Am I the only one who was annoyed by the way The elegant universe was about twice as long as it needed to be? Incredibly repititious, it was! And all the cutesy blinky annoying CGI effects were just over the top–calm down, people!
lieu:
Point three: Hi Opal!
I had roughly the same thought, and was actually a little surprised that they didn’t mention the possibility that periodically weak magnetic fields could be the engine of evolution.
Those who don’t believe in evolution point to the seeming lack of mutations occurring today. Besides the time scale problem (we haven’t been around long enough to have a reasonable expectation of actually witnessing evolution in action), it may also be the case that, because the magnetic field has been fairly robust for the last few hundred thousand years, the mutations that propel evolution just haven’t been occurring very frequently of late.
So, I guess this means that it’s not a question of if mutations will occur, but a question of when!
(Funny, I’ve never felt suicidal before.)
Anything that makes a person start a geology-themed post is a good thing.
I think one of the dirty little secrets of evolution is inbreeding. Of course, I live down here. 
But seriously folks, tip your waitress – and doesn’t inbreeding force evolution, albeit not all good? Fold a universe inside your napkin and be sure to drive carefully!
I’d just like to say Permian. As in, whatever happens (apocalyptic TV/reality eventwise: asteroid, caldera, magnetic field, retrovirus, nuclear war, etc.), I hope it’s not permianant. Nothing says humor like corny end-of-all-human-life jokes. 
[QUOTE]
*Originally posted by genie *
**Am I the only one who was annoyed by the way The elegant universe was about twice as long as it needed to be? Incredibly repititious, it was! **/QUOTE] Maybe four times as long, considering how little we know about strings (item 1: do they even exist?). A point they made approximately 458 times in three hours. But a discussion of what force might keep them in motion would have been nice.
At least the magnetic field simulations worked. I don’t know how many Novas I’ve sat through, sitting on the edge of my seat waiting for them to get an experiment to work, only to have them give up because the experimenters ran out of vacation time to work on it.
Beagle: All inbreeding does is bring out recessive tendancies, good, bad, and indifferent. Look at it this way: When you outbreed, each parent has a different mix of recessive traits lying dormant in their genes. Therefore, the children get a mix of recessives that can’t match up with anything, and therefore stay recessive.
When you inbreed, each parent most likely has the same mix of recessives. Therefore, the children get recessives that can meet up with recessives of the same kind, and so get expressed.
When a recessive gene is a cleft palate or deafness, it does have a negative impact on survival. If a recessive is genius-level intelligence, however, it has a positive effect on survival. If a recessive codes for an eleventh toe, it doesn’t affect survival one way or the other.
So, how can you counteract the negative effects of bringing out all of those recessive genes? By ruthlessly culling the population of the unfit ones. Certain wolf populations inbreed as a matter of course, but the number of unfit members of the population is kept down by the harshness of the environment.
It’s all so confusing, what with evolution happening so “fast,” apparently.
What happens when a population is destroyed almost entirely, but rebounds from near extinction by inbreeding? Does that have an effect, let’s say, on evolution? Just building any large population from a small seed population forces the genetic traits in one direction, right? Then, other stuff happens. :o
I’m not suggesting we "force"evolution through inbreeding, duh. I just think it must happen over and over.
Which would be why Europe’s royal families, remaining fit, if a wee bit psychotic, back in the day when they were constantly culling with murders and wars, have degenerated into what they are today.
…it seems to me you lived your life like a candle in the wind…
Beagle: If a population is brought to the edge of extinction and only survives as a pocket of close relatives, the problems of inbreeding still apply. However, if that pocket was indeed the most fit (as opposed to the most lucky), the anti-suvivalistic recessives may have already been culled from the genome (everyone who carried them has been wiped out and none of their descendants survive). But that kind of thinking is risky: It assumes that evolution can `perfect’ a genome, which it cannot. More likely, it will just make all members of a species susceptible to the same conditions, both genetic and environmental. Such a population is at a rather increased risk for extinction. Biodiversity within a species is a good thing.
As for forcing the traits in a specific direction: maybe. Evolution is mutation filtered by environment, remember, so if the surviving members of the population lack some mutations that would have enabled them to evolve some traits, then the population as a whole won’t evolve those traits. Or they may get the mutations back randomly. Or they may get different mutations randomly, which propel them on a different tack. It’s all about chance.
Actually, I was thinking more along the lines of pure luck. BOOM A few Australians and the South Pole expedition survive. I’d prefer to take humans out of it because we are organized, mobile, and number in the billions. Not to mention the whole “Dr. Strangelove” factor.
If a small population of Nile Monitor lizards makes it into the Everglades won’t that population “soon” evolve into the “Florida” monitor lizard, due to whatever – mutations of course – but partly inbreeding.
This is a good point. At least it is intelligent alarmism. I think I will give NOVA another few shots. Plus, where I live there is NOTHING on at 8:00 on Tuesday anyway.
Beagle: OK, you didn’t really tell me that. I was assuming something like a horrible plague or efficient predators moving in or humans with big guns.
Assuming it’s like On The Beach, but the people aren’t going to die off when the radiation clouds reach them. Then you still have the problems of inbreeding eventually, but as the population doesn’t start out related, you won’t have them for n generations (where n is related to how related everyone is to begin with and how many of them there are).
But you may never have to worry about inbreeding: If you have at least 50 people, none of them related and all of them breeding-age and healthy, you have a healthy population (genetically speaking). There is probably a sufficient mix there to ensure that the problems of expressing too many recessives don’t crop up. (My cite is a thread I posted to which I don’t have time to track down. Run a search on my posting history and look for a GQ thread about population size.)
As for your second one: While parallel evolution happens, you could just as easily get a completely different animal. Inbreeding hasn’t anything to do with it, really: Evolution is driven by mutation. If you plopped a small population of related Nile Monitor lizards in the Everglades, you could re-create an indigenous species. You could also create a totally different species. Or the group could die off from some parasite that affected all of them, since there wasn’t sufficient diversity within the group.
Uh…just for the record, magnetic field changes have occurred quite frequently in the Tertiary period (< 67Myr ago). It was these reversals that finally cinched plate tectonic theory as real, rather than an educated guess. It was the discovery that materials around a rift zone (the Atlantic rift is the classic textbook example), would show that the magnetic field’s direction would be “frozen” into place once the basalt(?) solidified. What convinced every one was 1) as one moved further away from either side of the rift zone, the material would suddenly reverse in direction, and 2) when one dated the material from each side, you found the age would match one-on-one for each “band,” reversal (along with a roughly equi-distance from the rift axia), would occur at the same time.
So if you’re looking for major planetary extinction occurring as a result of a switching magnetic field–look to you and me first as the cause, rather than watching your compass getting squirrelly.
In regards to “Nova” being sensationalistic, I am reminded that they used the same tactic in a program about “strategic materials” in the early eighties. It started with “the end of the US as we know it, w/o these materials.” but in the end explained that this happens all the time and new substitutes being are found–don’t worry, science is looking out for you!
Nova is one of the few shows that impresses me in trying to communicate rather than talk down to the audience. I cut that episode some slack 20 years ago, and I’ll do it agian with this one.
Uh…just for the record, magnetic field changes have occurred quite frequently in the Tertiary period (< 67Myr ago). It was these reversals that finally cinched plate tectonic theory as real, rather than an educated guess. It was the discovery that materials around a rift zone (the Atlantic rift is the classic textbook example), would show that the magnetic field’s direction would be “frozen” into place once the basalt(?) solidified. What convinced every one was 1) as one moved further away from either side of the rift zone, the material would suddenly reverse in direction, and 2) when one dated the material from each side, you found the age would match one-on-one for each “band,” reversal (along with a roughly equi-distance from the rift axia), would occur at the same time.
So if you’re looking for major planetary extinction occurring as a result of a switching magnetic field–look to you and me first as the cause, rather than watching your compass getting squirrelly.
In regards to “Nova” being sensationalistic, I am reminded that they used the same tactic in a program about “strategic materials” in the early eighties. It started with “the end of the US as we know it, w/o these materials.” but in the end explained that this happens all the time and new substitutes being are found–don’t worry, science is looking out for you!
Nova is one of the few shows that impresses me in trying to communicate rather than talk down to the audience. I cut that episode some slack 20 years ago, and I’ll do it agian with this one.
Awww, c’mon guys! Can’t you be generous? How often do the guys down in the Geology Dept. get urgent calls to appear on the local TV station?
Summary: There have been quite a few, as well as minor extinctions. It’s a mystery. Um, cometary, climatalogical, geologic, or unknown factors (don’t forget the aliens!) might be involved. Maybe it’s periodic, or not.
The bright side is, geologic time isn’t something to set your watch by. Also of course, the mass extinctions result in success for the species that survive and then eventually thrive.
To me this is one of the more fascinating subjects in science. There they are in the fossil record. Why? The best guess seems to return to killer space objects in many cases. I suggest revisiting the death ray.
Uh oh! Pretty soon you’ll be watching it regularly, then you will decide to check out an episode of “American Experiance” and pretty soon, you’ll be experimenting with “Frontline” and before you know it…YOU’RE A PBS JUNKIE!!
I’ve seen it happen so many times before.
She told me she loved me like a brother. She was from Arkansas, hence the Joy!
Well, if you guys really want to scare yourselves silly with possible end-of-the-world scenarios, check out the Exit Mundi Web site. It does not yet have a page on the diminuition of the Earth’s magnetic field, but I’m sure that runaway greenhouse effect, nanotech gone mad, or quantum vacuum collapse should be enough to terrify you guys into joining the fundie Rapture cult.