Were our ancestors tadpoles swimming around until evolution took us from fins to fingers? Paleontologists have not had luck connecting fins with hands, because they were studying the wrong fish, according to a study published in the "Proceedings of the National Academy of Sciences."
The genome of the spotted gar was recently sequenced and scientists found the genetic components necessary for the transformation.
"Fossils show that the wrist and digits clearly have an aquatic origin," said Neil Shubin, the Robert R. Bensley Professor of organismal biology and anatomy at the University of Chicago, according to Science Daily. "But fins and limbs have different purposes. They have evolved in different directions since they diverged. We wanted to explore, and better understand, their connections by adding genetic and molecular data to what we already know from the fossil record."
Teleost fish, the group of fish that are usually caught for sport, were studied extensively, but the researchers found "a lack of sequence conservation" in teleost species, according to Science Daily. Teleost fish have gone through whole-genome duplication after the fish broke out of the group that became tetrapods.
"The genetic switches that control autopod-building genes were able to drift and shuffle, allowing them to change some of their function, as well as making them harder to identify in comparisons to other animals, such as mice," said Andrew Gehrke, a graduate student in the Shubin lab and lead author of the study, according to Science Daily.
The spotted gar is one boney fish that did not go through whole genome duplication, according to Science Daily. The North American freshwater fish took their own path before the genome duplication.
Scientists tested their theory by inserting gar gene switches that control fin development into mice and found activity that was "nearly indistinguishable" from the mouse genome, according to Science Daily.
"Overall, our results provide regulatory support for an ancient origin of the 'late' phase of Hox expression that is responsible for building the autopod," researchers concluded.
