What is nylonase, and why is it important in the investigation of the question of evolution
by natural selection
? Well here we go.
is a man-made polymer
, a collection of chemicals
brought together in a way found nowhere in nature. It was invented
in the past century and began getting dumped
into the environment
beginning around the 1930s. Now, if you were to eat a bunch of nylon, your body would be unable to digest
it. Thing is, no chemicals manufactured by the chemical-manufacturing centers in your cells are able to break nylon down in a way which makes anything useful come of it. At best, you'll poop
it out. At worst, some of it will get lodged in the toxin-absorbing cells in your kidneys
and your liver
, and they won't be much use to you after that. In fact, nowhere in nature has any living thing ever produced the enzymes effectively and efficiently capable of digesting nylon. Until the mid-1970s, that is, when it was discovered that bacteria
living amidst the wastewater
of nylon-producing factories
had evolved exactly such a capacity.
Nylon-eating bacteria survive in this way because they produce nylonase
-- an enzyme
which can dissolve nylon into the sort of particles which the organism may then use to power itself or build copies of itself. One claim made against evolution is that copying errors in the DNA only ever degrade it, but can add no new information. This is, as it turns out, was an easy proposition to check: a researcher need simply copy the genetic code of an organism, then breed until a mutation causes a new feature to be evidenced, then compare the new code to the old. Following exactly this recipe, the ability to breed nylonase-generating (and so nylon-eating) bacteria has been duplicated in laboratories beginning in the 1990s (with the initial species of bacteria which initially evolved this ability, and later with a different species altogether). This was done in much the same way as the E. coli long-term evolution experiment
resulting in citrate
-eating bacteria. And in every instance, it has been shown to involve an addition
to their DNA
. What was found to have happened when the DNA itself was examined was that a new segment had 'popped in' from a mutation, a copying error in the portion of the DNA instructing the chemical factories how to make digestive enzymes. A segment of the code was duplicated, and the double-section created a new instruction causing the little chemical factories within the bacteria to produce a new chemical. This mutation literally expanded, the bacteria's DNA, adding a new piece of information in a way which enabled the bacteria to generate nylonase, with which they then digested nylon.
Some antievolutionists, confronted with this fairly raw fact, fall back on the contention that this simple duplication of existing segments of DNA did not constitute the creation of 'new information.' But if that constitutes 'no new information' then no mutation
which has ever occurred in this way does, hence there is no problem with man evolving from a common ancestor shared with apes, because that's all that any
mutation of any DNA ever does -- human DNA and chimpanzee DNA are the same code, combined differently; that entire course of evolution generated 'no new information' by any standard which would make such a claim of nylonase.
Now, to be clear, this was not something which occurred simply in response to the presence of nylon in the bacteria's environment. Mutations do not happen because DNA strands decide current circumstances would make it useful for this or that particular segment to be duplicated. Remember my claim that nature had never before produced the enzymes effectively and efficiently capable of digesting nylon
? That's somewhat true, but there's a glaring error there. For, you see, the mutation which enabled bacteria to produce nylonase was simpy that, a random mutation. With countless trillions of bacteria out there reproducing several times a day, it is highly probable that some variation of the exact same
mutation which made the manufacture of nylonase possible has indeed occurred millions of times before in nature. But every single time it did, it was useless, possibly even harmful, a redirection of the organism's limited resources and energy towards the production of an enzyme that digested nothing in its environment, and so did the organism no good and allowed its competitors and their descendants to crowd it out of the field of reproduction.
It is important to understand here that bacteria reproduce by mitosis
, so unlike sexually dimorphic
animals (including humans, and everything else with a male/female split), each bacterium has but a single line of ancestry
. If two bacteria each have a different nifty and helpful mutation, there is no chance that they will get together and jointly produce a collection of offspring
of which some have both
And indeed, the combining of genes is the great benefit of sexual dimorphism -- two members of a species each having a particular advantage can get together and produce an offspring with both advantages. Or each can get with ten others and create a population where both advantages are floating around, and eventually somewhere down the line those advantaged genes will end up coming together.
But bacteria have no 'gene pool
,' so where one is successful it and its descendants will overtake the whole population, consume all the resources, and deprive its less advantaged competitors and their descendents from getting the resources needed to reproduce. Such would have been the case with every then-disadvantageous nylonase-producing mutation occurring up until the moment when one happened amongst a population of bacteria living in the industrial waste of a nylon maker. And when that combination of circumstances came to be, the tables were turned, and now it was the mutant nylonase producer and its descendants who had the advantage; and once that line was established, it was the carriers of that gene who would have further mutations solidifying this advantage and building upon it. And so the story of nylonase, friends, is the story of every evolutionary event in the history of our world, going all the way back to our universal common ancestor
*There is, naturally, transference, the rare occurrance of a piece of DNA getting separated from the organism itself and ending up stuck in another one, and getting incorporated into that other organism's own genetic code. This has happened to a species of sea slug (Elysia chlorotica) which eats a certain kind of algae and at some point in its biological history picked up that algae's photosynthetic DNA through transference. Once it eats enough of that algae to absorb it's chloroplasts, the pinched DNA allows its cells to produce food through the photosynthetic process otherwise reserved for plants. However, the chances of the right bit of DNA jumping organisms in this way is probably less than the likelihood of it simply evolving on its own.
There is as well a somehwat deeper Talk Origins discussion of Nylonase Enzymes responding to some technical gibberish about plasmids and codons put forth by reality's loyal opposition.