> but the creationist has a point that some of the more fantastic parts of evolution are harder to directly observe in the same way as, say, gravity.
Honest question: which parts?
Honest question: which parts?
But I have many creationist friends, and the parts they don't seem to accept as "fact" are:
- Speciation (how given any amount of time we could get things as distinct as flowers and dogs and humans from a common ancestor)
- Emergent complexity (how given any amount of time, small changes in the genetic code could have led to things as complex as eyes and brains and so forth)
- Sentience and self-awareness (how given any amount of time our brains could have evolved to possess this seemingly magical and qualitatively different trait)
Again, I want to emphasize that I don't personally think any of these are great mysteries solvable only by appeals to spirituality. However, I hope everyone reading this could see how there's a bit of a jump from the 'fact' of (say) evolution of drug resistance in bacteria to the 'fact' of longer-term cumulative evolutionary effects like speciation and the eventual emergence of "eyes from non-eyes", etc.
Population bottlenecks cause species that were once very fit to no longer be fit for an environment, enabling vastly different organisms to become dominant very quickly.
Then there are phenomena like Chromothripsis[1] (only discovered last year), whereby the genetic code of a cell is literally smashed into thousands of pieces and seemingly randomly reassembled. No one is saying that Chromothripsis is a major driver of evolution, but it is interesting in that massive rearrangements of this nature can still provide cells capable of reproducing. In the case of cancer, where it was first discovered, these cells are even able to reproduce faster than normal cells.
The other thing is that even advanced life like mammals and humans have more than 10 times as many bacterial cells than human cells[2]. Since bacteria can evolve very quickly, they play a very important role in evolution.
The eyes from no eyes makes no sense to me, since the entire array of light sensing capabilities are seen in nature. From eagles to plants. The same is true for many of the examples of emergent complexity that are thrown out there.
[1] http://en.wikipedia.org/wiki/Chromothripsis
[2] http://www.scientificamerican.com/article.cfm?id=strange-but...
A few articles addressing eyes from a creationist perspective, the first addresses your point most directly. I'll give author and credentials as it seems fitting.
* http://www.answersingenesis.org/articles/2009/01/13/eyes-hav... DeWitt (Ph.D in neuroscience);
* http://www.answersingenesis.org/articles/2010/09/14/darwin-a... Mitchell (MD, FACP, BA (cell bio & biochem)
* http://www.answersingenesis.org/articles/cm/v18/n4/eye-for-c... interview with Marshall a PhD in Opthalmic science
These, indeed the first alone, should make sense at least of the argument from Christian creationist scientists against Darwinian evolution providing a convincing argument for the undirected formation of the eye.
Interestingly this, http://www.answersingenesis.org/articles/am/v3/n3/seeing-eye, answers a question that I've seen raised about the development of the retina and cornea+lens and how they can possibly combine if they develop separately; it gives a very brief acknowledgement of the retina and rearward parts forming from a brain "bud" and the cornea and lens forming from the over-covering flesh of the to-be-formed eye socket. Of course Haeckel's fraud makes one rightly nervous about assuming 'ontogeny recapitulates phylogeny' but it at least provides an insight in to a potential evolutionary process.
I found this http://www.answersingenesis.org/articles/am/v3/n3/seeing-eye from the same source quite interesting, on microscopic eye movements that are apparently essential to proper functioning.
Blood's ability to coagulate is a cascading system with over 30 parts. Remove one part and it's fatal for the individual. How could a system like that evolve gradually over time?
He lists quite a few such systems. Bacteria having motors, the cell's operational system, the anti-body system (again a cascading system of large complexity).
These things that are claimed to fall apart when a single step is removed were not there from the ground up to provide that specific function, separately they would have provided different functions and when they fell together in a certain way provided a huge benefit. The little bones in our ears were a part of our skulls before they were requisitioned by the ear.
The issue seems to be that the argument looks at how things are and assumes that it was the only thing that these parts have ever been working towards. That any steps in between were useless until put together in this way. Where it is more accurately a bunch of different things coming together to perform all these different functions.
From what I remember from the book the coagulation system looked to be one monolithic piece and not built up of smaller systems.
Also, I did give further reading with the selfish gene for a specific example of a bacteria's flagellum.
Also, the simian species from which we evolved in fact no longer exists. I emphasize this is just a coincidence and doesn't prove one or another point about evolution.
Darwin's finch species from the Galapagos Islands all coexisted, even though most of them branched off from each other, or from a single initial species. There is no reason to assume a priori that species B, which branches from species A, requires that species A must go extinct.