達(dá)爾文自然選擇學(xué)說的核心內(nèi)容是“適者生存”,。毋庸置疑,，自然選擇偏愛最合適的生物體，但一直以來進(jìn)化生物學(xué)家并不清楚,，從長遠(yuǎn)來看這種選擇是否也具有最優(yōu)性,。美國科學(xué)家近日發(fā)展了一種新理論認(rèn)為，選擇出的生命可能并不一定是最佳的,。相關(guān)論文發(fā)表在《公共科學(xué)圖書館 計算生物學(xué)》（PLoS Computational Biology）上,。
遺傳突變?yōu)樽匀贿x擇創(chuàng)造了賴以行事的原料。突變的短期命運(yùn)相當(dāng)清楚——制造更合適的生物體的突變能一代代持續(xù)下去,，有害的突變更易于隨著生物體消亡,；突變的長期結(jié)果則并沒有被進(jìn)化生物學(xué)家很好地理解。新的研究表明,，短期有利的選擇可能會阻礙長期的進(jìn)化,。
美國德州大學(xué)奧斯汀分校的Matthew Cowperthwaite和Lauren Ancel Meyers領(lǐng)導(dǎo)研究小組創(chuàng)建了由突變和自然選擇進(jìn)化而來的RNA分子的計算機(jī)模型。RNA在許多關(guān)鍵的生命過程扮演重要角色,，是流感,、HIV等病毒的遺傳材料。
模型顯示,，最佳生物體的進(jìn)化往往需要一段長的相互作用的突變序列,，每個突變都是偶然產(chǎn)生，并能在自然選擇中存活下來,。Cowperthwaite解釋說：“一些特征很容易進(jìn)化——它們由突變的許多不同聯(lián)合構(gòu)成,；另外一些特征則很難進(jìn)化——它們由不太可能的遺傳‘處方’構(gòu)成,。進(jìn)化選擇了容易的，即使它們并不是最好的,。”
研究人員分析了大量不同物種的RNA分子,，結(jié)果表明，生命確實由“容易”的特征所支配,，或許以犧牲最好的為代價,。（生物谷Bioon.com）
生物谷推薦原始出處：
PLoS Computational Biology，doi:10.1371/journal.pcbi.1000110,，Matthew C. Cowperthwaite,，Lauren Ancel Meyers
The Ascent of the Abundant: How Mutational Networks Constrain Evolution
Matthew C. Cowperthwaite1*, Evan P. Economo2, William R. Harcombe2, Eric L. Miller2, Lauren Ancel Meyers1,2
1 Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America2 Section for Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
Abstract
Evolution by natural selection is fundamentally shaped by the fitness landscapes in which it occurs. Yet fitness landscapes are vast and complex, and thus we know relatively little about the long-range constraints they impose on evolutionary dynamics. Here, we exhaustively survey the structural landscapes of RNA molecules of lengths 12 to 18 nucleotides, and develop a network model to describe the relationship between sequence and structure. We find that phenotype abundance—the number of genotypes producing a particular phenotype—varies in a predictable manner and critically influences evolutionary dynamics. A study of naturally occurring functional RNA molecules using a new structural statistic suggests that these molecules are biased toward abundant phenotypes. This supports an “ascent of the abundant” hypothesis, in which evolution yields abundant phenotypes even when they are not the most fit.
