Why does natural selection take so long to get results?
Survival of the fittest
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Also in this week's column:
Why does natural selection take so long to get results?
Asked by Colin Jackson of Telford, UK
The reader further asks, "when controlled breeding programs can get results in a relatively much shorter period of time, wouldn't more rapid evolution itself be a good species survival trait and thus have been selected for?"
Although there is fierce debate as to how fast natural selection can proceed and if natural selection is still proceeding in humans due to our technology, there is a short answer. Speed is probably not very important in natural selection and is certainly not the only consideration in natural selection.
There is a danger in mutation. Most mutations do not help the species survive. A species and an environment exist in balance with each other. Populations simply adapt to their current surroundings and to changes in those surroundings. They do not necessarily become better in any absolute sense over time.
A change in the environment may require a change in the species for that species to survive. But if a mutation spreads too quickly across an entire species it may prove maladaptive to the species if the environment undergoes a further change. More diversity in mutations and hence change is probably better than speed in a mutation becoming widespread in a species.
Related to this question, an important principle of natural selection is that a trait that is successful at one time may be unsuccessful at another. This principle was demonstrated by the classic experiments of C Paquin and J Adams of the University of Laval in Quebec, Canada, and published in Nature in 1983.
Paquin and Adams developed a yeast culture and maintained it for many generations. Every so often a mutation would appear that allowed its bearer to reproduce better than its contemporaries. These mutant strains would crowd out the formerly dominant strains. Samples of the most successful strains from the culture were taken at a variety of times.
In later competition experiments, each strain would out-compete the immediately previously dominant type in a culture. But interestingly, some earlier strains could out-compete strains that arose late in the experiment. Competitive ability of a strain was always better than its previous type. Yet competitiveness in a general sense was not increasing.
The success of any organism depends on the traits of its contemporaries. There is likely no optimal design or strategy for most traits, only ones based on chance such as the competition and the environment.
Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au
COMMENTS
Specious species
I've posted a riposte to some of Dr Juan's remarks on my site. The main thrust of which points out the fatal flaw in his discussion that natural selection somehow acts on populations, it doesn't, it acts on individuals.
http://www.sciencebase.com/science-blog/why-does-natural-selection-take-so-long.html
Evidence please?
David,
Thank you for your comments. I especially like the red vs. blue argument. I'll have to remember that one. If red changed to blue then it would no longer be red. Being an artist, I can relate to this. The fact is that red can never be changed to blue no matter what colors you add because they are both primary colors! But thanks for playing.
Colors are not why I'm posting a reply comment though. I am posting a reply because you said that if I "take a look at the fossil and DNA patterns of - interestingly - birds, you find that at one time they were, in fact, dinosaurs" I have yet to see these "patterns" in fossils or DNA. Could you provide the evidence for these?
You also said, "At some point, they changed quite a bit, stopped being dinosaurs, and were birds. I'm oversimplifying for expediency's sake, but that's the basic idea."
That's a wonderful idea, but please do elaborate. It seems like nothing more than a hypothesis to me. At what point did dinos become birds? Where is an example of a scale transitioning into a feather? When they are found in the fossil record they are found in their current, moddern form.
Lastly, please do not associate me with ID. I know who my creator is. Thanks for the intelligent reply!
Danny
Oh boy, Danny
Danny:
"A bird," you write, parroting an oft-used ID line, "can adapt to a new environment and get a label as a new species of bird. But, it is still a bird."
This is my favorite type of argument: One which as its premise states something entirely untrue. Overlooking for the moment that 'species', 'genus', and 'family' are rather arbitrary classification points used to clarify what is essentially a continuum of fauna variants, let's continue:
If you take a look at the fossil and DNA patterns of - interestingly - birds, you find that at one time they were, in fact, dinosaurs. At some point, they changed quite a bit, stopped being dinosaurs, and were birds. I'm oversimplifying for expediency's sake, but that's the basic idea.
I'm consistently amazed by the ability of some people to wilfully ignore the forest for the trees. Suppose we reframe the argument in terms of color.
In effect, Danny, then, your argument is this: Red can change a little bit if you change its hue or brightness, but it could never change into Blue. Red and Blue are different colors - they can't change into each other!
Well, as anyone who's seen a gradient knows, this isn't true. There's something called purple in between, and it's the reason your argument is, satisfyingly, specious.
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