Plantinga has, along with Humble Don and the Shaved Chimp and many other apologists, tried to argue something along these lines:
Proper function of the heart is the pumping blood around the body.
If the heart fails to pump blood around the body, the owner of the said heart dies.
However, proper function implies conformance with specifications, which in turn implies a designer.
Therefore, god exists, or you die of heart failure … your choice.
Ironically, Plantinga had a triple bypass operation earlier this year (discovered when trying to find his quote using the string “Plantinga and the heart”). Thank god for those surgeons, eh?
The idea behind this argument is that the human heart (or whatever human organ you want to use) does a particular job, and apparently does it exceptionally well. Without it we would die – unless science stepped in. But if you are going to argue along evolutionary lines, what did the heart do before it pumped blood? How did it get from there to where it is today?
This is sort of where the argument of “irreducible complexity” tries to get purchase. One can understand how a heart might scale up along with the owners. A small shrew-like mammal precursor would not need the half-kilo heart that humans carry around with them.
However, there comes a point where there are simply not enough cells in a heart to support any pumping at all. In the “irreducible complexity” argument there is a gap between a few cells joining up together and not doing anything particularly important, and a quite large number of cells being assembled with the express purpose of pumping (the smallest known mammal has a heart which weighs about 15mg which comprises in the order of half a billion cells). People like Plantinga try to slot god into this gap.
A problem with this argument (apart from the fact that the mammalian precursor had a lineage which included smaller creatures with smaller heart like structures – for example insects, the smallest known of which is 0.139mm long) is that it assumes a continuity of function. Nature doesn’t seem to consider itself thus constrained. For example, scales and feathers and fur are variants of the same basic thing, petals and leaves and thorns are variants of the same thing. Plants didn’t specifically develop “pointy things to dissuade grazing animals”, they simply co-opted and perfected pointier than average leaves. (Don’t take this too literally – there was no Supreme Council of Plants with a 1,000 Year Plan to develop thorns.)
The problem comes in when you assume design and you assume that a function that you are bright enough to recognise must have been designed in (and you’re not overly bright). This is understandable, to a certain extent, in a technological society like ours. Everything is designed with function in mind (and somewhere close to half of the population are of below average intelligence – not my readers of course, you are all brilliant).
However, getting back on track … I draw your attention to the Swiss Army knife. This is a perfect example of something specifically designed for one purpose being co-opted for another.
My variant of the Swiss Army knife has a number of goodies:
two sharp blades – occasionally used
(when I can’t be bothered getting a proper knife)
two screwdrivers – occasionally used
(when I can’t be bothered getting my screwdriver set)
a corkscrew – never used (I have better corkscrews around)
a fish-scaler – never used
a helping you to tie fishing line thingie – never used
a thingie for getting stones out of horses hooves (I assume) – never used
a can opener – never used
a toothpick – lost and never used
a tiny pair or tweezers – never used
a little pair of grips – occasionally used
(when I can’t be bothered getting my socket set)
solid construction (ie a hammer) – occasionally used
(when I can’t be bothered getting anything more hammer-like)
a lovely pair of scissors – used all the freaking time to cut my nails
In terms of evolution, the Swiss Army knife is in a transitional state between being something which does various things not particularly well into a magnificent device that appears to be designed specifically for cutting nails. Nothing cuts nails better.
Now, I am pretty sure that the gnomes in Switzerland are not designing towards a perfect pair of nail scissors. They are just churning out variants of their product, trying to maximise sales. All that has happened is that I, representing natural selection, have favoured a variant of the Swiss Army knife which performs a key task well. If the vast majority of Swiss Army knife buyers, like me, purchase them primarily to cut their nails, and a later design change eliminates that function, the Swiss Army knife will die out. If a later design change maintains the heft of the Swiss Army knife and the scissors but removes unnecessary stuff like the fish-scaler and thus improves its attractiveness on price, then it will become more popular at the expense of more awkward variants.
I suggest that the same thing happened with the heart. A bunch of cells were already huddled together with some other goal in mind, or even a range of goals, (entirely metaphorically, cells don’t huddle and they don’t have intentions) before being co-opted into the pumping blood malarkey.
(Similarly, at a much smaller scale, the supposed “irreducible complexity” involved in the inner workings of a cell would also have involved the co-opting of an existing function.)So, as a last word, if something that was specifically designed for a purpose, like the Swiss Army knife being designed to deprive tourists of their hard-earned Euros, can be co-opted for another purpose, like cutting my toe-nails, then it is surely not too much of a stretch to think that non-directed “design” could co-opt existing structures and modify them to suit a new purpose. Is it?