The primitive streak, a structure that emerges during mammalian and avian gastrulation, might be a byproduct rather than a landmark of the embryonic development process.
A handful of new studies moves the needle toward a consensus on the long-disputed question of whether insect wings evolved from legs or from the body wall, but the devil is in the details.
Immunoglobulin genes might have evolved much earlier than previously expected, perhaps even in the common ancestor of Cnidarians and Bilateria, a study suggests.