"Your Inner Fish" is the first episode of a documentary series about a vertebrae paleontologist named Neil Shubin. The focus of this episode is to discuss how humans evolved from fish. It considers Darwin's common ancestor theory and talks about how the same basic structure of forelimbs exists in both mammals and their fish-like ancestor. Birds and reptiles also share this common ancestor. There are significant similarities between the human embryo and the fish embryo. The portion of the human embryo that corresponds to gills in the fish embryo forms the lower jaw, middle ear, and voice box in humans. This correspondance represents the developments of evolution. A gene called hedgehog tells cells how to carry out events in a specific order during development. When this gene is overexpressed, it can result in extra fingers. When underexpressed, it can result in less than five fingers. The episode ends on the Tiktaalik, the missing link in the line of evolution between fish and humans. This is the creature that paleontologists have been searching for as it has the same forelimb pattern as humans.
Comments
"A gene called hedgehog tells
"A gene called hedgehog tells cells ..." is an anthropomorphism. I would avoid the word "tells" in this case.
Fewer
As the number of fingers is countable, it should be "fewer than five" instead of "less than five"
"This is the creature that paleontologists have been..."
This may be pedantic, but this sentance seems to imply that this organism in particular is one that scientists have been searching for, rather than the scientists looking for all organisms along this evolutionary line.