fantôme profane;2165666 said:
1. If two species are capable of producing a hybrid offspring then they are the same kind. This is true even if the hybrid offspring is infertile and/or has genetic defects that make it unable to survive for very long.
Yes, true.
fantôme profane;2165666 said:
2. If two species are incapable of reproducing a hybrid then they are different kinds.
This is true. Generally, the point where fertilization ceases, is the point that determines if an animal is of a different 'kind'.
However, in some cases, not all within a kind will be able to reproduce due to the extreme differences in phenotype. An example being a small horse trying to breed with a large horse...there will be difficulties in this happening naturally due to size. Even if artificially inseminated, a small horse will not be able to carry a large baby for long before something goes wrong.
fantôme profane;2165666 said:
3. Created kinds are immutable. In other words it is absolutely impossible for one kind to evolve into another kind, or for one kind to split into two different kinds.
this is true.
Their is a barrier between the kinds...its fertilization. There is no fertilization between different 'kinds' and for that reason its impossible to cross a chicken with a dog...they wont hybridize however, different bird 'species' can hybridize as
this article lists numerous examples. Notice in all the examples listed, the birds are of the same type, ie different species of penguins can hybridize with other penguins but not with a duck or a swan or an eagle.
fantôme profane;2165666 said:
4. Change is possible within kinds. Changes are possible to both the phenotype and the genotype of created kinds, but only within kinds. Kind is still immutable.
Yes changes happen, but the genotype does not have to change much for the phenotype to change dramatically. The genotype is the hereditary information and it will change very slightly, but not enough to change one kind into another. Its the phenotype which can produce the big changes that we see which makes a lion a lion and a leopard a leopard. But the genotype of both are still the same 'kind'
fantôme profane;2165666 said:
I want to know if these four points are correct. If they are then we can make the following inference.
Lets consider two separate species that are just barely capable of producing a hybrid. This hybrid is completely infertile and usually dies shortly after birth (especially in the wild, in a zoo it might live a little longer). Now since these hybrids are infertile there is no gene flow between these two species. And since change is possible within kind both these species may continue to change over time.
yes its true that the species will continue to change over time...but they will not change into a new 'kind'... big cats will remain as big cats no matter what they look like.
fantôme profane;2165666 said:
We can infer that if the four statements above are correct then it is impossible for a mutation to occur in the genotype of either species that will have the result of rendering them no longer able to produce this hybrid.
Do you agree that this inference logically follows from the first four points? Do you believe that this inference is correct?
I dont know if this inference is correct. I dont believe that mutations have ever been shown to be able to produce a new 'kind' of anything.
the problem with bringing mutations into the picture is that mutations dont produce new 'kinds'. Yes they can produce some small changes in existing oranisms, but mutation experiments have shown that mutations dont lead to anything 'new' and are mostly harmful to the organism. look up the fruitfly mutation experiments.