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Message |
    
Cavebear
cave painter
Username: Cavebear
Post Number: 2481
Registered: 9-2003
| | Posted on Wednesday, March 08, 2006 - 6:05 am: |     |
I've been thinking about genes lately (a lot actually), and I'm beginning to think they work in groups.
Some parts of our bodies seem to go together, like teeth that can chew meat or vegetables and intestines that are adapted to that. Or genes that are separately responsible for stereo vision and hand-eye coordination.
I'm thinking that groups of genes succeed in self-reinforcing ways. Some tend to succeed better in the company of other genes that complement them.
Genes don't just succeed individually, they succeed in the presence of other genes that they fit with.
Machiavelli was pretty devious. For a guy... |
Pine
flint knapper
Username: Pine
Post Number: 1165
Registered: 5-2003
| | Posted on Thursday, March 09, 2006 - 6:55 am: | |
Dawkins explains that in The Selfish Gene with his rowing team coach model. The same rower may make a different contribution to a team, depending on who else is on that rowing team.
Cohen's Law: 'Unless you fail at more than 10% of the things you try, you aren't trying enough things.' |
Cavebear
cave painter
Username: Cavebear
Post Number: 2482
Registered: 9-2003
| | Posted on Thursday, March 09, 2006 - 6:57 pm: | |
I'll have to read that book.
But to use that analogy, I would picture a random group of good rowers, enough for two boats. Some are naturally going to be a bit faster rowers (but not has durable), and some will naturally be able to row longer (but not as fast). Random combinations of the rowers will show that there is one combination that wins in short races and the other wins in longer ones. As rare replacements are made on the team, each specializes in their strength. Eventually, you have two "species" of rowers, each successful in their own niche.
I think that is how speciation occurs. Not with some single genetic mutation that confers a single change, but one which ALSO works better with other existing genes. A gene that promotes a higher level of activity would seem an obvious advantage, but not to an animal that depends on not being noticed (like a walking stick).
We have a common ancestor with chimps. The population of that common ancestor had many different genes, and each individual was an experiment in different gene combinations (or really, versions of those genes). Type "1" genes worked together to make a larger stronger body. Type "2" genes worked together to make a smaller faster body. Most of the population would be about an equal mixture of both, but some individuals would have a preponderance of one or the other and show a real effect from that. In other words, an individual might have almost all A1, B1, C1…X1, Y1, Z1 gene variations. The few Type 2 gene variations introduced by a mate in reproduction might find an almost hostile "working environment" and not develop well. And the same in reverse, of course.
Assuming that either or both gene "packages" were viable in the environment, that would start to set up individuals at one or both ends of their genetic bell curve who would be less successful at producing viable offspring with the other end, but more successful among themselves. It seems to me that, once some package of genes starts working together better than the general population's genes (not just a single one), a new species in starting to develop.
What use is a single gene variation that causes a change the other genes can't support? I don't mean that one gene change will change a squirrel into a carnivore. But I did see a squirrel capture and eat a small bird once. Something in that squirrel's genes said "catch and eat small moving things". Now for all I know, that squirrel died as a result of eating meat. But maybe another squirrel had genes that made for stronger stomach acids than average for squirrels (or whatever it takes to digest meat instead on acorns). They still mostly ate acorns. But maybe they mated and combined those variations of their genes and the "catch and eat" gene found it coordinated well (in fetal squirrel development) with the "stomach acid" gene. And when they meet again in a few generations, they find a "longer claw" gene variation, and say "hey welcome to the club"! That group of genes together don't work quite right with the "acorn-chewing teeth" gene in one mating, but do like the "sharper tooth" gene in another mating.
My point is that a squirrel with a totally "acorn-eating" gene package is not going to be as successful with one single "catch and eat bird" gene. That won't lead to a new species. But a package of genes that work together in a different direction will. And that will change some squirrels into omnivores and new species.
The more I read and think about how natural selection and speciation seems to work, the more complicated it seems to get. 
Machiavelli was pretty devious. For a guy... |
Matt
hunter
Username: Matt
Post Number: 477
Registered: 5-2003
| | Posted on Thursday, March 09, 2006 - 11:05 pm: | |
Killer squirrels?! Good heavens! What are you trying to do...revive Monty Python, or frighten us all into reverting to Creationism?
Interesting ideas though, Cavebear. I'm hardly any kind of expert in evolutionary processes but I'm enjoying following along with these lines of thought.
We sit together,
the mountains and I,
until only the mountain remains.
-- Li Po (701-762 A.D.) |
Cavebear
cave painter
Username: Cavebear
Post Number: 2484
Registered: 9-2003
| | Posted on Friday, March 10, 2006 - 12:25 am: | |
Matt, I actually changed it from rabbits to squirrels when I thought of Monty Python! LOL!
Machiavelli was pretty devious. For a guy... |
Pine
flint knapper
Username: Pine
Post Number: 1166
Registered: 5-2003
| | Posted on Monday, March 13, 2006 - 5:58 pm: | |
Cavebear, I should have expanded on the rowing team analogy. An example: Is an English speaking rower better than a french speaking rower? Depends on what the others speak. Is a right-handed rower better than a left-handed rower? There is more to rowing in team than just getting better at rowing.
Speciation as you described is called sympatric speciation. There are several theoretical models explaining how it occurs but few demonstrated examples from nature.
speciation summary
sympatric speciation
Looking at complexity may also be of interest
Sympatric speciation in Nicaraguan crater lake cichlid fish abstract of recent Nature paper.
Cohen's Law: 'Unless you fail at more than 10% of the things you try, you aren't trying enough things.' |
Cavebear
cave painter
Username: Cavebear
Post Number: 2496
Registered: 9-2003
| | Posted on Tuesday, March 14, 2006 - 9:18 pm: | |
Thank you, Pine, those were interesting articles. I found the first one especially helpful as it listed the technical terms for all the ways I could think of for genetic isolation to occur.
The rowing team analogy makes more sense now that it is expanded. As I interpret that, I picture a boat with 2 rows of rowers in such a way that the handle ends of the oars can interfere if not coordinated. A new rower joins the team. He and his opposite seatmate are the best rowers. But if they do not coordinate well, problems occur.
So if a singly advantageous gene joins a group of genes, but does not coordinate well with that particular group, it it does not function well, though it might with a different group of genes.
The first group of genes, working well together, and the singly advantageous gene in a different group, both work well within their groups. Over time, the successful groups of genes tend to reinforce their differences, leading to distinctions in the bodies they build.
Over enough time, those gene groups will no longer accept enough of the genes from the other group in a reproductively viable combination, and a new species exists.
Machiavelli was pretty devious. For a guy... |
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