Question 3: Where Did the First Living Cell Come From?
In order for the principles of mutation and natural selection in the theory of evolution to work, there have to be living things for them to work on. Life must exist before it can to start diversifying. Life had to come from somewhere, and the theory of evolution proposes that it arose spontaneously out of the inert chemicals of planet Earth perhaps 4 billion years ago.
Could life arise spontaneously? If you read How Cells Work, you can see that even a primitive cell like an E. coli bacteria -- one of the simplest life forms in existence today -- is amazingly complex. Following the E. coli model, a cell would have to contain at an absolute minimum:
- A cell wall of some sort to contain the cell
- A genetic blueprint for the cell (in the form of DNA)
- An enzyme capable of copying information out of the genetic blueprint to manufacture new proteins and enzymes
- An enzyme capable of manufacturing new enzymes, along with all of the building blocks for those enzymes
- An enzyme that can build cell walls
- An enzyme able to copy the genetic material in preparation for cell splitting (reproduction)
- An enzyme or enzymes able to take care of all of the other operations of splitting one cell into two to implement reproduction (For example, something has to get the second copy of the genetic material separated from the first, and then the cell wall has to split and seal over in the two new cells.)
- Enzymes able to manufacture energy molecules to power all of the previously mentioned enzymes
Obviously, the E. coli cell itself is the product of billions of years of evolution, so it is complex and intricate -- much more complex than the first living cells. Even so, the first living cells had to possess:
Otherwise, it is not really a cell and it is not really alive. To try to imagine a primordial cell with these capabilities spontaneously creating itself, it is helpful to consider some simplifying assumptions. For example:
- A cell wall
- The ability to maintain and expand the cell wall (grow)
- The ability to process "food" (other molecules floating outside the cell) to create energy
- The ability to split itself to reproduce
These examples do simplify the requirements for the "original cell," but it is still a long way to spontaneous generation of life. Perhaps the first living cells were completely different from what we see today, and no one has yet imagined what they might have been like. Coming up with an explanation for where the first cell came from is important to the theory of evolution, because life can only have come from one of two possible places:
- Perhaps the original energy molecule was very different from the mechanism found in living cells today, and the energy molecules happened to be abundant and free-floating in the environment. Therefore, the original cell would not have had to manufacture them.
- Perhaps the chemical composition of the Earth was conducive to the spontaneous production of protein chains, so the oceans were filled with unimaginable numbers of random chains and enzymes.
- Perhaps the first cell walls were naturally forming lipid spheres, and these spheres randomly entrapped different combinations of chemicals.
- Perhaps the first genetic blueprint was something other than DNA.
- Spontaneous creation - Random chemical processes created the first living cell.
- Supernatural creation - God or some other supernatural power created the first living cell.
And it doesn't really matter if aliens or meteorites brought the first living cell to earth, because the aliens would have come into existence through either spontaneous creation or supernatural creation at some point -- something had to create the first alien cells.
Most likely, it will be many years before research can completely answer any of the three questions mentioned here. Given that DNA was not discovered until the 1950s, the research on this complicated molecule is still in its infancy, and we have much to learn.
The Future of Evolution
One exciting thing about the theory of evolution is that we can see its effects both today and in the past. For example, the book "Evolution" mentions this:
The earliest known reptiles are so amphibian-like that their assignment to one category or the other is largely a matter of opinion. In this area of life, however, there was no missing link; all the gradations from amphibian to reptile exist with a clarity seldom equaled in paleontology.
In other words, there is plenty of evidence, past and present, for some sort of evolutionary process. We see it in bacteria and insects today, and we see it in the fossil record through the development of millions of species over millions of years.
After thinking about questions like the three mentioned in the previous sections, different people come to different conclusions. In the future, there are three possible scenarios for the theory of evolution:
- Scientists will come to a complete understanding of DNA and show how mutations and natural selection explain every part of the development of life on this planet.
- Scientists will develop a new theory that answers the questions posed above to almost everyone's satisfaction, and it will replace the theory of evolution that we have today.
- Scientists will observe a completely new phenomenon that accounts for the diversity of life that we see today. For example, many people believe in creationism. In this theory, God or some other supernatural power intervenes to create all of the life that we see around us. The fossil record indicates that hundreds of millions of new species have been created over hundreds of millions of years -- Species creation is an intense and constant process with an extremely long history. If scientists were to observe the creation process occurring the next time a major new species comes into existence, they could document it and understand how it works.
Let's assume that the theory of evolution as currently stated is the process that did bring about all of the life that we see today. One compelling question is: "What happens next?" Evolution must be at work right now. Our species, Homo sapiens, only appeared about 40,000 years ago. What does evolution have in store for human beings, and how will the change manifest itself?
These are all fascinating questions to think about. They reveal just how big an effect evolution can have. Given enough time, evolution could completely alter life on this planet by disposing of the species we see today and creating new ones.
- Will a child appear one day whose brain is twice as big as any normal human brain? If so, what will be the capabilities of that brain, and how will it differ from the brain seen today? Or are our brains slowly evolving right now?
- Will children appear one day who have more than 23 chromosomes? If so, what will be the effects of the new chromosomes?
- Will man learn how to control or accelerate evolution through genetic engineering? Once we completely understand different genomes, will we be able to engineer evolutionary steps that lead to new species on a much faster schedule? What would those species look like? What would we design them to do?
For lots more information on evolution and related topics, see the links on the next page.
Lots More Information!
Related stuff.dewsoftoverseas.com Links
Other Great Links
Sites About Evolution
Sites Against Evolution
Transposons and Polyploidy
Abiogenesis and RNA World
- "Extinct Humans," by Ian Tattersall, Jeffrey Schwartz
- " The Spark of Life: Darwin and the Primeval Soup," by Christopher Wills, Jeffrey Bada
- "The Dragons of Eden: Speculations on the Evolution of Human Intelligence," by Carl Sagan
- "Defeating Darwinism by Opening Minds," by Phillip E. Johnson
- "Evolution," by Ruth Moore & Time-Life Books
- "Molecular Biology of the Cell," by Bruce Alberts, et al.
- "Walking with Dinosaurs: A Natural History," by Tim Haines
- "Dawn of Man: The Story of Human Evolution," by Robin McKie
- "Breed Your Own Vegetable Varieties," by Carol Deppe
- "The Naked Ape: A Zoologist's Study of the Human Animal," by Desmond Morris