Electric Gene Discovery Stuns Biologists
Challenging evolutionary assumptions, a new study reveals that the same set of genes powers electric fish the world over—despite their different ancestry.
In order to account for all types of electric fish through evolutionary theory, the same intricate organ would have needed to evolve at least six separate times, according to a study published June 27 in the journal Science.
The team, led by Michael Sussman of the University of Wisconsin-Madison, Harold Zakon of the University of Texas at Austin and Manoj Samanta of the Systemix Institute in Redmond, Washington, identified the genes behind the electric organs that give six different groups of fish high voltage to catch their food, defend against predators, navigate their habitats and communicate with mates.
As part of their research, the group sequenced the genome of the South American eel. A top predator in the Amazon River, almost 90 percent of this fish is electric organ. In a University of Wisconsin news report, Dr. Sussman describes a six-foot electric eel as “in essence a frog with a built-in five-and-a-half-foot cattle prod.”
Electric fish and evolution
The eel and other electric fish have fascinated humans for millennia. Ancient Egyptians pressed them on epileptics as shock therapy. Benjamin Franklin probed them to understand electricity, and Victorians used them as a titillating party game, according to the University of Wisconsin-Madison.
Charles Darwin himself, in his book On the Origin of Species, identified electric fish as posing two potentially major obstacles to his theory. First, he was not sure if an electrical organ could evolve through a series of small steps; and second, he recognized that all the varieties of fish with electric organs could not have inherited them from a common ancestor.
In response to these obstacles, he proposed the idea of analogous structures: “I am inclined to believe that in nearly the same way as two men have sometimes independently hit on the very same invention, so natural selection, working for the good of each being and taking advantage of analogous variations has sometimes modified in very nearly the same manner two parts in two organic beings, which owe but little of their structure in common to inheritance from the same ancestor” (p. 173).
In other words, Darwin proposed that similar environments and needs could independently produce features that appear similar and fill similar roles without having a shared history (like a moth’s wing and a bird’s wing). Indeed, most of these fish are nocturnal and live in murky environments. More than a weapon, electric fields are a kind of second sight for all six groups of electric fish, as sound is for dolphins and bats.
And yet it’s hard to believe each fish’s electric organs could have evolved independently when they have so much in common.
The complexity of electrocytes
All electric organs are made of millions of cells called electrocytes, stacked in series like batteries in a flashlight and all firing at the same time.
Electrocytes are similar to muscle cells. Both create a difference in charge by pumping positively charged ions across the cell membrane to create an electrical gradient. However, an electrocyte must be bigger than a muscle cell. It must not contract. It must have a different distribution of ion pumps to produce a much higher voltage. All the electrocytes must be working correctly in tandem.
Moreover, an electric fish must be able to withstand the electrical discharge, perhaps by keeping its vital organs partially insulated from shock or by being large enough that a much greater current would be necessary to damage it.
Electric fish are indeed amazing creations, but our admiration properly belongs to the God who made them.
This complexity, noted by Darwin, remains a challenge to evolutionary biologists today. Responding to the study in an NPR news story, Leonard Maler, who conducts research on electric fish at the University of Ottawa, explains that none of the changes necessary to become an electric fish would be beneficial on its own. A muscle that does not contract, for instance, is pretty worthless. “You have to simultaneously co-evolve genes that do very many different things in some kind of directed manner,” Dr. Maler points out, adding, “They’ve raised the problem beautifully in this paper.”
Then there are the similarities between the genes themselves. As Darwin predicted, modern evolutionists agree that the fish could not have inherited their electric genes from a common ancestor. The half-dozen fishes studied have around 30 special genes in common. However, all 30 genes would have needed to develop independently for each species—that is, six different times!
Given the incredibly low probability of even one useful change, staggering odds weigh against the evolution of these electric organs!
Students of the Bible realize that God, the Designer of every living thing, “created great sea creatures and every living thing that moves, with which the waters abounded. … And God saw that it was good” (Genesis 1:21).
The researchers, nonetheless, come to a very different conclusion. “I consider ‘exotic’ organisms such as the electric fish to be one of nature’s wonders and an important ‘gift’ to humanity,” says Dr. Sussman. “Our study demonstrates nature’s creative powers and its parsimony, using the same genetic and developmental tools to invent an adaptive trait time and again in widely disparate environments.”
Whose creative powers?
Whose “creative powers” do the electric fish manifest? Again, the Bible has the answer: “For since the creation of the world [God’s] invisible attributes are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse” (Romans 1:20). Electric fish are indeed amazing creations, but our admiration properly belongs to the God who made them.
If you want to learn more about intelligent design vs. evolution and what the Bible has to say on the subject, read the articles in the section “Is There a God?”