(单词翻译:单击)
Hey there! Welcome to Life Noggin. Oh that's the classic subscribe button! Very vintage!
大家好，欢迎来到脑洞大开的生命奇想！奥这是经典的订阅按钮！非常古老！
Around 50 million years ago, an ancestor of the common day whale lived and walked on land with four legs.
5000万年前，普通鲸鱼的一个祖先用四条腿在陆地上生活和行走。
Like other aquatic mammals, such as dolphins and porpoises, this wolf-sized animal, known as Pakicetus, is part of the cetacean group.
像其他水生哺乳动物，如海豚和鼠海豚一样，这种狼大小的动物被称为巴基鲸，是鲸类动物的一员。
It is one of the earliest whales and the oldest cetacean discovered that had functional legs.
它是最早发现的鲸类动物之一，也是最早发现的有腿的鲸类动物。
And that begs the question - what if current day whales had legs?
这就产生了一个问题-如果当今的鲸鱼有腿的话会怎么样呢？
And, no, I'm not sure anyone actually asked for this, not a single soul, but I'm going to do it anyway.
我不认为有人真的问过这个问题，没有人，但是我要回答这个问题。
Whales today are much bigger than Pakicetus was. And I mean MUCH bigger.
今天的鲸鱼比巴基鲸要大得多。我是说大太多。
The largest whale, the blue whale, can weigh up to 180,000 kilograms and reach 30 meters in length.
最大的鲸鱼蓝鲸重量可达18万千克，长度可达30米。
That is 4,000 times bigger than the estimated 45 kilogram Pakicetus,
据估计，巴基鲸有45千克，蓝鲸的重量比它大4000倍。
and 30 times bigger than the current largest land animal, the African Elephant, which weighs around 6,000 kilograms.
而且蓝鲸比目前最大的陆地动物非洲象大30倍，非洲象重约6000公斤。
As fish-eaters, this walking monstrosity would need to reside near coastlines or riverbeds so it could spend its days fishing in the water,
作为食鱼动物，这种会走路的怪物需要生活在海岸线或河床附近，这样它才能在水中捕鱼，
similar to Pakicetus who ate fish as well as small land animals.
类似于吃鱼和小的陆地动物的巴基鲸。
However, since they are much bigger, if they stuck to their current diet and ate solely fish,
然而，因为它们要大得多，如果它们坚持现在的饮食，只吃鱼的话，
these whales would need to feed more and therefore spend more time in the water.
那么这些鲸鱼就需要吃更多的鱼，因此它们要在水里待更多的时间。
Perhaps they would look a bit like their other ancestor, Ambulocetus natans, whose name actually translates to "walking whale that swims."
也许它们看起来像是它们的其他祖先，陆行鲸，这个名字的翻译就是“会游泳的行走鲸鱼”。
They lived about 50 to 48 million years ago and had shorter legs with webbed feet and was a similar size and shape of an American alligator.
它们大约生活在5000万到4800万年前，腿较短，脚上有蹼，大小和体形与美洲鳄相似。
So when did whales lose their legs? Well, over the 15 million years following Pakicetus,
所以鲸鱼的腿是什么时候消失的呢？在巴基鲸后的1500万年前，
they transitioned to a solely aquatic lifestyle and their limbs slowly became smaller and smaller.
它们转变成一种完全水生的生活方式，它们的四肢慢慢地越变越小。
Eventually, their front limbs became flippers and their hind limbs became weak and unnecessary.
最终，它们的前肢变成了鳍状肢，而它们的后肢变得虚弱和多余。
However, according to a 2006 study, they didn't completely lose their hind limbs until about 1 million years later, or 34 millions years ago.
然而，根据2006年的一项研究，它们直到大约100万年后，也就是3400万年前才完全失去了后肢。
This study aimed to pinpoint the genetic changes that led to hind limb loss
这项研究旨在找到导致后肢消失的基因变化。
and discovered a drastic change that inactivated a gene essential for limb development called, and I'm not joking, Sonic hedgehog or Shh.
他们发现了一个使对四肢发育重要的基因失活的重大变化，我没开玩笑，这个基因叫做音猬因子。
Without Shh, they are unable to grow a partial or complete limb. Through evaluating dolphin embryos, which are a relative of the whale,
没有音猬因子，它们就不能长出部分的或完整的四肢。通过分析鲸鱼的亲戚海豚的胚胎，
the scientists found that the Hand2 gene, which turns on the Shh gene, was inactive and therefore hind limb development was impossible.
科学家们发现，开启音猬因子的Hand2基因是没有活性的，因此后肢发育是不可能的。
They were able to trace back when this first occurred by using fossil data.
通过使用化石资料，他们可以追踪到这种情况第一次发生的时候。
But while this study helps to explain the evolution of whale hind limbs, the timeline is still up for debate,
但是，尽管这项研究帮助解释了鲸鱼后肢的演变，但是具体时间还是有待讨论。
as the deactivation of Hand2 and subsequently Shh could have happened gradually up until our modern version of the whale came about.
因为Hand2基因和随后的音猬因子的失活可能是逐渐发生的，直到我们现代版本的鲸鱼出现。
I for one am happy that these giants have to stay in the water in your world.
我很高兴这些庞然大物在你们的世界里呆在水里。
In my world some whales still have legs and it is almost impossible to throw a beach party!
在我的世界里，一些鲸鱼仍然有腿，几乎不可能举办海滩派对！
So are there any other animals that you want us to talk about next? Which animal is your favorite?
接下来你还想让我们讨论其他动物吗？你最喜欢哪种动物？
Let me know in the comment section below! Curious to know how we can engineer ourselves to live underwater? Check out this video!
请在下面的评论区告诉我！想知道我们如何在水下生活吗？看看这个视频！
since water is H20, a combination of hydrogen and oxygen, can we get oxygen from water then too?
既然水是由氢和氧构成的，那我们能从水中获取氧气吗？
Unfortunately, no, to get oxygen through water we probably need to have gills like a fish.
不幸的是，不能，我们可能得像鱼一样拥有鱼鳃才能在水中获取氧气。
Thank you so much for watching and liking this video!
非常感谢观看并点赞这个视频！
And as always my name is Blocko! This has been Life Noggin!
我是宝高，这里是脑洞大开的生命奇想。思考不要停！
