[as usual, my own comments are in square brackets]
Held 25 August 2000, Woodmont Hills Family of God (a Church of Christ), Nashville
Follow the "spirit of Huxley" — we should admit only facts in grave scientific debate So are these matters of prejudice or truth? (please, no argument by ridicule) Communism, for example, was rooted in an evolutionary notion that might makes right.. This killed 120,000,000 people in the 20th century. Ideas have consequences. Three definitions of evolution:
He was directed by a skeptic to the evolution exhibit at Chicago’s Field Museum, where one read, "Once upon a long time ago, something amazing happened…" Very helpful.
[This is a bit slippery, being an argument from incredulity or presumption about future knowledge or its lack. Not that I think he’s wrong, just noting that it’s a tough argument to make philosophically.]
All 70 known phyla are there after the Cambrian explosion, none since (read my lips, no new phyla). That is, we don’t see major groups of organisms in the act of transition to new major groups. Evolutionary theorist Niles Eldridge summarized the quandary of paleontologists at not seeing the continuous change expected from simple Darwinism (he and Steven Jay Gould proposed the idea of punctuated equilibrium, in which evolution between very different organisms or even new species happens rapidly in fairly isolated populations.) [The skeptic might describe this with some justice as "miracles happen where you can’t see them". There is lively debate about what exactly a transitional form would look like, even within evolutionary biologists. Take the question "are birds dinosaurs?" and watch the, er, feathers fly. Or scales scale. ] Taking example of fins to legs. Each waystation must be a viable organism, let alone internal and biochemical changes that accompany structural changes between organisms. The universe does indeed look designed (as remarked by arch-evolutionist Richard Dawkins in The Blind Watchmaker, "appear to be designed for a purpose").
The argument from design
Relevant aspects of the emerging RTB creation model: [the Reasons to Believe staff has been trying to put together a specific model for creation which makes distinct and testable predictions about the natural world, fossil record, etc., since testability and falsifiability are such important parts of natural sience]
Supernatural origin of life (Gen 1:2)
- Primordial ocean, thick atmosphere, dark above
- Originally lifeless
- Classic paradigm — expect evolution of prebiotic soup
- Placid conditions for development
- Gradual emergence of life
- Single origin of life
- Minimal life would be biochemically simple
Creation paradigm — early appearance of life
- Hostile conditions (protected supernaturally,"hovered" like mother eagle?
- Sudden appearance of life
- Minimal form of life is complex
- Chemical features of design
Earliest life: 12C-enriched carbonaceous deposits 3.86 billion years old
Fossils 3.6 (these were like photosynthetic cyanobacteria)
Just after the Hadean era of frequent giant impacts, which melted the crust multiple times prior to 3.9 billion years ago. Oldest rocks are from 3.9 billion years.
Frustrating events — impacts, about 30 averaging 10 million years apart powerful enough to melt the crust. This would suggest multiple origins of life in order for it to be there immediately afterward from 3.5-3.9 billion years ago [or deliberate introduction knowing the last killer asteroid had already hit… Random chemistry arguments have real trouble with life appearing in a few million years unless its production is hardwired into the fabric of physical and chemical law, which doesn’t sound very random either.]
No geochemical evidence for primordial soup.
12C/13C ratio of earliest carbonaceous deposits looks biological in origin. [The longtime presumption was that life originated in some kind of warm, shallow body of water which was very rich in the appropriate chemistry, especially carbon-rich substances.]
Early terrestrial conditions inappropriate for it anyway.
Complexity of the simplest organisms
Least known genome size is 470, theoretical estimates have been 256 BUT these are not freestanding organisms, but parasites which use the host’s chemistry. E. coli has 4100. Smallest free organisms (some thermophiles) have 1500-1850, consistent with their being close to minimal.
Origin of information in the peptide chain
P=0.0125 per element, N=110, P=4,6e-280
Thus, in the nonexistent primordial soup, continued reactions at a rate at 1/second gives characteristic formation timescale of a trillion Hubble times. (for this single protein).[Hubble time = rough current age of the Universe, 15 billion years]
Harold Horowitz’ calculation gives odds of 1:10e10e11
Or mass of the Universe together at 1 million trials/second for 15 billion years, 1:10e99,999,999,916. The newer minimal genome sizes make this problem worse.
Internal organization of bacteria. They aren’t just an internal molecular soup — lots of inside structure and time-based localization. Needed for survival, universal among bacteria, so LUCA must have had it.
How about panspermia? — solar system/interstellar, directed (deliberate)
Problems:
- Doesn’t solve the origin question, just moves it
- Genetic code does trace to an age younger than the Earth
Natural history of Mars — could we be transplanted Martians?
Wet-dry (warm-cold) transition now thought to be 3.6 billion years ago (impacts stripped atmosphere), too long ago to be much help.
Interstellar?
- Radiation exposure, 40K internal decay.
- (for light sufficient to drive nanobacteria by its pressure)
- Star bright enough to drive them away has lethal UV. [The idea is that some tiny bacteria have such a small area/mass ratio that, if blown free of their home world, the pressure of starlight could accelerate them across the interstellar distances in several million years. The problem is that the stars that could do this most effectively, hot and bright ones, would also be the very ones that are brightest ion the ultraviolet radiation which would be most damaging to the microscopic passengers.]
Directed panspermia (alias "There is absolutely positively no God in the gaps")
- Crick and Orgel Icarus paper (=intelligent design, so testable)
- Also John Ball Icarus adjacent paper in 1973, "zoo hypothesis"
Necessary chemical elements were not available [in our neighborhood, which is what’s relevant here] via stellar evolution, recycling until 4.5 billion years ago, so there couldn’t be much of a head start. On top of that, the Sun has unusually high heavy-element abundances for its mass and age, sometimes attributed to a nearby supernova. [Something of the kind seems to be true as well for other nearby stars with detected planets, of which there are at last count about 50.]
Giant impactor seems to have produced the unique set of Earth/Moon properties and made Earth clement for life, which seems a bit much to ask of two successive abodes
Clearly (this is standard biology) a trait linked consistently to reproductive success will differ predictably between parent and offspring populations. This kind of natural selection can be observed (i.e. antibiotic-resistant bacteria). How far can this go? Can it account for the very disparate body plans we see?
Big problem: how these plans are assembled in "developmental time".
Crick: need this understanding before we can talk sensibly of evolution.
A —> B evolution requires process for building A —> process for building B, which each involve division of a single cell into billions, and must be viable at each step of this huge decision tree. Example: sea squirt, a sessile filter feeder, 8 cm long. Starts as a 1-cm gutless "tadpole" larva with notochord. Metamorphoses after sticking to a rock.
Developmental fate of cells is continually restricted during early cleavage stages (which intermediate stages are not independently viable). (Sea Squirt example) This is a process with a directed endpoint.
"Marching band problem" — instructions are present at the outset, independent elements all mesh. Change one without a plan, you have a mess.
James Valentine 1977 — the development pattern or field is what we need to trace in the history of life. Ancestors of both the organism and its development.
C. elegans has been well-studied in this regard — one can kill single cells during development and get nonviable result — it’s irreducibly complex in this sense. To build something by natural selection, the mutated cells must be dissociated from the process so they’re free to change and do something new without destroying the process (Cameron et al. 1998, in context of Cambrian explosion)
BUT these developmental changes must precede the body plans on which natural selection operates. Natural selection can’t anticipate.
Selection sees only final form; it’s causally inefficacious for ontogenetic networks. [Natural selection doesn’t operate on reproductive success, it can only operate on DNA which directly controls the development of the organism from an initial egg cell. This throws a major wrench into the simple and intuitively appealing idea of how natural selection works for larger and larger changes.]
This relates to Rupert Riedl’s (1978) paradox of teleological evolution. These are all classic problems in evolutionary biology, no big secrets here.
What is the deep, fundamental difference in ontogenetic paths? Is it possible to change one?
Drosophila (fruit fly) experiments have been especially important in genetics — when they are zapped with mutagens (chemicals, radiation) result sticks to the same basic body plan, viable organisms aren’t very different.
Early developmental mutations have the most leverage, but are least likely to be viable. Late changes (probably viable) can’t accumulate backwards in the developmental tree to get an early (hence major) change (Wallace Arthur 1997).
Nelson prefers to distinguish natural/intelligent causes rather than natural/supernatural.