|photo credit: chefranden|
Scientists love to organize things into categories. Scientists also love to re-organize the same things into different categories. This happens constantly when it comes to phylogeny, or the history of the evolution of a species. Often the re-organization takes place after new clarifying evidence emerges. Last week a series of papers were published in the journal Science, after a study that was literally an international collaboration took place over the course of the past four years. Scientists joined forces globally to map and analyze the genomes, or the genetic material, of 48 different bird species. With these new genetic maps they were then able to reorganize the family tree of many bird species. What they found was surprising, but sensible.
The new evolution map (see it in this article) shows very clearly the population and diversity explosion that resulted after a large asteroid collided with Earth and caused mass extinction about 66 million years ago. Although land birds suffered during this time, flying birds flourished. With this new data it is obvious that prehistoric birds evolved into just a few groups. Paleognathae branched off as two groups of land birds, the ostrich and tinamous, a group of land birds found in Mexico, Central and South America. Another large group, Neognathae, branched twice. One branch is the Galloanseres, which are land fowl and water fowl, birds like chickens and ducks. The other branch is the Neoaves, which includes all other birds. So, lets put aside the scientific names and break this down- unless you are a land bird or fowl, you are very closely related (genetically speaking) to all other birds. Of course there are many groups within Neoaves: birds of prey, water birds, songbirds, etc. What is mind-boggling is how many different species evolved after that asteroid hit. Scientists have seen a similar pattern in the evolution of mammal species. Mammals and birds capitalized on filling the newly open niches left behind by the dinosaur's extinction.
Scientists learned a lot through this collaboration. Other papers in the series dealt with evolutionary connections in vocal learning, bird's loss of teeth and the cold tolerant adaptations of penguins. Although science is often collaborative, it is rare that it is on such a grand scale. I believe that due to cooperation on the part of scientists globally these studies were able to happen much more quickly than they usually do. Hopefully this will spur many other team efforts. Science certainly does not happen in a bubble!
- Science: "A Flock of Genomes" (Introduction)
- NPR: "Birds of a Feather aren't Necessarily Related"
- Nature: "Flock of geneticists redraws bird family tree"
Bird and General Phylogeny Learning Resources:
- Animal Diversity Web
- Cornell All About Birds
- PBS Life of Birds: Bird Evolution Lesson Plans
- Biointeractive: "Biodiversity and Evolutionary Family Trees" Lesson (Seashells)