idea was that the eruption might have nearly wiped out humanity,
他认为火山喷发可能会导致人类几近灭绝，
reducing the global population from around 100,000 people to around 10,000.
将全球人口从约十万减少至约一万。
People of African ancestry are more genetically diverse than other humans,
非洲血统人群相比其他人类拥有更多基因多样性，
which seems to suggest that the rest of humanity experienced a genetic bottleneck at some point
这似乎表明剩余人类在某些时期经历了一种种群遗传瓶颈效应
— a dramatic drop in population that resulted in a loss of genetic diversity.
—人口的骤降导致遗传多样性的损失。
According to the Toba catastrophe theory, the giant volcanic eruption and the global winter that followed were the culprits.
根据多峇巨灾理论，巨型火山喷发和随之而来的全球冬季是元凶。
Africans' tropical home, the theory goes, helped buffer them against the effects of the volcanic winter
按照该理论，非洲人的热带家园帮助他们缓冲火山冬季的影响
and prevented the huge population declines that happened in other areas. Which sounds plausible.
并防止其他地方人口骤降情况的出现。这听起来貌似有些道理。
But as we've continued to look for evidence of the so-called Toba catastrophe, things have become a lot less clear.
但随着我们继续寻找所谓多峇巨灾的证据，事情变得更加模糊。
For one thing, scientists don't all agree on just how bad the eruption's effects on the climate actually were.
有一件事是科学家们都不同意的—火山喷发影响对气候的影响到底有多糟糕。
In 2010, researchers created a mathematical model of the eruption's possible climate effects,
2010年，研究人员创造了一种火山喷发可能气候影响的数学模型，
based on how the particles it shot into the atmosphere would have reflected solar energy.
该模型是基于火山向大气层发射的颗粒对太阳能的影响。
Their results showed that the eruption's global effects may have been milder and shorter-lived than originally theorized
他们的结论表明火山喷发的全球影响或许比原来理论上所认为的更加温和，间期更短
— like a three to five degree drop in temperature for two or three years, instead of a ten degree drop that lasted a decade.
—可能是在2到3年间，温度会下降3到5度的样子，而不是下降10度，持续10年。
That's still a really big deal — a drop of just one degree was enough to cause the year without a summer.
这一点仍然很关键—哪怕是一度的变化都足以引起全年无夏。
But maybe it wasn't a big enough deal to kill off 90% of the world's population.
但或许还不足以消灭全球90%的人口。
Recent research has also found that charcoal and plant particles in sediment samples from Africa's Lake Malawi
近期研究还发现来自非洲马拉维湖的泥沙试样中的碳屑和植物颗粒
don't show any big change in plant life before and after the eruption.
并未显示火山喷发前后植物生命有任何大的变化。
Which is something you'd definitely expect to see if there had been a ten-year-long winter.
如果经历十年冬季，那么你绝对会看到大的变化。
And, the more archaeologists look for evidence of what actually happened to humans around this time,
科学家寻找的这个时期人类遭遇的证据越多，
the more it looks like the answer is … nothing too devastating.
答案就越像是—并没有发生什么毁灭性事情。
A recent study from the coast of South Africa didn't find any interruption in human activity there.
南非海岸的一项近期研究并没有发现那里的人类活动有任何中断。
There is a layer of tiny volcanic glass shards from the eruption in archaeological deposits,
在考古沉积物中有一层来自火山爆发的火山玻璃屑，
but the human artifacts from before and after are pretty much the same.
但来自前后的人类手工艺品也差不多。
Some of the researchers involved suggested that living in a warm,
一些参与其中的研究人员表示生活在温暖、资源丰富的
coastal area with lots of resources might have helped people there thrive despite the eruption.
海岸地区或许帮助那里的人们在火山喷发时也能兴旺。
But archaeological studies from much closer to the blast zone in India
但来自印度喷发区附近的考古研究
don't show much change in human communities there around the time of the eruption, either.
没有表明该地人类群落在火山喷发时期出现很多变化。
Humans probably were affected by Toba — the largest volcanic eruption in our history would be hard to ignore.
人类或许受到了多巴山的影响—这个历史上最大的火山喷发很难忽略。
But the latest evidence makes it seem pretty unlikely that 90% of the global population was killed off,
但最近的证据表明这次事件很难消灭世界90%的人口，
and today most scientists consider the Toba catastrophe theory to be debunked.
如今多数科学家考虑要揭穿多峇巨灾理论的真面目。
But that still leaves the question of what caused the genetic bottleneck as humans were expanding out of Africa.
但还是有些遗留问题—人类从非洲走出来时，到底是什么造成了种群遗传瓶颈效应。
The most widely accepted explanation today is that it was a simple case of what's called the founder effect.
如今普遍接受的解释是—这是一种建立者效应。
Only relatively small groups of humans ever made the trek out of Africa,
仅有相对一小群人得以长途跋涉离开非洲，
limiting the genetic diversity of their descendents as they populated the rest of the world.
在他们散落世界各地时，限制了他们后代的遗传多样性。
Perhaps the closest parallel to Toba threatening the world today is the massive volcano underneath Yellowstone National Park.
或许能够和多巴威胁相提并论的是黄石国家公园地底下的巨大火山。
One of the Yellowstone supervolcano's past eruptions, around two million years ago, was almost on the scale of Toba,
黄石公园之前超级火山喷发之一是在两百万年前，其规模和多巴爆发几乎一样，
spewing about 2500 cubic kilometers of magma.
喷射出了约2500立方公里的岩浆。
And today, humans rely on way more technology that would be negatively affected than we did at the time of Toba, from agriculture to airplanes.
如今，人类依赖的科技，比如农耕科技和飞机，相比多巴山时代会造成更加负面的影响。
In some ways, our society is more fragile than it was back then.
在某些方面，我们的社会比以往更加脆弱。
So a modern Yellowstone eruption would be really bad news.
因此现代黄石公园火山喷发真的是个坏消息。
But volcanologists say the chances of Yellowstone blowing up any time soon are incredibly small, so don't lose too much sleep over it.
但火山学家表示黄石公园火山喷发的可能性很小，因此不用担心的睡不着觉。
Ultimately, though, even an eruption as large as Toba's didn't really alter the course of humanity's genetic history.
最后和巴山一样大规模的喷发并不会对人类遗传历史进程有什么大影响。
Mind-bogglingly huge volcanic eruptions like Toba are a reminder of just how violent our planet's geology can be
令人难以置信的大型火山喷发，如多巴山，就像是在提醒我们，我们这个星球的地质可以有多么的暴力
— but in this case, it also showed that our species can be pretty resilient. Go humans!
但这也表明我们这个物种的恢复力相当好。进击吧，人类！
Thanks to Brilliant.org for sponsoring this episode, and this whole week, of SciShow.
感谢 Brilliant.org对本节目的赞助。
Trying to unpack natural disasters from the past, or make predictions about the future
想要了解过去的自然灾难或是对未来做出预言
is a lot more interdisciplinary than we tend to think.
比我们想的更加复杂，领域涉及更广。
Scientists need to know about geology and weather, and in this case anthropology, but also probability.
科学家需要了解地质学和气候，以及人类学，还有概率学。
All this week we're pointing out fun, interactive courses on Brilliant.org, and one of my favorites is Probability in Science.
本周我们将推荐Brilliant.org上好玩的交互性课程，《Probability in Science》是我的最爱之一。
This particular quiz starts you out learning about probability from the point of view of a medical doctor,
该课程向让你从医师的角度了解概率学
but soon you're in deep space trying to use probability to disprove aliens. I mean, it's never been aliens...yet.
但很快你就会身处外太空尝试利用概率学反驳外星人观点。我是说，现在还没出现过外星人。
You can check out the wide array of courses by going to Brilliant.org/SciShow.
你可以登录Brilliant.org/SciShow学习各种课程。
Right now, the first 200 SciShow viewers to sign up will get 20% off of the annual premium subscription.
现在前200名通过连接注册的用户将获得订阅年费八折优惠。
And let me know how you do on the Probability quiz! Or if you prove the existence of aliens!
让我看看大家在概率小测试中做得怎么样！或是你证明了外星人的存在！
