Did Fish Gills Evolve?

A team reports in the journal Proceedings B that fish gills may not have evolved to help fish breathe—the standard belief among evolutionary biologists. Rather, the team concluded that fish gills evolved as a chemical-regulation mechanism. The research was based on examination of gill development in rainbow trout larvae.

It is still unclear why fish evolved gills in the first place.

The scientists observed that, in the larvae, the gills’ ability to regulate chemicals appears earlier than their ability to take in oxygen. By analogy, the team inferred that the same environmental pressures which prompt gill development may have led to an equivalent evolutionary process millions of years ago.

University of San Diego biologist Rick Gonzalez noted that despite being a “very interesting first step,” it is still unclear why fish evolved gills in the first place. “The physical and chemical nature of the water can play an important role in [gill] function. So how these all work together to get the various jobs done is very interesting and offers insight into how natural selection works.”

To the contrary, this study (and others like it) seems to commit a fallacy similar to that of Haeckel’s embryo drawings, suggesting that we can learn about evolution by studying the development of an individual organism. Yet no aspect of the study explains how gills—or any aspect of fish anatomy—could have evolved given that we have not observed information-adding genetic mutations. To watch the development of these features in larvae is, rather, to catch a glimpse at the Creator’s handiwork—reproduced time and time again since creation by the genetic code He built into each created kind of plant or animal and into humans.

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