Scientists have long acknowledged that dinosaurs are extinct, and that’s why children have a passion for this large reptile. Sixty-five million years ago, an asteroid hit the Earth, causing the death of dinosaurs. The impact opened the fifth extinction of the Earth’s species, instantly freeing up a large number of vacant niches for mammals.
However, technically speaking, dinosaurs may not be completely extinct. Whether on swaying branches or at rich banquets, their offspring can be found all over the world. Genes and fossils have proved that modern birds are descendants of theropods. The theropod dinosaur is a bipedal dinosaur, including some of the surviving Tyrannosaurus Rex from the fifth mass extinction. Taxonomists suspect that when asteroids hit Earth, the ancestors of modern birds, like mammals, faced excellent evolutionary opportunities.
This week, the Journal Science published the results of a major project that fully supports the theory. The project sequenced the genomes of 48 modern bird species. By building a tree of bird evolution, scientists found that after the impact of asteroids on the Earth, species began to evolve explosively millions of years ago, forming Neoaves, which includes 95% of modern bird species.
The project also explains how science and technology are changing biology. In the past, biologists allocated different parts of the evolutionary tree of birds by studying the physiological and behavioral characteristics of different birds. However, biologists have different opinions about which characteristics are considered to be the most important ones. Gene analysis opens another window for biologists, through which the evolution of birds can be seen at a glance. But because of limited technology, taxonomists can only use a small number of genes to construct evolutionary trees.
Unlike the bird evolutionary tree constructed in the past, the new evolutionary tree is constructed through the whole genome. This has benefited from two major advances. First, the cost of gene sequencing has dropped rapidly, and it is thousands of times cheaper than it was in 2007. Secondly, computer power has increased (much slower than the cost of gene sequencing). Biologists put genomic data from the project into huge supercomputers, screened and aligned DNA sequences, and in a few weeks the final evolutionary tree was obtained.
Genome-wide sequencing also allows scientists to study the evolution of individual characteristics. Modern birds share a common predatory ancestor. But under different isolation conditions, they lost their ancestral habits. Similarly, learning and singing abilities (interestingly, they are genetically similar to human language abilities) seem to have evolved at least twice.
This method is not limited to bird research. Similar research projects for mammals are also possible using the genomes that have been measured. The cost of DNA sequencing will continue to decrease, the computing power of computers will be stronger, and the evolutionary tree constructed by taxonomists will become more realistic.