Skeptic Blog

Since Charles Darwin published The Origin of Species on 24 November 1859, some groups have tried to declare evolution as faulty. They say it lacks evidence, or even has evidence against it. Do these claims have any merit? Let’s take a closer look.

What is evolution?

One of the most respected evolutionary biologists has defined biological evolution as follows:

“In the broadest sense, evolution is merely change, and so is all-pervasive; galaxies, languages, and political systems all evolve. Biological evolution … is change in the properties of populations of organisms that transcend the lifetime of a single individual. The ontogeny of an individual is not considered evolution; individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest protoorganism to snails, bees, giraffes, and dandelions.”

- Douglas J. Futuyma in Evolutionary Biology, Sinauer Associates 1986

Evolutionary theory argues that all the organisms alive on earth today share a common ancestor. As unlikely as it sounds, life forms from spiders to spider monkeys belong to the same family tree. Even fungus merits an invitation to the family reunion. A simple way to think of evolution is “descent with modification” — over many generations, organisms change into something different. 

In everyday use, theory means a guess or a hunch, something that maybe needs proof. In science, a theory is not a guess, not a hunch. It’s a well-substantiated, well-supported, well-documented explanation for our observations.² It ties together all the facts about something, providing an explanation that fits all the observations and can be used to make predictions. In science, theory is the ultimate goal, the explanation. It’s as close to proven as anything in science can be.

Well, where is the evidence for evolution?

Like all scientific theories, the theory of evolution must make predictions that are testable. Testing a prediction means that you predict what evidence you should find if the theory is correct, and then you look to see if you actually find that evidence. So what does the theory predict we should find, and do we actually find it?

First of all, the theory predicts we should see examples of populations of one species evolving into new species. Do we? Yes we do.http://www.talkorigins.org/faqs/speciation.html

Secondly, the theory predicts the existence of a Tree of Life. The Tree of Life is a family tree, of which every single living thing that has ever existed on the planet is a member. The existence of the Tree of Life (if true) would mean that the differences between living things would be organized into a nested hierarchy, such that two recently separated species would share numerous characteristics, of which a portion would also be shared by all species sharing a more distant common ancestor, of which a portion would also be shared by all species sharing an even more distant common ancestor; and so on.

 The Tree’s existence would also mean that two species branching from a common ancestor should be located in places that populations of the ancestor could have reached. It also means that the fossils we find should fit into the general pattern of hierarchical similarity, location, and timeframe established by the Tree.

 Finally, the hierarchical patterns of similarity established by present and past species on the Tree should be roughly the same regardless of whether we are comparing morphological characteristics, or genes, or non-coding DNA, or endogenous retroviruses, or proteins. We say “roughly the same” rather than “exactly the same” because various processes such as convergent evolution or fluctuating population sizes can somewhat throw off the hierarchical patterns established by the different traits being compared.

So what do we find?

The Tree of Life is continually vindicated by study after study. Morphologically, humans are most similar to other apes, and some of those similarities are shared by monkeys, and some of those are shared by all primates, and some of those are shared by all mammals, and so on. We could as easily find the same treelike pattern starting from house finches, or from any other species. Comparisons of DNA sequences confirm and provide additional information regarding the treelike organization shown by morphological comparisons. http://www.sciencedaily.com/releases/2006/03/060303111420.htm

An important point to remember about DNA comparisons is that only about 2 percent of the genome codes for proteins, and another 2 percent regulates transcription, so that leaves about 96 percent of the genome essentially independent from morphological considerations. So we can’t argue that DNA must be similar because morphologies are similar. They are independent tests. Independently derived models of the tree tend to converge and reinforce one another, including, but not limited to:

1. Anatomical homologies
2. DNA and RNA code
3. Endogenous retroviral insertions
4. Pseudogenes
5. Embryology
6. Chromosome fusion
7. Convergence
8. And many more. 

I wouldn’t even have the space to list every piece of evidence that backs up the tree of life prediction. But it is overwhelming. At this point, evolution is proved beyond any reasonable doubt. More can be found here: 

http://www.talkorigins.org/faqs/comdesc/

Evolution is not just a theory, it’s triumphantly a theory!

 Sources: Talkorigins.com, notjustatheory.com, other sources listed in article.