The Greatest Show on Earth - The Evidence for Evolution Richard Dawkins 2009
CHAPTER 2 DOGS, COWS AND CABBAGES
WHY did it take so long for a Darwin to arrive on the scene? What delayed humanity’s tumbling to that luminously simple idea which seems, on the face of it, so much easier to grasp than the mathematical ideas given us by Newton two centuries earlier – or, indeed, by Archimedes two millennia earlier? Many answers have been suggested. Perhaps minds were cowed by the sheer time it must take for great change to occur – by the mismatch between what we now call geological deep time and the lifespan and comprehension of the person trying to understand it. Perhaps it was religious indoctrination that held us back. Or perhaps it was the daunting complexity of a living organ such as an eye, freighted as it is with the beguiling illusion of design by a master engineer. Probably all those played a role. But Ernst Mayr, grand old man of the neo-Darwinian synthesis, who died in 2005 at the age of 100, repeatedly voiced a different suspicion. For Mayr, the culprit was the ancient philosophical doctrine of – to give it its modern name – essentialism. The discovery of evolution was held back by the dead hand of Plato.
THE DEAD HAND OF PLATO
For Plato, the ‘reality’ that we think we see is just shadows cast on the wall of our cave by the flickering light of the camp fire. Like other classical Greek thinkers, Plato was at heart a geometer. Every triangle drawn in the sand is but an imperfect shadow of the true essence of triangle. The lines of the essential triangle are pure Euclidean lines with length but no breadth, lines defined as infinitely narrow and as never meeting when parallel. The angles of the essential triangle really do add up to exactly two right angles, not a picosecond of arc more or less. This is not true of a triangle drawn in the sand: but the triangle in the sand, for Plato, is but an unstable shadow of the ideal, essential triangle.*1
How desperately unevolutionary that picture is! The Platonist regards any change in rabbits as a messy departure from the essential rabbit, and there will always be resistance to change – as if all real rabbits were tethered by an invisible elastic cord to the Essential Rabbit in the Sky. The evolutionary view of lifes radically opposite. Descendants can depart indefinitely from the ancestral form, and each departure becomes a potential ancestor to future variants. Indeed, Alfred Russel Wallace, independent co-discoverer with Darwin of evolution by natural selection, actually called his paper ‘On the tendency of varieties to depart indefinitely from the original type’.*2
*1 これは、おそらくイデアの限界であると思う。その意味で、洞窟の比喩と、ニーチェの真理批判とは違う意味だろう。しかし、より高次の次元から考えるとそれは些細な違いに過ぎないとおもう。というのは、イデアというものが、まさにニーチェの言葉を借りるなら、遠近法的仮像なのだから。そして、それも、ご存知の通り影の思想なのだから。その意味で、ビトゲンシュタインと同じ。その限りで、無我の思想というのが、もっとも完成された思想のうちの一つになるのかもしれない。
*2 やはり、今日の進化論的にはイデアの思想は批判されるものかもしれないが、おそらく、そのような批判はプラトンの主張を文字通りの意味にしか、表面的にしか理解してないものがするのだろう。洞窟の比喩とイデアということを考慮するなら。というのは、何かのイデアを正確には、知覚できないのだから。つまり、もし、ある特定の対象について、あるイデアを想起したとしても、それは影にすぎないのだから、イデアというものが、一つの仮定にすぎないということを前提としているから。
このようなことから、理論モデルではなくて、実際の具体的な人間のア・プリオリと、ア・ポステリオリとの関連の探求が今後の課題になるのではないだろうか。しかし、ある人にとっては、それは、完全にア・プリオリだと思うけれども。というのは、因果律を純粋に受け入れるとそうなるのだから。もっとも、ア・プリオリすら超越しているということはできると思う。そのような意味で、神の存在を肯定はできるだろうし、事実、正確にこのような方法ではないと思うけれど、信仰とはそのような形で成り立つと説明されてきた。だけれども、その信仰も、形而下に還元される時、誤りになるという問題点を抱えていることに注意しなければならない。人間的であるということを。
If there is a ‘standard rabbit’, the accolade denotes no more than the centre of a bell-shaped distribution of real, scurrying, leaping, variable bunnies. And the distribution shifts with time. As generations go by, there may gradually come a point, not clearly defined, when the norm of what we call rabbits will have departed so far as to deserve a different name. There is no permanent rabbitiness, no essence of rabbit hanging in the sky, just populations of furry, long-eared, coprophagous, whisker-twitching individuals, showing a statistical distribution of variation in size, shape, colour and proclivities. What used to be the longer-eared end of the old distribution may find itself the centre of a new distribution later in geological time. Given a sufficiently large number of generations, there may be no overlap between ancestral and descendant distributions: the longest ears among the ancestors may be shorter than the shortest ears among the descendants. All is fluid, as another Greek philosopher, Heraclitus, said; nothing fixed. After a hundred million years it may be hard to believe that the descendant animals ever had rabbits for ancestors. Yet in no generation during the evolutionary process was the predominant type in the population far from the modal type in the previous generation or the following generation. This way of thinking is what Mayr called population thinking. Population thinking, for him, was the antithesis of essentialism. According to Mayr, the reason Darwin was such an unconscionable time arriving on the scene was that we all – whether because of Greek influence or for some other reason – have essentialism burned into our mental DNA.*3
*3 結局は、イデアの基礎の元、ヘーゲルの弁証的方法を進化論的な意味での使用でやっているに過ぎないのか。あるいは、それは過ぎないという表現で軽視してはいけなくて、我々に決定的な避けることのできない、そして逆に、それどころかこのような思想にしか還元できないということなのであろうか。
CHAPTER 2 DOGS, COWS AND CABBAGES
WHY did it take so long for a Darwin to arrive on the scene? What delayed humanity’s tumbling to that luminously simple idea which seems, on the face of it, so much easier to grasp than the mathematical ideas given us by Newton two centuries earlier – or, indeed, by Archimedes two millennia earlier? Many answers have been suggested. Perhaps minds were cowed by the sheer time it must take for great change to occur – by the mismatch between what we now call geological deep time and the lifespan and comprehension of the person trying to understand it. Perhaps it was religious indoctrination that held us back. Or perhaps it was the daunting complexity of a living organ such as an eye, freighted as it is with the beguiling illusion of design by a master engineer. Probably all those played a role. But Ernst Mayr, grand old man of the neo-Darwinian synthesis, who died in 2005 at the age of 100, repeatedly voiced a different suspicion. For Mayr, the culprit was the ancient philosophical doctrine of – to give it its modern name – essentialism. The discovery of evolution was held back by the dead hand of Plato.
THE DEAD HAND OF PLATO
For Plato, the ‘reality’ that we think we see is just shadows cast on the wall of our cave by the flickering light of the camp fire. Like other classical Greek thinkers, Plato was at heart a geometer. Every triangle drawn in the sand is but an imperfect shadow of the true essence of triangle. The lines of the essential triangle are pure Euclidean lines with length but no breadth, lines defined as infinitely narrow and as never meeting when parallel. The angles of the essential triangle really do add up to exactly two right angles, not a picosecond of arc more or less. This is not true of a triangle drawn in the sand: but the triangle in the sand, for Plato, is but an unstable shadow of the ideal, essential triangle.*1
How desperately unevolutionary that picture is! The Platonist regards any change in rabbits as a messy departure from the essential rabbit, and there will always be resistance to change – as if all real rabbits were tethered by an invisible elastic cord to the Essential Rabbit in the Sky. The evolutionary view of lifes radically opposite. Descendants can depart indefinitely from the ancestral form, and each departure becomes a potential ancestor to future variants. Indeed, Alfred Russel Wallace, independent co-discoverer with Darwin of evolution by natural selection, actually called his paper ‘On the tendency of varieties to depart indefinitely from the original type’.*2
*1 これは、おそらくイデアの限界であると思う。その意味で、洞窟の比喩と、ニーチェの真理批判とは違う意味だろう。しかし、より高次の次元から考えるとそれは些細な違いに過ぎないとおもう。というのは、イデアというものが、まさにニーチェの言葉を借りるなら、遠近法的仮像なのだから。そして、それも、ご存知の通り影の思想なのだから。その意味で、ビトゲンシュタインと同じ。その限りで、無我の思想というのが、もっとも完成された思想のうちの一つになるのかもしれない。
*2 やはり、今日の進化論的にはイデアの思想は批判されるものかもしれないが、おそらく、そのような批判はプラトンの主張を文字通りの意味にしか、表面的にしか理解してないものがするのだろう。洞窟の比喩とイデアということを考慮するなら。というのは、何かのイデアを正確には、知覚できないのだから。つまり、もし、ある特定の対象について、あるイデアを想起したとしても、それは影にすぎないのだから、イデアというものが、一つの仮定にすぎないということを前提としているから。
このようなことから、理論モデルではなくて、実際の具体的な人間のア・プリオリと、ア・ポステリオリとの関連の探求が今後の課題になるのではないだろうか。しかし、ある人にとっては、それは、完全にア・プリオリだと思うけれども。というのは、因果律を純粋に受け入れるとそうなるのだから。もっとも、ア・プリオリすら超越しているということはできると思う。そのような意味で、神の存在を肯定はできるだろうし、事実、正確にこのような方法ではないと思うけれど、信仰とはそのような形で成り立つと説明されてきた。だけれども、その信仰も、形而下に還元される時、誤りになるという問題点を抱えていることに注意しなければならない。人間的であるということを。
If there is a ‘standard rabbit’, the accolade denotes no more than the centre of a bell-shaped distribution of real, scurrying, leaping, variable bunnies. And the distribution shifts with time. As generations go by, there may gradually come a point, not clearly defined, when the norm of what we call rabbits will have departed so far as to deserve a different name. There is no permanent rabbitiness, no essence of rabbit hanging in the sky, just populations of furry, long-eared, coprophagous, whisker-twitching individuals, showing a statistical distribution of variation in size, shape, colour and proclivities. What used to be the longer-eared end of the old distribution may find itself the centre of a new distribution later in geological time. Given a sufficiently large number of generations, there may be no overlap between ancestral and descendant distributions: the longest ears among the ancestors may be shorter than the shortest ears among the descendants. All is fluid, as another Greek philosopher, Heraclitus, said; nothing fixed. After a hundred million years it may be hard to believe that the descendant animals ever had rabbits for ancestors. Yet in no generation during the evolutionary process was the predominant type in the population far from the modal type in the previous generation or the following generation. This way of thinking is what Mayr called population thinking. Population thinking, for him, was the antithesis of essentialism. According to Mayr, the reason Darwin was such an unconscionable time arriving on the scene was that we all – whether because of Greek influence or for some other reason – have essentialism burned into our mental DNA.*3
*3 結局は、イデアの基礎の元、ヘーゲルの弁証的方法を進化論的な意味での使用でやっているに過ぎないのか。あるいは、それは過ぎないという表現で軽視してはいけなくて、我々に決定的な避けることのできない、そして逆に、それどころかこのような思想にしか還元できないということなのであろうか。