begin to
speculate on why
. Was it camouflage, speed, intelligence, fecundity (having lots of offspring easily), disease resistance, some combination or none of these, or just "blind luck"? Ecclesiastes 9:11 says, "The race is not to the swift, nor the battle to the strong [in our fallen world] …but time and chance happeneth to them all" (ASV).
Natural selection is a fact because it's a
tautology
or
truism,
a form of
circular reasoning. It is argued that the fittest are those that survive in greatest relative numbers and those that survive in the greatest relative numbers are defined as the fittest
. That's definitely
true
, but it's really just an observation, not a profound theory, and begs the question of what makes some organisms fitter than others.
The story is told of a student walking to school who saw in the grass a mouse that remained absolutely motionless as a hawk soared overhead. When she asked her teacher why, the teacher explained that mice which ran were seen and killed by the hawk, so natural selection produced those which remained motionless. The next day, the student saw a mouse running to its burrow as a hawk soared overhead. When she asked her teacher why, the teacher explained how mice that remained motionless were easy targets for the sharp-eyed hawk that killed and ate them, so natural selection favored survival of the mice which ran. The "nice" thing about "survival of the survivors" is that it can explain anything: why mice run or stay put, why some species (e.g., horseshoe crabs) never changed in "600 million years" while others changed rapidly and quickly (e.g., an insect-eater thought to have evolved into horses, whales, and bats in less than "5 million years"). The so-called "proof" that natural selection produced evolution is too often merely the argument that survivors survived!
(b)
Natural selection versus ecological competition
. Most people just assume "natural selection" for the "fittest" means the selected variety must be increasing. Actually, natural selection has nothing to do with whether a species as a whole is increasing or decreasing in numbers or staying the same (static or stable). Look back at the calculation of fitness in Figure 12. In case A, the population was static or stable; the second generation had 100 individuals like the first one did. Now imagine the population doubled to 200, and the second generation contained 40 AA, 120 Aa, and 40 aa. What would the new fitness values be? The winner ("fittest") being "naturally selected" is still Aa, and its reproductive efficiency is 120/30 = 4.0, which is the highest value. That means the standardized fitness of Aa, 4.0/4.0, is 1.00, the maximum value, just as it was in the static population. The fitness values for the other two groups are also exactly the same in the expanding population as they were for the static case. The reproductive efficiency for aa is 40/20 = 2.0, so its standardized fitness is 2.0/4.0 (the "winning" efficiency) = 0.5, "one-half" the maximum, as before. The numbers for AA are 40/50 = 0.8, and 0.8/4.0 = 0.2, exactly 20 percent of maximum as in the static population.
What if the species population is decreasing? Who's the fittest then? Imagine the population declined by half, and the second generation was 10 AA, 30 Aa, 10 aa (50 total). Again, Aa is the best survivor or fittest, this time because it declined the least in population. Aa's numbers are 30/30 = 1.0, and 1.0/1.0 (the highest) is 1.0. The aa's again did "half" as well: 10/20 = 0.50, and 0.5/1.0 = 0.5. The AA "losers" got a fitness score of "20 percent" maximum, just as before: 10/50 = 0.2, and 0.2/1.0 = 0.2. Notice, however, the species population is decreasing dramatically.
In this case, being the
"
fittest
" only means being
the high scorer on the losing team!
Being the fittest, then, is no guarantee of survival at all .
It may only mean you are likely to be the last of your kind to die out!
Fitness has to do with competition
within
a group;
speculate on why
. Was it camouflage, speed, intelligence, fecundity (having lots of offspring easily), disease resistance, some combination or none of these, or just "blind luck"? Ecclesiastes 9:11 says, "The race is not to the swift, nor the battle to the strong [in our fallen world] …but time and chance happeneth to them all" (ASV).
Natural selection is a fact because it's a
tautology
or
truism,
a form of
circular reasoning. It is argued that the fittest are those that survive in greatest relative numbers and those that survive in the greatest relative numbers are defined as the fittest
. That's definitely
true
, but it's really just an observation, not a profound theory, and begs the question of what makes some organisms fitter than others.
The story is told of a student walking to school who saw in the grass a mouse that remained absolutely motionless as a hawk soared overhead. When she asked her teacher why, the teacher explained that mice which ran were seen and killed by the hawk, so natural selection produced those which remained motionless. The next day, the student saw a mouse running to its burrow as a hawk soared overhead. When she asked her teacher why, the teacher explained how mice that remained motionless were easy targets for the sharp-eyed hawk that killed and ate them, so natural selection favored survival of the mice which ran. The "nice" thing about "survival of the survivors" is that it can explain anything: why mice run or stay put, why some species (e.g., horseshoe crabs) never changed in "600 million years" while others changed rapidly and quickly (e.g., an insect-eater thought to have evolved into horses, whales, and bats in less than "5 million years"). The so-called "proof" that natural selection produced evolution is too often merely the argument that survivors survived!
(b)
Natural selection versus ecological competition
. Most people just assume "natural selection" for the "fittest" means the selected variety must be increasing. Actually, natural selection has nothing to do with whether a species as a whole is increasing or decreasing in numbers or staying the same (static or stable). Look back at the calculation of fitness in Figure 12. In case A, the population was static or stable; the second generation had 100 individuals like the first one did. Now imagine the population doubled to 200, and the second generation contained 40 AA, 120 Aa, and 40 aa. What would the new fitness values be? The winner ("fittest") being "naturally selected" is still Aa, and its reproductive efficiency is 120/30 = 4.0, which is the highest value. That means the standardized fitness of Aa, 4.0/4.0, is 1.00, the maximum value, just as it was in the static population. The fitness values for the other two groups are also exactly the same in the expanding population as they were for the static case. The reproductive efficiency for aa is 40/20 = 2.0, so its standardized fitness is 2.0/4.0 (the "winning" efficiency) = 0.5, "one-half" the maximum, as before. The numbers for AA are 40/50 = 0.8, and 0.8/4.0 = 0.2, exactly 20 percent of maximum as in the static population.
What if the species population is decreasing? Who's the fittest then? Imagine the population declined by half, and the second generation was 10 AA, 30 Aa, 10 aa (50 total). Again, Aa is the best survivor or fittest, this time because it declined the least in population. Aa's numbers are 30/30 = 1.0, and 1.0/1.0 (the highest) is 1.0. The aa's again did "half" as well: 10/20 = 0.50, and 0.5/1.0 = 0.5. The AA "losers" got a fitness score of "20 percent" maximum, just as before: 10/50 = 0.2, and 0.2/1.0 = 0.2. Notice, however, the species population is decreasing dramatically.
In this case, being the
"
fittest
" only means being
the high scorer on the losing team!
Being the fittest, then, is no guarantee of survival at all .
It may only mean you are likely to be the last of your kind to die out!
Fitness has to do with competition
within
a group;
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