Evidence For Evolution

At the Christ and Creation conference last Friday morning Dennis Venema and Scot McKnight gave back to back talks based on their new book Adam and the Genome. The major points in 25 minutes each. Both excellent talks followed by a joint (but brief) Q&A time. Both talks were excellent and inspired many in attendance to buy the book. (Baker ran out of the supply on hand well before the afternoon sessions were over.) I am slowly working through the book, starting with the evidence for evolution in general and human evolution in particular. Whatever you think of the pathways for integrating the evidence with Christian faith, it is important to take the evidence seriously. If you are not a biologist and wonder why biologists and most other scientists find the evidence compelling, buy this book and read Dennis’s overview. This is an excellent introduction to a complex topic.

Analogy to Language. In Chapter 2 of the book Dennis uses several different illustrations to help the lay person understand the basic principles of evolutionary biology. None of the analogies are perfect, as Dennis makes clear, but each is helpful. We can understand elements of the evolutionary process better if we step back and consider the case of language. Consider six “English” versions of John 14:6:

  1. ca. 990 AD. Se Hælend cwæð to him: Ic eom weg, and soðfæstnys, and líf: ne cymð nan to Fæder, buton þurh me. (Anglo-Saxon)
  2. ca. 1395 AD: Jhesus seith to hym, Y am weie, treuthe, and lijf; no man cometh to the fadir, but bi me. (Wycliffe Bible)
  3. ca. 1535 AD: Iesus sayd vnto him: I am the waye ye truthe and ye life. And no man cometh vnto the father but by me. (Tyndale Bible)
  4. ca. 1611 AD: Iesus saith vnto him, I am the Way, the Trueth, and the Life: no man commeth vnto the Father but by mee. (King James)
  5. ca. 1769 AD: Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me. (King James)
  6. ca. 1982 AD: Jesus said to him, “I am the way, the truth, and the life. No one comes to the Father except through Me. (New King James)

Over the course of 1000 years there was a clear change in alphabet, spelling, and word choice. We can consider the translations above akin to fossils. They provide snapshots of various states of language. Dennis takes this example and uses it to illustrate the process of evolution.

As we know, these various translations are not instantaneous changes from one to the next. Rather, they are samples drawn at intervals from a continuous process. All along the way they remained the “same language” in the sense that each generation could easily understand their parents and their offspring. Over time, however, changes accumulated that gradually shifted the language. Word spellings, grammar, and pronunciations changed. Given enough time, it becomes more and more of a stretch to say the languages are the same – such as Anglo-Saxon and Modern English. Despite the striking differences we see now, the process that produced them was gradual. Additionally, there is no convenient point where we can say Anglo-Saxon “became” Modern English; the process was a continuum.

In the same way, average characteristics of a species can shift over time. (p. 21)

No individual living in any of these times, from 990 to 1982, felt that language was “evolving” and yet it was. No creature observes its species evolving, yet it does.

When communities are separated, by a large body of water, a mountain range, a difficult to cross river, or mere distance, one language can gradually morph into two or three or more. In isolation, the changes are distinct. Each will retain evidence of the common ancestry, even if clearly different. But again, there is no one time when it can clearly be claimed the languages are now different. At every step in the gradual process each generation could understand both parents and children and would claim they all spoke the same language. Nonetheless, after enough time, the incremental changes add up, making the languages distinct.

This is how evolution works. Each generation is the same as its parents and as its offspring. Most effective mutations are mild, and changes accumulate gradually over many generations. Red in tooth and claw is a flawed image. Transitional forms are abundant – but we only recognize them when we consider a well defined starting and ending point. Like Anglo-Saxon and Modern English. Yes, mutations that afford an advantage will accumulate, but many changes are neutral. They accumulate by chance. The pattern of accumulated changes allow us to draw conclusions regarding the evolutionary bush that led to the current diversity of life on our planet. There are fossils in our genome and the genome of other animals that point to an interconnected past.

New features develop out of old features. “One of the things evolution predicts is that seldom will any feature in an evolutionary lineage be truly “new.”” (p. 37) It is the accumulation of minor changes that lead to new features. The gradual migration of a nasal opening to the top of the head over generations produced the whale’s blowhole. In this case each minor variation produced an advantage for the aquatic mammal and the changes accumulated. Function can change as well, a reptilian jaw bone gradually becomes a key structure in the mammalian ear.

Dennis provides a number of examples, looking at specific regions of mammalian genomes for similarities and differences, whale evolution – from land dwelling tetrapod to ocean dwelling mammal, and the genes and gene remnants for the production of egg yolk.

Converging lines of evidence point to the same overall pattern – paleontology, embryology, and the genome. Evolution is not a theory in trouble. It continues to be refined and developed, but the overall framework has been secure for more than a century. The genetic evidence has refined and corrected some details of the bush of life proposed on the basis of embryology or paleontology, but by and large it has confirmed prior conclusions and advanced our understanding of the evolutionary process.

Given the abundant lines of DNA evidence that support the hypothesis that humans are the product of evolution, it is no exaggeration to say that (the very, very few) trained biologists who reject common ancestry do so because of prior religious commitments, not for scientific reasons.

So where do Adam and Eve fit into this picture? In the next post on the book, we will look at the evidence for human evolution and the emergence of our species Homo sapiens.


If you wish to contact me directly, you may do so at rjs4mail[at]att.net

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One Response to Evidence For Evolution

  1. I take it the book argues for human evolution, not humans as a product of evolution. If the latter, how do they deal with the absence of evidence for morphology of species? How do they explain Cambria? What’s their explanation for how there became a ‘common ancestor’ of all?

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