Among the most iconic evolutionary fish stories is a tale about fish: once upon a time fish evolved lungs and legs, crawled out onto land, and evolved into terrestrial vertebrates. Fishy fables claiming that “gill slits” in human embryos show that terrestrial vertebrates recapitulate their evolutionary heritage back to a fish stage have been a long-standing (though often refabricated) component of this fairy tale collection. The colorfully named Sonic hedgehog gene’s similar functions in the embryonic development of chicken wings, fish fins, and human fingers livens the tale of our alleged ancestral relationship with fish. Living fish that do push-ups, leave the water, or have lungs or lung-like organs fuel this fantasy with tantalizing hints of what might have been. Like Henry Limpet (Don Knotts) in The Incredible Mr. Limpet of fictional movie fame, evolutionists have illustrated charts depicting transitions from fish to terrestrial vertebrates like us. Despite their rampant worldview-based colorization of a black-and-white reality that demonstrates no such thing, evolutionists are confident that there really was a fish-to-walker transformation (not the zombie kind). The latest research claiming to shed light on life’s evolutionary leap to land includes a study cataloging land-loving fish, another peering into the pelvis of a blind cavefish, and a third using Sonic hedgehog to resurrect an evolutionary tale tracing our legs back to the gills of cartilaginous fish.
Designed for Diversity of Respiration ... or Evolving to Breathe?
All fish are vertebrates with gills and require water to live, but some are able to venture out of the water under the right conditions. Assuming that such amphibious varieties of fish should offer clues about the origin of amphibians (like salamanders) as well as terrestrial vertebrates like us, Australia’s Terry Ord and Georgina Cooke wondered how many fish families have amphibious varieties. They found 130 such species spread across 33 fish families. They concluded that the leap to land was more common than commonly thought. Taking a closer look at the blenny family, they determined that geography and ecological diversity repeatedly encouraged development of a wide range of amphibious varieties. The Pacific leaping blenny, for instance, spends the majority of its time on land, absorbing oxygen through its moist skin and gills while hiding in rocky nooks and leaping away from incoming waves that could wash it out to sea.