Monday, September 16, 2013

The fossil record

This is a follow-up to a previous post:

I'm going to quote from a standard evolutionary textbook, citing one standard line of evidence for evolution. D. Futuyama, Evolution (Sinaur 2005), 528.

The fossil record is extremely incomplete for reasons that geologists understand well (see Chapter 4). Consequently, the transitional stages that we postulate in the origin of many higher taxa have not (yet) been found…Critically important intermediates are still being found…including feathered dinosaurs.

i) Although Futuyama treats transitional forms and intermediate forms as synonymous, they need to be distinguished. There's a sense in which semiquatic animals share characteristics of fish and land animals, but not because they are transitioning from fish to land animals, or vice versa, but because they are ecological intermediates. Their traits are suited to the ecological zone they occupy. 

ii) And, of course, they could be created that way. That's not evidence for macroevolution.

iii) Stephen Meyer recently argued that the problem for evolution is not the generally incomplete state of the fossil record, but the selectively incomplete state of the fossil record, contrary to Darwinian projections. Cf. Darwin's Doubt (HarperOne 2013).

iv) Keep in mind, too, that gaps in the fossil record preclude inferring ancestors and successors, for you can't establish a direct lineage. 

The fossil record, moreover, documents two important aspects of character evolution: mosaic evolution (e.g. the more or less independent evolution of different features in the evolution of mammals). And gradual change of individual features (e.g., cranial capacity and other features of hominids).

Encephalization is often correlated with intelligence. Larger brains, smarter hominids. Yet the facile link between brainpower and intelligence invites counterexamples. For instance:
…bees have cognitive capabilities and a plasticity of behaviors that otherwise are known only in the vertebrates, and no less surprisingly, other features such as exhibiting sleep-like states. Or is it surprising? Sleep may have several functions, but one widely agree purpose is the need to consolidate memories. 
Given that these organisms [ciliates] lack any sort of nervous system, the function of these neuropeptides is somewhat enigmatic. Nevertheless in their own way the ciliates are sophisticated organisms and use of messenger molecules is to be expected.
Other types of complexity in both bacteria and various eukaryotic microbes have been comparatively well known for many years…There is, however, newly emerging information, across a wide front of enquiry, that is demonstrating hitherto unappreciated  levels of complexity that correspond in a number of interesting ways to the social behavior of animals and higher organisms. Thus, aspects of sociality such as foraging and cooperative hunting, specialized dispersal forms, genetic altruism, and (perhaps most surprisingly) communication, using various chemicals….the social interactions, synchronized activity, and communication between microbes confer on them multicellularity of a sort. S. Morris, Life's Solution (Cambridge 2003), 202, 236-237.
Back to Futuyama:

The earliest fossil ants, for instance, have the wasplike features that had been predicted by entomologists, and the discovery of feathered dinosaurs was to be expected, given the consensus that birds are modified dinosaurs…the fossil record often matches the predicted sequences (as we saw in Chapters 4 and 5): for example, prokaryotes preceded eukaryotes in the fossil record, singles insects (the phylogentically basal bristletails) precede winged insets, fishes precede tetrapods, amphibians precede amniotes, algae precede vascular plants, ferns and "gymnosperms" precede flowering plans.

i) The basic problem with his inference is how the distribution pattern appears to be fundamentally spatial rather than chronological: 


fish>amphibians>land animals


On the face of it, these reflect different ecological zones or higher and lower latitudes. For instance, a tropical latitude has different flora than a temperate latitude. A swamp has different fauna than a desert. So it's unclear how Futuyma infers an evolutionary sequence from the fossil sequence, given his examples. 

ii) Perhaps the missing premise is superposition. Is he assuming that what's lower is older? Lower layers are earlier? 

Even if we grant that assumption, that's, at best, a necessary rather than sufficient condition for his position. After all, progressive creationists can accept the assumption that what's lower is older.

iii) I'm not a geologist or hydrologist (neither is Futuyama), so I'm not qualified to evaluate stratigraphy. But offhand, it's not obvious to me that superposition is a universal or even general indicator of relative chronology. On the face of it, beaches, sand dunes, sand drifts, and riverbeds undergo regular erosion and replenishment. Layers don't form bottom to top, but simultaneously. Underlayers aren't older than upper layers. And there's a constant process of addition and subtraction. Barrier islands and sea islands are subject to a similar dynamic. So you can't infer the duration of solidification or stratification from superposition alone. At least, that's my understanding. 

Of course, if you go down far enough, what's lower may be older. But that raises the question of initial conditions. 

I'm not claiming that's applicable to the geological column in toto. Just pointing out that appeal to superposition can give rise to hasty generalizations. 

iv)  How do young-earth creationists account for the sequence? 

a) They usually invoke their models of flood geology.

b) I'd add that if the earth is thousands of years old rather than billions of years old, then the layers don't have the same chronological significance. You don't have the same vast intervals between upper and lower layers. So, if you accept the operating premise, young-earth creationists have less explaining to do, since the sequence, even if it's chronological, is a very compact relative chronology. Of course, young-earth chronology is hotly contested. They exchange one challenge for another.

c) If, moreover, God created animals everywhere, but created man in one particular locale (e.g. Eden), then animals would be dying in other parts of the world before man fanned out from his provincial point of origin. Therefore, we'd expect human remains to be above animals remains in many or most cases.

d) I assume we also need to distinguish between fossilized wild animals and fossilized livestock. Due to selective breeding, there's a sense in which domesticated animals are more highly "evolved." So when we draw inferences from fossil record, we ought to distinguish between natural selection and selective breeding. 

e) Furthermore, whether, and in what setting, human remains are preserved isn't just a natural process–unlike animal death. Some cultures cremate the dead (e.g. funeral pyres). Other cultures bury in dead. So the distribution pattern of human remains in time and place is somewhat artificial. 

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