[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-1-en-105":3,"doc-seo-219397-105":53,"doc-detail-219397-en":126},{"code":4,"msg":5,"data":6},0,"success",[7,14,19,24,29,34,39,44,49],{"id":8,"doc_module":9,"doc_module_name":10,"category_name":11,"show_sort_weight":12,"slug":13},11,1,"Template","Presentations",90,"presentations",{"id":15,"doc_module":9,"doc_module_name":10,"category_name":16,"show_sort_weight":17,"slug":18},12,"Resumes",80,"resumes",{"id":20,"doc_module":9,"doc_module_name":10,"category_name":21,"show_sort_weight":22,"slug":23},14,"Invoices",70,"invoices",{"id":25,"doc_module":9,"doc_module_name":10,"category_name":26,"show_sort_weight":27,"slug":28},15,"Posters",60,"posters",{"id":30,"doc_module":9,"doc_module_name":10,"category_name":31,"show_sort_weight":32,"slug":33},16,"Social Media",50,"social-media",{"id":35,"doc_module":9,"doc_module_name":10,"category_name":36,"show_sort_weight":37,"slug":38},17,"Forms",40,"forms",{"id":40,"doc_module":9,"doc_module_name":10,"category_name":41,"show_sort_weight":42,"slug":43},18,"Letters",30,"letters",{"id":45,"doc_module":9,"doc_module_name":10,"category_name":46,"show_sort_weight":47,"slug":48},21,"Paper Templates",5,"papers-templates",{"id":50,"doc_module":9,"doc_module_name":10,"category_name":51,"show_sort_weight":4,"slug":52},158,"General","general-158",{"code":4,"msg":54,"data":55},"ok",{"site_id":56,"language":57,"slug":58,"title":59,"keywords":60,"description":61,"schema_data":62,"social_meta":119,"head_meta":121,"extra_data":123,"updated_unix":125},105,"en","a-case-study-in-evolutionary-contingency","A CASE STUDY IN EVOLUTIONARY CONTINGENCY","","Biological evolution unfolds through intertwined stochastic and deterministic processes that produce long historical trajectories in a changing world. The extent to which these properties make evolution historically contingent—and thus render outcomes sensitive to prior events—has been actively debated. Microbial evolution experiments provide direct tests, especially the E. coli Long-Term Evolution Experiment (LTEE), where parallel lineages develop novel traits under identical conditions. Replays show Cit+ depended on earlier mutations that made the novelty accessible, highlighting how contingency can arise from core evolutionary mechanisms.",{"@graph":63,"@context":118},[64,80,101],{"@type":65,"itemListElement":66},"BreadcrumbList",[67,71,74,77],{"item":68,"name":69,"@type":70,"position":9},"https://docshare.wps.com","Home","ListItem",{"item":72,"name":10,"@type":70,"position":73},"https://docshare.wps.com/template/",2,{"item":75,"name":51,"@type":70,"position":76},"https://docshare.wps.com/template/general/",3,{"item":78,"name":59,"@type":70,"position":79},"https://docshare.wps.com/template/a-case-study-in-evolutionary-contingency/219397/",4,{"url":78,"name":59,"@type":81,"image":82,"author":87,"headline":59,"publisher":90,"fileFormat":93,"inLanguage":57,"description":61,"dateModified":94,"datePublished":95,"encodingFormat":93,"isAccessibleForFree":96,"interactionStatistic":97},"DigitalDocument",{"url":83,"@type":84,"width":85,"height":86},"https://docshare.wps.com/thumbnails/a-case-study-in-evolutionary-contingency/219397.png","ImageObject",442,249,{"name":88,"@type":89},"Gelato","Person",{"url":68,"name":91,"@type":92},"DocShare","Organization","application/vnd.openxmlformats-officedocument.wordprocessingml.document","2026-09-21","2026-09-08",true,{"@type":98,"interactionType":99,"userInteractionCount":79},"InteractionCounter",{"@type":100},"ViewAction",{"@type":102,"mainEntity":103},"FAQPage",[104,110,114],{"name":105,"@type":106,"acceptedAnswer":107},"What does evolutionary contingency mean in this discussion?","Question",{"text":108,"@type":109},"Evolutionary contingency refers to how evolutionary outcomes depend on historical events such that similar starting points can lead to unpredictable differences. The text frames this as sensitivity to prior mutations and the order in which they arise.","Answer",{"name":111,"@type":106,"acceptedAnswer":112},"How does the E. coli LTEE illustrate historical contingency?",{"text":113,"@type":109},"In the LTEE, twelve replicate populations evolved in parallel under identical conditions, yet one evolved the Cit+ trait after many generations. Experimental replays indicate Cit+ required earlier mutations that potentiated access to the trait.",{"name":115,"@type":106,"acceptedAnswer":116},"Why are outcomes path dependent even when selection is deterministic?",{"text":117,"@type":109},"Selection deterministically favors adaptation, but it acts on heritable variation introduced stochastically by mutation and other processes. Genetic drift, pleiotropy, and epistasis cause different mutation orders to change the fitness landscape, producing divergent evolutionary paths.","https://schema.org",{"og:url":78,"og:type":120,"og:title":59,"og:site_name":91,"og:description":61},"article",{"robots":122,"canonical":78},"index,follow",{"doc_id":124,"site_id":56},219397,1788866331,{"code":4,"msg":5,"data":127},{"doc_id":124,"user_id":128,"nickname":88,"user_avatar":129,"doc_module":9,"category_id":50,"category_name":51,"doc_title":59,"doc_description":61,"doc_content":130,"file_id":131,"file_url":132,"file_type":133,"file_size":134,"view_count":79,"is_deleted":4,"is_public":9,"is_downloadable":9,"audit_status":9,"page_count":32,"language":135,"language_code":57,"site_id":56,"html_lang":57,"table_of_contents":136,"faqs":137,"seo_title":138,"seo_description":61,"update_tm":125,"read_time":40},19241457091524,"https://us-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c","A CASE STUDY IN EVOLUTIONARY CONTINGENCY\nZACHARY D. BLOUNT1,2\nBEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI, USA\nDepartment of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA\nABSTRACT\nBiological evolution is a fundamentally historical phenomenon in which intertwined stochastic and deterministic processes shape lineages with long, continuous histories that exist in a changing world that has a history of its own. The degree to which these characteristics render evolution historically contingent, and evolutionary outcomes thereby unpredictably sensitive to history has been the subject of considerable debate in recent decades. Microbial evolution experiments have proven among the most fruitful means of empirically investigating the issue of historical contingency in evolution. One such experiment is the E. coli Long-Term Evolution Experiment (LTEE), in which twelve populations founded from the same clone of E. coli have evolved in parallel under identical conditions. Aerobic growth on citrate (Cit+), a novel trait for E. coli, evolved in one of these populations after more than 30,000 generations. Experimental replays of this population’s evolution from various points in its history showed that the Cit+ trait was historically contingent upon earlier mutations that potentiated the trait by rendering it mutationally accessible. Here I review this case of evolutionary contingency and discuss what it implies about the importance of historical contingency arising from the core processes of evolution.\nKeywords: Historical Contingency; Evolutionary Contingency; Evolutionary Novelty; Experimental Evolution; E. coli; Long-Term Evolution Experiment\nHistory is subject to a tangled tension between chance and necessity. Humans have long been conscious of this fact, with one consequence being that human conceptions of history have generally fallen on a continuum between extreme poles that may be thought of as fate and fortune. In Greco-Roman mythology, fate is personified as the three stern Fates who see that history unfolds inevitably according to their inflexible plan. Fortune is personified by Fortuna, the goddess of luck and the “million to one shot.” Whereas the Fates are steady and implacable beings, the workings of whom cannot be altered even by the gods themselves, Fortuna is fickle, plays favorites as she pleases, and can whimsically change the course of events at any time. In the fatalistic view, historical outcomes are inevitable and predetermined, whereas in the view governed by fortune no historical event is inevitable until it has occurred, because chance can always intervene. Of course, both polar extremes are problematic, and most take a mixed view between the two.\nLike human history, biological evolution is also subject to a tension between chance and necessity. Its core processes involve a complex interplay of the random and the deterministic (Monod 1971). Natural selection works deterministically to adapt populations to their environments, but it must act upon heritable variation stochastically introduced by random mutation, gene flow, and recombination. Beneficial variation introduced by any of these mechanisms may be lost at random by genetic drift. Mutations can vary greatly in their effects on multiple traits (pleiotropy) and in their interactions with other genes (epistasis), so that the order in which beneficial mutations arise can change the fitness value of subsequent mutations (Mani and Clarke 1990; Lenski et al. 1991). Due to these effects, populations starting from the same ancestral genotype can evolve along divergent paths that vary in their evolutionary potential, thereby making evolutionary outcomes path dependent to at least some degree (Wright 1988; Cooper and Lenski 2000; Weinreich, Watson, and Chao 2005; Weinreich et al. 2006). For instance, different evolutionary paths can lead to states with similar fitness in a prevai","cbCaingqmqwSQc53","https://ap.wps.com/l/cbCaingqmqwSQc53","docx",1453675,"English","# Abstract\n# Historical contingency: chance and necessity\n## Fate versus fortune\n# Evolutionary mechanisms and path dependence\n## Random mutation, selection, and drift\n## Pleiotropy and epistasis\n# Long histories and Gould’s contingency arguments\n## Burgess Shale and mass extinction\n## The “tape of life” idea\n# Controversy and convergence\n## Limits from selection and constraints","[{\"question\":\"What does evolutionary contingency mean in this discussion?\",\"answer\":\"Evolutionary contingency refers to how evolutionary outcomes depend on historical events such that similar starting points can lead to unpredictable differences. The text frames this as sensitivity to prior mutations and the order in which they arise.\"},{\"question\":\"How does the E. coli LTEE illustrate historical contingency?\",\"answer\":\"In the LTEE, twelve replicate populations evolved in parallel under identical conditions, yet one evolved the Cit+ trait after many generations. Experimental replays indicate Cit+ required earlier mutations that potentiated access to the trait.\"},{\"question\":\"Why are outcomes path dependent even when selection is deterministic?\",\"answer\":\"Selection deterministically favors adaptation, but it acts on heritable variation introduced stochastically by mutation and other processes. Genetic drift, pleiotropy, and epistasis cause different mutation orders to change the fitness landscape, producing divergent evolutionary paths.\"}]","A CASE STUDY IN EVOLUTIONARY CONTINGENCY | DOCX"]