Soapberry Bugs: Evidence for Evolution (Part 1)

by Patricia Engler on September 9, 2020
Featured in Patricia Engler

Natural selection in soapberry bugs is supposed to be a textbook case of “evidence for evolution.” Let’s apply the 7 Checks of Critical Thinking to see if that’s true.

“Evolution is supported by an overwhelming amount of evidence.”1

At least, that’s what a heading in my first-year biology textbook asserted. The chapter presented an array of classic arguments for evolution, honed to convince students that Darwin had the right idea about life’s origins—and to equip students to become evolutionary apologists. To begin thinking through these arguments biblically and critically, let’s cross-examine the first witness my textbook called to testify for evolution: the lowly soapberry bug.

Soapberry Bugs

Look closely at balloon vines growing in southern Florida, and you might see black-and-red soapberry bugs probing their long “beaks” into the vines’ fruits to access tasty seeds deep inside. In central Florida, however, where balloon vines are scarce, you’re more likely to find soapberry bugs savoring the shallower seeds of golden rain tree fruits.2

Researchers have found that soapberry bugs which dine on balloon vine seeds sport longer beaks than the bugs living in areas with golden rain trees. Short-beaked bugs can feed more efficiently on golden rain trees’ shallow seeds, so it makes sense that natural selection would remove long-beaked bugs from regions with golden rain trees. However, in regions with deep-seeded balloon vines, natural selection apparently favors bugs with longer beaks.

My textbook presented this study as prime evidence for Darwinian evolution. But is it really? Let’s apply some Critical Thinking Checks to find out.

Check 1: Check Scripture

We can infer from Genesis that God created living things to reproduce according to their kinds. And in this study, we see that soapberry bugs did indeed produce . . . soapberry bugs. So, the real observations are quite consistent with Scripture.

Check 2: Check the Challenge

Even though the study’s observations don’t challenge Scripture, my textbook leveraged them to claim that all life evolved from a single ancestor. As other articles document, this belief does contradict clear teachings from Scripture. So, let’s move onto Check 3.

Check 3, Check the Source

Where is the information about soapberry bugs coming from? It’s coming from evolutionary textbook authors whose worldview starting point is human reasoning, based on naturalistic presuppositions rather than God’s Word.3 Our worldview presuppositions affect the way we interpret information, which will be important to keep in mind for Check 6.

Check 4, Check the Definitions

Are there any keywords in this textbook message which may have more than one meaning? You bet: evolution. The study is about “evolution” in the sense of variation within the soapberry kind, as natural selection apparently did not favor the genetic potential for long or short beaks in certain soapberry populations. However, the textbook claims this is evidence for “evolution” in the sense of variation between kinds of living things, from a single-celled ancestor onwards.

As even some prominent evolutionists recognize, mechanisms like natural selection and mutation, which cause within-kind variation, can’t account for the new genetic information required to produce changes between kinds. (For example, evolving a soapberry bug from a single-celled ancestor would require the emergence of functional genetic information for buggy body bits like internal organs, eyes, and wings.) So, stating that both types of “evolution” are equal is an example of a bait-and-switch fallacy.

Check 5: Check for Propaganda

Despite hinging on a bait-and-switch fallacy, why might the claim that soapberry bugs demonstrate Darwinian evolution sound persuasive? As a student, I noticed that messages seemed harder to resist when they came from an authoritative textbook . . . with a professional-looking diagram . . . that an intelligent professor presented in a classroom . . . where everyone else seems to agree. All these elements contribute to a message’s persuasive punch, but none of them automatically makes the message true.

Check 6: Check the Interpretations

What part of this message is fact from observational science? The observation is that soapberry bugs tend to have different beak lengths in different environments, as natural selection favors genetic variation for certain beak sizes in different bug populations. The interpretation from historical science is that this type of change is evidence that all life evolved from a single ancestor. (For more articles about the issues with this interpretation, see here.)

What’s an alternative, biblical interpretation for the same observation? God created soapberry beetles with built-in genetic variation, which we see natural selection favor (or disfavor) in the present. This explanation is not only consistent with the facts from observational science but recognizes that living soapberry bugs’ intricacies—including flight, reproduction, and metamorphosis—point to a Designer.

In the end, soapberry bugs are excellent witnesses to the truth about origins, testifying that living things resulted not from blind natural processes, but an all-knowing Creator.

For more on how to think critically about any faith-challenging message, stay tuned for future blog articles and my new video series, CT (Critical Thinking) Scan, available now on the AiG Canada YouTube channel and the AiG Canada Facebook page.


  1. Jane Reece, et al., “Descent with Modification: A Darwinian View of Life,” in G. Bennett, L. Rahn, D. Kamo, E. Bush, & S. Bindernagel (Eds.), Campbell Biology (Canadian ed.) (Upper Saddle River, NJ: Pearson Education, 2012), 494–494.
  2. Scott P. Carroll and Christin Boyd, “Host race radiation in the soapberry bug: natural history with the history,” Evolution 46, no. 4 (1992): 1052–1069.
  3. Some may argue that only naturalistic presuppositions are allowable in science. For responses to this idea, see What Is Science? Is Science Secular? or dig deeper on the What Is Science? topic page.


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