posted
I watched a documentary on Discovery Channel last night on human evolution (Homo Futurus). It centered around the discovery of a French scientist that the sphenoid bone (sits at the base of the human skull behind the eyes) has lowered its angle periodically. The result of this lowering has been the evolution of the human skull, and by extension the whole body. It's more complex than I can explain here, but basically as the angle of the sphenoid dips the face changes from a horizontal axis (man's earliest ancestors) to an eventual vertical axis (humans today). The change in the angle of the sphenoid also results in greater skull capacity (more room for a bigger brain), a change in the angle that the spine enters the skull (creating an upright stance). The scientist has been able to pinpoint the times when these changes took place through examination of the fossils, and determine that the changes didn't take place gradually but at particular points, ie no change, no change, change. She's determined that these changes are genetic, that they are programmed into us. The lowering of the sphenoid angle takes place at a specific point in the development of the fetus (7 - 8 weeks). Also, the changes recorded in the fossil record show that they took place at specific times in human development, and in all areas of the world hominids lived, independently. The thing that makes this sound like intelligent design to me is that it's programmed into us genetically, and that it has happened independently in all areas of the world. The interesting thing too is the impact the change in the sphenoid bone has had on brain size, vertical stance, language ability, stereoscopic vision, and so on. According to the scientist the traditional view that hominids took up a vertical stance because they needed to stand up to see over the long grasses on the African savannah is false, that the cause of this sort of change was internal, genetically programmed. I'm trying to find a link.
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posted
I think the idea of spontaneous evolution has been pitched for a while. I don't remember the specifics, but I've seen that theorized elsewhere. I don't know if anyone ever found proof like what you're talking about though.
quote: Also, the changes recorded in the fossil record show that they took place at specific times in human development, and in all areas of the world hominids lived, independently.
If this can be proven, that would be a major blow to the theory of natural selection. I strongly suspect, then, that it's hyperbole and/or baseless; otherwise, the biosciences would be in an uproar.
Spontaneous acquisition of a trait among a worldwide population without requiring time for that trait to migrate would indeed be a major discovery.
Edit: but as I Google her theory, she primarily posits that something in DNA is coded to "trigger" under certain situations, and that those situations, when global, trigger massive selection events. There's nothing incompatible with natural selection in that.
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posted
We would not expect there to be long periods of gradual change, that wouldn't make sense absent a very gradually changing environment. What we know of human development is that there were fairly major, periodic environmental changes leading to increased capabilities. In such cases evolutionary theory leads us to expect periods with little change followed by increments of rapid change.
That it happens in many areas of the world just suggests the evolutionary advantage conferred in common condition changes is elastic over the common degree of variation found for that feature.
For example, if I took two identical bunches of finches, and switched both groups food out for nuts that were harder to crack, I'd expect to see larger, stronger beaks in both groups. This is just because there's variation in the beaks, and when conditions change in certain (common) ways, beak size of the overall population will be affected because relatively small differences will convey relatively large evolutionary advantages.
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posted
BTW, "independently" is extremely unlikely, as we have significant evidence (some of it relatively recently) there's never been a period in time where human populations were divided up into little non-interacting patches. Humans have always wandered and interacted and interbred.
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"Gee... go figure. Evolution's been able to explain that sort of thing for decades. Who'da thunk it."
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posted
Also, what do you mean by pinpoint? I'd better there's a several thousand year period, which is quick, but not spontaneous, and certainly leaves time (theoretically) for propagation.
Not saying its not ID, but I'd need to read more about the assertions made by the researcher.
Nice to see your excellent bedside manner, again, Jay.
posted
Another thought, there's no reason why this couldn't occur "simultaneously" across the globe, if there was a sufficient global condition that strongly selected this trait, for whatever reason.
quote:Edit: but as I Google her theory, she primarily posits that something in DNA is coded to "trigger" under certain situations, and that those situations, when global, trigger massive selection events. There's nothing incompatible with natural selection in that
I think the example I saw for this was in the event of world-wide catastrophe (meteor or something) that fundamentally changed the composition of our atmosphere, the next generation of humans would be born with adapted lungs to handle the new air composition.
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quote: I think the example I saw for this was in the event of world-wide catastrophe (meteor or something) that fundamentally changed the composition of our atmosphere, the next generation of humans would be born with adapted lungs to handle the new air composition.
Well, THAT particular example is just standard selection at work. Unless she's theorizing that the genetic trait for adapted lungs did not exist until that event.
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posted
My understanding of standard selection would be the next generation would have a small percentage with adapted lungs, and that percentage would be more likely to live and procreate than everybody else. Thus making it more likely they pass that trait along to their offspring, and so on and so forth until everyone alive has the adapted lungs.
If it happens simultaneously, and within a generation or two, it's not standard selection.
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posted
El JT: because of limits on our "resolution", the further you go back in time, the longer a period considered "simultaneously" simply because we can't judge accurately. Back a few million years, for instance, and "simultaneously" can be 10,000 years. Quite some time.
Also, your example misses some ways in which selection can occur -- for instance, a different trait might have been selected for which includes a potentiality for another trait, leading to extremely rapid switches to that other trait given the right conditions.
Not to mention that in certain sorts of populations, for certain traits, "standard selection" as you outline it can dominate a population very rapidly; this is easily shown by computer simulation. Experience, too; are you familiar with the moths around factories in britain during the industrial revolution?
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posted
It doesn't prove anything about intelligent design, but it is certainly an interesting point.
My take on intelligent design is that it doesn't dispute evolution, but is just a possible explaination for why and how creatures have evolved.
Simultaneous global change in a species, such as man, can't easily be explained by saying it was purely a change in the environment. The globe is a very vast place and things such as the Ice Age have had different impacts on different parts of the planet.
There's just so much to ponder on the hows and whys. Someone once said that if an old scientist says something is set in stone, that they are generally wrong; and if an old scientist says something is possible, chances are good that they'll be proven correct.
Evolution is pretty obvious, one only has to look at the fossil record, the genetic evidence and the millions of examples around us. It does a remarkable job of explaining the "How."
But when Evolution comes to the question of "Why?" it only offers the answer of "Because that's the way it is." That answer may be the purest and most precise one, but I've always been reluctant to agree wholeheartedly when someone's reason basically boils down to "Because I said so."
And in my mind, when we speak of the beginning of life on this planet, I find the idea of a Prime Mover more palatable than the idea that the conditions were just right in the primordial soup.
Your mileage may vary greatly, though.
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posted
Right, but what I was going for with my example is a trait that isn't bred into existence; one which merely happens.
My example isn't selection, because it just happens all at once. And by 'at once' I mean in a single generation. The DNA 'key' or whatever is turned in the womb and the new generation all has the adapted lungs. Maybe it was a poor example, or maybe I just didn't explain it thoroughly. Either of those is possible.
EDIT: This is to Fugu.
FURTHER EDIT: I reread my example, and I think the problem is I didn't adequately explain. When I say the next generation is born with adapted lungs, I mean the entire generation. Everybody. If only some people are born with the trait, it is indeed standard selection at work.
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posted
That's the thing that made me wonder if this would qualify as intelligent design, the fact that this change appears to be programmed into us, rather than arising from purely environmental stresses. Dunno, no evolution expert me...
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posted
Cashew, “genetic” does not mean a trait didn’t arise through natural selection. On the contrary, differences in genes are what natural selection is all about.
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I would like to recommend an excellent book Finding Darwin's God This was written by a Biology prof from Brown University who is also a devout Catholic.
He does an excellent job of explaining the premises behing Evolution, Creationism and Intelligent Design. He also covers modern variants of Evolutionary theory. The last 1/2 of the book covers his take on how belief in God and Evolution fit together nicely.
Anyway, I just wanted to say that the mechanism of evolution is phenotypic change brought about through genetic change. I suspect that there is not a genetic change that could not be used to explain any change in the human body from an Evolutionary perspective.
Basically, since this IS tied to a genetic change, it is something that Evolution is likely to explain quite well.
One thing to bear in mind when thinking about evolution: changes take place all the time. If a new trait (a change) confers some benefit to the species-members who have it, it will spread through the population. If there are enough changes, or there is geographic isolation, there may also arise from this a new species.
Another thing to bear in mind is that gradualism is a term that only implies long spans of time. It is not necessarily the case that eons have to pass. The real key is that Evolution requires more time when there are more things to change. And it requires that the intermediate forms be viable. Every link in the chain from one species to another has to be a successful variant.
Otherwise, of course, the chain is broken.
ID folks like to look for things that "spring up" fully formed. That's why they look for complicated systems that seem to not have a useful function if any piece is not in place.
So far, they've failed to find things like that which further research hasn't figured out a reasonable evolutionary sequence for. In fact, the ID folks have probably given a few grad students some excellent Ph.D. research topics over the years in debunking their latest claim for irreducable complexity.
So far, they've not been very successful.
The reason, apparently, is that Evolution has been at work afterall. But more importantly, the ID proponents don't really go very deep in their understanding of the biology. They know the biochemistry or biomechanics really well, but often seem to neglect the comparative anatomy and paleontology evidence before they go to press.
It seems to bite them every time.
So, IMHO, even if someone is currently crowing about some irreducibly complex or "sudden appearance" in a trait today, I'd be very leary of betting on it standing up to rigorous scrutiny by the research community for very long.
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Another thing to remember is that proponants of evolution have been saying for YEARS that a lot of evolution has been in starts and fits. It isn't a gradual, steady increase from one end to the other, it happens in fits, leaps and bounds.
Because we are looking at it from such a distance it probebly looks smmother than it was...so even if a trait happens to appear to have sprung into existance fully formed that does not disprove evolution at all.
Actully, it reinforces the newer throries fo evolution quite nicely. Posts: 15082 | Registered: Jul 2001
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posted
In my Basis of Evolution class, we read about one theory that said the development of our brains and our intelligence coincided with the increase in temperature over time. It isn't a gradual thing, sort of leaps around a bit. It seems an odd theory, but I think coupled with a few other theories about the development of our brain size and our intelligence, it may work at least somewhat.
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quote: When I say the next generation is born with adapted lungs, I mean the entire generation. Everybody.
Hm. I find this unlikely. Moreover, I can't imagine what kind of archaeological evidence could exist to support this claim.
But there are a few possibilities, even if you grant this bizarre claim. Consider that everyone may have a latent gene which only triggers certain lung formations under certain environmental conditions. Under other conditions, this gene was largely useless; it didn't provide a significant benefit or a significant cost, but WAS important enough at some point in the distant past to spread through the gene pool. When those environmental conditions went away, the lung formation also went away. When they came back -- or when something close enough to the original trigger happened -- the lung formation came back.
I think it's far more likely that she's just misunderstanding the fossil record, but I'll give her the benefit of the doubt.
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posted
My understanding was that the lung thing was a hypothetical example -- not something that the author claimed had actaully happened.
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posted
From what I can remember, one of the things she said was that the sphenoid change was a trigger for a whole raft of other changes, like a domino effect, that under traditional evolutionary theory required a lot of mhit and miss, but didn't with her idea. This is because the sphenoid bone is the foundation of the skull, and by extension (because of the effect its positioning has to do with the angle the spine enters the skull) the whole body. For example, the sphenoid angle tilts, the face lowers, the eyes "move" to a position which allows for stereoscopic vision. The sphenoid tilts, the spine enters the skull at a different angle, resulting in a more erect stance. I have no idea whether this qualifies for ID or not, and she made no mention of that in the show, I just find it fascinating, the whole idea I mean, and it made me wonder if that could possibly be applied to intelligebt design, the fact that these changes don't seem to be accidental, but "built in", for want of a better phrase. I haven't been able to find a decent link that isn't in French!
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quote:I think it's far more likely that she's just misunderstanding the fossil record, but I'll give her the benefit of the doubt.
Tom, she has the enthusiastic support of Philip Tobias, Nobel prize-nominated South African paleoanthropologist, so I don't think she can be dismissed that simply.
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posted
Tom, what dkw said. My lung hypothesis was just an example of a way I thought her findings might manifest. It never happened. I just said I thought her evidence said such a thing might be possible.
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posted
This might be an instance of intelligent design, but it could also be a variation of evolution. That's the trouble with these two theories - most evidence fits both mechanisms equally well.
quote:Hm. I find this unlikely.
Yes, but isn't the reason you find it unlikely because it would violate evolution's paradigm? Are you sure you aren't rejecting the evidence against the conclusion just because it is evidence against a conclusion you believe in?
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"Yes, but isn't the reason you find it unlikely because it would violate evolution's paradigm?"
Yep. When there are two possible and approximately equally likely interpretations of the same data -- see that sphenoid thing -- the one that doesn't require a new paradigm seems likelier.
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