創造論者の攻撃に対して"共通祖先"が無傷である理由を語る"若い地球の創造論者"Todd Wood

進化論は科学的には正しいと言う"若い地球の創造論者"Todd Woodは、科学理論におけるハイレベルとロウレベルの関連を説明する。

まずTodd Woodはハイレベルな考えとして「共通祖先」を例にする。

Take for example the idea that species evolved from a common ancestor. This is a very simple high level idea that lots of people thought of before Darwin. There are several observations that support this model: (1) the "progress" recorded in the fossil record, (2) comparative biology (e.g., comparative anatomy, comparative embryology, etc.), and (3) the biogeography of species of high affinity. If you like, you could add the philosophical "consilience of induction" of common ancestry to explain many types of data. In my estimation, and I think most evolutionary biologists would agree, these evidences are sufficient to support the common ancestry of all species.

種は一つの共通祖先から進化したという考え方を例にしよう。これは非常に単純なハイレベルの考えで、ダーウィン以前にも多くの人々が考えていた。このモデルを支持する観察が幾つかある。(1) 化石に記録された"進展" (2) 比較生物学(比較解剖学、比較胎生学など)(3) 類縁の種の生物地理学。お望みなら、多くのタイプのデータを説明する共通祖先の哲学的統合帰納を加えてもいいだろう。私の推定では、大半の進化生物学者はこれらの証拠が全種の共通祖先を支持するに十分な証拠だということに同意するだろう。

In Origin, Darwin laid these evidences out in a very compelling fashion, but in doing so, he often drew comparisons between his own model and what he called "special creation." These comparisons were intended to illustrate the explanatory superiority of his model over the idea that God created species independently. Sometimes these comparisons were effective, and sometimes he got his logic a little muddled. The appearance of these arguments in Origin gives the impression that Darwin had formulated his theory as an anti-God hypothesis, which Darwin himself denied. In any case, it's important to realize that he had a compelling argument without the theological comments. Religious considerations might have influenced his thinking and arguments, but they certainly did not drive his science.



Now here's where it gets weird. By itself, the idea of common ancestry is somewhat useless scientifically. Common ancestry is a sort of nebulous idea without more empirically-driven hypotheses (low level theories) to connect it more directly to data. For example, how do species evolve? Do they simply adapt to their circumstances as Lamarck believed? Is there an internal drive to adapt? Do they evolve neutrally by genetic drift? Or is natural selection involved? All of these ideas have more or less specific empirical consequences. In other words, they're all fairly predictive, whereas the high level idea of common ancestry is not.

ここから次第に妙になってくる。共通祖先という考え自体は、科学的にはある意味、役に立たない。共通祖先は、より経験的に作られた仮説(ロウレベル理論)のない、ある種の雲のような考えで、データとはより直接的にはつながっていない。たとえば、種はどう進化するだろうか? ラマルクが信じたように、種は環境に適応するのだろうか? 適応を推進する内在的なものがあるのだろうか? 遺伝的浮動で"自然に"進化するのだろうか? あるいは自然選択は関与するのだろうか? これらすべての考えは、大なり小なり経験的な帰結を持っている。言い換えるなら、これらにはハイレベルな考えである共通祖先にはない、予測力がある。

Likewise, we could look at the pattern of evolutionary inheritance. Do species evolve one into another wholesale, resulting in an unbranched linear pattern, like the great chain of being? Or do species diverge and branch, giving a pattern that looks more like a tree? Once they've diverged, do they ever come back together again, as in the case of hybridization? Again, these ideas are low level ideas close to the empirical data but separate from the higher level concept of common ancestry.

同様に、我々は進化の継承のパターンを見ることもできる。種は分岐することなく、大いなる存在の鎖のように、一つの種全体が別の種へと進化するだろうか? それとも、種は多様化し、分岐し、樹木のようなパターンを呈するのだろうか? ひとたび分岐した種は、交雑のように再び一つの種にもどってくることはあるだろうか? これらの考えもまた、経験的データに近いロウレベルの考えであり、共通祖先というハイレベルの概念からとは別物である。


そして、このロウレベル理論に対して戦いを挑むことで、共通祖先というハイレベルの概念は打倒できない。そのことをTodd Woodは次のように語る:

I think you've already figured out an important corollary to this line of thinking, that squabbling over low level theories has very little to do with the acceptance of the high level model. Scientists can argue over the effectiveness of natural selection without ever questioning the high level concept of common ancestry. Likewise, new fossils can be heralded as "changing our understanding of evoluion" in the sense that low level theories have to be modified. The strength of the high level model is relatively impervious to these changes.

このように考えてくると、誰もが重要な当然の結果を見出しているはずだ。ロウレベル理論での戦いが、ハイレベルのモデルを受け入れることと、ほとんど関係していないということを。 科学者たちは共通祖先というハイレベルの考えを問題にすることなく、自然選択の有効性を議論できる。同様に、新たな化石は、ロウレベル理論を修正するという意味で、「進化についての理解を変える」ことはある。これらの修正には、ハイレベルのモデルの強さはほとんど影響を受けない。

This can be seen in history also. Darwin only partially triumphed in his lifetime. He convinced most scientists that common ancestry was true, but the majority of his friends and colleagues remained skeptical of natural selection. In other words, the evidence Darwin presented to argue for the high level model of common ancestry convinced most readers of Origin, but they generally disagreed about his low level theory of how new species originate. In this way, I find it unfortunate that some creationists today doggedly attack the neodarwinian synthesis, a particular low level theory to explain the origin of species, as if the acceptance of the high level model of common ancestry depended on it. I assure you that the evidence of common ancestry does not depend on any particular low level theory of the mechanism of evolution. The history of science between 1859 and the 1930s bears this out: Nearly everyone accepted evolution, but few agreed on how it happened. Even if the neodarwinian synthesis could be discredited (and that's a big if), acceptance of common ancestry would be unscathed.



それを、一蹴する"若い地球の創造論者"Todd Woodである。