eklhad@ihnet.UUCP (K. A. Dahlke) (08/13/85)
< Here we go again > Consider the following argument from our friend Ted. > A change from one species to > another with no possibility of interbreeding could > only happen if more than one of the new species > appeared at one time > [ Discussion about how unlikely it is for a point mutation, > that produces a new species, to appear twice at the same place and time ] the offending word in the above paragraph is "only". Dan, now that I understand *your* evolution, I am not surprised that you don't believe in it. It is absurd! Not only is speciation unlikely (given this mechanism), it is all but impossible, for advanced organisms. two coincident mutants don't have enough of a gene pool to support a thriving species. This would have been a better argument than your "gut feeling" probabilistic reasoning. Now, perhaps, if you take the time to understand *true* evolution, you will understand why we accept it. The actual mechanisms for speciation do not relie on two point mutations producing a *new* species, in the *same* place, at the *same* time. In most scenarios, physical separation precedes speciation. In fact, perfectly viable mutationless speciation mechanisms exist, driven solely by geographic isolation and natural selection. Allow me to present an admittedly simplistic example. A community of birds lives in an environment containing both prey and predators. These birds have several genes controlling their size (which could range from quite small to very large). These genes are basically additive (no dominance/recessive here). Birds that are too small have a hard time catching their food, and are selected against. Birds that are too large require more energy to fly, making it harder to evade their predators. So the population remains in equilibrium. One year, the weather is abnormal, and there is not much prey. The birds travel farther to find sufficient food. A group, caught in a storm, winds up on an island, completely separated from the original flock. This island contains prey, but no predators. Content, this group (and its descendents) remains on the island. Since there are no preditors, the "optimal" bird is now larger. There is plenty of prey to support the increased size. The environment simply selects the "large" genes, no mutations necessary. As the birds change morphologically, the shape/size of their sexual organs also changes. They become a new species. As far as genes are concerned, our fascination with speciation (in this case) is completely artificial. The ideal morphology is selected for, regardless of its status as a new/old species. In fact, the above is a common enough scenario. Further evolution (probably incorporating some mutations) may make these birds flightless (no need to fly here). These patterns are repeated time and time again. Now that you understand *some* aspects of speciation, please don't erect, and then feebly take potshots at, strawman arguments. -- This .signature file intentionally left blank. Karl Dahlke ihnp4!ihnet!eklhad
eklhad@ihnet.UUCP (K. A. Dahlke) (08/13/85)
< Here we go again > Consider the following argument from our friend Ted. > A change from one species to > another with no possibility of interbreeding could > only happen if more than one of the new species > appeared at one time > [ Discussion about how unlikely it is for a point mutation, > that produces a new species, to appear twice at the same place and time ] the offending word in the above paragraph is "only". Ted, now that I understand *your* evolution, I am not surprised that you don't believe in it. It is absurd! Not only is speciation unlikely (given this mechanism), it is all but impossible, for advanced organisms. two coincident mutants don't have enough of a gene pool to support a thriving species. This would have been a better argument than your "gut feeling" probabilistic reasoning. Now, perhaps, if you take the time to understand *true* evolution, you will understand why we accept it. The actual mechanisms for speciation do not relie on two point mutations producing a *new* species, in the *same* place, at the *same* time. In most scenarios, physical separation precedes speciation. In fact, perfectly viable mutationless speciation mechanisms exist, driven solely by geographic isolation and natural selection. Allow me to present an admittedly simplistic example. A community of birds lives in an environment containing both prey and predators. These birds have several genes controlling their size (which could range from quite small to very large). These genes are basically additive (no dominance/recessive here). Birds that are too small have a hard time catching their food, and are selected against. Birds that are too large require more energy to fly, making it harder to evade their predators. So the population remains in equilibrium. One year, the weather is abnormal, and there is not much prey. The birds travel farther to find sufficient food. A group, caught in a storm, winds up on an island, completely separated from the original flock. This island contains prey, but no predators. Content, this group (and its descendents) remains on the island. Since there are no preditors, the "optimal" bird is now larger. There is plenty of prey to support the increased size. The environment simply selects the "large" genes, no mutations necessary. As the birds change morphologically, the shape/size of their sexual organs also changes. They become a new species. As far as genes are concerned, our fascination with speciation (in this case) is completely artificial. The ideal morphology is selected for, regardless of its status as a new/old species. In fact, the above is a common enough scenario. Further evolution (probably incorporating some mutations) may make these birds flightless (no need to fly here). These patterns are repeated time and time again. Now that you understand *some* aspects of speciation, please don't erect, and then feebly take potshots at, mythical evolutionary mechanisms. -- This .signature file intentionally left blank. Karl Dahlke ihnp4!ihnet!eklhad