Observation and Evidence for Evolution

Lack of Direct Observation is Not a Lack of Evidence for Evolution

Human Evolution
Human Evolution. Emmet Doherty/EyeEm/Getty

Creationists like to argue that evolution can't be science because we can't directly observe evolution in action — and since science requires direct observation, evolution is necessarily excluded from the realm of science. This is a false definition of science, but more than that it's also a complete misrepresentation of how humans actually work when it comes to forming conclusions about the world.

Observation & Evidence in Courts of Law

Can you imagine what would happen if it became a generally accepted principle that you couldn't legitimately form conclusions about what has happened unless you directly observed it happening? Suppose the following evidence is presented to a jury in a murder trial:

  • the suspect is a large male and the victim is a small female
  • the suspect was found holding a smoking gun and standing over the victim's body
  • the gun is owned by the suspect
  • there were no fingerprints but the suspect's on the gun
  • there were no other weapons found at the crime scene
  • the bullet that killed the victim has been shown to have come from the suspect's gun
  • the suspect was seen arguing with the victim before the shooting
  • the suspect had a known hatred of the victim and previously had threatened the victim
  • the suspect had a history of violence that had been directly witnessed
  • gun shots were heard just before the suspect was found standing over the victim
  • no one else was seen in the vicinity

Without any direct witnesses to the actual shooting, would it be reasonable to find the suspect guilty of murder? Of course.

Steve Mirsky writes in Scientific American (June 2009):

The claim makes me think of the trial where a man was charged with biting off another man’s ear in a bar fight. (Incredibly, Mike Tyson was not involved.) An eyewitness to the fracas took the stand. The defense attorney asked, “Did you actually see with your own eyes my client bite off the ear in question?” The witness said, “No.” The attorney pounced: “So how can you be so sure that the defendant actually bit off the ear?” To which the witness replied, “I saw him spit it out.”
We have the fossils, the intermediate forms, the comparative anatomy, the genomic homologies—we’ve seen what evolution spits out.

Criminal trials are a good analogy to use with evolution when creationists start complaining that we can't "observe" evolution and therefore scientists' conclusions about what happened in the past are suspect at best. People are frequently charged with crimes, found guilty of crimes, and imprisoned for crimes which no one directly witnessed. Instead they are charged, tried, and imprisoned based on evidence left behind.

Role of Evidence

It's generally accepted that this evidence can used as a foundation for conclusions about what really happened and if multiple lines of evidence all point in the same direction, then the conclusions are far more secure and certain — perhaps not absolutely certain, but certain "beyond a reasonable doubt." If we adopt the creationist way of thinking, though, then no amount of DNA evidence, fingerprint evidence, or other forensics can justify imprisoning anyone.

So we should ask creationists: if direct observation is necessary to accept that evolution occurred, then why isn't direct observation necessary before finding someone guilty of a serious crime like murder? Indeed, how can we even conclude that a crime really occurred if no one was there to witness what happened? How many people should be released from prison because they were found guilty based on the same sort of evidence creationists reject when it comes to evolution?

Observation & Evidence

We don't have direct observational evidence of past evolution in action, but we do have an abundance of evidence that all support the actuality of common descent. We have the "smoking gun." While you can philosophically argue that the evidence isn't complete, this ignores the fact that, when it comes to the real world, the evidence is never complete.

There is always something that can be called into question. Holes in the evidence should not be ignored, but the idea that the huge amount of evidence that supports evolution means nothing if there are missing pieces is absurd. There is as much evidential support for the general theory of evolution as there is for any other scientific theory.

The evidence for common descent comes from a variety of sources and there are two basic types: direct and inferential. Direct evidence consists of observations of actual evolution and knowledge of the principles involved therein. Inferential evidence is evidence that does not involve direct observation of evolution but from which we can infer that evolution has taken place.