Wednesday, February 17, 2010

Evolution for Christians

Conservative Christians frequently reject evolution out of hand for a variety of reasons. Some of these reasons are sound, others are not.
I’m going to try to explain what evolution is and demonstrate that it is a very broad science, containing many elements that ought to be perfectly acceptable to Christians.

Definition of evolution
An academic definition of evolution is Change in the distribution of alleles in a population from one generation to the next.

Alleles are defined as alternative DNA sequences at the same physical gene locus, which may or may not result in different phenotypic traits.

A phenotype is defined as any observable characteristic or trait of an organism

Common descent is the notion that all organisms today are descended from a smaller number of organisms that lived in the past. For example, amphibians evolved from fish, etc.

Common descent begins with speciation – the separation of an interbreeding population into two populations that cannot interbreed.

Why the definition is important

  1. It’s difficult to get anywhere in a discussion without being agreed on definitions – or at least understanding how the other side defines its terms.
  2. Some hint of where I’m going should have already shown up in the definition. Note that it says nothing about fish evolving into salamanders, etc. Note that most evolutionary biologists believe that new species can evolve from earlier species. But in academia far less controversial changes go under the rubric of evolution. (e.g. bacteria developing resistance to antibiotics) The form of evolution conservative Christians object to (often called macroevolution, but more properly called common descent) begins with speciation—the separation of an interbreeding population into two populations that can’t interbreed.


Conservative Christians have developed a number of objections to evolution. Here I deal with the most common ones.

  1. The genetic code doesn’t permit evolution. This is entirely too restrictive. First, the genetic code does permit evolution defined as above. One example has already been mentioned: the development of resistance to antibiotics among bacteria. A second example is the peppered moth in England. In the early part of the 20th century there were more white peppered moths than black. Later it was noted that the proportion of black peppered moths had increased. Finally, in the latter part of the 20th century the proportion of white peppered moths increased. Eventually it was noted that the reduction in the proportion of white peppered moths coincided with the increasing use of coal in British industry, which caused the tree barks to darken in color. When clean air legislation began to take effect there was less soot in the air and the tree barks lightened. The proportion of light colored moths increased. In each case the moths that contrasted with the tree bark were more visible to predators and were removed from the population, causing future generations to increasingly match the tree bark. This is just natural selection in action. Note that evolution provides populations of living creatures with a very effective, elegant defense against environmental factors that could result in their demise. If for example the peppered moths referred to above did not carry the genes for white spots on a dark background as well as those for dark spots on a white background, the population of peppered moths might have been wiped out. What about macroevolution? Here the genetic code does provide some barriers. Evolutionary researchers don’t believe they’re insurmountable, many conservative Christians believe they are. First, for one population to separate into two that can’t interbreed (in other words, for one species to become two) all that is necessary is for a mutation to occur that prevents the mutated members of the population from interbreeding with the non-mutated members. The mutated members don’t necessarily differ from the non-mutated members in physical appearance – they just can’t interbreed with them. However, for a new species to be formed (an interbreeding population) the same mutation must occur in at least two individuals of the opposite sex. If this occurs, then you have two populations that can evolve independently.
  2. Evolution depends on death – those individuals that are less fit for the environment they live in die off. Thus death preceded Adam’s sin, which they claim is contrary to Scripture. However, the Scriptures say nothing about animal death resulting from sin. Gen 2:17 says
    but from the tree of the knowledge of good and evil you shall not eat, for in the day that you eat from it you will surely die.
    Since Adam did not die physically for many more years, you could make the case that God is talking about spiritual death here – separation from God. Since animals are not spiritual beings, the warning does not apply to animals.
  3. Another problematic aspect of evolution for many Christians is the contention that random mutations provide the richness of variation that natural selection works on. Here we need to be very careful. What appears random to a human researcher does not necessarily appear random to God, who is omniscient. Indeed a Christian view would eliminate “necessarily” in the previous sentence. Furthermore, nonlinear processes can exhibit behavior that appears random but is not. Without knowing the differential equations or the recursion relations and the initial conditions to infinite precision, trying to predict the evolution in time of a complex process is a hopeless task. One would achieve as good a prediction using random numbers.

What does all this mean to Christians?

Rejection of evolution by the Christian community leads some Christian young people to avoid careers in the biological sciences, and it leads secular biologists to reject Christianity. In Matthew 28 Jesus tells the disciples
Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age."

Jesus did not say to avoid making disciples of scientists.

Worse, rejection of evolution by the church will lead some Christian students to abandon their faith when they are faced with the evidence for evolution. A good friend of mine, who has had a very successful career as a petroleum geologist, nearly abandoned Christianity for exactly this reason.
If Christians accept evolution but not necessarily common descent, they are accepting a very large part of the science of evolution, without compromising any Christian principles. This opens the field of evolutionary biology to Christian students. This is important for several reasons:

  • Scientists are more likely to hear Christian testimony if some of their colleagues are Christians
  • They are less likely to reject Christianity if they have colleagues whom they respect, who are Christians
  • Much progress has been made in immunology and biology by evolutionists. Let’s encourage Christians to potentially make advances in these fields

One caution: don’t go around saying “I accept microevolution but not macroevolution.” Academics don’t make a distinction between microevolution and macroevolution. If you must, say, “I don’t accept speciation.”