BUILDING A BIRD: Avian Ontogeny and Evolution
Developmental and evolutionary transformations are key to understanding animal body plans. Over a 500 million year history on Earth, vertebrates have invaded dramatically different environments, acquiring new body plans and modes of locomotion. Natural selection can explain how these body plans work in their fully developed states, but if morphology evolves slowly, through incremental adaptive stages, how do organisms acquire new and complex structures that seem to be useful only in their fully assembled forms? What is the advantage of half a wing or only part of an eye? This “dilemma" of incipient or rudimentary stages is central to understanding the tree of life and greatly intrigued Darwin and his critics. Rudimentary stages are less studied, but equally relevant, among extant developing organisms and animals with vestigial features. Juveniles of many species navigate environments using underdeveloped structures that not only lack specializations of adults, but that often resemble features of extinct relatives. Similar forms occur in animals with secondarily or temporarily reduced structures. Rudimentary or “transitional” features like these lie at the core of evolutionary theory and are extensively discussed, yet their functional attributes often remain poorly understood. Using birds and their theropod dinosaur ancestors as a focal group, the Heers lab addresses this knowledge gap by integrating biological, paleontological, and engineering disciplines to explore the functional and ecological significance of rudimentary locomotor structures.
Developmental and evolutionary transformations are key to understanding animal body plans. Over a 500 million year history on Earth, vertebrates have invaded dramatically different environments, acquiring new body plans and modes of locomotion. Natural selection can explain how these body plans work in their fully developed states, but if morphology evolves slowly, through incremental adaptive stages, how do organisms acquire new and complex structures that seem to be useful only in their fully assembled forms? What is the advantage of half a wing or only part of an eye? This “dilemma" of incipient or rudimentary stages is central to understanding the tree of life and greatly intrigued Darwin and his critics. Rudimentary stages are less studied, but equally relevant, among extant developing organisms and animals with vestigial features. Juveniles of many species navigate environments using underdeveloped structures that not only lack specializations of adults, but that often resemble features of extinct relatives. Similar forms occur in animals with secondarily or temporarily reduced structures. Rudimentary or “transitional” features like these lie at the core of evolutionary theory and are extensively discussed, yet their functional attributes often remain poorly understood. Using birds and their theropod dinosaur ancestors as a focal group, the Heers lab addresses this knowledge gap by integrating biological, paleontological, and engineering disciplines to explore the functional and ecological significance of rudimentary locomotor structures.
Research Areas:
Development of flight
Incipient wings in developing birds Most young birds lack "flight adaptations", yet use their wings for a variety of locomotor behaviors! We use several approaches to understand how they do this. |
Evolution of flightIncipient wings in extinct theropod dinosaurs Early "winged" dinosaurs also lacked "flight adaptations", but may have used their forelimbs like developing birds do. We use musculoskeletal modeling to examine what these animals might have been capable of. Image in public domain. |
Loss of flight
Reduced wings in adult birds Many adult birds have temporarily or permanently reduced wings. We are exploring how these birds use their small wings - very little is known at this point! Images in public domain. |