One hundred seventy years ago Charles Darwin presented his Theory of Evolution, which attempts to explain how life evolved from simple one-celled organisms into more advanced species. This theory challenged the Christian religious teachings that all life forms were directly created by God. To this day a debate has raged between scientists who embrace Evolution, people who believe in Creationism, and another group of scientists who hypothesize that life is too complex to have evolved and, therefore, a supremely intelligent entity facilitated evolution (Intelligent Design). A major argument used by Intelligent Design advocates is “irreducible complexity,” which suggests that certain aspects of living creatures are too complex to have developed through a natural evolutionary process. This article, the second in a series that started with “The Emergence of Life: Abiogenesis and Intelligent Design,” [1] will explore how science attempts to explain irreducibly complexity and major evolutionary jumps that are not easily explained by the Theory of Evolution.
Darwinism suggests that all life forms evolved through natural selection, noting that the offspring of organisms are subtly different from one another. If these differences result in an improvement in how the organism adapts to its environment, it will be passed on to future generations. When genetic material was discovered early in the 20th Century, scientists proposed that genetic mutations resulted in these incremental differences. When a mutation occurred, three things could happen: it would be lethal and not passed on, it would result in no change, or it would result in a beneficial change and be passed on to offspring. Biologists have more recently sorted all life into classifications which show how classes of species may have evolved from simpler classes. However, there are many unanswered questions in how life first emerged; then evolved into today’s diversity which includes Homo sapiens.
At numerous points in the evolution of life, leaps occurred that were well beyond the subtle changes suggested by Darwin. Two prime examples go all the way back to the beginning: the emergence of the first life form from lifeless chemicals and the formation of the molecules RNA and DNA, which hold the genetic code for life forms. Earlier, an incremental route of chemical evolution was discussed that may have resulted in the very first life form. However, there is no generally accepted scientific theory for the formation of the first molecules of RNA and DNA. [2] Therefore, RNA and DNA are often cited as an example of “Irreducible Complexity,” defined by Biochemistry professor Michael Behe as “a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning.” [3]
One of the most commonly cited examples of irreducible complexity is the bacterial flagellum, the whip-like appendage that propels bacteria. Two others are the function of blood clotting in vertebrates and the camera lens eye found in higher order vertebrates. The claim made for both flagella and blood clotting is that too many proteins are required to have developed all at the same time to have happened by natural selection. The sheer complexity of the eye coupled with the even more complex biochemistry required for perceiving sight are cited as being irreducibly complex. [4] Other examples cited include the heart, the ear, and single-celled organisms. [5]
Scientists have already made progress in refuting these arguments. They have linked the development of bacterial flagella to a more elementary needle-like structure found in Salmonella. Blood clotting has been demonstrated in fish and other organisms despite lacking some of the proteins found in Mammalian blood clotting systems. Current evidence supports an evolutionary route for the eye stemming from very simple photoreceptor patches in primitive animals; however, biologists have not yet fully explained a path for the biochemistry of sight, which Michael Behe is quick to point out in supporting Intelligent Design. [6]
Another area that sparks controversy is the numerous discontinuous leaps that have occurred in the evolution of more advanced life forms. One example is the emergence of vertebrates – there is no clear evolutionary path between vertebrates and lower life forms. [7] Other examples of evolutionary jumps: colonization of land by plants, evolution of modern birds from dinosaurs, and the Cambrian Explosion, where 600 million years ago complex animals exploded from very simple ones such as jellyfish and sponges. [8, 9, 10] Quoting Zoologist Christopher McGowan: “We have so many gaps in the evolutionary history of life, gaps in such key areas as the origin of the multi-cellular organisms, the origin of the vertebrates, not to mention the origins of most invertebrate groups.” [11] There are also smaller evolutionary jumps evidenced by discrete appearances or increases in an organ or structure, for instance, going from two to four wings on an insect or a bacteria that learns to generate two spores as opposed to one. These types of features can’t result from a gradual evolutionary process because an insect can’t have 2.1 wings nor can a mammal have 0.1 livers. [12]
Scientists, however, have developed theories as to how these types of leaps may happen. For instance, complex biological systems may be created from simpler systems that have a different function. [13] Philip Hunter suggests that evolutionary leaps result from changes in gene regulation as opposed to the emergence of new genes, and that the presence of a certain type of RNA in certain species facilitates these changes. [14] Another theory is partial penetrance, which is a genetic mutation that causes only a percentage of organisms in a species to develop a new, potentially improving feature. [15] Rupert Sheldrake presents a radical idea where all individual species have an external organizing field called a “morphogenetic field,” which also facilitates a collective memory within a given species. He suggests that this field facilitates evolutionary development. [16] The concept of biological fields has also been broached by others and may date all the way back to the philosopher Plato. [17,18] Microbiologists Johnjoe McFadden and Jim Al-Khalili went a step further and showed a demonstrable link between constructive genetic mutations and quantum physics, citing the quantum theory of entanglement would link the genome with its surroundings:
“Living cells could similarly act as biological quantum computers, able to simultaneously explore multiple possible mutational states and collapse towards those states that provide the greatest advantage.” [19]
Quantum mechanics may therefore underpin the concept of biological organizing fields, and would link the modern understanding of physics with biology.
Although science seems to be well on the way to explaining major evolutionary jumps and “irreducibly complex” organs, there appears to be one common theme: the DNA required for these developments existed BEFORE the leaps occurred. The genes fueling the Cambrian explosion existed long before the actual event. Molecular biologist Sean Carroll mentions that some genes date back to the early origin of life. These so-called “immortal genes” “…are so essential that their text has been preserved for over 3 billion years. They’re involved in very fundamental ways with the decoding of the genetic machinery shared among all organisms. Without these genes you couldn’t express your genetic information and produce the proteins you need to live.” He further goes on to mention that this DNA had the potential to grow a variety of different appendages and features. [20] A related enigma that came out of the human genome project is the fact that humans have far fewer genes than were originally anticipated. Our genome contains about the same number of base pairs, 3.3 billion, as the fruit fly, one-fortieth that of the lung fish, and only falls at the mid-point of the range found in mammals. [21] This goes against the concept that if humans were the most advanced life form, they would have the most complex genome.
This leads to the following questions. Why does a fruit fly need such a complex genome? It is hard to fathom how DNA that was capable of coding the incredible diversity of life could have evolved so quickly before the Cambrian explosion; if there is a miracle to examine, it is the existence of this pre-Cambrian DNA and “immortal genes.” It is not known how RNA and DNA emerged from a pool of lifeless chemicals. Biologists continue to search for answers to these questions and current research efforts continue to add pieces to the puzzle that life presents. One thing is clear, though. The very existence of DNA is amazing and the genetic language that it contains is even more miraculous. One does not have to believe in Creationism or Intelligent Design to see the miracle of life. Freeman Dyson, the author of Disturbing the Universe, states: “The more I examine the universe and study the details of its architecture, the more evidence I find that the universe in some sense must have known we were coming.” [22]
References:
1. Gregory M. Berube, “The Emergence of Life: Abiogenesis and Intelligent Design,” http://exploringtheamazing.blogspot.com/2012/01/emergence-of-life-abiogenesis-and.html
2. Ibid.
3. http://www.talkorigins.org/faqs/behe.html, which quotes Michael Behe from his book Darwin's Black Box: The Biochemical Challenge to Evolution. (1996), The Free Press.
6. See 4.
9. Dawkins, R, The Blind Watchmaker, W.W. Norton & Company, New York, 1996, pp. 229-230. Via http://www.talkorigins.org/faqs/quotes/mine/part1-3.html
11. McGowan, C., In the Beginning... A Scientist Shows Why the Creationists are Wrong, Prometheus Books, 1984, p. 95. Via http://www.talkorigins.org/faqs/quotes/mine/part1-3.html
13. See 4.
14. See 7.
15. See 12.
19. McFaddan and Khalili, “A quantum mechanical model of adaptive mutation,” BioSystems Vol. 50 (1999), p 203–211
20. See 8.
22. Freeman Dyson, Disturbing the Universe, Harper and Row (1979).
Photo credit: http://www.robertreckmeyer.com
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