關於地球知多少（中）

05-18

關於地球知多少（中）

來自專欄動物君

中文字：815，建議閱讀時間：1.1分鐘；英文字：521

What is the deal with whales and dolphins, they are mammals but they live in the water with fish. These animals spend their whole life in the water but need oxygen to

live, if the strongest survive why are these animals still alive. A lot of

people think that evolution has stopped but it is still going on and it cannot be

stopped, even humans are still evolving. First, we will explain how the whales

and dolphins evolved to the point that they are up to now. The closest living

mammals on land that』s related to the whales is the hippopotamus or hippos for

short.

The whales came from an animal called Pakicetus which lived on the earth,which means when all the creatures left the ocean to evolve the ancestors of the whale decided to go back into the ocean. This is the time line of the whale to show how it

looked before it became a whale.

48 million years ago – Pakicetus

these animals looked like giant slim rats, these animals walked on the land. Which

use to forage for food near water so it would live next to water.

47 million years ago -Ambulocetus

which took the form of something that look between a crocodile and a rat and would hunt for food in the water.

46 million years ago - Maiacetus

which took on a sea lion appearance, which kept mainly in the water and just like other animals which spend their time in the water may have only gone on land to

breed.

37 million years ago – Dorudon

Now it』s completely an aquatic animals, the forelimbs have become flippers, hind limbs have reduced to a point they do not do anything and the tail has changed into a fin.

34 million years ago – Llanocetus

Starting to take the shape of the modern whale, teeth have been reducing which shows evidence of filter feeding, the nostrils are on the back of the skull, fore

limbs are the shape of modern flippers and the hind legs have completely gone.

As you can see the changes of these animals has made just from feeding near a lake for so long, the lungs got stronger over time and the offspring of the animals would

have benefited from this. this has also happened for humans as well,let』s take

the same scenario of the evolution of the whale of going into the water a lot. This

type of evolution has been seen in Japan with the female population in a

fishing village. The women of this village have been shell divers for 2000 years,

these women were able to fill their lungs and dive under water for long periods

of time. The offspring of these women would have developed stronger lungs, so

after 2000 years. the time the woman could spend under water would have

increased with ever generation, although with new laws with fishing means that

the last mermaids wouldn』t be able to carry on with this tradition so that the

ability to breathe for a long time underwater would be lost by each generation

that started to breathe normally on land.

中文翻譯：

我們該如何認識鯨魚與海豚呢，它們屬於哺乳動物，但是它們又與水裡的魚類生活在一起，它們一生都活在水裡，但是又離不開氧氣，如果是強者生存的話，為什麼它們依舊還活著。很多人認為進化停止了，但事實上它還在進行，也不可能停止，甚至是人類也在進化著。這期我們就來討論鯨魚與海豚是如何進化到如今的程度，與鯨魚血緣關係最近的陸生動物是河馬。

鯨魚來源於一種生活在陸地上，稱之為巴基鯨的物種。當所有的生物離開海洋，為陸地生活開始進化時，鯨魚的祖先卻又返回了海洋。隨著時間線軸，各位可以發現鯨魚是如何一步步進化出如今的形態的。

48000000年前——巴基鯨

這些動物看起來就像身材苗條的大型老鼠，它們行走在陸地上，但是經常在水域附近覓食，這也就是為什麼它們生存在沿岸地區。

47000000年前——陸行鯨

從外觀上看它界於鱷魚與老鼠之間，此時這類動物能夠在水中覓食。

46000000年前——慈母鯨

此時這類動物有著海獅的外表，它們大不部分時間生活在水中，跟其他海獅類似，只有在繁殖期間才會在陸地活動。

37000000年前——矛齒鯨

此時的它是一種完全的水生動物，它們的前肢進化成為鰭，後肢萎縮到只剩下一個點，基本起不了任何作用，尾巴也進化成為強有力的鰭。

34000000年前——刻齒鯨

這階段，刻齒鯨開始有了現代鯨魚的外形，牙齒也開始逐漸退化，這也證明，該階段它們採用濾食性攝食的策略。鼻孔長在頭蓋骨的上方，前肢就是現在鯨魚的鰭，後肢則完全消失。

正如大家所發現的，動物會根據獵食環境而發生相應地進化。它們的肺功能變得越來越強大，後代也是得益於此能夠在水中生存下去。在人類中也有這樣的例子，由於長期生活在水中，肺的功能得到了極大得提升。在日本的一個捕魚村落里，生活在這裡的一群女性因生活所需，有潛水的傳統，世世代代長期潛水長達2000年，現如今，她們能夠在肺部吸滿氣後，在水中閉氣相當長的一段時間，這群女性的後代都進化出了一個異於常人的肺。但是現存法律已經禁止了潛水這一傳統，所以關於這個「美人魚」的傳說恐怕會遺失，畢竟大自然始終遵循用進廢退這一亘古不變的法則。