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What is Evolution?

Properly understood, evolution is a scientific theory about the development of life and is consistent with Christian theology.


Properly understood, evolution is a scientific theory about the development of life and is consistent with Christian theology.

Properly understood, evolution is a scientific theory about the development of life and is consistent with Christian theology.


Providing a definition of “evolution” is tricky because the word is used in different ways. First we need to distinguish between the broader worldview some associate with evolution and the scientific theory of evolution.

Evolution as worldview

Some people consider evolution to be equivalent to atheism, thinking it replaces God or otherwise rules out God’s involvement in the development of life. But that is a philosophical or worldview position (sometimes called “evolutionism” or simply “naturalism”), not a strictly scientific position.

At BioLogos, we are against evolutionism and instead hold to the worldview of Christian theism. We call our position on origins “Evolutionary Creation.” That is to say, we believe God is the Creator and also accept that evolution is the best scientific description for how life has developed. This is similar to saying we believe God provides for the growth and development of plants while we also accept that the theory of photosynthesis is the best scientific explanation for that process.

Evolution as a scientific theory

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.

The theory of evolution states that all the lifeforms on earth share a common ancestor as a result of variation and selection over a very long time (currently thought to be around 4 billion years). Variation means that offspring are not exact replicas of their parents, and selection occurs when only some of those offspring go on to produce more of their own offspring. Common ancestry does not mean the species we find today have evolved from each other—dogs did not evolve from cats, and humans did not evolve from chimpanzees. Instead, if you go back far enough in the ancestral tree of any two organisms, common ancestry predicts that you’ll come to a “grandparent” of which both current organisms are descendants. For humans and our closest relatives the chimpanzees, you have to go back around 300,000 generations to find that common ancestor (that would be your 299,998th-great grandparent!). What did that process look like?

Chimpanzee and her baby

That ancient population (which was neither human nor chimpanzee) split into two groups, and these groups were reproductively isolated—that is, the members of each group only mated with other members of the their own group. Then over the many generations of offspring, different variations were preserved in each group. Eventually the characteristics of each group were different enough for scientists to recognize them as different species. The theory of evolution claims that a similar story could be told for the ancestral lineage of any two species that have ever lived.

Debates about evolution

There is very little debate in the scientific community about this broad characterization of evolution (anyone who claims otherwise is either uninformed or deliberately trying to mislead). 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.

But that is not to say there are no debates and controversies about evolution among those who accept this core view of the theory. Evolutionary scientists debate the extent to which the variation element is explained by random genetic mutations, and how important other selection mechanisms are beyond reproductive fitness. Scientists have different views on topics like how gradual evolutionary change is and on the details of how natural selection works. And as we’ve already seen, there are significant differences of opinion about how to interpret various aspects of evolution with respect to worldviews, such as whether there is overall direction to evolution, and what the significance of evolution is for theology.

At BioLogos we believe the best contemporary science is consistent with Christian theology. Find more information on evolution and the BioLogos perspective on origins in the other resources on this page or by searching on particular terms in our search box.

Last updated on November 20, 2023