Vibr8gKiwi

I don't understand the details of the question, however in general I think these "irreducible complexity" arguments need to be responded to with the fact that evolution will often create seemly irreducible complexity.

Evolution can take paths that won't seem to be traversible backwards. For example, say A depends on B, and B depends on A. It might seem A and B would have had to evolve at the same time from one mutation, but this simply isn't the case. Interdependence can evolve in an infinite number of ways. Here's a few possible ways for A and B to evolve interdependence:
- A and B existed independently. A and B incrementally changed over time to depend on each other.
- A existed independently, B arose to depend on A. Once B was there, A changed to depend on B.
- There could've been a third thing, C which bridged A & B in some way and then wasn't needed and went away leaving A and B interdependent.

[ September 03, 2002: Message edited by: Vibr8gKiwi ]</p>

Mageth

All I know is that however I hang up my gardenhose, it always comes out tangled.

Sorry, this thread had gone on too long without an irrelevant post...

One of the last sane

Siamese cats are not albino. What they have is a sensitivity to temperature in the hair follicles, so the hair on the torso (warm) is pale while hair on the extremities (face, ears, tail and feet; all relatively cold) is pigmented. A Siamese cat that has a sinus infection, causing elevated temperature on the face, loses its striking "mask". A Siamese cat with an inflamed paw will lose color on that paw. If the infection and elevated temperature is brief in duration, you get stripes of light and dark in the indivdual hairs.

scigirl

Well I don't think anyone ever speculated that there was a "gradual switching" of the nerves. The cells that these nerves derived from embryonically either migrated across, or they didn't. Similar to the crossing of our sensory/motor system: the left side of the brain percieves the right side of the body, and vice versa. In this case, it is a digital response.

Now why did we evolve 'backward' optic nerves? Well here's what Eckert says in my Animal Physiology, 4th edition:
Hmm, interesting how the pattern follows an evolutionary tree, isn't it?

scigirl

RufusAtticus

pz,

Is that the same gene that causes "pointed" coat coloring? Or are they tightly linked?

pz

As "One of last of the sane" mentioned, it's the Himalayan temperature-sensitive albinism gene. As near as I can tell from the literature, it is specifically that same gene, although I haven't seen anything to explicitly rule out some other very tightly linked gene.

It's not surprising, though. Lots of different albinism alleles seem to affect visual pathways in odd and unexpected ways.

RufusAtticus

Thanx. One more example of plieotropy in my head.