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The Theory of Evolution: Evolving!
Medopine
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This is a thread about theories of evolution as it relates to biology, that is, the development of life. I would like to discuss theories of evolution and how they differ, what kind of scientific evidence they rely on, and so forth. This discussion idea stems from a recent conversation with someone I know who is skeptical of evolution as a widely accepted and rarely questioned theory. Her points are spoilered below and you may choose to respond to them if you wish as a jumping off point:
- It's not good science to form a theory of evolution and then go looking for the evidence. You should have evidence to base a theory on to start with.
- "Graduated evolution" isn't a good theory because there is not enough evidence, specifically not enough intermediary forms have been found (when asked about Archeopteryx, she expressed skepticism as to that famous fossil's authenticity)
- No one can talk about evolution critically because if you question the theory you are immediately thrown into the camp of the creationists
- If forced to choose a current theory, she would choose Punctuated equilibrium over "graduated evolution"
- "Graduated evolution" isn't a good theory because there is not enough evidence, specifically not enough intermediary forms have been found (when asked about Archeopteryx, she expressed skepticism as to that famous fossil's authenticity)
- No one can talk about evolution critically because if you question the theory you are immediately thrown into the camp of the creationists
- If forced to choose a current theory, she would choose Punctuated equilibrium over "graduated evolution"
More generally, some questions:
- Is there a unified or widely accepted model for evolution within the scientific community?
- Is evolution a fact or a theory? Is it both?
- What are the problems with our theories of evolution?
- What is the concrete scientific evidence for the theory? How has the theory been tested and proven?
Basically, I'd like to hear what people know about evolution and really get into specifics as to how it works. Also I'd like to hear about any sort of alternative theories or differences in the scientific community that exist (for example punctuated equilibrium evolution). Additionally, we can discuss the problems with finding scientific evidence through a fossil record that is inherently going to be incomplete and sometimes insufficient. Drifting into geology might be acceptable here.
Please do not
- Talk about why religion is bad
- Talk about how creationists are stupid or intelligent design supporters are stupid
- Talk about religion at all, really
- Also please let's not talk about evolutionary psychology please please
I know this will be terribly terribly hard to do, but maybe we try hard, yes? I'm looking to talk about evolution and discuss possible scientific criticisms of the theory. Let's do it!
Addendum: Evolution theory describes the development of life but not the origins (see http://en.wikipedia.org/wiki/Abiogenesis). If you want to talk about the origins of life, leaving out religion entirely of course, make sure to follow the distinction between evolution and abiogenesis theories.
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Evolution is going to happen at the pace that happens to work, not in some predictable wavelength.
It's entirely possible for, say, a niche to become suddenly vacant and for no local creatures to happen to develop the mutations that would allow them to take over that niche. It's possible for this to NEVER HAPPEN before the sun envelops the planet. It's possible for it to happen entirely because this one bird took a crap on the wrong butterfly and bam, end of the first step in insectoid unicorns with eye rays, which is never again possible, ever.
EDIT: Never mind, clicking through your link now.
- Neil A. Campbell, Biology 2nd ed., 1990, Benjamin/Cummings, p. 434
So in other words:
Evolution occurs. Animals share common descent. These are facts.
How exactly the evolutionary process works - that's where the theories and debates lie.
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Technically speaking, all fossils are transitional, as evolution is an on-going process.
But for more specific exaples, talkorigins has a good page here.
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--
And yes, every fossil is transitional, and the connections are pretty easy to find if you just put a little thought into it.
I mean hell we still basically function the same way worms do. Food in through one tip and out the other.
More or less. Any controversy among actual scientists, when compared to the evolution vs. creationism/ID debate, is minor quibbling about details.
Pretty much the following are true about any mainstream definition of evolution:
Evolution is a change in allele frequencies in a population. In other words, take any particular group of organisms (a population), watch them over multiple generations, and some genes (alleles) will be more common (frequencies) in future generations than they were in prior generations (change). One common misconception is that evolution is concerned with how life began. It's not... life may have arisen from primordial carbon soup on earth, it may have come from a meteorite, it may have been magicked into existence by God. It doesn't matter; regardless of how the first organism came to be, evolution has guided its reproduction ever since then. (That said, the origin of life is a pretty interesting subject with implications for evolution, even though it is basically a separate discussion.)
There are multiple mechanisms for this change. Natural selection and random mutation are the most famous, but not the only mechanisms. Genetic drift and migration are also major forces. Horizontal gene transfer (where foreign genetic material becomes incorporated into the genome, either as a regular process among bacteria or caused by a virus). Another common misconception is to assume that all evolution is due to one or two mechanisms. Scientists may argue about the relative importance of the various mechanisms, but they will still acknowledge that multiple mechanisms exist.
This change need not necessarily happen at a constant rate. (See: your comments about punctuated versus gradual evolution above.) Evolution is definitely "punctuated," but how punctuated it is is subject to some debate.
This change eventually results in speciation.
Current or future generations need not be more complicated than prior generations. There are many parasites whose evolution seems to progress towards simplicity (fewer organs, structures, or stages in the life cycle) rather than complexity.
We have seen and recording immediate evidence of this process. Antibiotics resistance in bacteria is probably the most famous.
the "no true scotch man" fallacy.
It detailed the scientific history of evolution and quite simply enhanced my considerable appreciation and love of this, the corner stone of biology.
Essentially it seems your friend is A) wholly ignorant of how science actually progresses in general (regarding "going out and looking for evidence" and what does or does not make good science)
Though, on further introspection I'm not sure what exactly her position is. I mean, differentiating between Gradualism and Punctuated Equilibrium and criticising either is not even remotely verboten in any scientific circles. But both of them take for granted that common descent is a fact and that evolution occurs - and it's questioning that that gets you lumped into the same basket as the crazies. Her preferring a post-Modern Synthesis theory would rather suggest that she doesn't have a problem with the stuff which is beyond the pale to deny.
My confusion turns on the equivocation between theory of evolution as "common descent is a biological fact" (a misnomer, the theory of evolution explains the fact of common descent) and theory of evolution as "the mechanism and history by which modification via descent occurs".
I think that's mostly true, so I'd prefer to discuss it!
The average intelligent people that I know believe evolution is the correct theory of life's origins and development probably don't know exactly why it is the best theory possible. I confess I don't know that myself though I strongly believe evolution makes the most sense.
is this an acceptable discussion topic
They pop out of some hidden corner and spread like a virus, infecting all until they develop an immunity and it recedes into darkness
Actually I don't know what Lamarckian means
Well you've got a problem right there, because the origin of life is a separate issue from evolution.
That would be abiogenesis.
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Both.
There are two definitions to the word "theory."
When laypeople use the word "theory" in everyday conversation, they mean "something I think might be true but I'm not totally sure of."
When scientists use the word "theory" in professional discussion, they mean "an explanation for observed phenomena that predicts future related phenomena."
It's really unfortunate that the same word is used in both senses, because they're really two totally different things. It would be easier if laypeople used a totally different word, like ohidunno, "floogle." "I have a floogle that Mary got the promotion because she's screwing the boss."
Anyway, a scientific theory may be well-supported to the point where it is basically a fact, or it may be somewhat unfounded. "String theory" is almost purely conjecture. The theory of relativity is strongly supported. And the theory of evolution is even more strongly supported, to the point where it is both a scientific theory and a fact.
the "no true scotch man" fallacy.
Apo, I'm not sure what her position is either. She seems to believe that there is "a lot of misinformation out there" about evidence to support commonly accepted theories. She is studying biology in school but is heavily influenced by her boyfriend, who is religious but not rabidly so, and somewhat of a philosopher. I think she is struggling with aspects of her newly embraced faith and her strong grounding in science. I know she is an intelligent person. /shrug
Awesome. Viruses are really really interesting actually.
I'll edit the OP re: the origins thing.
One of my favourite stories of transitional fossils is that of Sphecomyrma freyi.
Back in the 60s one of the common ancestries that creationists latched onto as being "unsupported by the fossil record" was that of ants and wasps. As it turns out, the morphology of ants and wasps strongly suggests that ants descended from wasps, and at the time no transitional forms had been found.
This was considered by creationists as one of the jewels in their crown, a trump card, a killer argument (though, of course, those more knowledgeable about science and its practice as well as logistical realities of finding a particular transitional form saw through it). And so, creationists carped on with their usual tripe about how evolution was all unsupported malarkey.
Then, in 1966 a fossilised insect was found in amber, a perfect transitional form between wasps and ants, with the particularly characteristic features of both. A transitional form by the name Sphecomyrma freyi. and guess what, you never hear creationists talk about wasp ant transitionals anymore. Of course, that isn't to say that they've acknowledged S. freyi in any fashion whatsoever, they just ignore it completely and pretend the whole episode never occurred.
Didn't Darwin believe in a form of this too? With his gemmules and stuff? It was more of his explanation for genetics than evolution, IIRC.
the "no true scotch man" fallacy.
NOVA tries to be even-handed in presentation, however the evidence for Evolution is overwhelmingly strong even in this brief summary. The film makers do believe that god and evolution are not mutually exclusive, but from their footage alone god would have played little if any role in the resulting complexity of life. I was particularly impressed with the explanation for the missing chromosome in Humans (we have 23 as opposed to 24 in apes and chimps) and how evolutionary theory predicts how this might have happened. It's in chapter 6: A Very Succesful Theory.
Meanwhile we see the same debate playing out, all over again, over the evolution of the eye.
the "no true scotch man" fallacy.
I think talking to her would end up hurting me. But I am fascinated to know what her position actually is...
But Mendel's work didn't attract attention until basically the 1900s, after the important parts of the Darwinian revolution had come and gone.
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Yea, if some creationist walked up to me on the street and asked me to name a transitional fossil, I'd be fucked. I've got too much going on in my life to research this myself. But scientists tell me gravity makes the planets spin, and they invented garage door openers and jet engines, they've got a pretty good track record so far.
I think we understand gravity less than we understand evolution, and the only reason this is a muddy issue is the religion factor.
Actually, I'd be more interested in reading a gravity thread if there's any physics buffs around. I heard an interesting theory a while back that gravitational force bleeds across dimensions, which explains (A) why the gravity we measure off specific objects seems so much weaker than the other forces, and (B) why our measurements of the universe require an assload of "dark matter" to account for all the extra gravity. Much more elegant I think than there being a huge amount of stuff that happens to be completely undetectable.
I suspect she may not actually have a position. One need not have a position to feel smugly free-thinking by doubting all those pompous scientists, one merely needs to proclaim that the scientists don't have the whole truth (man, they aren't that smart)!
The irony being, of course, that scientists never claim that they have the whole truth; they merely claim that they have enough of the truth to ask the most intelligent set of questions.
the "no true scotch man" fallacy.
This is a fundamental truth about creationists, they never actually update the fundamental core of their tactics, just update it with new or otherwise interesting specifics no transitional forms for ants -> no transitional forms for dolphins -> no transitional forms for eyes and then the eye couldn't have evolved, too complex/what use is half an eye? to flagellar motor could not have evolved/what use is half a protein?
But on the other hand, we have pretty good series' of eye evolution in all sorts of realms, the problem is it's a little less discrete and concrete than a single critter which sits between two other creatures in terms of its features. So, they've opted to pretend like the fossils don't exist instead.
Yeah I think she's mostly skeptical at this point. It took a lot of pressing to get her to commit to punctuated equilibrium. I think she knows she can't discount evolution wholly. She's more likely looking for a way to distance herself from it, or something. I really don't know.
That so many different kinds of eyes exist is proof that they can develop.
An important thing to remember is that just because something is irreducibly complex now, it does not mean it was always irreducibly complex.
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Hey look there's an organism with a photosensitive cell!
Hey look there's an organism with a cluster of photosensitive cells!
Hey look there's an organism with a cluster of photosensitive cells, some of which are more sensitive to variations in frequency and others are more sensitive to variations in intensity!
Hey look there's an organism that's grown a protective membrane over its heterogeneous cluster of photosensitive cells!
Hey look there's an organism whose protective membrane focuses light on its heterogeneous cluster of photosensitive cells!
Oh shits look who just evolved an eye!
This isn't rocket surgery!
the "no true scotch man" fallacy.
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