Evolutionary theory assets that fish that could breathe both air and water emerged on land and became the distant relatives of amphibians, reptiles, birds, and mammals about 400 million years ago. Researchers at McGill University led by Dr. Emily Standen are the first to design an experiment that proves the concept that fish became land animals is a viable reality. The research was reported in the Aug. 27, 2014, edition of the journal Nature.
The researchers used a living fish called Polypterus that can walk on land and breathe air as well as water to examine the evolutionary concept. Juvenile Polypterus were raised on land for a year. The fish developed specific traits that are different from the same species of fish that lives in water and occasionally visits land. Several species of Polypterus are found in Africa. A film of the fish walking can be seen here.
Environmental stress can produce anatomical adaptations in any species in order for the species to survive. The Polypterus that were raised on land learned to negotiate a land environment more easily by keeping the fins closer together and raising their heads. The fish that were bred on land were as mobile on land as fish that began life in water. The land-bred fish also changed anatomically to produce more support for their bodies on land.
The anatomical changes in the Polypterus that were raised on land mirror the fossil record of fish that emerged onto land. The research proves that fish climbed out of the ocean onto land using their fins as support at least 400 million years ago. This is the first proof of the concept that uses living fish that adapted to a new environment in a relatively short time. The research also shows that environmental stress can speed up a normally slow evolutionary process that includes anatomical changes.