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Additionally, scientists have determined that some endogenous retroviruses are indispensible.<ref>http://agnews.tamu.edu/dailynews/stories/ANSC/Sep1106b.htm</ref>  This presents the possibility that retroviruses were used as part of the creative process.

Additionally, scientists have determined that some endogenous retroviruses are indispensible.<ref>http://agnews.tamu.edu/dailynews/stories/ANSC/Sep1106b.htm</ref>  This presents the possibility that retroviruses were used as part of the creative process.

== Bases for disbelief ==

=== Common DNA-based genes in diverse species ===

The most persuasive argument for common ancestry is existence of common DNA-based genes in diverse species. But there are at least three other plausible explanations -- [[parallel evolution]], [[horizontal gene transfer]], and [[creationism]].

The most persuasive argument for common ancestry is existence of common DNA-based genes in diverse species. But there are at least three other plausible explanations -- [[parallel evolution]], [[horizontal gene transfer]], and [[creationism]].

=== Parallel evolution ===

* '''Parallel evolution''':  Some people who believe in evolution deny universal common ancestry.  They point out that there is still no good theory for how DNA-based life could have arisen from non-life. If it happened once, it may have happened many times. Some people say that separate evolution might have had an entirely different genetic code, but no one knows. It may well be that DNA-based life evolved from non-life many times, and the descendants of that life are living today.

Some people who believe in evolution deny universal common ancestry.  They point out that there is still no good theory for how DNA-based life could have arisen from non-life. If it happened once, it may have happened many times. Some people say that separate evolution might have had an entirely different genetic code, but no one knows. It may well be that DNA-based life evolved from non-life many times, and the descendants of that life are living today.

=== Horizonal gene transfer ===

* '''Horizonal gene transfer''': It is also known that genes sometime migrate somehow from one species to another species, so having a common gene is not proof of common ancestry.  Maybe there is no universal common ancestor, and important genes were spread by horizontal gene transfer.

It is also known that genes sometime migrate somehow from one species to another species, so having a common gene is not proof of common ancestry.  Maybe there is no universal common ancestor, and important genes were spread by horizontal gene transfer.

 

* '''Creationism''': Creationists argue that common genes in diverse species is no more evidence of ''common descent'' as it is of ''common design''.

== References ==

== References ==