Scientists showed the step-by-step evolution of the origins of the human face via the fossils of a 410-million-year-old jawless fish.
Nature World News reports:
Today, most vertebrates are jawed; the only jawless vertebrates are hagfishes and lampreys. More than 50,000 species, including humans, are considered jawed vertebrates. But jawed vertebrates evolved from their jawless counterparts, which the researchers likened to a process that effectively turned the face inside out.
“In embryos of jawless vertebrates, blocks of tissue grow forward on either side of the brain, meeting in the midline at the front to create a big upper lip surrounding a single midline ‘nostril’ that lies just in front of the eyes,” the researchers said in a statement. “In jawed vertebrates, this same tissue grows forward in the midline under the brain, pushing between the left and right nasal sacs which open separately to the outside. This is why our face has two nostrils rather than a single big hole in the middle. The front part of the brain is also much longer in jawed vertebrates, with the result that our nose is positioned at the front of the face rather than far back between our eyes.”
The Romundina represents an intermediary phase in this facial evolution. It has separate right and left nostrils, but they sit back behind its lips, like a jawless vertebrate’s.