A recent report noted that studies that rely on evolutionary processesto explain, say, antibiotic resistance among pathogens, tend not to use the "E-word" in medical journals, instead using terms like "emerging", "spreading" and "increasing". The reason appears to be the bad connotations "evolution" has in American contexts.
There is much misunderstanding of this term, and people often pack a lot of differing concepts under it. Consider this rant by a creationist in The American Spectator: there are "six types of evolution" according to him. They are cosmic evolution, chemical evolution, stellar evolution, organic (or organice [sic]) evolution, macroevolution and microevolution. Apart from being deeply ignorant about all the topics he classifies, some of this is just ridiculous. Why is chemical evolution (or as scientists refer to it, nucleosynthesis), which occurs in stars, separate from stellar evolution, which is the sequence of transformations stars undergo as they use up their fusion fuel? Does evolution require "something from nothing" as in spontaneous generation? This is a classic case of the sorts of strawman view of evolution that Edward Humes discusses when he notes that there is the real theory of evolution, as discussed by biologists, and the cartoon version that creationists discuss in order to inflame rejection against evolution itself.
So, what is evolution? Is it true that evolution requires all the transforming processes from the beginning of our universe to now to be accepted?
Let's look at cosmic evolution - this is a process that is fully deterministic, given what the universe started with (mostly hydrogen and some helium). These elements plus the energy of gravity necessarily requires that stars and galaxies will form, that there will be novas and supernovas that form heavier elements, and that planets will aggregate around some stars. None of this is controversial. And it has nothing whatsoever to do with biological evolution. It is entirely possible that a universe such as ours would share the same physical laws, but never actually include a planet where life developed. Or in other words, cosmic evolution is consistent with a lack of biological evolution.
Next, let's look at the origins of life. Typically, this is held to be something yet to be explained, and it is not in itself an evolutionary process. Why? The answer is that whatever processes that generated the first living beings, they had to be chemical processes, and would be a matter of the deterministic (that is, necessary) outcomes of the properties of chemicals of that kind. We know that most of the building blocks of living systems, apart from, so far as I know, nucleotides, can be synthesised in natural conditions, such as outer space. We know the properties of these chemical. We may one day be able to make something very like the origins of life occur in a lab, although we'd have no way of knowing if that was the same as the historical event, especially if there are, as seems likely, many ways this could have occurred. But that there is life is the necessary condition for evolution to occur, and it is not explained by biological evolution. [I would argue though that the processes that give rise to diversity of life can be used to explain the origins of life, through a process called chemical selection, which is different to selection in biology in many ways.]
A cautionary note: spontaneous generation was always the notion that modern organisms rise spontaneously, and not from nothing, but from the by-products of life, such as decaying matter. I have a historical review of this here. What we are talking about now is abiogenesis, which is the origin of life, again not from nothing, but from non-biologically derived chemicals. Creationists systematically misstate abiogenesis and deliberately conflate it with spontaneous generation.
So now we reach biology. Evolution requires that there is at least a few kinds of living organisms, interacting in ecological ways. The biological theory of evolution is really a family of concepts, and the crucial ones here are common descent and natural selection. To be clear about what we are discussing, let us call the first phylogeny and the latter selection models.
Phylogeny is the theory that if there is a group of closely related organisms, as determined by their sharing many characters such as spines, beaks or anatomical specialisations, then the most parsimonious explanation is that they inherit these similarities from a shared ancestral species. Individual characters (like the peacock's tail, or the tail sword of a guppy species) can be individually evolved, but even so, the entire group of guppies will be similar in most other respects. Likewise, the shared anatomies of the African and Asian apes and humans indicates that we shared a common ancestor, despite our individual differences. When a species splits into two (speciation), this is called "macroevolution", or evolution at or above the level of species. Large-scale patterns of speciation form macroevolutionary patterns or trends.
Notice that this implies that it is not true, as our creationist ranter has it, that any animal (or other kind of organism) can give birth to any other. Cats will never give birth to dogs, because the number of characters that differ between them are too great. Cats, if they evolve into anything, will give rise to some very catlike creature, not dogs. If we did see a dog born of a cat (or a dog species born of a cat species), that would be a disproof of the general phylogenetic hypothesis.
Selection models treat each variable in an organism's genes or morphology as having different fitness values. This means that variants will be better or worse at enabling the organism to survive and breed. Genes form a kind of "space" in which combinations of genes in genomes have a higher or lower average fitness, and the fitter ones usually end up taking over the population, or finding some balance between the varieties.
Now when we speak of "evolution", we sometimes mean phylogeny, and sometimes mean selection. But the two are not the same thing. Macroevolution can occur without there being any selection involved in separating species. And selection can either change a population, or make it more tightly focused around the "wild type" or the mode of a genome. Selection acts as a brake, as a tractor, or as a trench digger dividing a population, depending on the conditions. So when medical researchers use the terms "emerging", "spreading" and "increasing" to talk about antibiotic resistance, they are talking about changes in the genetic varieties in a population. They aren't talking about phylogeny, necessarily. But they might be, if the selection occurring makes the pathogens separate into two distinct groups.
The word "evolution" comes from the Latin, in which it means the unrolling of something (like a scroll) which is already there. Cosmic, chemical and stellar evolution are evolution in this sense. So too is the older meaning of "evolution", in the 17th and 18th centuries, which applies to what we now call development, the growth and maturation of the organisms in a typical lifecycle. Nothing is new. But biological evolution is a different process. Novelties are formed from prior structures and functions that did not have the new features potentially or unexpressed.
So it would be best to restrict the word to the evolution of new varieties over time, including novel species, and larger groups. Selection, and other population level mechanisms, are the causes of these processes, and should be taken separately. There is nothing sacred about the "e-word" - note that Darwin did not even use it in our sense in his Origin of Species in 1859, because the term had been used previously for views of the transformation of species, like Lamarck's, that saw it as development writ large, and in which all evolution was an inevitable unfolding of prior potentialities. Darwin's view is quite different, and I would be happy not to use the "E-word" at all. So long as we are talking about the current views in science that matter, and not some grubby decaying strawman.
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Nicely done, John!
http://www.gookalian.com/oolong/gallery/3/iya
Eh, well it's been awhile since I engaged the discussion so I may be a little rusty on my arguments, but here goes.
~ What we are talking about now is abiogenesis, which is the origin of life, again not from nothing, but from non-biologically derived chemicals.~
Uh, so we aren't talking about life coming from nothing, but life coming from non-life chemicals? (which came from nothing?) Seems like a little bit of rewording the same thing. Can life come from non-life?
~ Phylogeny is the theory that if there is a group of closely related organisms, as determined by their sharing many characters such as spines, beaks or anatomical specialisations, then the most parsimonious explanation is that they inherit these similarities from a shared ancestral species. ~
Ok, that's fine. I would think that the Creationist term, baraminology, would be a similar kind of term. But, who is to say (or more specifically, where is the evidence) that the "shared ancestral species" isn't just a previous variation on the same animal? A hundred species of guppies might all point back to a single species of guppies, but does that mean the guppies at one time were something other than guppies? I could just as easily say that the shared ancestral species is just a "kind".
~ When a species splits into two (speciation), this is called "macroevolution", or evolution at or above the level of species. Large-scale patterns of speciation form macroevolutionary patterns or trends.~
Sure, but is there evidence of this? Your interpretation of the data is that a certain species can be traced back through the evolutionary steps into another species and so on down through the chain. But my interpretaion of the same data leads me to see that species do adapt and change but not enough to be something other than what it already is. You can call it macroevolution if you want but that doesn't mean a guppy came from a non-guppy or a cat from a non-cat somewhere far in the past.
~ Cats, if they evolve into anything, will give rise to some very catlike creature, not dogs.~
But, what you are also saying is that somewhere in the distant past, there was some form of a cat/dog species that split and evolved into the two separate animal types. But why couldn't it be that there was no cat/dog species but always has just been cats and dogs? What evidence is there to indicate a creature that preceeded the two animals?
Ok, your turn. :) heh.
z.
Can life come from non-life?
If there was once no life and then there was, then of course. Even the Bible suggests this. But what is "non-life"? It is simply the set of all things that aren't alive. It is only a problem is "life" is defined as something quite distinct from non-living things, but modern science recognises that there is nothing that is true, physically, of living systems that is not true of non-living systems, apart from the dynamics of reproduction (and even there, similar processes occur in non-living things).
I would think that the Creationist term, baraminology, would be a similar kind of term. But, who is to say (or more specifically, where is the evidence) that the "shared ancestral species" isn't just a previous variation on the same animal? A hundred species of guppies might all point back to a single species of guppies, but does that mean the guppies at one time were something other than guppies? I could just as easily say that the shared ancestral species is just a "kind".
"Baraminology" is a bastard term (it's bad Hebrew, to begin with) that just means "kinds of things that are not derived from other things". It's question begging, in other words. The theory of phylogeny (not a bastard term, based on good Greek and scientific practice), is the hypothesis that shared traits indicate shared ancestry. If we define the term "guppy" as "fishes that share traits A.. N", then we can define the group guppies are part of as "A...X" and so on. Guppies are Acanthomorphs, Teleosts, Halecostomes, Actinopterygians, Gnathostomatans, Vertebrates, Craniates, Chordates, Deuterostomes, Bilaterans, Animals, and Eukaryotes, in increasing levels of generality. Where do we draw the line, if the evidence works at all levels?
my interpretaion of the same data leads me to see that species do adapt and change but not enough to be something other than what it already is. You can call it macroevolution if you want but that doesn't mean a guppy came from a non-guppy or a cat from a non-cat somewhere far in the past
What it already is, depends very much on how we draw our categories. There's no evidence that there is some privileged level of class or kind in biology, and plenty of evidence that kinds shade into larger more inclusive kinds. A "non-cat" is either everything that lives and is not a (modern) cat, including fungi, grass and bacteria, or it is just some arbitrarily chosen break point in the taxonomic tree. Either way, evolution is not dependent on us and our categorisations.
what you are also saying is that somewhere in the distant past, there was some form of a cat/dog species that split and evolved into the two separate animal types. But why couldn't it be that there was no cat/dog species but always has just been cats and dogs? What evidence is there to indicate a creature that preceeded the two animals?
Yes, there was once a carnivore that was neither a cat nor a dog (nor a bear, nor a weasel, etc). We have some fossil evidence for these kinds of carnivores. More compelling, though, is the evidence of molecular data, in which the more phenotypically similar organisms, those which share anatomical differences, also share gene and protein similarities not shared by other organisms. The evidence compels those who are working in the field. Of course it is always logically possible, or conceptually possible, that they did not have a common ancestor. It is also possible the universe, is rotating once every 24 hours or so. But the evidence is against it.
This is not a forum for extended debate, though, and I'm very pushed for time. You might like to take this to talk.origins if you'd like to honestly debate these issues.
Here's a reference on nucleotide synthesis:
JournalOrigins of Life and Evolution of Biospheres (Formerly Origins of Life and Evolution of the Biosphere)
PublisherSpringer Netherlands
ISSN0169-6149 (Print) 1573-0875 (Online)
SubjectBiomedical and Life Sciences and Earth and Environmental Science
IssueVolume 6, Numbers 1-2 / January, 1975
CategoryPart III/Abiotic Organic Synthesis and Interactions: Polymers
DOI10.1007/BF01372401
Pages163-168
Alan W. Schwartz1, M. van der Veen1, T. Bisseling1 and G. J. F. Chittenden1
Dept. of Exobiology, University of Nijmegen, Nijmegen, The Netherlands
(Abstract) Mineral phosphate (apatite) is activated for the synthesis of nucleotides when dilute solutions containing nucleoside and ammonium oxalate are evaporated in its presence. A natural, igneous flourapatite was found to be even more effective in nucleotide synthesis than the more soluble hydroxylapatite. The phosphorylation is considerably more efficient if urea or cyanamide is also present. Hydrolysis of solutions of cyanogen to form oxalate and urea among other products is a spontaneous process that provides a geologically plausible model for nucleotide synthesis on the primitive earth.
http://www.springerlink.com/content/u79339n3vwh85885/
Geologically plausible, but not yet observed. We have precursor molecules for almost everything else, but I am unaware of any observed natural synthesis of nucleotides. Of course this may just be because we'd not be able to discriminate naturally occurring nucleotides from biotic ones. Or maybe one day we will find some volcanic spring which generates some.
Yep, I suspect it's effectively impossible to distinguish chemically generated nucletides from biological debris, they're just too pervasive. It's a problem even in the lab, just keeping random bits of RNA out of experiments, so in the dirty old world outside, I wouldn't fancy the chances.
Found a much more recent abstract proposing a more detailed mechanism. Seems plausible, but organic chemistry was a long time ago! I appreciate your distinguishing proposed and observed, though.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1550712
~~This is not a forum for extended debate, though, and I'm very pushed for time. You might like to take this to talk.origins if you'd like to honestly debate these issues.~~
Yeah, I know. I just figured I would post a few comments considering the topic of the post is on evolution. I won't drag out any kind of argument here.
~~Of course it is always logically possible, or conceptually possible, that they did not have a common ancestor.~~
That is what I was basing my first comment on. I am just trying to point out the other interpretation of observed data. Its the old common ancestor vs common creator argument.
z.
That list of 6 types of evolution is almost verbatim from a Chick tract: http://www.chick.com/reading/tracts/0055/0055_01.asp
Ah, yes, my memory censored that piece of tripe...
Short proof of common descent/phylogeny/macroevolution:
Empirical: all animals have parent(s)
Empirical: once there were no mammals
QED
(not original; Lewontin, I think)