I
get the concept that animals with similar features could be related
via a common ancestor. It's not an entirely unreasonable conclusion.
However, we also see similarities in animals that are not closely
related according to evolutionary theory. There's the example of
marsupial moles and placental moles. Marsupial mammals and placental
mammals supposedly split tens of millions of years ago. Marsupial/placental moles are not supposed to be as closely related as humans and chimps
are supposed to be yet I believe the different moles resemble each
other far more than humans and chimps do. If similarity is supposed
to be evidence for common descent, then why are the different moles
(who are far more distantly related) more similar than humans/chimps
(who are supposed to be more closely related)?
When
animals that aren't closely related resemble each other,
evolutionists say that it's the result of convergent evolution. They
say that form-follows-function and since both moles live in similar
environments, over “millions of years” of undirected mutation,
they evolved similar traits. The
Encyclopedia of Science put it this way,
“One
of the reasons that convergence happens is that some body structures
and shapes are simply the best biological solutions to basic problems
in physics.... Convergent animals may look alike but it is easy to
show that they are entirely different creatures with very unlike
ancestors – their resemblance in appearance is not due to close
relationship. The structures which give the resemblance often do not
develop from a common feature in an ancestor.”
That's
interesting. OK, it's not really that interesting; I mean to say
it's revealing. It's an example of evolutionists wanting to have it
both ways. Creationists have attempted to point out to evolutionists
that similarity is not necessarily evidence of common ancestry. To
demonstrate this, we sometimes point to similar created things as
examples. Evolutionists object saying it's not fair analogy to
compare living things with created things. However, in the case of
moles we see two living things that are similar and not closely
related. What's their objection now?
So
let me get this straight: similar features between creatures could be
due to common ancestry (as in humans and chimps) or not due to common
ancestry (as in marsupial/placental moles). Is that right? How
convenient that, either way, evolutionists still see it as evidence
for their theory! It seems to me that evolutionists already know
that similarities between creatures is not de
facto
evidence that they are closely related in an evolutionary sense.
We've been trying to tell them that for years! What I wonder is why
do they keep trotting out similarities between humans and chimps like
it's somehow proof
of something?
What
we're left with is a bifurcation: similarity is either the result of
common ancestry or convergent evolution. They stubbornly leave out
the third option – similarity is the result of design!
I need to throw some technical jargon at you. Homology is similarity that is explained by common ancestry; homoplasy is similarity that is explained by convergent evolution. Now, that may seem either circular or arbitrary, but the concept of homology was derived before evolution was invoked to explain it, and homology can be recognized without resort to evolution. Richard Owen, in the early 19th century, defined the term as "the same organ in different animals under every variety of form and function." A modern definition would be something like "detailed similarity in structure that is not required for similarity in function" (e.g. given that bats can fly, we know that the wings of a robin and an eagle -- much less a robin and a penguin -- don't need to resemble one another as thoroughly as they do in order to function). Homoplasy, by contrast, is recognized by and might be defined as similarity that does not go beyond that required by similarity in function.
ReplyDeleteNote that the same structure might be homologous and homoplastic at the same time in different respects. Just as a bat wing and bird wing are homologous as forelimbs but analogous as wings, the forelimbs of marsupial and placental moles are homologous as mammalian forelimbs but homoplastic as burrowing adaptions to that common small mammal heritage (in most respects, both animals retain the basic mammal body plan that you can see in, e.g. Juramaia which you wrote about earlier).
Now, about chimps and humans: the detailed similarities in our GULO pseudogenes is surely an example of homology by the definition I offered above. Todd Williams has pointed out rightly that it has not been proved that the GULO pseudogene is without function (note that the original evolutionist definition of vestigial structures, offered by Charles Darwin, noted that a structure could lose its most important or conspicuous function but remain perfectly functional for secondary purposes), but given that it clearly doesn't help us make vitamin C, there's no reason it has to be prevented from making vitamin C by the exact same feature that is also seen in chimpanzees, gorillas, orangutans, gibbons, and macaques.
There are a host of such detailed similarities between humans and other African apes, both genetic and anatomical (e.g. we can't clutch our feet into fists like a chimp, but we -- or most of us (some humans lack it entirely) have a plantaris tendon with detailed resemblance to the one chimps have. There's no reason to suppose these similarities are required for similarities of our lifestyles: were that the case, we'd expect chimps to show more genetic similarities to gorillas, or orangutans, or even to macaques, than to us.
Unfortunately, evolutionists are committed to the philosophy of methodological naturalism, so they MUST find a natural cause for everything. And if something appears to contradict the current evidence they're running with, then they invoke a new rule that takes care of all the exceptions. Voila, convergent evolution! Voila, punctuated equilibrium! Or as in the case of Richard Dawkins and the discovery of function in most of our so-called 'pseudogenes,' he'll just do a complete 180 and pretend he had it right all along. It's intellectually dishonest.
ReplyDeleteI just wish they would admit that it's simply a worldview, rather than pretend it's as evident as...I believe 'gravity' is the term they like to use.
Todd: first of all, everyone is a methodological naturalist in all areas except where he has arbitrarily carved out exceptions: "here, evidence is irrelevant; my conclusions are justified by my faith."
ReplyDeleteSecond, it's hard to see how convergent evolution can contradict evolution: what mutations and natural selection can do once, one would presume they could do more than once (cf. Nilsson & Pelger's "A Pessimistic Estimate of the Time Required for an Eye to Evolve" -- note that this "pessimistic" estimate is 200,000 generations -- and the wide variety of box-camera eyes in different phyla).
Third, "punctuated equilibrium" was devised as a theoretical concept by Ernst Mayr before Gould and Eldredge sought to demonstrate it using the fossil record. Note that "punk eek" doesn't mean, e.g. "a Compognathus laid an egg and a bluebird hatched out of it;" it means that speciation, rather than occurring over hundreds of thousands or millions of years over the entire range of a population, occurs over mere hundreds or thousands of years in isolated populations while most of the species continues unchanged until replaced. Darwin anticipated something of the sort when he noted that species probably spent more time not evolving than they did evolving.
Fourth, pseudogenes are defined by not coding for the proteins that are coded for by the functional genes they closely resemble, not by doing nothing whatsoever. As I noted in my post above, a vestigial structure may retain some secondary function; in principle, it may even evolve some entirely new function (again, think of penguin wings, functional as flippers but not so much so as wings). Whatever, e.g. the singular GULO pseudogene, or the nine broken copies of the single functional cytochrome-c gene in our and chimp genomes, might do, they don't code for the enzymes l-GGLO or cytochrome-c.
Note that Mayr, when first hearing about "junk DNA," assumed that these sequences must do something; he thought that natural selection would weed out sequences that did nothing for the organism. One of Dawkins' ideas in The Selfish Gene was that some sequences might be purely parasitic: they do something for themselves (get copied from generation to generation), but not necessarily anything for their host.
I don't, by the way, think that functions have been discovered for "most" pseudogenes. Creationist articles mention findings of function, not findings of pseudogenes that don't have known functions. For that matter, even mainstream science journals are unlikely to run articles saying "yet again, we fail to find a function for this or that pseudogene."
Steven J., you said, "first of all, everyone is a methodological naturalist in all areas except where he has arbitrarily carved out exceptions: 'here, evidence is irrelevant; my conclusions are justified by my faith.'"
ReplyDeleteI don't agree with a couple of the things you said here. I think this statement might assume a priori that naturalism is true, and that the theist just makes exceptions for certain phenomena. RK and I differ in that I lean heavily towards an old-earth progressive creationist model, so I feel I'm still open to evolution being true. (I know this opens a can of worms theologically) So I don't feel like I "arbitrarily carve out exceptions," but rather weigh the evidence. And the more I study evolution, the more unlikely it seems to be true. Philosophically, materialism itself is very weak in my opinion, which weakens the argument for evolution for me significantly.
The other thing you mentioned, and I'm not sure where you quoted it from, is about faith in absence of evidence. I think this idea is a big misnomer about creationists like myself. I'll grant that I don't have a clue as to how God engineered us, but it's not that belief in and of itself that causes me to discount evolutionary mechanisms, although the presupposition probably does have an impact on how I view evolution's theories. (after seeing a tumor disappear with my own eyes, it's not a stretch at all for me to believe God can create us miraculously "from the dust of the earth.") Do know that I fight my creationist assumptions and attempt to view evidence in a neutral light, however. I'm honest enough to admit that two things make this especially difficult for me, though. One, the unlikelihood of a purely materialistic beginning to our universe and two, my sensory, circumstantial and historical evidences of Christ.
Anyway, I know this is way off-topic, but perhaps will offer an understanding of my views. I appreciate you reading.
You mentioned PE in reference to speciation. I don't doubt the rapid speciation during the Cambrian Period. I just doubt that PE is what kicked off the sudden appearance of higher life forms in such a short period of time like I hear many evos argue. It just seems too convenient for evolutionists to say in effect, "Evolution takes hundreds of millions of years, except when it doesn't." I think this is in effect what RK is saying about moles, if I may paraphrase him, "Similarity is evidence of linear evolution along a particular clade, except when similarity to an organism on a different clade shows convergent evolution."
A couple of points:
ReplyDelete"Methodological naturalism" is less a conclusion than a method; it is not an ontological position (a position about the sorts of things that can exist), but rather an epistemological one (a position about how we can know things -- in this case, by discovering consistent patterns of cause and effect).
"Speciation" means how, e.g. something like a brown bear gives rise to something like a polar bear. Something like a weasel giving rise to the first bears, or something like a lungfish giving rise to the first bears, involves many, many incidents of speciation and adaption (which are not the same things and may or may not occur at the same time). Punctuated equilibrium is not offered as an explanation for the Cambrian explosion, but for, e.g. the geologically-instantaneous replacement of one species of trilobite by another in the same genus, without intermediates between the two species (a series of species, on the other hand, will often provide intermediates between two genera).
Many different evolutionary explanations have been offered for the Cambrian explosion; one is the first appearance of hard parts (shells, etc.) that make fossilization much more common. There are Precambrian fossils, including animal fossils, but they are rare and often hard to interpret.
I appreciate that you don't try to shoehorn PE as an explanation for the Cambrian Explosion. Unfortunately, it's the typical response I get from atheists/materialists/evos.
ReplyDeleteYou said, "Many different evolutionary explanations have been offered for the Cambrian explosion; one is the first appearance of hard parts (shells, etc.) that make fossilization much more common."
It may not have been your intention, but this seems to imply there was an incremental addition (hard parts) to what was already a very diverse selection of fauna. I wouldn't consider the Ediacaran organisms to be an obvious evolutionary precursor to the complex body plans of the Cambrian organisms by a long shot. Even the apparent appearance of sponges 650mya isn't particularly compelling, as sponges are really just colonial aggregates, not true multicellular organisms--and pushing eumetazoans into the Precambrian is very suspect.
Second, wouldn't this explanation contradict the existence of thousands of soft-bodied fossils that have been found in the Cambrian period that fossilized just fine?
Todd and Steven J,
ReplyDeleteI'm sorry I haven't been responding to your comments lately. I see, though, that you have been keeping each other busy with discussion.
I've had more demands on my time than usual. Into the indefinite future, I'm not sure how much time I'll have to even write on my blog. I certainly don't want to abandon my blog; I don't even want to post too infrequently because I know people will stop visiting unless new content is posted fairly regularly. I'm trying to think of better ways to organize my time. Until then, please keep visiting.
Let me just make one quick response to Steven J: I think you've once again dodged the main point of my post and taken off onto a tangent. I'm not going to accuse you of using a red herring but I know that you're bright enough that you should at least understand the point I'm making so I'm not sure why you won't address it directly.
Thank you for the technical definitions but they aren't relevant to my point. Evos have used the similarity between humans/chimps as evidence that they have a common ancestor. However, animals that aren't closely related can be similar. Therefore, similarity is not NECESSARILY evidence for common descent. So the similarity between dinos/birds, for example, isn't necessarily evidence for common descent – even according to your own theory.
Thanks for your comments. Keep visiting. God bless!!
RKBentley
Todd: there are rare sites (Lagerstätten is the technical term) that preserve soft tissue in fine detail. They are not typical of fossil sites, and the details that are preserved in Lagerstätten are absent from most fossils and most places. The Burgess Shale, a famous mid-Cambrian Lagerstätte, preserves only a tiny slice of the Cambrian in one small area. The fossil record gets worse the older it is (the older the period, the less likely that unaltered sedimentary rocks from it will remain on the surface where paleontologists can find them), and consequently, the "gappier" the fossil record becomes.
ReplyDeleteRKBentley: I think you're conflating two points. The human-chimp genetic homologies are systematic: these are not adaptive similarities in a few areas, but throughout the genome. Comparing different suites of genes (or different parts of the anatomy, for that matter) yields the same results. This is not "these two very distantly related moles have similarly adapted forelimbs and similarly vestigial eyes, but not unusually similar genes or other features not directly related to a burrowing lifestyle." This is "these two species of primates are eerily similar in respect after respect, even where the similarities (e.g. the plantaris tendon) make no adaptive sense whatsoever." Consistent and systematic similarities of this sort are explained in terms of common descent.
Now, yes, in principle, one need not do so. I concede this. One could explain this in terms of common design. The trouble is, as noted, that there is common design where there is no common function (that plantaris tendon again, or the GULO pseudogene if you compare it to, e.g. the functional GULO genes in New World monkeys). Elsewhere in nature, there is common function not using common design (e.g. insect eating birds and bats). You can attribute all of this to the ineffable design philosophy of a special Creator, but without such an a priori faith commitment, the obvious explanation, in terms of observed processes (reproduction, inheritance, mutation, selection, etc.) is common descent with modification.
Steven, you said: "The fossil record gets worse the older it is (the older the period, the less likely that unaltered sedimentary rocks from it will remain on the surface where paleontologists can find them), and consequently, the 'gappier' the fossil record becomes."
ReplyDeleteIf I'm understanding you right, this once again infers a gradual accumulation of fossil data as time progresses. But this is not what is seen in the fossil record.
You used the word 'gappier,' but I think that is an incredible understatement to explain the sudden onset of fossils, especially since soft-bodied fossils are preserved just fine in the Cambrian. There was a lot of nothing, then a lot of fossils. With due respect, that's not a gap. I'm also not sure what Lagerstätten fossil sites have to do with the ongoing evolutionary problem of the sudden arrival of fossils in the Cambrian.