Post details: The Problem With Evolution

Sun, 27 February 2005

Permalink 02:37:49 pm

The Problem With Evolution

I'm no Charles Darwin or Richard Dawkins, I don't even have any qualifications in biology, but there's a part of evolution that I've never seen properly explained. When I was at school, the teaching of evolution went something like this:

'Life started as single cell amoebas. Over millions of years these developed into multi-cell organisms, which in turn evolved into invertebrates.' Ok, fine so far, seems plausible. 'These invertebrates then gradually evolved into fish-like vertebrates. After another few million years fish began crawling out of the sea, using their fins as legs, to become amphibious...' Whoa, hang on there, rewind a second, fish began crawling out of the sea?

My understanding of evolution is that, through natural selection over many thousands of generations, genetic mutations that are beneficial to the species become dominant. The 'using their fins as legs' part I can accept, I can imagine that they were crawling on the sea bed well before they moved to land, it's how they breathed that I don't get.

What type of freak genetic mutation is it that suddenly gives a fish the ability to breathe in water and in air? You can either breathe in air or you can't, there's no in between, so it's a huge leap.

I'm sure that there's a very good explanation, it's just I haven't been able to find it. Everything I've read on the subject explains the transition from fins to legs, not the change in breathing mechanism. From single-cell amoebas to vertibrates I'm fine with, and likewise from land-crawling 'fish' to mammals and birds, it's just the bit in between I get stuck on. And in case you're wondering, this isn't an argument for creationism, it's questioning the current evolution teachings.
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Comment from Murk ·
One goes via dry spots... having to 'hold the breath'.

One can imagine going from having to survive on stored oxygen (for a brief 'sprint' overland to another bit of water) to a gradual increase in that time due to diffusion of oxygen. (E.g. the gill doing it's job in air with VERY poor efficiency). Adapting for air will reduce effectiveness in water though.

As the creature spends more time dashing from pool to pool, water effectiveness becomes less important and air effectiveness mroeso, the 'diffusing layer' becomes more complex for bigger surface area -> fractal -> lung

Eventually the effectiveness in air is good enough that water is not needed. Past that point one can go all out air breathing.

You may like to look at Richard Dawkins' 'Selfish Gene' and 'Blind Watchmaker'. Get the later editions as in the appendices he responds to may questions like this.

The classic example which comes to mind in a similar vein is evolution of the eye - this is in Dawkins.

The difficult part, the really tough bit isn't the lung, it's the single celled organism!

One can also say that the really tricky part for creationists is the fossil record, as this implies a tricksy creator who is trying to mislead... a creationist will also have a hard time with vestigial organs, e.g. the appendix, why the nerve connections for the human retina come out of the front rather than the back of the retina (as they do in the octopus, which has a very human-like eye - but evolved independantly) and so on.
27/02/05 @ 17:15

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