A groundbreaking study on bird genomes has provided a clear understanding of the bird family tree. Published in the journal Nature, the study reveals that most modern bird groups emerged within 5 million years after the extinction of dinosaurs. While birds are widely studied and beloved by the public, classifying them into a family tree has proven challenging. By analyzing the genomes of over 360 bird species, the study has identified the fundamental relationships among major bird groups. The new family tree challenges previous notions while also unveiling new groupings.
Previous research indicated that the bird family tree consisted of three main branches. The first branch included flightless birds like emus, kiwis, and ostriches. The second branch comprised landfowl and waterfowl such as chickens and ducks. The third branch, known as Neoaves, encompassed 95% of bird species. Neoaves consisted of ten groups, including the “Magnificent Seven” (landbirds, waterbirds, tropicbirds, cuckoos, nightjars, doves, and flamingos) and the “orphans” (shorebirds, cranes, and hoatzin). Determining the relationships among these groups, particularly the orphans, has proven challenging. However, the genome study offers hope for resolving these relationships.
The study introduces a new grouping called “Elementaves,” named after the four ancient elements of earth, air, water, and fire. This group includes birds adapted for success on land, in the sky, and in water. Some birds in this group have names related to the sun, representing the element of fire. Elementaves comprises hummingbirds, shorebirds, cranes, penguins, and pelicans. Additionally, the study confirms a close relationship between two well-known Australian bird groups: passerines (songbirds and relatives) and parrots.
The study also aimed to establish a timeline for the bird family tree. By using a tool called the “molecular clock” and incorporating information from nearly 200 fossils, researchers were able to estimate the ages of certain branches. The study reveals that all living birds share a common ancestor that lived over 90 million years ago. However, most modern bird groups emerged approximately 25 million years later, shortly after the mass extinction of dinosaurs caused by an asteroid impact. This suggests that birds capitalized on the opportunities available after the demise of dominant life forms.
The genome study is part of the Bird 10,000 Genomes Project, which aims to sequence the genomes of all 10,000 living bird species. The current phase focused on including species from every major bird group or family. Led by researchers from the University of Copenhagen, University of California San Diego, and Zhejiang University in China, the study involved analyzing 363 genomes. Despite the vast amount of genome data, one branch of the bird family tree remains a mystery: the hoatzin. This distinctive bird found in South America is the sole survivor of its lineage, and its relationships could not be confidently determined in the analysis.
Overall, the study highlights the power of studying genomes and fossils together to gain insights into the evolutionary history of life on Earth. It also emphasizes that some relationships in the tree of life can only be determined through extensive genome analysis.
