Dewlap Dewlap A dewlap is a longitudinal flap of skin that hangs beneath the lower jaw or neck of many vertebrates. While the term is usually used in this specific context, it can also be used to include other structures occurring in the same body area with a similar aspect, such as those caused by a double chin or the submandibular vocal sac of a frog. In a more general manner, the term refers to any pendulous mass of skin, such as a fold of loose skin on an elderly person's neck, or the wattle of a bird. Dewlaps can be
Chicken or the egg distinction. Whatever criteria one chooses, an animal nearly identical to the modern chicken (i.e., a proto-chicken) laid a fertilized egg that had DNA identical to the modern chicken (due to mutations in the mother's ovum, the father's sperm, or the fertilised zygote). Put more simply by Neil deGrasse Tyson: "Which came first: the chicken or the egg? The egg—laid by a bird that was not a chicken." It has been suggested that the actions of a protein found in modern chicken eggs may make the answer different. Chickens produce a protein, ovocleidin-17 (OC-17), that is expressed in the uterus and