Trout swimming

Fish evolve in a 100 years, claims an article in Science News 1 June 2018, with the headline: “This saltwater trout evolved to live in freshwater—in just 100 years,” referring to a study also reported in ScienceDaily 31 May 2018, and Molecular Ecology, 26 May 2018; doi: 10.1111/mec.14726.

Steelhead trout live in the ocean off the west coast of North America, but swim up rivers to spawn. The young fish that hatch out in the rivers then migrate back to the ocean where they live until they are ready to spawn, when they swim up into rivers and streams.  Thus, during their life cycle they must adjust from living in freshwater, then saltwater, then freshwater again.  In the 1890s steelhead trout from California were introduced into Lake Michigan, one of the Great Lakes.  Although the lake is a freshwater environment, some of the saltwater trout survived and their descendants now live their whole lives in the Great Lakes system, treating it as if it was an ocean, and migrate up rivers and streams when they were ready to spawn.

A group of scientists from Purdue University compared the genomes of fish living the lakes with fish living in the ocean off California. They found an overall decrease in genetic diversity in the lake fish, and significant differences in three regions of DNA between the two populations.  Two of these contained genes for controlling salt balance, the other involved wound healing.  The salt balance genes are particularly important as freshwater fish must take in salt from their environment, whilst marine fish must excrete salt.

So how did the fish end up with the right salt balance genes? According to Science News, “they didn’t have to mutate” because “there were likely a few steelhead among the first batch of transplants that already had the right versions of these genes—they simply survived and reproduced much more successfully than their peers. Eventually, the less well-adapted steelhead disappeared.”

The research team entitled their report: “Rapid genetic adaptation to a novel environment despite a genome‐wide reduction in genetic diversity”.


Editorial Comment:  The Science News description of what the trout did is correct, but their headline claim of evolution happening is fake news. The research team are closer to the truth – this is an example of adaptation and selection. However, it is not evolution, because the genes for modifying the salt function already existed!  If they didn’t the fish would die, i.e. be selected out.

Adaptation is the ability to modify a function in response to a change in the environment, but it only works if the genes for change already exist. That is what happened here.  Note well: because ocean trout live part of their lives in freshwater they already have genes for changing their salt balance when they move from salt to freshwater.  The trout that survived the initial transplant were the ones that already had gene variants that did this more efficiently and could keep them in “freshwater mode” throughout their adult lives.  The trout that couldn’t do this died.  No evolution is involved, just a selection pressure due to a man-made change in their circumstances.

This study is a good reminder that change is real, but not all change is evolution, and scientific news services should not be using the term “evolution” for any and every change in function. In fact, it is getting worse than that – every biological process is now being called “evolution” in journals and news services.  Whenever, you come across a claim that something has evolved, ask yourself: what has changed, and does that change involve a new structure or function that the organism didn’t have before.

In fact, adaptation is evidence for creation, because it only works if the Creator built in the means of modifying a needed body function to cope with environmental change, before any actual change in an environment occurs.

The only genetic change found in this study was the overall decrease in genetic diversity, i.e. a loss of genetic information. This is not evolution either.  It is evidence that the livings things are going downhill, not evolving upwards.  Again, this confirms the Bible history of the world, starting with a good world of created fully functional organisms according to their kinds, followed by degeneration as a result of man’s sin and God’s judgement.

Evidence News vol. 18 No.6
13 June 2018
Creation Research Australia

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