RE: Genetic comparisons

["Neil, David M" <neildm@id.doe.gov>]

Ruth Sponsler wrote:

<<It makes sense that insects are genetically closer to humans than

nematodes. >>



Actually, no.  While insects may be the most specialized (= evolutionarily

advanced) invertebrates, that does not equate to closer to human. Rather the

opposite in this case; insects are considered the tip of a collateral branch

which shared a presumably wormlike ancestor with the vertebrates.  



However, all worms are not created equal. :-)  The common ancestor was

presumed to be a segmented worm, as both arthropods and vertebrates share

segmentation, and C. elegans is a relatively primitive unsegmented worm.

What this does indicate is that the "distance" down one branch and up the

other is less than the distance down the trunk to the nematodes.



Jim - You're both right in your own way.  Cephalopods are the "brain trust"

of the inverts, and have eyes that are more rationally designed than those

of vertebrates, but insects are more advanced in total.  



Dave Neil		neildm@id.doe.gov



	



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