Evolution as a Scientific Theory


The theory of evolution holds that all the lifeforms on Earth have a common ancestor. The process works through what is known as variation and selection over a period of time, which is roughly taken to be four billion years.

Variation is a term used to describe how an organism’s offspring is not an exact copy of its parents. Selection occurs when some of an organism’s offspring produces more of their own offspring. Common ancestry does not mean that species have evolved from each other. For example, chickens did not evolve from cats and humans did not evolve from chimpanzees. Instead, what evolutionary theory holds is that if one were to go back far enough in time one will find a “grandparent” of which both organisms are descendants.

Is evolution a theory in crisis? One writer for an Intelligent Design website maintains that it won’t be too long until the “evolution bubble is about to pop” (1). But this is far fetched. It is true that scientists debate the specifics of the theory, after all, that is how science functions. Although debates exist across several areas (i.e. the extent to which variation is explained by random genetic mutations and how important other selection mechanisms are beyond reproductive fitness), the general framework of evolutionary theory which includes the common descent of all species is widely supported. The theory does not present any reason to believe that it will be “popping” any time soon. For example, 98% of the members of the American Association for the Advancement of Science (AAAS) accept human evolution. According to the American Association of University Professors, “The theory of evolution is all but universally accepted in the community of scholars and has contributed immeasurably to our understanding of the natural world” (2). National Association of Biology Teachers Scientists claims that scientists have “firmly established evolution as an important natural process” (3).

Although many religious people still struggle to accept evolutionary theory (4), an increasing number of religious organizations are receiving it warmly. Biologos, for example, explains that “There is very little debate in the scientific community about this broad characterization of evolution”, and they seek to present harmony between religion and evolutionary theory. The group claims that  “the observational evidence explained by common ancestry is overwhelming. Of course, new data causes scientists to adjust some of the specifics (like how long ago species diverged, or which species are most closely related), but this core view is overwhelmingly supported and agreed upon by the vast majority of scientists in the field” (5).

Some critics of evolution charge that it is “just a theory.” In other words, it is just an idea that scientists uncritically accept. But this is not accurate. Although it is true that evolution is a theory, just like the theory of gravity and the Big Bang, and is therefore open to falsification, this is not to say that it is an unconvincing idea. Hypotheses that are tested and do not stand up to scrutiny are revised or rejected. For a hypothesis to constitute a theory scientists must agree that it is supported by persuasive evidence and has explanatory power. The following explanation offered by Biologos is sufficient,

“In non-scientific contexts, “theory” usually means something like a guess (e.g., I have a theory about…). But in its scientific sense, a theory is a tested and well-confirmed explanation for a set of observations. The observations explained by the theory of evolution come primarily from the fossil record, comparative morphology, biogeography, and now most importantly, genetics. Evolution does not attempt to give a scientific explanation for the origin of life, but only for the development and diversification of lifeforms after the first life began” (6).


1. Luskin, C. 2014. What to Expect When the Evolution Bubble Is About to Pop. Available.

2. American Civil Liberties Union. n.d. What the Scientific Community Says about Evolution and Intelligent Design. Available.

3. American Civil Liberties Union. n.d. Ibid.

4. Nadelson, Louis., and Hardy, Kimberly. 2015. “Trust in science and scientists and the acceptance of evolution.” Evolution: Education and Outreach 8(9); Pew Research. 2015. Chapter 4: Evolution and Perceptions of Scientific Consensus. Available.

5. Biologos. What is Evolution? Available.

6. Biologos. What We Believe. Available.


  1. James Bishop’s post above presents a standard theistic evolutionist position. Formerly an atheist (sometimes) and agnostic (other times), I moved to theism and Christianity when I learned more about science, logic, history and worldview. Theistic evolutionism has a certain appeal, and I would have adopted that view – except that it lacks both science and good reasoning.

    Mr. Bishop’s post makes several points, each is addressed here. First, the post uses a common formulation of what “evolution” means. Under the theory of evolution, the post states, all life forms on Earth have a common ancestor.

    Understand that the post is asserting humans and lawn grass and fish and insects all have a common ancestor – the same ancestor. That’s an assertion of historical fact, which cannot be tested in the laboratory using the “scientific method.”

    Further, per the post, the theory of evolution works via “variation and selection.” Variation describes “how an organism’s offspring is not an exact copy of its parents.” And: “Selection occurs when some of [those] offspring produce more of their own offspring.”

    Certainly the post is designed to be very short. But the definition and explanation of “evolution” given here is so shallow that it cannot possibly explain how an initial life form became via these factors all of the species ever seen or known. The post does mention in a sentence or two a little more about scientific debates concerning how “mutation” works to create the “variation,” and how “natural selection” operates. That depth of explanation just cannot be enough to prove the origins of all species.

    The post moves to argue that the theory of evolution (as described) “is overwhelming supported by scientists,” that “98% of the members of AAAS accept human evolution.” This fact is interesting but it does not establish anything factual about evolution itself. This fact appeals to an authority but it does not offer scientific reasoning.

    The post quotes Biologics as saying: “There is very little debate in the scientific community” that evolution is a proven fact. The post asserts “anyone who says anything different is ‘either uninformed or deliberately trying to mislead.’” (Ostensibly quoting Biologos again.) The absolute generalization here commits immediately the fallacy of hasty generalization. Neither the post nor Biologos can actually testify from personal knowledge to these claims about “anyone saying anything” to challenge evolution theory. So this is rhetoric aiming to intimidate. The rhetoric does not support any scientific claim made in support of evolution as defined.

    The post further says “the observational evidence explained by common ancestry is overwhelming.” Actually, that statement itself betrays ignorance of the arguments. If the “observational evidence” refers to fossils or common features among life forms, then the argument is about “similarity.” But similarity between forms of life does not prove they have a common ancestor. Similarity is also evidence of a common designer who used a common basic plan.

    The post deals with “the charge that evolution is only a theory.” Fact is, the scientists, researchers and thinkers involved in critiquing evolution never use an argument that depends upon what “theory” means. Lay people do that, and the post correctly puts that issue to bed. Those of us working in the field never attack evolution because it is called a “theory.”

    The post then summarizes the position of Biologos – and here is where a serious problem becomes evident. Biologos reportedly believes in a theory of “evolution” that is “God-ordained.” Biologos “reject[s] ideologies that claim that evolution is a purposeless process or that evolution replaces God.”

    The standard neo-Darwinian synthesis (the currently reigning theory of evolution) is exactly the opposite of what Biologos believes. I don’t know why Biologos tries to hide that fact. The current theory of evolution – the one presumably that 98% of AAAS members agree with – is the theory that holds all species arose via the operation of random (undirected) mutations and natural selection – and that there is no design or purpose behind the mutations.

    The current “scientific” theory of evolution holds that all life is the result of purposeless material forces operating with purposeless matter – random mutation and natural selection. The current theory says there is no intelligence and no designer.

    So Biologos, and theistic evolutionism generally, criticizes people who challenge that materialist theory of evolution, calling such critics “uninformed” and “deliberately misleading.” Yet Biologos itself does not agree with materialist evolution as the “scientists” define it. (I can supply great numbers sources and quotes upon request.)

    In addition to many other weaknesses, the theory of evolution (as the scientists describe it – undirected, purposeless) is entirely incapable of explaining the existence of code systems and biological software. There are several articles in Salvo Magazine online that discuss this with citations to secular sources – search there on “code” and “software.”

    The new book by Perry Marshall, entitled Evolution 2.0, demolishes the theory of standard theory of evolution by showing the impossibility of undirected physical forces creating code systems. Because evolution cannot create code systems, it cannot create or modify software. That means evolution cannot create or modify DNA, the backbone of all life, and make new species. At best, undirected mutation and natural selection can result in small changes of features within a species.

    The new book by committed atheist Thomas Nagel, entitled Mind & Cosmos, shows logically how what we call “mind” cannot have arisen by unconscious material processes. That conclusion contradicts the neo-Darwinian theory that says everything in our mind and body came by undirected material processes.

    Theistic evolutionism is a mindset that allows a person to escape the problem of challenging the scientific establishment. That’s fine, I guess. Theistic evolutionism seems like a quiet little place to retreat. If you’re following the evidence and logic, however, you cannot stay a theistic evolutionist and retain intellectual clarity.

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