Although evolution is often presented as a simple upward hill, in reality, it is a complex topology of hills and valleys. 1 Because evolutionary adaption says that populations tend upward, a population can easily become “stuck” on a very small hill, 2 never making it to larger hills, because to do this, it would have to “come down” (devolve), slide across the valley, and evolve upward again.
A real-life example of a local fitness peak is present in sickle-cell anemia, in which the best allele pair is actually eliminated by natural selection because of its short-term detriment. 3
Debate
Evolutionist: The existence of species causes a warping in the fitness terrain. Thus, as a species approaches a barrier, the barrier moves out of the way (Red Queen hypothesis). 4
Response: First, there is the problem of scope. Do only small fitness barriers move out of the way, or do very large ones, too? If a species causes the fitness terrain to warp, allowing it to cross canyons, then it is entirely possible that a species devolve over time in the overall sense. This is the direct opposite of evolution.
Evolutionist: The fitness terrain changes based on the environment, and so the species stay near the top of the local fitness peak which moves, allowing them to travel across canyons, etc. (stationary hypothesis) 5
Response: Moving “waves” in the fitness terrain could cause a species to “surf” down a mountain just as easily as surfing down through a canyon. It seriously damages the slow, upward progression presented to the public. 6
Evolutionist: Deleterious processes resulting from close inbreeding, mutations, and genetic drift, decrease the fitness of a population, carrying it down the fitness slope (Shifting Balance hypothesis). 7
Response: First, this contradicts punctuated equilibrium, where evolution is said to happen rapidly in small populations. Second, it presents differing modes of evolution: downward and upward, arbitrarily shifting the “balance,” making evolution unreliable, and certainly not inevitable.
Evolutionist: Brute force and chance can cause organisms to devolve down a local fitness peak and cross a fitness canyon (saltation hypothesis).
Response: This goes against gradual natural selection and mutations, sounding more like a miracle. It is no longer a popular explanation (it was in the 1950s). 8
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Sources
ReMine, W. J. (1993). The Biotic Message: Evolution Versus Message Theory. Saint Paul, Minn.: St. Paul Science.
Notes
- http://en.wikipedia.org/wiki/Fitness_landscapes ↩
- ReMine, 1993, p. 121: “Suppose that when the population comes to a hill, survival of the fittest moves the population up the hill to higher fitness. This hill may only be a small local hill, in which case the population gets stuck on top by survival of the fittest. Thus, survival of the fittest can prevent evolution from occurring. Small hills can be traps, preventing the evolution of new adaptions.” ↩
- ReMine, 1993, p. 190: Sickle-cell anemia demonstrates a local fitness peak. In the chart provided, “The CC genotype has a selective value of 1.3, the highest of any allele pair. Yet surprisingly, this genotype is eliminated by selection.” ↩
- ReMine, 1993, p. 134: “According to the Red Queen hypothesis, as the species evolves toward a fitness barrier the barrier conveniently moves out of the way. This is precisely the goal of the Red Queen model. The model assumes the terrain warps in a favorable way to eliminate barriers in the fitness terrain.” ↩
- ReMine, 1993, p. 134: “The stationary hypothesis suggests that a species sits on a fitness peak and waits for the environment to alter the terrain. The species adapts as the terrain deforms, so the species stays near the moving peak.” ↩
- ReMine, 1993, p. 133: “If the fitness terrain is bobbing up and down like a choppy sea, then nothing can guide evolution. If a peak becomes a valley (and vice versa) in an indiscriminate way, then natural selection becomes a random process.” ↩
- ReMine, 1993, p. 191: “[The Shifting Balance hypothesis] depends on deleterious processes (such as mutation, close inbreeding, and genetic drift) to decrease the fitness of a population and carry it down a fitness slope.” ↩
- ReMine, 1993, p. 132:
“How can evolution go from a local fitness peak to the other side of a fitness canyon? … On solution is pure chance. Supposedly, massive mutations sometimes happen to take an organism to the other side of the fitness canyon in one large step. This is called evolutionary saltation. It is a brute force approach that evolutionists avoid when they can. Saltation was a popular idea through the 1950s.”
“Academic evolutionists no longer openly endorse saltation to any significant extent.” ↩