Comments on: The Incredible Shrinking Genome

By: Iddo

Iddo — Thu, 02 Jul 2009 15:25:55 +0000

@IU_Undergrad Ouch, fixed. So sorry. As faculty at Miami University (and not University of Miami) I should really know better.

By: IU_Undergrad

IU_Undergrad — Thu, 02 Jul 2009 12:26:41 +0000

FYI: We are called Indiana University. University of Indiana is different.

By: Leon Barrett

Leon Barrett — Wed, 01 Jul 2009 18:14:04 +0000

I would tend to explain this with selection pressure. Mammals, with our more flexible brains, can handle changes in body shape without requiring as much change in our brains and reflexes. If an insect gains a new ability, like a stinger, it must also coevolve behaviors to go along with that, and it will have these behaviors genetically, with no learning. However, mammals (and birds) are not born with all our skills–instead, we learn them during childhood (e.g. each bird learns to fly, but each fly is hatched with the ability).

Requiring coevolution slows down evolution immensely. Instead of just one mutation being sufficient for a new skill, now we need two closely related mutations, which are much less likely to occur. Thus, mammals (and birds) should be able to fill new niches much more easily than our slower-evolving cousins.

So, if the most adaptable animals spread the best, then mammals will have a selection pressure for more adaptability and less specialization. I imagine that this might well result in a shrinking genome.

By: Pierre

Pierre — Wed, 01 Jul 2009 16:10:03 +0000

What if you’re looking at it backwards?

Species depletion would also result in less mobile DNA carriers and source material. The ones left would have a much narrower band of transmission.

Isn’t there a way to statistically compare the variability of inserted DNA before vs after the KT? You would expect to see a big difference if species depletion is the root cause, you would not see a significant difference if not (if it’s “random”).