Dragons: the Evolution of a Mythic Beast Sarah Rubin*, Diana Patrick*, Helen Dailey*, Matthew Haynes*, Eric Przybyszewski* *Montana State University, Bozeman MT
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Dragons: The Evolution of a Mythic Beast Sarah Rubin*, Diana Patrick*, Helen Dailey*, Matthew Haynes*, Eric Przybyszewski* *Montana State University, Bozeman MT Abstract With the rich legendary traditions involving dragons, it is possible to determine the traits that define a dragon. Given these traits, it is reasonable to assume that they will fall somewhere within Sauropsida, despite their fictional status. A definition of what constitutes a dragon was determined by characteristics such as reinforced scales, a degree of intellect, the lack of an herbivorous nature, and a predominantly terrestrial lifestyle. These and other traits, adding up to 150, were derived from many mythologies and stories and input into a discrete matrix, using 0 if the trait was absent and 1 if the trait was present. A phylogenetic tree was generated using the program Mesquite; the same program was used to create a control tree based off of the Tree of Life Web Project (39). After an analysis of the created tree in comparison to the control tree, part (a) of our hypothesis, that they do not form a distinct clade, was rejected due to them falling outside of existing clades. The generated tree failed to reject part (b) of the null hypothesis, that dragons fall within Sauropsida, because there is not enough evidence to prove that dragons would not be related to reptiles. Introduction Nearly every culture on the planet has had myths about large reptiles, often intelligent and with supernatural powers, creatures generally referred to in English as “dragons.” Throughout this rich mythological history, there is some consistency in the way dragons supposedly appeared and in the way they behaved. However, differences in all of these aspects are based upon the location at which the dragon in question supposedly lived. This history is supplemented by the equally rich fictional tradition of dragons, which have appeared in a great many novels and short stories, as well as most fantasy role playing games. As dragons are consistently described as reptilian, able to fly, intelligent, possessing a breath weapon (whether this is fire, ice, poison, or even lightning), reinforced scales, and as generally territorial, the authors have attempted to place dragons within the clade Sauropsida. The null hypotheses for this study are that a) dragons do not form a distinct clade, and that b) that dragons fall within Sauropsida. Due to the frequently sprawled legs and forked tongues of many dragons, the alternative hypotheses are that a) dragons form a distinct clade, and that b) dragons will fall within Lepidosauria. While dragons are obviously a fictional species, they provide an effective proxy for historical species that have been poorly documented scientifically, but are documented informally, either within literature or art. The methods used in this research may be easily applied to these real-world scenarios in order to further understanding of biological diversity and extent. Additionally, tracking the traits of dragons across the globe may provide insight into the spread of world religions. 1 Methods Dragons were defined as having the following traits: they are reptilian, with a high degree of intellect and the ability to use a breath weapon. Additionally, they have an elongated neck and tail, are never herbivorous, but may be carnivorous or omnivorous, have a territory that they will defend, are brightly colored, may have reinforced scales (hereafter referred to as osteoderms), have a lifespan of a century or more, live at least largely on land, and reproduce naturally via sexual reproduction. To be considered a “dragon” for the purposes of this project, a species had to have all of these traits present. Those that did not were entirely omitted. In order to place dragons within a phylogenetic tree, myths surrounding the dragons of Europe, Asia, Australia, Africa, and the Americas were examined. Traits for each of these species were found based on visual depictions in historical art, as well as written records of legends and influential works of fiction. There were 13 generalized dragon species solidified based on geographical regions associated with legends. Asiatic/Pacific dragons consisted of Chinese, Japanese, Korean, Vietnamese, Tibetan, Indian, Persian, and Marsupial dragons. Land Wyrms were found in both Europe and Asia. European dragons included Classical European dragons, and Wyverns, which were also found in Africa. Dragons from the Americas were the Mesoamerican Feathered Serpent and the Amphithere. In some cases, modern literature was used to find generalized versions of dragons; for instance, the Red Dragon of the role-playing game Dungeons and Dragons and Smaug from The Hobbit by J.R.R. Tolkien were used to approximate traits of European dragons (14, 29). All draconic traits were made discrete and put into the program Mesquite, together with traits of various archosaurs (crocodilians, non-avian and avian dinosaurs), lepidosaurs (specifically squamates), and mammals (specifically humans), in order to place dragons within Sauropsida as it is currently defined. 150 traits were used in total. Traits of one particular myth for each species were added as a type specimen, in order to give unfamiliar audiences an idea as to the type of animal each species refers to. The data matrix, showing each taxa and discrete trait, is given in the supplemental data. The matrix was imported into Mesquite and an initial 3 consensus trees were created from the matrix. These consensus trees were then run through Mesquite’s heuristic search, with the search criterion set to minimize tree value using the character matrix. An “SPR rearranger” was run as the type of heuristic search, which added and subtracted various branch lengths as well as adjusted branch positions randomly. The goal of such a search was to find the most simplistic tree, defined as the smallest tree value. Tree value is a measure of the size and complexity of a tree: the smaller the value, the more simplistic the tree. A tree search analysis of this type applies Ockham's razor to find a tree which is the most simplistic while conforming to the data matrix. SPR rearranger ran through various combinations until it found one with a smaller tree value, then switched to that new tree and proceeded to restart the process, attempting to find a tree with an even smaller tree value. In total, 1,412,789 rearrangements were examined. The search was repeated until no smaller tree value was found after many trees: over 9000 in total (Figure 1). The constant tree produced had a tree value of 315 and is shown below (Figure 2). 2 Results Within the larger Asiatic/Pacific group, the Chinese and Japanese dragons grouped closely, as did the Korean and Vietnamese. The Tibetan and Indian dragons were not sister groups to any others, but were closer to the other Asiatic/Pacific dragons than the European, American, or Land Wyrm dragons. The Marsupial dragon is the exception in the Asiatic/Pacific group; coming out as the last dragons before non-fictional creatures on the tree, between Amphitheres and Squamates. In the final tree, four major groups were resolved. Most of the Asiatic/Pacific dragons (Chinese, Japanese, Korean, and Tibetan) all grouped together, with Chinese and Japanese dragons grouping as sister taxa, as well as the Korean and Vietnamese. The Wyverns and the classical European dragons grouped together as sister taxa. The Land Wyrms, found in Europe as well as Asia, formed a clade with the American dragons. The two American species, the Feathered Serpent and the Amphithere, formed a sister group. The non-fictional animals all grouped together, though humans grouped within reptiles and were the closest to birds. Figure 1: The dragon family tree with squamates, archosaurs, and mammals as references. Note the unusual way mammals have grouped together with birds here, compare Figure 2. 3 Figure 2: The amniote family tree, as it should appear (39). Added for reference with the tree created from the data. Discussion Based on the number of times the tree search was allowed to run, the placement of dragons is quite well supported given the matrix. The lack of data on living squamates, archosaurs, and humans caused their placement within the tree to be inaccurate, however. This may be fixed by using more established data from the Tree of Life project or a similar database; these were not used due to the fictional species of dragons that would not have been found in any database. It was believed it would be most accurate to use the collected data, due to the mythical nature of dragons. Due to the fact that limb number and type is typically a defining feature of dragons in mythology, it was expected for legless dragon species to generally group together, while those with no wings will group together, and those with both legs and wings, regardless of the number of legs, will group together. Additionally, the geographical distribution was thought to be a key trait to separating the dragon species. The distribution of the dragon species on the tree seems to indicate that geographical location was a more influential factor than number of limbs. The two exclusively European species, the Wyvern and Classical European dragon, grouped closely together, despite the fact that they have different numbers of limbs (four and two respectively). The geographical influence is further supported by the grouping of the American dragons and Land Wyrms. Though the Amphithere and Land Wyrm both have the same number of limbs, two, the Amphithere grouped more closely with its fellow American dragon, the Feathered Serpent. However, it is possible that the influence of limb number can be seen on the large scale of the 4 tree. There is a weak trend of the dragon species losing limbs over time; the Asian/Pacific dragons on the left of the tree having four limbs and the Land Wyrms and American dragons on the right of the tree having two or less limbs.