Horizontal Gene Transfer Masquerades as Common Ancestry

Horizontal Gene Transfer Masquerades as Common Ancestry

Masquerade parties are a lot of fun. Inspiration for costumes comes from all kinds of sources. At these types of gatherings, it’s not unusual to find people dressed up as princesses, soldiers, superheroes, movie stars, historical figures, and other famous people. Sometimes the inspiration for the costume comes from a well-known children’s story. Last Halloween, my wife and I attended a costume party dressed as Thing 1 and Thing 2 from Dr. Seuss’ The Cat in the Hat. (My wife’s idea.)

Recently, a team of evolutionary biologists discovered that, when viewed from an evolutionary perspective, the process of horizontal gene transfer can masquerade as common ancestry.1 This new insight indicates that the most commonly cited evidence for biological evolution may in fact indicate something entirely different.

Common Ancestry

According to the evolutionary paradigm, all life on Earth is related through the process of common descent. The idea is this: in the distance past an organism called the last universal common ancestor spawned a number of lineages that evolved separately and continued to diverge, diverged, ultimately generating the diversity of life that exists today and has existed throughout Earth’s history.

Evolutionary biologists’ tasks include trying to discover the presumed evolutionary history of life. To do this, they build evolutionary trees—diagrams that putatively describe the ancestral and descendent relationships of Earth’s life displayed in a branching tree-like pattern.

Researchers employ a number of different approaches to construct evolutionary trees. For example, they use anatomical similarities and differences to discern what they believe to be evolutionary relationships. Organisms that display a high degree of anatomical similarity are interpreted as sharing an ancestor in the more recent past than organisms that possess only a few features in common.

As a corollary to this idea, evolutionary biologists interpret shared similarities as evidence for organisms’ common ancestry, with differences arising after the two lineages diverged from one another.

In recent years, evolutionary biologists have turned to DNA sequences to construct evolutionary trees. As with the use of anatomical features, organisms with highly similar DNA sequences are viewed to have shared a common ancestor more recently than organisms that display greater sequence differences. Evolutionary biologists also interpret genetic similarities among organisms as evidence for common ancestry, with differences arising post-divergence.

Horizontal Gene Transfer Mimics Common Ancestry

However, new work complicates the interpretation of DNA sequence similarity among organisms—at least for bacteria and archaea. Researchers from the University of Connecticut discovered through modeling studies that horizontal gene transfer among microbes has the same genetic signature as common ancestry.

Horizontal gene transfer encompasses any mechanism that transfers genetic material to another organism without the recipient being the offspring of the donor. A consequence of horizontal gene transfer, when viewed from an evolutionary standpoint, is that organisms unrelated through common descent will have the same DNA sequences.

Horizontal Gene Transfer and the Case for Biological Evolution

Many people regard shared DNA sequences as the best evidence for evolution and common descent. But as this most recent work demonstrates (as so do other studies), from an evolutionary vantage point, other mechanisms beside common ancestry can introduce the same DNA sequences in organisms unrelated via common descent.

These types of studies indicate that evolution’s best evidence may not be evidence for evolution at all. It could be the consequence of another mechanism such as horizontal gene transfer. Or the shared DNA sequences may actually point to something beyond natural mechanism as the explanation for features shared among organisms.

Common Ancestry or Common Design?

Before Darwin advanced his theory of evolution, many scientists (like Sir Richard Owen) regarded the similar anatomical features possessed by organisms as the handiwork of a Creator. Instead of a common ancestor, these pre-Darwinian scientists believed Earth’s life-forms represented variations on a hypothetical  archetype. From this perspective, the shared features reflected common design elements employed by the Creator, not shared evolutionary history.

It is possible to view the similarity in DNA sequences in the same way. Instead of explaining shared genes as a consequence of horizontal gene transfer via a natural process, they could be understood as originating by a Creator’s hand. In fact, artificial horizontal gene transfer is another term given to genetic engineering, in which laboratory researchers (i.e., intelligent agents) introduce genes into the genomes of organisms.

New discoveries, like the one made by the scientists from the University of Connecticut, pull the mask off the evolutionary paradigm.

  1. Cheryl P. Andam, David Williams, and J. Peter Gogarten, “Biased Gene Transfer Mimics Patterns Created through Shared Ancestry,” Proceedings of the National Academy of Sciences, USA 107, no. 23 (June 8, 2010): 10679–84.