bird branches:https://news.nationalgeographic.com/2018/03/ravens-animals-evolution-species/
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……For a long time, we’ve tended to think of the evolution of species as a branching tree, with new species splitting off as their own branches, says Anna Kearns, an evolutionary biologist at the Smithsonian Conservation Biology Institute.
“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 Kearns, who led the new study.
But occasionally, the branches of a family tree do merge back together, and two lineages—or groups that were on their way to becoming separate species—become one. Scientists call this “reticulate evolution,” says Kearns, and it’s been seen in only a handful of other species, including finches and two kinds of fish.
The findings suggest that many other species may have evolved “in reverse” from the merging of species, and highlights how complex the very notion of a species actually is. Though many of us learned in school that two species can’t interbreed, scientists say, biology isn’t always so clear-cut.
A Tale of Three Ravens
Today, the common raven is……” see link