What missing link? Filling the 'holes' in the theory of evolution

Kristen Blanchard

Originally published March 4, 2015

 Photo by: Kristen Thomas

Photo by: Kristen Thomas

When Georgia Congressman Paul Broun was asked about his views on evolution, he claimed it was an idea “straight from the pit of hell.” However, despite being framed as a conflict between religion and science, the basic tenets of evolution do not preclude faith or religion. Unfortunately, the topic of evolution still evokes passionate debate from both supporters and detractors, such as the one that occurred between Ken Ham and Bill Nye earlier this year. Sadly, in many of these debates, those who disagree with so-called Darwinian evolution disseminate information that simply isn’t true. Such misinformation hinders the public’s conception of evolution and obscures the true questions that still remain in our understanding of how organisms change over time. What follows are some of the common misconceptions held by opponents of evolution and the reasons these talking points are false.

The fallacy: It’s possible to believe in both evolution and Intelligent Design.

Some proponents of Intelligent Design, Creationism, or other “alternatives” to the theory of evolution will argue that their views can coexist with those of evolution. They might argue, for instance, that there is no disagreement. They agree that organisms change over time, hence, they accept that evolution occurs. They just believe it occurs as part of a directed and pre-planned course.

The facts: The theory of evolution is directly antithetical to pre-planned, “directed” series of changes.

Evolution occurs through a series of random changes. In a large enough population, mutations will occur, leading to genetic diversity. The genes that are best at propagating (i.e., the “fittest”) will propagate the most and become the largest portion of the population. On an individual level, the organisms that are thus best at reproducing will reproduce the fastest, and overtake the population. To argue that these genetic mutations are not random, but rather preordained, runs directly counter to the definition of evolution. This distinction may seem like an issue of semantics – if both sides agree that organisms change over time through genetic mutations, why does it matter whether these changes are random or planned? The answer is because the latter runs contrary to what scientists see in the lab. As scientists monitor organismal changes over time, mutations are random. Populations experience both beneficial and deleterious mutations, not merely preordained changes according to a design. This observation forms the foundation how we understand genes, proteins, and whole organisms to change over time. Applications of evolutionary science, such as tracking infectious disease transmission, would be impossible without this framework for understanding how changes occur. Thus, to argue that evolution and Intelligent Design are synergistic theories is simply disingenuous.

The fallacy: Entropy disproves evolution – the natural tendency is for things to become more disordered, not more complex.

The second law of thermodynamics states that in a closed system, entropy can never decrease. Technical jargon aside, this immutable postulate means that absent outside influence, things cannot become spontaneously more ordered. An unordered set of molecules cannot suddenly become ordered without external force. For opponents of evolution, this argument means that the development of complex biological structures (i.e., living organisms) requires a designer in order to be consistent with this law of thermodynamics.

The facts: The energy provided by the sun powers the creation of ordered molecules.

The important caveat in the second law of thermodynamics is that it holds true for a closed system. With external input, entropy (or disorderedness) can decrease. This input can take many forms, without necessitating the existence of a designer. For example, we know that plants can utilize energy from the sun to form sugars from smaller molecules. Entropy decreases due to the addition of energy to the plant. Our natural environment is not a closed system. Energy is constantly added to the system and no external designing force is needed to explain the decrease in entropy as life forms evolved.

The fallacy: Scientists have never observed speciation, or seen the evolution of new or separate species.

Some opponents of evolution also make the distinction between “microevolution” and “macroevolution.” They might concede, for instance, that bacterial populations can develop antibiotic resistance over time, but argue that bacteria can’t evolve into separate species. Implicit in this claim is that such evolution, the development of offspring into separate or new species, has never been directly observed.

The facts: Large-scale organismal changes have been observed both in the lab and in nature.

The Cohan laboratory at Wesleyan University studied adaption over time in communities of Bacillus subtilis, a type of bacteria. In this experiment, not only did they observe B. subtilis descendants develop into unique ecological subtypes (“macroevolution”), they observed that these drastic changes occurred on a similar frequency as changes within an ecological subtype (“microevolution.”) In fact, most scientists do not make a distinction between microevolution and macroevolution. As the work of the Cohan laboratory shows, both small-scale changes and large-scale changes happen concurrently as organisms reproduce; microevolution and macroevolution are occurring through the same process.

Despite our certainty that evolution can and does occur, there are plenty of exciting questions that remain. Research is constantly underway to refine our understanding of evolution. In fact, labs here at Emory are currently investigating diverse topics ranging from evolution of antibiotic resistance to host parasite interactions. The question of how organisms evolve is still a rich and exciting mystery – but that they evolved, and continue to do so both in nature and in the laboratory, is simply not up for debate.