Update: New research on coelacanths shows that ‘beyond the cover’ things are going on.
Some organisms show little change over a (very) long period of time. Often, species that have undergone little morphological change are known as living fossils (for more about the possible definitions, and a list of examples, check the Wikipedia page).
Coelacanth (or Latimeria menadoensis)
(Source: National Geographic, photographer: Mark V. Erdmann)
Perhaps the best known example is the coelacanth, a fish long thought to be extinct until living ones were found near South Africa in 1938, closely resembling fossils. In fact, a recent study proposes that similar looking species of coelacanth have been around for even longer than previously thought.
Sadly, examples of morphological stasis (little external change) such as these are often used by those opposing evolution. “Where’s your evolution now, huh?,” so the reasoning goes. Should we let this slide, or should we react? A column (also discussed by Prof. Jerry Coyne on Why Evolution Is True) in the latest issue of Nature, entitled Reach out to defend evolution, suggests the latter option.
Harvestmen (Phalangium opilio)
(Source: Wikimedia Commons, author: Mehran Moghtadai)
In it, a palaeontologist, Russell Garwood, recounts how surprising and interesting findings concerning evolution are frequently co-opted for the creationist cause. One of the examples that is given does indeed revolve around living fossils (in this case, fossil harvestmen).
He suggests in the column:
If research is to appear that will attract an obvious creationist interpretation, an accompanying blog post could explain the work and highlight flaws in any anti-evolution attacks.
Back to the living fossils then. Why do these NOT present any threat whatsoever for evolutionary theory? Well, there are a few points to note:
- No obligation: Evolutionary theory does not state that species have to evolve. Only that they will tend to do so when their environment (broadly construed, including interactions with other species) changes.
- Stability: The main suggestion as reason for morphological stasis. Basically, if the environment doesn’t change, then there’s not really a strong selection pressure that results in change. There’s no real ‘incentive’ to change (careful, incentive here does not imply any foresight or conscious decision!)
- Constraints: Potential evolutionary change is constrained in several ways. this means that an organism follows a certain developmental pathway, has a certain evolutionary history and a particular genetic and functional composition, all of which limit the amount and type of evolutionary change that can occur. ‘Anything goes’ doesn’t work in evolution.
- Beyond the cover: Not all evolutionary change is visible on the outside. A lot might have changed on the inside. The internal mechanisms and molecules could have changed significantly without necessarily producing an external cue.
These are of course only brief and general points, but I hope the idea is clear: living fossils are easily accommodated by evolution and in no way provide evidence against it.
But surely, we don’t know everything? Of course not. There are still mysteries and unknowns waiting to be uncovered and explained. And that’s wonderful. They are one of the reasons science is so exciting. And, as the column says:
We should not let creationist pressure alter the way we do science — the day that researchers become reticent about highlighting inconsistencies and uncertainty would be a dark one.
________________________________________________________________
Garwood, R., Dunlop, J., Giribet, G., & Sutton, M. (2011). Anatomically modern Carboniferous harvestmen demonstrate early cladogenesis and stasis in Opiliones Nature Communications, 2 DOI: 10.1038/ncomms1458
Garwood, R. (2012). Reach out to defend evolution Nature, 485 (7398), 281-281 DOI: 10.1038/485281a
Zhu, M., Yu, X., Lu, J., Qiao, T., Zhao, W., & Jia, L. (2012). Earliest known coelacanth skull extends the range of anatomically modern coelacanths to the Early Devonian Nature Communications, 3 DOI: 10.1038/ncomms1764
Evolution deniers are unable to understand simple scientific concepts like natural selection. Perhaps it’s because they’re too lazy to study science or perhaps they’re too stupid to understand science. But that doesn’t stop them from pretending they know more about biology than all the world’s biologists. darwinkilledgod dot blogspot dot com
The problem is, if by “living fossil” you mean that they disappear from higher layers in the fossil record, such living fossils falsify the evolutionary idea that most fossils are a gradual record of millions of years of burials. If so, since those creatures kept on living since their first burial, we should find them all throughout the layers. Especially when they are found buried in huge numbers in lower layers, and are still alive today in huge numbers.
Living fossils fit better with biblical creation and the global Flood, so for most of the fossil record the layers represent order of burial during a single event in time. Under this theory the “facts in the ground” make perfect sense; you’d expect to see those less able to flee floodwaters buried first, thus in the lower layers, and to be missing from higher layers, yet perfectly capable of still being alive today.
I don’t know if harvestmen are specifically this kind of living fossil but you’re the second person I’ve seen using that label of them. Calling them living fossils doesn’t help your case, especially since they’re known to be so common today (I see them all the time). Unless living fossil has lately come to mean something new and harvestmen -are- found across the layers?
Let me first clarify that both coelacant and harvestmen are orders, not species. So, the species alive today are not the ones alive in the distant past. They simply belong in the same order and look quite similar.
As to your remarks about the fossilization process and sequence, it’s important to realize how difficult and rare the fossilization process actually is. Conditions have to be right for fossils to be left.
For example, in the coelacanth case, these fish live in relatively deep waters, and as such, finding recent fossils is very difficult (most, if not all, fossil hunting expeditions take place on land). Only layers of sufficient age might have been transported to a current terrestrial environment due to plate tectonics. This would result in a ‘gap’ in the fossil record not because of the flood, but because the fossils are either not formed, or not available.
With regard to the harvestmen, very few fossils are known of them, exactly because their body structure is extremely delicate and will thus only be fossilized under extremely favorable conditions. So, it is actually pretty normal that only a few harvestmen fossils are known…
It seems then, that so-called living fossils and/or gaps in the fossil records in now way threaten evolutionary theory.
Those are interesting points, GunnarDW. The problem is that the whole fossil record perfectly matches the biblical global flood scenario. Coelacanths buried in low levels now on land can be explained by the Flood easily, as can harvestmen or anything else I’m aware of. While there can always be “patches” to make evolution seem to fit the evidence, the biblical account already does fit it, predicting it accurately.
If that was the only subject where that was the case, I could see this not being much of a problem for evolution, but the problem is there are similar problems on countless other subjects, like missing links, striations, too-distinct layers, carbon-14 found in fossils supposedly too old, etc. etc. etc. On every subject, the evolutionists come up with some patch to explain away the discrepency, but this is a dangerous tactic in terms of finding the truth because it could be used to make -anything- seem to fit the facts.
When all of it is considered fairly in light of the Bible, it fits already with no patches. The Bible accurately predicts what we find.
Also, with harvestmen, since they’re so common nowadays, doesn’t it seem like there should be as many fossils found in higher layers as below, if the majority of the record was really laid down over millions of years? You said with the Coelacanth that them being deep makes the fossils hard to find. But it sounds like with harvestmen that they are only found deep — but shouldn’t it be easier to find their higher fossils by the same reasoning, if indeed those exist?
I can imagine how it could happen by sheer weird luck — that many would happen to get buried long in the past, and somehow they rest would just happen not to in more recent times, or that we just haven’t happened to find them, but this would require more faith than the biblical position which is simply that most of the record is from the global Flood.
See what I’m saying? 
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I’ve never really liked the term “living fossils”, it implies no change whatsoever has ocurred and this is almost never the case. The coelocanth is a good example, it’s considered a living fossil yet the extant species doesn’t doesn’t date that far back at all. Plus of course, as you said, there may have been significant change at the molecular level that is not preserved in fossils.
The problem with creationists is that no matter how may times you explain why stasis is not a problem for evolution they continue to repeat the same arguments over and over again….
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