Evolutionary history of the Raven
The common raven evolved in the
Old World and crossed the
Bering land bridge into North America.
[21] Recent genetic studies, which examined the
DNA of common ravens from across the world, have determined that the birds fall into at least two
clades: a
California clade, found only in the southwestern United States, and a
Holarctic clade, found across the rest of the Northern Hemisphere. Birds from both clades look alike, but the groups are genetically distinct and began to diverge about two million years ago.
[22][23]
The findings indicate that based on
mitochondrial DNA, common ravens from the rest of the United States are more closely related to those in Europe and Asia than to those in the California clade, and that common ravens in the California clade are more closely related to the
Chihuahuan raven (
C. cryptoleucus) than to those in the Holarctic clade.
[22] Ravens in the Holarctic clade are more closely related to the
pied crow (
C. albus) than they are to the California clade.
[24] Thus, the common raven species as traditionally delimited is considered to be
paraphyletic.
[24]
One explanation for these genetic findings is that common ravens settled in California at least two million years ago and became separated from their relatives in Europe and Asia during an
ice age. One million years ago, a group from the California clade evolved into a new species, the Chihuahuan raven. Other members of the Holarctic clade arrived later in a separate migration from Asia, perhaps at the same time as humans.
[25]
A recent study of raven mitochondrial DNA showed that the isolated population from the
Canary Islands is distinct from other populations.
[26] The study did not include any individuals from the North African population,
[26]and its position is therefore unclear, though its
morphology is very close to the population of the Canaries (to the extent that the two are often considered part of a single subspecies).
[16]
