Why do some believers claim that macroevolution cannot happen?

Utter desperation, and insufficient moral character.

As others have pointed out, microevolution IS macroevolution. It's up to the person who denies "macroevolution" to demonstrate that somehow the DNA magically reach out and prevent scientists from referring to the organism as a member of a new species. Imagine the kind of mechanism that would take - some kind of magical long-range DNA molecule floating through the air to effect very specific changes in the brains of everyone who ever pays any attention to the organism.

I kinda don't think they realize what they're asking for. If you can believe in that kind of thing, you're WAY out of touch with reality.

"Microevolution", more accurately called natural selection, is the narrowing down of specific genetic information in a populaiton. If a rabbit population has white fur and black fur, and all the black furs keep getting eaten until only white furs are left, there is less genetic diversity in the population.

There is also beneficial or neutral mutation. Beneficial mutation is a mutation that destroys a part of a creature's genetic code, that wind up having a good result, such as a bacteria that has a mutation that causes it to not release a substance that antibiotics use to identify the bacteria, so that bacteria will be less affected by antibiotics. However, once it is back in an environment where it loses this advantage, it will be at a disadvantage.

A neutral mutation doesn't affect a creature either way, like a mutation making a spot on the skin. This still results in decreased or damaged genetic information.

Then of course there is the rest of mutations, twhich cause either death or a major disadvantage.

"Macroevolution", on the other hand, requires an ADDITION of genetic information caused by mutation. However, mutation has only been show to either damage or destroy genetic information, resulting in either death, disadvantage, or at the very best a temporary, environmental advantage. There is never an increase in information.

First off, there is no macroevolution or microevolution...just evolution. The creation of this distinction is a way for creationists to try and drive a wedge into the the clearly viewable phenomenon of evolution and say it's explains everything else, but it doesn't explain us, since we're special and God made us.

"Macroevolution" or to use an actual term, speciation, does occur, is observed to occur, and we can give a myriad of examples, such as horses and donkeys not producing fertile offspring, fossil records showing clear evolution of different species from common ancestors, and even more simple examples like the evolution of culled plants like corn and bananas.

I am not sure where these terms - macro-evolution or micro-evolution -came into being. Evolution of species is a slow process with the changes being minute. No species is going to change from one to another suddenly or overnight. I have a feeling that these terms were invented by people posing as scientists just to discredit the fact of evolution.

There are examples that demonstrate macro evolution does not occur. For instance, scientists have bred, hybridized and manipulated beets in an attempt to make the sugar content as high as possible. What they find is that there is a ceiling beyond which they cannot go. No matter how much they manipulate the beets they do not produce a higher percentage of sugar than about 18% (I am guessing on the 18%, but a ceiling has been found).

Also, for instance, fruit flies have been radiated, chemotherapied and otherwise manipulated to produce something other than fruit flies. The flies reproduce and an enormously fast rate (which should allow scientists to speed up any evolutionary process). The end result is some pretty ugly, not very resistant fruit flies. But, they still have not been able to even manipulate the fruit flies to produce a house fly.

Macro evolution does not exist. Or, provide an example where it does, other than in the ever fertile minds of believers in evolution.

Observed incidents of speciation:

http://www.talkorigins.org/faqs/comdesc/

Macroevolution: Definition and history:

http://www.talkorigins.org/faqs/macroevolution.htm...

Because the concept of faith was invented to force a belief even when the facts are blaring in their faces. They will keep on this until we find life outside of Earth and then they can start on that... Oh wait, we have and they are (Martian bacteria)...

Many atheists don't believe that macro evolution happened. Perhaps since atheists are big on the whole proof thing you should ask those who don't agree with your theory to provide you with proof that macro evolution didn't happen.

You need to understand the fact that many who make that claim do not fully understand evolution at all. They work only off of what they have been told.

As a Christian let me just be upfront with you. Those who claim that macro-evolution does not occur (not myself included) are NOT basing this on evidence. They are simply extrapolating their preconceived ideological and theological ideas.