Essay: The Tree of Life

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This essay is an original work by Philip J. Rayment. Please comment only on the talk page.


Contents

Background

On 23rd January, 2009, I posted the following entry in the Main Page News section[1].

Evolution is dead. Long live evolution! It looks like a "central tenet" of evolution—the evolutionary "tree" of life"—is being discarded.[1] But does this evidence mean that evolution is wrong? Of course not! We just invent a new version of evolution, because we can't have those "blinkered" creationists being right!.[2]

This was subsequently challenged, both off-site (in the Sock Drawer), and on the main talk page. I responded to one off-site challenge by User: Kallium[1]. The main-talk-page challenges are reproduced below:

The headline asks: "But does this evidence mean that evolution is wrong? Of course not! We just invent a new version of evolution, because we can't have those "blinkered" creationists being right!." This is problematic for several reasons. (1) Evolution is not the same as the tree of life. Descent with modification is still occurring, there are just more sources of modification than anticipated. (2) New "versions" are not just "invented" out of the blue. Revised versions of theories are generated using extant theory and research findings and, moreover, must account for as much or more phenomena than their predecessors. Anyone who thinks new theories are just conjured out of thin air has never been involved in scientific research. (3) It is a false dichotomy to assert that if some part of evolution is wrong then creationism is right. Many, if not most, creationist explanations I've seen use a model of separate creation where "kinds" are not related to one another. Evolution argues there should be relationships among all organisms. DNA evidence overwhelmingly supports the interrelatedness of all living things- it's just more complex than Darwin's original thinking led us to believe. This is not surprising as scientific theories get revised in light of new evidence. Yet, that added complexity doesn't negate the DNA evidence showing that all life is massively interrelated. In sum, then, certain details of a model can be wrong without that necessarily favoring an alternative explanation. Or, if you prefer an analogy, finding evidence that Catholicism is "wrong" doesn't automatically mean that Hinduisim is correct. (4) The article you cite remarks, "While vertical descent [i.e. the tree of life] is no longer the only game in town, it is still the best way of explaining how multicellular organisms are related to one another." Thus, the tree of life remains a useful approximation at one level of analysis, much as Newtonian mechanics remain a useful approximation of relatively for most day-to-day activities. One could argue that Einstein showed Newton to be wrong (specifically: he showed why Newton was wrong) but it's more appropriate to say that Einstein produced a model that was more accurate. -Drek
I have to thank Conservapedia for bringing this article to my attention, I can't remember the last time I've seen a major scientific theory go through a revision like evolution is facing. The article does mention, many times, that just because the "tree of life" is being rethought to be more like a "web of life" by no means makes evolution wrong. It's a blessing to live in this day and age with so many advances in what we can see, measure, and experiment with. The outcome of these debates will serve to refine and strengthen the theory of evolution and help fill i some of the "holes". It is amazing to be able to watch scientific history being made.ShawnJ 10:25, 23 January 2009 (EST)
I find it annoying the degree of sensationalism applied to the New Scientist article. We even have an article on the key point as to why the tree of life metaphor is out dated. There is nothing in the article that "Kills" the theory of evolution. If anything the research into HGT and LGT has been through enough testing to shift some of the unclear areas of evolutionary theory into better focus. To add the tree of life metaphor is still useful to illustrate the connectivity of organisms on the planet, just not to the degree needed in the molecular sciences. After all how many non-biological science people truly understand the differences in eucaryota, archaea and bacteria? (This is important since it is the key area where HGT and LGT really make a difference).--Able806 11:15, 23 January 2009 (EST)

Clarification

First, as I noted in my reply to Kallium, the news entry I posted was a little bit tongue-in-cheek and exaggerated. Or "hyped" may be a better word. Evolution is not, of course, dead, and that was the point: it should be dead, but isn't (hence the "long live evolution" remark). And of course the New Scientist article and editorial that the item was based on did not indicate that a motive for retaining evolution was because they didn't want the creationists to be right.

However, despite a bit of hype in the news entry, I believe that it makes a valid point, and I'm here going to defend the item against its critics.

Is evolution really dead?

No, of course not. But that's the point. It should be dead, but it won't die.

Drek claims that "evolution is not the same as the tree of life". Isn't it? Well, that's one of the problems. Evolutionists keep switching the definitions. So just what is evolution?

Actually, there's a point that needs to be made before even that is answered: Creationists don't disagree with everything that's claimed under the banner of "evolution". So what is it that creationists disagree with?

Well, there are a lot of details that creationists disagree with. But the main thing they disagree with is the whole "descent with modification" aspect, or the evolutionary "family tree". To clarify, they don't disagree with the following:

  • genetics (let alone the rest of science, as numerous anti-creationists claim. And genetic was discovered by a creationist),
  • speciation (they even claim that speciation occurs more readily than many evolutionists would consider),
  • natural selection (described by a creationist before Darwin),
  • the existence of inheritable mutations, or
  • horizontal gene transfer.

A key aspect of evolution is the claim that similarity of living things shows an evolutionary/heredity relationship between them. This is also one of the key pieces of evidence offered in support of evolution, despite it long ago being shown to be a fallacious argument (see next section). This is still evident in claims such as the similarity between humans and chimpanzee DNA: the argument is, we must be closely related because the DNA is so similar. The underlying argument is, only evolutionary descent with modification explains the similarity.

Indeed, Drek (above) used this very line of argument: "Evolution argues there should be relationships among all organisms. DNA evidence overwhelmingly supports the interrelatedness of all living things".

When is evidence for evolution really evidence for evolution?

One major problem with much of the claimed evidence for evolution is that is simply doesn't qualify, because it is not evidence that distinguishes between two competing claims.

To use a hypothetical example, suppose there was one camp who believed that the first people to reach Australia were southern Africans who sailed across the Southern Ocean, and there was another camp who believed that the first people to reach Australia were South Americans, who sailed across the Pacific Ocean. Then someone from the "out of southern Africa" camp finds fossilised human footprints dated to the time of the human inhabitants, and claims support for his camp, because his camp believes that the first inhabitants to arrive from southern Africa would leave footprints. Does this show that his view is correct? Of course not, because the opposing "out of South America" view would predict the exact same thing!

This is analogous to the homology argument of evolutionists and creationists, including Drek's argument quoted above. Evolutionists claim support for their view because of similarity of living things, which they claim demonstrates a common origin. They did this on the morphological level, and they do it on a genetic level. (More on this below.)

But creationists claim that their view also explains this. They attribute similarity of living things to a common designer. That is, they claim that the Creator would tend to use the same design for different living things. They further claim that this would apply both at a morphological level and a genetic level.

So Drek's claim that "Evolution argues there should be relationships among all organisms. DNA evidence overwhelmingly supports the interrelatedness of all living things" is matched by the creationist claim that "Creation argues that there should be some common design among all organisms. DNA evidence overwhelmingly supports some common design among all organisms". (For those wanting to read further on this, The Biotic Message by Walter ReMine is on this very topic of common design.)

Whilst the creationist claim that God would re-use some of His designs is not something explicitly stated in the Bible, the pertinent point in this debate is that this could be the case, whereas the evolutionary argument presumes that it's not the case. This is something that evolutionists have not shown.

So the "similarity" or "homology" argument fails to distinguish between the two competing claims of evolution and creation. We must look elsewhere for evidence that actually favours one view over the other.

Which argument better fits the evidence?

In the creation/evolution debate, we are talking about unique past events. We cannot recreate the original creation, to see if works. Neither can we recreate fish evolving into amphibians to see if that idea works. Both claims are beyond normal scientific testing. However, we can see which claim the evidence better fits, or is more consistent with.

Let's return to our hypothetical example. Suppose that someone found the remains of a boat on the west coast of Australia, and the design of the boat was identifiable as being southern African. Does this therefore prove the "out of southern Africa" hypothesis? Some might think so, but in fact the "out of South America" camp simply "revised" (Drek, ShawnJ) "rethought" (ShawnJ) "refined" (ShawnJ) "updated" (Able806) their hypothesis, making it "more complex" (Drek), by claiming that the South Americans didn't sail east to west across the Pacific. No, they actually sailed west to east across the Atlantic then the Southern Ocean, stopping off in southern Africa, where they traded in their worn-out boat for a new one. This "revised", "rethought", "refined", "updated", "more complex" theory thereby explained the evidence of a southern African boat on the west coast of Australia when it had in fact been settled by people from South America.

Do you think that the "out of southern Africa" camp would find the explanation convincing? And which argument do you think that an undecided bystander would find the most convincing?

Evolution argues that similarity is due to common descent. So when scientists find similarity that is not due to common descent, it should be a problem for evolution. Thus "convergent evolution" is tantamount to an oxymoron, because it's an example of similarity that is not due to common descent. The current claim about horizontal gene transfer is yet another example of similarity that is not due to common descent.

But just like the "out of South America" camp's argument, the hypothesis can be "revised", "rethought", "refined", or "updated" to accommodate the new evidence. But reject the idea in favour of a competing claim? Never!!

And that is one of the problems with evolution—it's so amenable to revision that it can "explain" almost any evidence, which is why it is not really a valid explanation. It's more of a just-so story than a truly scientific hypothesis.

As Zmidponk of the Sock Drawer said, "...if new evidence is presented, ... evolution is re-evaluated with that evidence in mind.". He didn't say, "if new evidence is presented, the competing hypotheses are re-evaluated with that evidence in mind.". No, evolution is "re-evaluated" (an understatement), because one must stick with evolution. Because evolution itself is not negotiable. Because the alternative, creation, is anathema (emphases added):

It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is an absolute, for we cannot allow a Divine Foot in the door.[3]
evolution [is] a theory universally accepted not because it can be proven by logically coherent evidence to be true, but because the only alternative, special creation, is clearly incredible.[4]

Edwin Hubble too wanted to avoid the idea that we were created. His research seemed to show that Earth occupied a special place in the universe, but that idea, which would support the biblical account, was unacceptable to him:

Edwin Hubble ... wrote in his book The Observational Approach to Cosmology:
'Such a condition would imply that we occupy a unique position in the universe... . But the unwelcome supposition of a favoured location must be avoided at all costs... . Such a favoured position, of course, is intolerable; moreover, it represents a discrepancy with the theory, because the theory postulates homogeneity [emphasis added].'
What prompted this comment was that he was seeing galaxies in all directions speeding away from him by the same proportion, that is, the more distant the faster they moved. This meant we must be at the centre of the universe—but he rejected that idea on philosophical grounds. Hubble went on to say:
'Therefore, in order to restore homogeneity, and to escape the horror of a unique position, the departures from uniformity, which are introduced by the recession factors, must be compensated by the second term representing the effects of spatial curvature [emphasis added].'
[5]

The second-last quote in particular is also a reply to Drek's claim that "finding evidence that Catholicism is "wrong" doesn't automatically mean that Hinduisim is correct.". On the contrary, it does, if they are the only two alternatives. And creation and evolution are the only two alternatives on serious offer. And indeed the only two possible alternatives in a broad sense (we came to be, either naturally or supernaturally; there can be no other alternatives).

The creationist argument

Creationists argue that a Designer would re-use His design in various ways, so we should expect to see similarity in living things. They also argue that it makes sense to use similar designs for similar creatures, so we should expect to find similar DNA in similar creatures, such as chimpanzees and men.

So far, then, creationists argue that we should expect to see similar results as what evolutionists would expect to see for different reasons. Evolution says that similarities are due to common descent.

However, creationists also argue that the Designer would be free to use the same design in unrelated organisms, and also free to use different processes to achieve the same result. This is contrary to what evolution would predict, because they are not explainable by common descent.

Take the well-worn evolutionary example of the pentadactyl limb:

Homologies suggest common ancestory [sic]

The evolutionary explanation of the pentadactyl limb is simply that all the tetrapods have descended from a common ancestor that had a pentadactyl limb and, during evolution, it has turned out to be easier to evolve variations on the five-digit theme, than to recompose the limb structure.

If species have descended from common ancestors, homologies make sense; but if all species originated separately, it is difficult to understand why they should share homologous similarities. Without evolution, there is nothing forcing the tetrapods all to have pentadactyl limbs.

Figure[not included in this quote]: all tetrapods have a basic pentadactyl (five-digit) limb structure. The forelimbs of a frog, lizard and bird are all constructed from the same bones even though they perform different functions. [6]

So the pentadactyl limb of the the frog and the human is due to, and evidence of, common ancestry. Of course limbs are not inherited; genes are. So the argument is that the genes responsible for the pentadactyl limb have been inherited from a common ancestor.

However, this argument is seriously undermined by the fact that the fingers of the limb develop differently.[7]. The genetic program that produces similar outcomes is not the same in frogs as humans, and therefore is an argument against a common ancestor. This is easily explainable by the "common designer" argument, but not so easily by the "common descent" argument.

Conclusion

Is evolution dead? Of course not. It can't be killed! Just like the "out of South America" camp, nothing can shake their faith. Sure, they will readily change the details, and even when necessary the "central tenets" of their idea. But discard it in favour of another explanation that fits better? Never! They will "just nail on the rationalizations like armour plate", to pinch Kels' line.

Is this just a case of "modifying" the theory, or is it a case, as with heliocentricity, of continually patching and stretching it to the point that it needs to be discarded? Of course its supporters will downplay the problems as "details", and the critics will highlight them as serious problems. Who is closer to the mark in that respect is something that each one of us must judge for themselves.

It is easy, when looking at one issue in isolation, to dismiss problems such as these as minor. But creationists contend that issues such as this are not isolated cases, but part of a large body of evidence that fits better (not "proves") the creationary explanation.

And so often the anti-creationists fail to actually address the argument. In this case, the critics above and in the Sock Drawer have spun the problem as a triumph of science, showing how scientists are willing to change when the evidence leads that way. And falsely claiming that creationists do not do likewise.

However, creationists acknowledge that evolutionists are willing to change some aspects. And the same applies to creationists (c-decay is but one of numerous examples, as Sid acknowledged). The issue is whether the evolutionists are willing to change their minds about whether evolution itself is correct.

However, it's also instructive to look at the type of arguments used. Much of the criticism from anti-creationists comprises false claims (e.g. creationists' "...single source is supposedly the infallible and inviolable Word of God": no, it's not the only source at all; "...no actual evidence points there...": creationists have supplied plenty, and I've supplied some in this essay), mockery, vilification (e.g. New Scientist calling creationists "blinkered"), misrepresentation (e.g. "...if the evidence is in conflict with their source, the evidence must be wrong.": no, the interpretation of the evidence must be wrong. Creationists and evolutionists have the same evidence), attacking the source rather than the argument ("Also, enough with the creation on the web [deleted] already. It's like your [deleted] bible. The world has more than one website, you know"), and complete fiction (e.g. Kallium's conversation between an evolutionist and a creationist), not to mention the subtle (since made unsubtle) false dichotomy originally presented in that fiction as being between a "biologist" and a "creationist", as if the two were mutually exclusive (why wasn't it between an evolutionary biologist and a creationary biologist? Because that would be to admit that biologists can be creationists too!).

If the arguments for evolution are so strong, why not argue the evidence instead of making all these fallacious argument?

Summary

The issue here is whether this is a minor modification of the evolutionary hypothesis, or a mortal blow. If it's just a minor modification, then I agree that this is a storm in a teacup. But my argument is that this is something much bigger than a minor modification. Even one of the critics above (ShawnJ) seems to recognise this, in saying that he hasn't seen this sort of revision himself before. And of course New Scientist referred to the evolutionary tree as a "central tenet". So I believe that the argument that it's just a minor modification of the hypothesis is unsupported. No, this is a very significant problem for the hypothesis, hence the headline. But of course evolution won't die, hence the second sentence of the headline.

Notes

  1. 1.0 1.1 Subsequently lost when Conservpedia crashed and was restored from a week-old backup.
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