Ask Eirik: What Evidence is There for Evolution?

Every now and then, I’m contacted by people who question the idea that living organisms, including humans, pandas, fungi, plants, and so forth, are a product of evolution. Some seem to be under the belief that an almighty God created all of life in its present form and that the Earth is just a few thousand years old.

I typically don’t answer these people. Not because I don’t know anything about the evidence on which the theory of evolution rests, but rather because the messages I receive from outspoken, hardcore creationists generally come across as rants and are filled with vicious remarks. Today, however, I found a message in my inbox that doesn’t conform to this pattern. It’s not hateful or ranty. For that reason I’ve decided to answer it here on the site.

Here’s the message:

Eirik,
Just purchased the latest Paleo magazine and saw your site under your bio. I have to ask you sincerely; what actual evidence is there for evolution? The pieces do not fit. Evolution is a theory (only) that does not stand scientific investigation. In fact, evolution is next to impossible by simple science. I would challenge you to not drift through life without exploring the other side of the “argument”. Here is my challenge: watch “Evolution’s Achilles’ Heels”- 15 Phd scientists present their case why evolution is impossible. There is a God Eirik, despite what you have been taught. The evidence is all around you and in you. Good luck, John

My answer:

Hi John,

Thanks for reaching out and for expressing your opinions in a cordial manner.

It’s clear from your message that you are not a habitual reader of scientific research. Several of your statements give you away. First off, you seem to misunderstand how the word theory is used in scientific contexts. The following quote from Wikipedia helps explain what I mean:

A scientific theory is an explanation of an aspect of the natural world that can be repeatedly tested, in accordance with the scientific method, using a predefined protocol of observation and experiment. Established scientific theories have withstood rigorous scrutiny and embody scientific knowledge.

The definition of a scientific theory (often contracted to “theory” for the sake of brevity) as used in the disciplines of science is significantly different from the common vernacular usage of the word “theory”. In everyday speech, “theory” can imply that something is an unsubstantiated and speculative guess, the opposite of its meaning in science. (1)

Second, you seem to be under the belief that the scientific foundation upon which the theory of evolution rests is weak, small, and fragile. Nothing could be further from the truth. It’s extremely solid, large, and dense. The evidence for evolution is beyond overwhelming! (2, 3, 4, 5, 6, 7) The theory of evolution is an established scientific theory, it’s not an untested or rejected theory, and it’s certainly not a wild idea or guess.

Virtually all scientists recognize that life is constantly evolving. There really isn’t any dispute about this. Only a very small minority of researchers reject the theory of evolution. The professors you mention in your message belong to this minority.

Evolutionary science is a ubiquitous part of the world of science. It’s a natural component of scientific papers that deal with topics that have to do with the living world, including papers that cover nutrition and medical-related matters. If you jump on PubMed and start exploring the world of science, this is something you’ll quickly notice. Here are some papers that can get you started: 8, 9, 10, 11, 12, 13.

Scientists don’t question whether organisms evolve or not, they just operate under the belief that they do. Not because they are reckless, but because they know that the science on evolution is air-tight. It’s an established fact that evolution occurs.

The idea that life changes over time as a result of evolutionary processes is supported by several lines of scientific evidence (2, 3, 4, 5, 6, 7). Perhaps the most convincing evidence comes from modern genetics research, which has revealed, not surprisingly, that organisms neatly fall into line on the tree of life/evolution when their genomes are examined, as explained in the video below.

One of the main reasons why some people question the idea that life is constantly evolving is undoubtedly that morphological evolution is typically a slow process. Our bodies obviously don’t change over night. Neither do the bodies of other animals. It typically takes many generations for major changes in the gene pool of a population of multicellular organisms to occur.

What’s important to point out though is that evolution can be rapid. Bacteria, for example, evolve at a much more rapid pace than large organisms such as us. This is clearly seen in the case of antibiotic resistance. If you expose a group of bacteria to an antibiotic compound, any bacteria that either carry or come into possession of genetic variations via mutation or horizontal gene transfer that make them resistant to the antibiotic in question will be at an advantage in the struggle for existence. Bacteria that are susceptible to the antibiotic on the other hand will be at a disadvantage. This is a classic example of natural selection. Basically, the infusion of the antibiotic compound into the population of bacteria initiates a selection event. We don’t have to look far and wide to find real-life examples of this type of evolutionary process. All we have to do is have a look back and see how the gradual incorporation of new antibiotics into clinical medial practice has shaped the evolution of bacteria, in particular the evolution of so-called superbugs.

For a thorough discussion of the evidence of evolution I suggest that you check out Richard Dawkin’s book The Greatest Show on Earth and Daniel Lieberman’s book entitled The Story of the Human Body: Evolution, Health, and Disease.

Final words

Before we wrap up, I’d like to ask you four questions.

1. Do you agree that there is variation in nature? I.e., some American black bears are bigger and stronger than other bears.
2. Do you agree that organisms pass on genes to their offspring and that some variable characteristics/traits are (at least partially) heritable? I.e., the children of tall people tend to become taller than the children of short people.
3. Do you agree that not all organisms are equally successful at surviving and reproducing? I.e., some pandas get more offspring than others.
4. Do you agree that an organism’s ability to attract a mate, survive, and reproduce is affected by the organism’s height, strength, skin color, and/or other variable traits that have a heritable basis? I.e., a leopard’s ability to get a hold of food and ultimately bring children into life is partly determined by how fast its able to run, which in turn is partly determined by the genes it inherited from its parents.

If your answer to all of these questions is yes, then you’re actually on board with the fact that living things evolve via natural selection. In other words, you recognize that Darwin’s primary assertion is correct.

The primary reason why I operate under the belief that evolution via natural selection is a real phenomenon is not that I have spent thousands of hours examining the evidence supporting Darwin’s most famous theory, but rather that the most logical explanation, by far, for why living organisms look and behave the way they do is that they were “designed” by natural selection. When evolutionary science is brought into the equation, the different pieces that make up life as we know it naturally come together and fall into order. I don’t see how any rational person could answer no to any of the four questions posed earlier.

The final thing I want to comment on with respects to your message is your comments about God. I get the impression that you think it’s impossible to believe in a God or some other type of divine force and acknowledge that evolution is real. That’s not true. Many of the beliefs and tenets that are integral to religions such as Christianity, Islam, and Buddhism do indeed conflict with Darwin’s teachings; however, it’s certainly possible to believe in overnatural phenomena, gods, or divine forces while at the same time believe that organisms descend from a common ancestor and evolve over time.

– Eirik

Picture: Creative commons picture by lorena rojas. Some rights reserved.