由生物實驗的設計來發現孟德爾定律的發現

Reconsidering Mendel's Principle of Heredity Based on the Logic of Experiment Design.

孟德爾的經典文章〈植物雜交的研究〉，其內容是觀察豌豆植株的外觀性狀在親子間的傳遞過程。這個育種研究的結果可以歸納出三項結論：顯隱律、分離律與獨立分配律，它們是現代遺傳學的開端，稱之為孟德爾遺傳定律。但是在孟德爾有生之年，這些重要的發現被忽略、被遺忘。孟德爾成就的爭議，不管是立基於科學自身的發現、除錯而進步的證據史觀，或是依據孔恩式的科學典範史觀，大多偏重於人如何理解既存的科學知識。它們可能可以解釋科學發現的起源並且釐清孟德爾在歷史中的定位，但是忽略了孟德爾的論文刺激新研究的可能性，以及生物科學本身避免被誤解的策略。本文就實驗的技術面來重建孟德爾的故事，並展示實驗科學背後的思考型式。孟德爾論文的主軸是記錄遺傳性狀的傳遞形式。在實驗的技術上，它跟舊的育種學典範和一般實證論者不相衝突，只是沿用選擇穩定的材料以及簡化觀察目標這兩項經驗原則，再加上將觀測值計量化。在理論的建構上，孟德爾預設物質性的遺傳單位的存在，提出性狀可分離的概念，形成可供思維的結構，應該足以稱得上是古典遺傳理論的雛型。但是對於實驗科學而言，概念必須有實物相對應，才能展現其存在的意義。孟德爾的虛擬遺傳單位，當時沒有任何生物物質實體可以對應，無法指引研究路線。直到二十世紀初，遺傳因子由虛幻的概念逐漸聚焦，落實到看得見的染色體之上，這個由孟德爾所領先的古典遺傳研究，才算富有新理論該有的價值。

Gregor Mendel used garden pea as experiment model to study the development of plant hybrids. His findings lead to three major conclusions that are coined as the fundamental laws of heredity: the law of dominance, the law of segregation, and the law of independent assortment. However, the significance of his findings has been neglected for 35 years. To explain this puzzle in science history, many efforts have been made by epistemological approaches including the evidence-based historiography and the Kuhnian paradigm-based historiography. They offered plausible pictures about the impact of Mendel’s discovery, but failed to provide a coherent strategy to avoid misinterpretation in science. To compliment previous efforts, I try to re-interpret the story of Mendel’s discovery emphasizing the logic of experiment design. The major outline of Mendel’s paper was to document the transmission of phenotypes from parent to offspring. Choosing stable and convenient experiment materials, simplifying the observable target, and quantitatively analyzing the results, gave guarantee of Mendel’s success to reach the reliable conclusions. The techniques he used were commonly recognized among scientific community in those days. Hypothesizing the phenotype controlled by divisible ’elements’ is enough to draw a primitive but adequate theory that can be fully developed to classical genetic theory. However, the heredity unit firstly indicated by Mendel was only a vague concept without concrete quality. Thus, it serves no ground for any new research in breeding. Along with the progress of genetic science in twentieth century, chromosomes were identified as the Mendel’s heredity units. This lays the foundation for understanding the significance of Mendel’s work. This example highlights the usefulness of methodological materialism in the development of biology.