The common raven can be found all over the northern hemisphere, and is known for its high intelligence and willingness to eat almost everything. This includes rodents, incents, berries, and garbage. Though they may look ordinary , if you look closely, the bird has been evolving. Using DNA samples taken from ravens for over 20 years, the study is able to prove that “common” ravens from the western coast of North America have split into three different genetically different groups. Two, of the three, have been found to be combining into one species again.

Three million years ago, there was only one species of raven in North America. The species would later evolve into two, the Holarctic raven and an ancestral western North American raven. In the last two million years, the raven split one more time, into the Chihuahuan raven. From DNA analysis, the Chihuahuan have been swapping DNA with the Holarctic and interbreeding. This caused the species to join back into one, and the merging is still going on today. Even as the two species have been merging back together, it’s important to note that the offspring will never be the same as the original raven. “‘This is a fascinating study, demonstrating, once again, that what we think of as the ‘tree’ of life is only approximately a tree,’” says Adam Siepel, a geneticist at Cold Spring Harbor Laboratory on Long Island.

For the longest time, everyone has understood that evolving means for a species to branch out, splitting off into different, more diverse species. “You see a split and then you see another split., and then you see another split, but you rarely see those two branches that are split come back together again,” says Anna Kearns, an evolutionary biologist at the Smithsonian Conservation Biology Institute. Sometimes, it is found that two branches of a family tree merge back together and this is called “reticulate evolution”. The studies made others believe that speciation reversal had happened to a handful of other species, including other birds and two kids of fish. We’ve always learned that two species cannot interbreed, but biology isn’t always definite.

Kaeli Swift, a graduate student who spends her free time helping people see the difference between crows and ravens on Twitter, was not able to see the difference between the Chihuahuan and Holarctic raven lineages without genetic analysis. This was helping show how hard it is to answer a simple question like what is a species? “With the new genomic analysis tools at our disposal, we can look at these questions in a deeper way than ever before. What were once two distinct organisms can collide and become one, weaving their previously distinct genomes into a single tapestry. It’s a complex but beautiful work of nature, really.” says Swift.