So now you claim that neither birds nor mammals experience genetic mutations from one generation to the next?
And your scientifically recognized source for this choice bit of misinformation is what, exactly?
Here's the truth of the matter:
Evolution consists of two key factors: descent with modifications and natural selection.
Since you have already admitted the fact of natural selection, I won't spend more time on it.
Descent with modifications begins with genetic mutations during reproduction.
These have been observed and confirmed innumerable times -- so they are facts.
How many mutations for each generation?
First, remember that the human genome -- the genetic code, those biological instructions by which DNA makes us -- that code has about 3 billion individual "base pair" instructions.
Not all perform useful work, a good many are sometimes called "Junk DNA", and mutations to "junk base pairs" have zero effect.
We all mutate, says study coauthor Philip Awadalla, a population geneticist at the University of Montreal.
And the mutation rate can be extraordinarily variable from individual to individual.
"Combined with the results of three similar recent studies, the rate indicates that, on average, about one DNA chemical letter in every 85 million gets mutated per generation through copying mistakes made during sperm and egg production.
"The new rate means each child inherits somewhere in the neighborhood of 30 to 50 new mutations."
The previous estimate was about 100 mutations per generation, but this new study reported high variability in the small sample, and one can imagine mutation rates increasing during times of high physical stress caused by new environmental factors.
In other words, individuals highly stressed by a changing environment might generate more mutations than others living in more species-friendly locations.
Regardless, "descent with modifications" is a scientifically confirmed fact.
So what exactly is your problem with it?
annalex: "I responded to your zebras about a week ago."
You have seriously responded to nothing, whether zebras or humans or anyone else, FRiend.
Again, you don’t understand. Thank you, however, for the brevity and the pointed character of your last post.
There is no dispute that random mutations occur in every species. They are called birth defects.
The dispute is that those of them that conform with the environment and even provide an environmental advantage, and occur so that the two species with it (or one if the mutation is not only advantageous but dominant) successfully mate, occur statistically insufficiently for the new species to be produced over generations of such lucky streak.
Let us not forget that for a random mutation to be advantageous something equivalent of improving a poem through letting a monkey retype it needs to happen. It is a probabilistic non-zero and that is about it. Not observed in organisms that reproduce like mammals or birds do: few and vulnerable offspring per mate.
Further, there is no fossil evidence of a gradual movement from one species to the next, but there is plenty of fossil evidence of stable, not mutating species.
Regarding zebras and dogs and cats — understand that selection of breeds is not the same mechanism, — no mutations of the genome are needed. This is why that breeding occurs does not speak to the issue of origin of species.