Saturday, July 19, 2008

Life is complex

In recent weeks I have raised the issue of Cit+ E.Coli in the Lenski experiment that proves positive mutation. In rebuttal to this, theists have made the statement: "That doesn't prove anything, you started off with E.Coli and ended up with E.Coli". This is, of course, a result of the theists lack of biological training. Its the equivalent of saying that a housecat that gives birth to a lynx is not a mutation because they are both cats:-

(Felis Catus) --> (Felis Lynx canadensis)

So, what is the difference between the common house cat Felis Catus and a lynx such as Felis Lynx canadensis? Well, its simply that one organism has genetic code that gives it smaller body mass, decreased aggression, no black tips on the ends of its ears etc. On the other hand, a significant amount of the housecats genome is the same or similar to that of a lynx (including for instance the colourings of its coat as seen above).

So, how do we determine these two species are different? In the past biologists have had to rely on the physical characteristics of the species. Their size, colourings, behaviour etc. But does that work out when we compare individuals within all species? What about man's best friend:-

Above: A St Bernard eyes of some lunch

Both the St Bernard and the Chihuahuas shown above are part of the same species Canis Lupis Familiaris and yet they have significantly different characteristics, or do they? The chemical structure of the St Bernard is the same as that of the Chihuahua, rather, the proportions of those chemical structures vary between the two individuals. They are effectively the same organism, but in the St Bernard certain genes are enhanced (Such as hair, body mass, slobbering etc). This, does however show that mutation alone does not cause significant changes in biology - those changes can also be a result of activity within an existing genome.

This is totally different to the Cit+ E.Coli which mutated in the Lenski experiment. Those E.Coli have a different chemical structure which allows them to digest Citrate. Thus, should Cit+ E.Coli be called E.Coli at all? Well, there is no problem with labelling them as E.Coli as that definition covers a variety of different microbes with different characteristics:-

A strain of E. coli is a sub-group within the species that has unique characteristics that distinguish it from other E. coli strains. These differences are often detectable only on the molecular level; however, they may result in changes to the physiology or lifecycle of the bacterium. For example, a strain may gain pathogenic capacity, the ability to use a unique carbon source, the ability to inhabit a particular ecological niche or the ability to resist antimicrobial agents. Different strains of E. coli are often host-specific, making it possible to determine the source of fecal contamination in environmental samples.

This is just a result of taxonomy, being the study of classifying living things. It is an interesting question, if the Lenski experiment is the first time we have observed a mutation from one species into a new species under controlled conditions - how will taxonomy react? Surely the old rules (which require species to be differentiated) will not apply when a new species comes from an existing one. Nevertheless, this is only a distraction from the main point.

Some theists argue that this is not evidence for evolution because the microbe did not evolve into a dog (or some other complex animal). I would respond by asking what the difference is between the microbe and a dog. Both have genetic codes which determine their chemical constructions - its just the construction that is different. E.Coli are asexual, bacteria (as opposed to eukaryotic), directly take food in through their cell walls, anaerobic replicators. Dogs are sexual, eukaryotic, with developed food processing tracts, aerobic replicators.
If we now know that mutations can result in additional characteristics then how many mutations would be required for a bacteria to become a dog. There could be thousands of mutations occuring at distant intervals of time - nonetheless, we are not dealing with a 20 year time period. In fact, fossils indicate that the first "big mutation" that would be necessary, being the transition from single cell (bacteria) to multi-cell (eukaryotic) organisms happened about 2.1 billion years ago. Over that time frame, the incredulity of theists does seem a little petty.

But, lets do the maths, the Lenski experiment showed a mutation happen in 25,000 generations - on average, E.Coli reproduce every 233 minutes. There have been about 1077300000000000 minutes since Bacteria first became Eukaryotic. Thus we could expect about 4623605150214 generations in that time, which, with a uniform mutation rate would be around 184944206 mutations. Do you think that 184944206 additions to the genes of a microbe could result in a dog? (Of course, this maths is flawed because the reproduction rate between microbes is shorter than later mutations, such as dogs - nonetheless, we should expect a significantly large number of mutations, or additions to genetic code, to be available to bring the genetic code from 500,000 base pairs in bacteria to 300,000,000 base pairs in humans).

But, perhaps the biggest problem for theists is not mutation and change in characteristics between bacteria and dogs. Their incredulity comes from the fact that they cannot accept this line of mutations and changes:-

--> --> -->
Apes --> Australopithecus --> Homo Antecessor --> Homo Sapien

But if you want some real evidence that life can take strange twists and turns, take a look at these squid (try to count the legs):-

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