The presence of branchial clefts in a human embryo suggests

Humans, as an embryo, temporarily have gills.

Branchial clefts are often a common birth defect and are actually looked at as "human gills" for a small period of time until they develop further into the jaw and inner ear bones. If they do not change into those two structures, the lesions can take the form of cysts and form in the neck or just below the collarbone, causing infection that could soon seep out of the skin.