Why can medieval texts be harder to classify through manuscript family trees than classical texts?

In the field of textual criticism, classifying medieval texts through manuscript family trees (stemma codicum) is often more difficult than for classical texts due to several factors related to how these works were transmitted and preserved.12

Key Challenges in Medieval Textual Criticism

• Contamination and Horizontal Transmission: The genealogical method assumes "vertical" transmission, where a copyist follows a single exemplar. Medieval traditions are frequently "open" or "contaminated," meaning copyists often consulted multiple sources or incorporated variants from different versions, making the construction of a clear, branching stemma difficult or impossible.12
• Multiple Redactions: Unlike many classical texts, which often passed through historical "bottlenecks" that reduced the surviving evidence to a single reconstructible version, many medieval works exist in several distinct redactions. These versions cannot always be winnowed down to a single archetype.2
• Linguistic and Stylistic Uncertainty: Classical Greek and Latin possess relatively strict, well-defined linguistic canons. In contrast, the vocabulary, grammar, and usage of many medieval authors—particularly those with an oral prehistory—are often too fluid to allow for the reliable discrimination between a variant and an error.2
• Nature of the Tradition: Medieval literature was frequently treated as a "popular" book rather than a sacred or fixed text. It was often subject to deliberate reworking, glossing, and amplification by readers and copyists, rather than being protected by a rigid scholarly tradition.34