The answers are the platypus and the opossum. The overall impression she conveys to the general public is that these species have not evolved for millions and millions of years.
I don't agree. I think it's important to teach the general public that such statements flatly contradict modern evolutionary theory. If, in fact, we discovered modern species that showed no signs of having evolved for millions of years, this would refute modern evolutionary theory.
The accepted minimal definition of evolution is ... [What Is Evolution?]
Evolution is a process that results in heritable changes in a population spread over many generations.... or something similar like "change in the frequency of alleles in a population."
The main accepted mechanisms of evolution are natural selection and random genetic drift.
The only way positive natural selection1 can stop is if an organism is so perfectly adapted to its current environment (external and internal) that every possible mutation is either deleterious or neutral. That includes all metabolic processes and every structure in the cell.
Nobody could rationally advocate such a claim.
The only way to stop random genetic drift is if there's no such thing as a new neutral or nearly neutral mutation and all such variation in the population has been eliminated.
No evolutionary biologist could possibly make such a claim with a straight face.
It's easy to test such ridiculous claims by looking at the genomes of the opossum and the platypus. The evidence shows that they have evolved at the same rate as all other species.
The article actually mentions this problem ...
“'Unchanged' is a tricky word,” Nizar Ibrahim, a paleontologist at the University of Chicago and 2014 National Geographic Explorer, says via email.Liz Langley did not pick up on this comment so she missed a wonderful teaching moment.
With only fossils to go by, scientists can examine an ancient animal's skeletal structure, but it's not the whole story. Physiology and DNA change somewhat over time, he says, both through the basic process of evolution as well as random genetic changes.
That said, two mammals that have undergone the fewest evolutionary shifts are the platypus and the opossum, says Samantha Hopkins, associate professor of geology at the University of Oregon.
It's possible that Liz Langley isn't aware of modern evolutionary theory and that she actually believes that evolution comes to a halt as long as species live in a relatively constant environment. It's possible that she disagrees with the minimal definition of evolution and prefers a definition that only counts significant changes in external phenotype. Or, it's possible that she thinks that National Geographic readers can't handle modern evolutionary theory. If it's the latter, I disagree.
1. You can't stop negative natural selection unless there are no new deleterious mutations. That's also impossible.