Tree of life

網誌：生命樹

            「同一綱目的生物，其相近性可用一棵大樹來代表。這比喻可真說出了真相：青綠和發芽的嫩枝代表現存的物種；而早前成長的可代表一貫系列已滅絕的物種。在每一生長時期，所有嫩枝都千方百計開展，務求高於旁邊的小枝分枝，使其湮沒；就像生死搏鬥之下，物種或一群物種會傾力壓倒其他物種一樣。…… 新生的樹上眾多茂盛的嫩枝中，僅兩三株能夠成長並開枝散葉；故此經歷地質歷史長河的物種中，能夠遺存後世的畢竟寥寥可數。

「由樹木生長開始，不乏衰敗的樹枝；而這些大小不一、倒下的樹枝代表了那些當今已無現存的典型、我們僅認出其化石狀態的全種目、科和屬。樹腳附近各處，看到細小、蔓生的樹枝，卻得天獨厚，自全盛期存活下來，故此我們不時碰上如鴨嘴獸或肺魚等動物。它們(鴨嘴獸或肺魚)與生物上兩大分支有些少相近，看來是因為居處受保護而能在殘酷的競爭下得以倖免。幼芽發展成嫩芽，如能茁壯成長，開枝散葉，令其他較弱的枝幹湮滅，則其世代能夠繁衍於那偌大的生命樹上；於是地面佈滿敗絮殘枝，其上則覆蓋著衍生不絕的枝幹和華麗的分支。」

以上出自達爾文＜物種起源＞第三章的結語 (原文在文末)。「生命樹」一詞源遠流長，＜創世紀＞有提及，更早則見於佛經，及古埃及、古希臘文化。達爾文用之作比喻：樹冠青蔥，下面卻滿佈殘枝，是一首送別曾經盛極一時的生命的輓歌。

上面的譯文當然表達不到原文的詩意。然而，達爾文的藝術情愫卻躍然紙上：初時用上「湮沒」、「生死搏鬥 」、「衰敗」、「倒下 」、「殘酷的競爭 」等字眼，中途發生逆轉，出現了「存活」、「倖免」、「嫩芽 」、「茁壯成長 」、「繁衍」等令人鼓舞，歌頌生命的章句。文章結尾時再來一次比拼，「地面佈滿敗絮殘枝」，對應的是「覆蓋著衍生不絕的枝幹和華麗的分支」。

再看＜物種起源＞最後的段落：

「……披上了林林總總的植物，雀鳥在叢中歌唱，蟲子在空中飛舞，蠕蟲在濕潤的大地上爬，以及 ……這些巧奪天工的形態，式樣不一，大異奇趣，卻複雜地互為依賴。它們都是按照縈繞我們周邊的定律而成 ……。此所以，隨著自然界的戰鬥、饑荒和死亡，接著而來的便是我們能夠想像得到最尊尚的目標，即高等動物的誕生。」

科學本應是客觀、冷漠和實際。大自然冰冷的生死觀，達爾文用了人文、感性的面向，不自覺地將美學融匯於文字之中。我們再不能將文章裡的科學觀察員與文藝創造者辨認出來。

討論教育，常說STEM(science, technology, engineering, mathematics)。其實，生命之中，藝術(art)不可或缺。工作、家庭、人際關係，不時會令情緒偏差，行為失常。藝術可喚醒一些沉睡了的特質，將深淵內裡帶回平衡的狀態。所以，不要再說 STEM，而是說STEAM。

也不要再說 STEAM，而是回復我們初小、老人家口中的「德、智、體、群、美」。

 

9-8-2018

〔作者保留版權〕

參考：O.B. Hardison, Jr., Disappearing through the Skylight, Penguin Books, 1989.

［註］完文:

From the summary of Chapter 3, The Origin of Species:

“The affinities of all the beings of the same class have sometimes been represented by a great tree.  I believe this simile largely speaks the truth.  The green and budding twigs may represent existing species; and those produced during former years may represent the long succession of extinct species.  At each period of growth all the growing twigs have tried to branch out on all sides, and to overtop and kill the surrounding twigs and branches, in the same manner as species and groups of species have at all time overmastered other species in the great battle for life. …… Of the many twigs which flourished when the tree was a mere bush, only two or three, now grown into great branches, yet survive and bear the other branches; so with the species which lived during long-past geological periods, very few have left living …… descendants.

“From the first growth of the tree, many a limb and branch has decayed and dropped off; and all these fallen branches of various sizes may represent those whole orders, families, and genera which have now no living representatives, and which are known to us only in a fossil state.  As we here and there see a thin, straggling branch springing from a fork low down in a tree, and which by some chance has been favored and is still alive on its summit, so we occasionally see an animal like the Ornithorhynchus or Lepidosiren, which in some small degree connects by its affinities two large branches of life, and which has apparently been saved from fatal competition by having inhabited a protected station.  As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications.”

From the closing paragraph:

            “…… clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and …… these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us.  …… Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows.”