So we have shown that the Earth is very possibly the only planet in the Universe that can support life as we know it. Now we move on to the next part of our series:
Searching Inward - Psalm 139:13 (NIV) "For you created my inmost being; you knit me together in my mother's womb." - Finding God in the formation of life and the human body.
We will start our search first with a look at what we consider as life and how secular science views the process of evolution, from the beginning of life to the great diversity we see around us. I believe, as a Christian, that God created all life but that does not preclude Him using that which He designed, i.e. genetics, to bring about parts of His Creation. Much like how we showed that God nurtured (The Hebrew word "râchaph") the Universe and the Earth to make it ready for life, He certainly could do the same to fine-tune the life He created.
So, what is life anyway? Within science there is no one clear definition of life that is accepted by all but most consider life to contain these characteristics:
At the border of living versus non-living things are viruses and single celled bacteria. Viruses are not really "alive" based on our definition but are more like a computer that runs a machine that makes more computers. On their own, they can not grow, reproduce, or take in and use energy, these functions are carried out by the host cell they infect. Viruses have been described as "organisms at the edge of life." They consist of genetic material made from either DNA or RNA, a protein coat, called the capsid, which surrounds and protects the genetic material and, in some cases, an envelope of lipids that surrounds the protein coat.
Viruses are extremely complex biological particles. So even if on the edge of life, they seem much too complex to happen by chance. Science considers the evolutionary history of viruses to be unclear, possibly coming from bacteria or plasmids, small DNA fragments that can move between cells. They are considered an important means of horizontal gene transfer, infecting and potentially modifying DNA in the host cell, which can increase genetic diversity.
Bacteria are prokaryotic microorganisms, being single celled and not containing a membrane-bound nucleus, the simplest form of life. They were among the first life forms to appear on Earth, and are present in most of its habitats. Here again, these organisms are extremely complex, more so than viruses, and seem highly unlikely to form by the random chance interactions of molecules, many of which themselves are complex and had to form randomly. As mutations did not occur at this stage in the proposed evolutionary process, bacteria are assumed to have been randomly formed from protocells, a self-organized, endogenously ordered, spherical collection of lipids. Science has yet to demonstrate how a protocell could be formed.
So the scientific expectation is that simple molecules formed from the elements under the harsh conditions of the early Earth via chemical reactions. These molecules then continued to become more complex until such a time as they formed amino acids (proteins), nucleic acids (DNA and RNA) and lipids (fats). These molecules can be formed by chemical reactions under specific conditions, but did these conditions exist on the early Earth and if so, would these reactions occur with sufficient frequency and consistency to produce these protocells? Again this seems unlikely.
Would these protocells, if they formed, then spontaneously combine in such a way to make a living cell? At what point does this non-living mass of molecules become able to function independently and to reproduce itself? The odds of this happening seem even greater than the odds that Earth would be capable of supporting life. The second law of thermodynamics requires that the universe move in a direction in which disorder (or entropy) increases, yet life is distinguished by its high degree of organization.
If we look past this dilemma and assume that prokaryotes formed, then we need to next move to the eukaryotes. Eukaryotes are organisms with a more complex cellular structure and many cells. Most plants and animals are eukaryotes. Now here science utilizes mutations to make this leap so lets look at the definitions.
Microevolution: Changes in the gene pool (primarily mutations) of a population over time which result in relatively small changes to the organisms in the population. Changes which would not result in the newer organisms being considered as different species. Examples of such microevolutionary changes would include a change in a species' coloring, size or bodily processes.
Macroevolution: Changes in organisms which are significant enough that, over time, the newer organisms would be considered an entirely new species. In other words, the new organisms would be unable to mate with their ancestors or reproduce as the older organism, assuming we were able to bring them together. Macroevolution is thought to happen when sufficient microevolutionary changes occur, resulting in a new species.
Natural Selection: The process by which traits that are favorable in a given environment become more common in subsequent generations, and traits that are less favorable become less common. This is considered a significant source of microevolutionary changes that can lead to macroeveolution. It is one process that works against mutational randomness by preferential selection of the "better" genetic change. An example in bacteria would be the development of resistance to antibiotics.
As we look at these processes and how they might occur and lead to more diverse genetics and the growth of the evolutionary tree, there seems to be some difficulties. One primary difficulty is the amount of time needed for evolutionary changes to occur and what the fossil record shows for the appearance of advanced life. Is there enough time from the formation of the earth until now to allow for all the diversity we see?
Or did God "Nurture" it along?
As He did with the formation of the Universe.
Earth formed 4.5 billion years ago and life started 3.8 billion years ago. But up until the Cambrian Explosion, which started about 452 million years ago, most life was prokaryotic (single celled) or organized into colonies. The Cambrian explosion was a period in the fossil record lasting anywhere from 2 to 50 million years, where there was the sudden appearance and diversification of almost every major group (phylum) of animal life (multicellular, eukaryotic organisms). Plants started to develop at about the same time but the rate of changes in diversity was slower than that observed for animals. Was this enough time for the massive changes in structure to occur from prokaryotes to advanced eukaryotes?
Some challenges that the Cambrian Explosion brings to evolution are (from Reasons to Believe):
- While evolutionary scenarios, as opposed to worked-out theories, exist for hypothesizing how new genera, new orders, and new families of animal life might appear, there is no rational evolutionary scenario for explaining how a new animal phylum might appear.
- From 50 to 80 percent of the animal phyla known to have existed at any time in Earth’s history appeared within no more than a few million years of one another, as the Cambrian geological era began.
- Of the 182 animal skeletal designs theoretically permitted by the laws of physics, 146 appear in the Cambrian explosion fossils.
- The Cambrian explosion marks the first appearance of animals with skeletons, bilateral symmetry, appendages, brains, eyes, and digestive tracts that include mouths and anuses.
- Virtually every eye design that has ever existed appears simultaneously in the Cambrian explosion.
- The moment oxygen levels in Earth’s atmosphere and oceans permit the existence of Cambrian animals, they suddenly appear.
- The Cambrian explosion occurs simultaneously with the drastic change in sea chemistry known as the Great Unconformity.
- The Cambrian explosion includes the most advanced of the animal phyla, chordates, including vertebrate chordates.
- Both bottom-dwellers and open ocean swimmers appear simultaneously in the Cambrian explosion.
- Optimization of the ecological relationships among the Cambrian animals, including predator-prey relationships, occurred without any measurable delay.
Fossils found in Yunnan province of China (at sites discovered nearly 100 years ago) and in the Burgess Shale deposits of the Canadian Rockies tell us that all animal phyla (more than 70) ever to exist in Earth’s history appeared “at once” during the Cambrian Explosion. Some 40 phyla have since disappeared and not a single new one has appeared since. This “burst” of life occurred in an extremely narrow window of geologic time, about 5-10 million years. Evidence from the Yunnan sites possibly narrows this window to less than 3 million years. Could 90+% of life have evolved in just 3 million years?
So the question becomes again, are the scientific theories of life's origin statistically possible in the context of the natural law of probability? When Darwin proposed his theory of evolution, the cell was barely visible under a primitive microscope. Scientists thought of it as only a blob of protoplasm. They could not see or know the vast complexity that is a living cell.
Up until the mid-twentieth century, science had considered the universe as eternal. This offered infinite time for infinite evolution and made probability considerations irrelevant. But then science moved to the big bang theory, which states that the universe had a beginning, limiting time for evolution. These time limitations make probability considerations crucial. It is statistically improbable that life as we know it could arise from a primordial soup in even a billion years. Given that, if life should appear, the current scientific theory then predicts a gradual evolutionary process in which simpler life-forms would be expected to appear first, followed by the more complex. Instead, the fossil record suggests "punctuated equilibrium" - long periods of stability followed by short bursts of change.
God could have again nurtured (The Hebrew word "râchaph") His creation, even manipulating the genes He created, in such a way as to "punctuate" life (and thus the fossil record) with rapid spurts of diversity in physical form and function. Molecular biologist Kenneth R Miller suggested as much when he said:
Psalm 104:27-31 (NIV) - "All creatures look to you to give them their food at the proper time. 28When you give it to them, they gather it up; when you open your hand, they are satisfied with good things.29When you hide your face, they are terrified; when you take away their breath, they die and return to the dust. 30When you send your Spirit, they are created, and you renew the face of the ground. 31May the glory of the LORD endure forever; may the LORD rejoice in his works!"