1 How Did Life Get Its Start?
WHAT SOME SAY. Life arose spontaneously from nonliving matter.
WHY SOME PEOPLE ARE NOT SATISFIED WITH THAT ANSWER. Scientists know more about the chemistry and molecular structure of life than ever before, yet they still cannot define with certainty just what life is. A wide gulf separates nonliving matter from even the simplest living cell.
Scientists can only speculate about what conditions on earth were like billions of years ago. They have differing views about where life began—for instance, whether within a volcano or under the ocean floor. Another belief is that life’s building blocks first formed elsewhere in the universe and arrived here embedded in meteors. But that does not answer the question of how life began; it just pushes the issue farther into space.
Scientists speculate about the existence of molecules that preceded genetic material as we know it today. These molecules are supposedly more likely to arise spontaneously from inert material and are self-replicating. Yet, science has found no evidence that such molecules ever existed, nor have scientists been able to create any such molecule in a laboratory.
Living things are unique in the way they store and process information. Cells convey, interpret, and carry out instructions contained within their genetic code. Some scientists liken the genetic code to computer software and the chemical structure of the cell to computer hardware. But evolution cannot explain the source of the information.
Protein molecules are necessary for the function of a cell. A typical protein molecule consists of hundreds of amino acids strung together in a specific sequence. Additionally, the protein molecule must fold into a specific three-dimensional shape for it to be useful. Some scientists conclude that the odds of even one protein molecule forming spontaneously are extremely improbable. “Since a functioning cell requires thousands of different proteins,” writes physicist Paul Davies, “it is not credible to suppose they formed by chance alone.”
CONCLUSION. After decades of research in virtually all branches of science, the fact remains that life comes only from preexisting life.
2 How Did Living Things Develop?
WHAT SOME SAY. The first living organism gradually developed into a variety of living things, including humans, through a process of random mutation and natural selection.
WHY SOME PEOPLE ARE NOT SATISFIED WITH THAT ANSWER. Some cells are more complex than others. According to one reference, how simpler cells could develop into more complex cells is “often rated the second major evolutionary mystery, after the origin of life.”
Scientists have discovered within each cell intricate molecular machines composed of protein molecules that cooperate to perform complex tasks. These tasks include transporting and converting nutrients into energy, repairing parts of the cell, and conveying messages throughout the cell. Could random mutations and natural selection account for the assembling and functioning of such sophisticated components? Many find that concept difficult to accept.
Animals and humans develop from a single fertilized egg. Inside the embryo, cells multiply and eventually specialize, taking on different shapes and functions to form distinct parts of the body. Evolution cannot explain how each cell “knows” what to become and where it should move within the organism.
Scientists now realize that for one kind of animal to develop into another kind of animal would require that changes take place within the cell, at the molecular level. Since scientists cannot demonstrate how evolution can produce even the “simplest” cell, is it plausible that random mutations and natural selection could be responsible for the different kinds of animals on the planet? Regarding the structure of animals, Michael Behe, professor of biological sciences, says that while research “has revealed unexpected, stunning complexity, no progress at all has been made in understanding how that complexity could evolve by unintelligent processes.”
Human beings are conscious and self-aware, have the ability to think and reason, and possess moral qualities such as generosity, self-sacrifice, and a sense of right and wrong. Random mutations and natural selection cannot explain the existence of these unique qualities of the human mind.
CONCLUSION. While many insist that an evolutionary origin of life is an indisputable fact, others are not satisfied with the answers that evolution provides regarding how life began and how life developed.