Biological processes: purpose or outcome?
Given below are dictionary meanings for three words, which are used routinely by biologists.
Purpose: the reason for which something is done or created or for which something exists.
Function: an activity or purpose natural to or intended for a person or thing.
Outcome: the way a thing turns out or the consequence.
Selfish DNA….hmmm, sounds like this kind of DNA has no purpose or objective in life other than some goal of its own! While other pieces of DNA are altruistic, providing coded information for the cell that harbors them, these selfish bits of DNA contribute nothing and at the same time ensure that they are passed on to future generations.
Selfish: lacking consideration for others. Concerned chiefly with one’s own profit or pleasure.
The questions I wanted to pose is the following: Is it right to use these kinds of expressions to explain the existence of a piece of a chemical because we don’t understand its function yet? Why not call it DNA of unknown function? Just like, genes in sequenced genomes with no apparent function are called FUN genes (FUN standing for function unknown). Does giving it any other name such as passenger DNA help? Are transposons more selfish than “selfish DNA’’? How selfish can DNA get? What is the scale for measuring selfishness in chemicals? Is Sodium chloride (common salt) also selfish? As sea water it got into my alimentary canal leaving a bad taste in the mouth and an upset stomach for my sensitive friends…all this to ensure that they get a free ride from Florida beach to Oakland, Pittsburgh doing nothing for me and my gang, when all other Sodium chloride molecules we ingested from the Cuban restaurant was making us feel good and also keeping our salt balance in the hot summer.
“The dogma is that teleology is unscientific, and in some contexts it is. Statements that the sun is for lighting the world, or that the moon is for calculating the date of Easter, have no place in science. But teleological language is often used by biologists, and can hardly be avoided except by circumlocution. Some biologists may regard it merely as appropriate shorthand, but for many of us it is the best way to convey what we have to say” * (Science, 1998, 281: p927).
Hence, another related question: Is a bacterium a mere manifestation of the sum total of all the reactions that take place inside of it? Is it an outcome without a purpose? Is the purported purpose just a result of interaction with its environment? Are there two ways to explain life of a bacterium? For example: a) bacteria live with a purpose such as multiply indefinitely, develop resistance to man-made antibiotics, infect and kill hosts whenever they get a chance OR b) is the life of a bacterium the outcome of all the chemical reactions that underlie its existence without any specific purpose. But the purpose we observe is just an outcome of its interaction with the environment?
I could make the question simpler by quoting “The main purpose of glycolysis is to provide pyruvate for the trichloroacetic acid (TCA) cycle, not to make adenosine 5-triphosphate. The glycolytic production of pyruvate reduces the cytosol by increasing the ratio of NADH [a reduced form of NAD+ (nicotinamide adenine dinucleotide)] to NAD+. Thus, glycolysis cannot continue without “something” returning the cytosolic redox potential to normal” * (Science, 1997, 277: 459-463). Really? So glycolysis has a purpose? Is it just one purpose that was put into glycolysis when it was assembled in its present form or did every glycolytic reaction have a purpose of its own and then all of them came together and decided on a larger common purpose?
How about something more simpler: The purpose of water is to sustain life on earth (everybody), is to dilute the coolant that is poured into the 21st century vehicle radiator (someone stuck with a can of concentrated coolant and a smoking car on a highway in the middle of nowhere), is to dilute the alcohol in your vodka (anyone?), is to solidify into ice at the artic poles (polar bears), is to fill large reservoirs so that golf courses can be made in a desert (Californians)…and so on and so forth.
Purpose in biological reactions, macromolecules and living systems? Is it not time we started talking about outcomes, especially when we are so close to making synthetic life in a lab from pure chemicals?
Finding answers to questions such as these is very important for expressing what we truly understand and report as science. Using the terms purpose (highly used), function (follows a close second) and outcome (very rarely used now) without sufficient thought puts us on a slippery slope.
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Pittsburgh, USA.
*Disclaimer: These references are just two examples. There could be (and there are) several other references in scientific literature that supports the general argument I am trying to make here.