The rise of antibiotic-resistant bacteria: Evolution before our eyes

Introduction

Creationists often argue that evolution is “just a theory,” since we don’t see it in action today — it is “hypothesized” to have occurred, but scientists have no proof. Intelligent design writers acknowledge that evolution might occur “within kinds,” but question whether it can occur beyond the limits of a “kind” (which probably means “species,” although ID writers have never crisply defined the term). Instead, they argue that evolution beyond the bound of a “kind” requires an intelligent designer.

The rise of evolution-resistant bacteria

Sadly, these arguments are being refuted before our eyes, with the frightening rise of bacterial strains that one-by-one are becoming resistant to every antibiotic drug in the arsenal of modern medicine.

This was driven home by the announcement on 27 May 2016 that a Pennsylvania woman, who was diagnosed with a urinary tract infection, was in fact infected with a strain of bacteria that was resistant to colistin, an antibiotic “of last resort” — used only when all other antibiotics have failed. This was the first instance of this strain in the U.S.

Attention was drawn to this strain in November 2015, when a team of Chinese and British researchers found that mcr-1, a new gene for colistin resistance, was circulating among both animals and people in China, and was housed in a piece of bacterial DNA known as a plasmid. Bacteria carrying this plasmid are able to share copies of it with other bacteria, allowing the colistin-resistant gene to spread rapidly.

Thus researchers fear that this mcr-1 gene will be acquired by other bacteria that are already resistant to leading antibiotics, such as strain known as Carbapenem-resistant Enterobacteriaceae, or CRE. According to Lance Price of George Washington University, infections with CRE are becoming more common, and at the present time, colistin is among the only drugs that can cure those who are infected. If CRE acquires the mcr-1 gene, the world may be faced with a strain of bacteria that is resistant to all known antibiotics, with catastrophic consequences.

Creationists often argue that bacteria are becoming resistant to antibiotics, but only because genetic variability was already incorporated in the bacteria. But this claim is refuted by the fact that the mcr-1 gene is new — it had not appeared in any strain of bacteria until recently.

Evolution of Zika and Ebola

Analysis of the Zika virus also underscores the fact that evolution is more than just rearrangement of existing genes. An April 2016 study of the Zika virus by researchers at UCLA and the Peking Union Medical College, which deduced a phylogenetic tree constructed from nucleotide data, identified “significant changes both in amino acid and nucleotide sequences during the past half-century.”

Genhong Cheng of UCLA added, “We believe these changes may, at least partially, explain why the virus has demonstrated the capacity to spread exponentially in the human population in the Americas.”

The Ebola virus has also undergone significant evolutionary changes, with similarly disastrous effects. Ebola has RNA, not DNA, and RNA is subject to many more mistakes when copied than DNA. This high mutation rate allows Ebola to evolve quickly. Indeed, a recent study found that the virus is mutating much more quickly than in the past. Why? Quite likely because Ebola has found a novel host, namely humans.

Human evolution in action

Some creationists acknowledge that bacteria and viruses might undergo evolution, but argue that it has never been observed in humans.

But this claim is also refuted in recent scientific research. Perhaps the most interesting case is the adaptation of Native Tibetans to a high-altitude environment. As it turns out, Tibetans have acquired a gene that significantly improves their tolerance of low oxygen levels, due in part to an unusual variant of a gene known as EPAS1. This gene appears in about 90 percent of Tibetans, and a few Han Chinese (who are closely related to Tibetans), but it is completely absent from other human populations.

Now it appears that the Tibetans acquired this unusual variant from the Denisovans, a group of early hominins that are more closely related (in DNA) to Neanderthals than they are to us.

The fact that species can adapt to a new environment is not a new notion — they can acquire spontaneous mutations that slowly spread through the population. But this is a relatively slow process. So instead, Tibetans acquired this gene by interbreeding with Denisovans, which evidently had acquired this gene through more conventional natural selection many years ago.

Conclusion

Many other examples of evolution in action could be cited. For example, there are numerous instances of species that are in the process of splitting into two or more species — see Speciation.

So claims that “evolution can’t happen,” or that “evolution can only occur within kinds” (whatever “kind” is assumed to mean) simply don’t hold water. Evolution does happen!

Comments are closed.