A common challenge to evolutionary theory is that while life does indeed change over time (what is known as microevolution), no one has ever seen one species evolve into another species (macroevolution).

If the tape was rewound and evolution started over from scratch, Conway Morris says, the evolutionary details would be different, but the end result would be similar: a species characterized by intelligence and complex civilization.

Polkinghorne discusses the origins and aims of natural theology in this series. It does not offer truth, but rather a “best explanation” for the world, answering primarily meta-questions. Two such questions asked by Polkinghorne are, “Why is science possible at all?” and “What makes the universe so special?” To explore the answers, he looks at the ability of human minds to penetrate mysteries of the natural world as well as the fine-tuning of the universe necessary to produce the fruitfulness of life.

Many independent measurements have established that the Earth and the universe are billions of years old. Geologists have found annual layers in glaciers that can be counted back 740,000 years. Using the known rate of change in radio-active elements (radiometric dating), some Earth rocks have been shown to be billions of years old, while the oldest solar system rocks are dated at 4.6 billion years. Astronomers use the distance to galaxies and the speed of light to calculate that the light has been traveling for billions of years. The expansion of the universe gives an age for the universe as a whole: 13.7 billion years old. (Updated April 16, 2012)

A complex biological structure with many interacting parts might appear, at first glance, as if it were originally created in its present form with all its interlocking components fully formed and intact. It doesn’t seem possible that they developed step by step via biological evolution. In Darwin’s Black Box, Michael Behe introduces a term that he and other proponents of Intelligent Design use for this concept: irreducible complexity.

Evolution is the biological model for the history of life on Earth. While some consider evolution to be equivalent to atheism, BioLogos sees evolution as a description of how God created all life. Evolution refers to descent with modification. Small modifications occur at the genetic level (in DNA) with each generation, and these genetic changes can affect how the creature interacts with its environment. Over time, accumulation of these genetic changes can alter the characteristics of the whole population, and a new species appears. Major changes in life forms take place by the same mechanism but over even longer periods of time. All life today can be traced back to a common ancestor some 3.85 billion years ago.

I ask the question, “Why is the universe so special?” Now scientists don’t like things to be special; we like things to be general, and our natural anticipation would have been that the universe is just a common specimen of what a universe might be like.

A common argument against biological evolution is that the theory contradicts the second law of thermodynamics. The second law says that disorder, or entropy, always increases or stays the same over time. How then can evolution produce more complex life forms over time? The answer is that the second law is only valid in closed systems with no external sources of energy. Since the Earth receives continual energy from the Sun, the second law does not apply.

Fine-tuning refers to the surprising precision of nature’s physical constants, and the beginning state of the Universe. To explain the present state of the universe, even the best scientific theories require that the physical constants of nature and the beginning state of the Universe have extremely precise values.