Posted on 03/27/2011 12:09:25 PM PDT by decimon
Darwin's notion that only the fittest survive has been called into question by new research published today (27 March 2011) in Nature.
A collaboration between the Universities of Exeter and Bath in the UK, with a group from San Diego State University in the US, challenges our current understanding of evolution by showing that biodiversity may evolve where previously thought impossible.
The work represents a new approach to studying evolution that may eventually lead to a better understanding of the diversity of bacteria that cause human diseases.
Conventional wisdom has it that for any given niche there should be a best species, the fittest, that will eventually dominate to exclude all others.
This is the principle of survival of the fittest. Ecologists often call this idea the `competitive exclusion principle' and it predicts that complex environments are needed to support complex, diverse populations.
Professor Robert Beardmore, from the University of Exeter, said: "Microbiologists have tested this principle by constructing very simple environments in the lab to see what happens after hundreds of generations of bacterial evolution, about 3,000 years in human terms. It had been believed that the genome of only the fittest bacteria would be left, but that wasn't their finding. The experiments generated lots of unexpected genetic diversity."
This test tube biodiversity proved controversial when first observed and had been explained away with claims that insufficient time had been allowed to pass for a clear winner to emerge.
The new research shows the experiments were not anomalies.
Professor Laurence Hurst, of the University of Bath, said: "Key to the new understanding is the realisation that the amount of energy organisms squeeze out of their food depends on how much food they have. Give them abundant food and they use it inefficiently. When we combine this with the notion that organisms with different food-utilising strategies are also affected in different ways by genetic mutations, then we discover a new principle, one in which both the fit and the unfit coexist indefinitely."
Dr Ivana Gudelj, also from the University of Exeter, said: "The fit use food well but they aren't resilient to mutations, whereas the less efficient, unfit consumers are maintained by their resilience to mutation. If there's a low mutation rate, survival of the fittest rules, but if not, lots of diversity can be maintained.
"Rather nicely, the numbers needed for the principle to work accord with those enigmatic experiments on bacteria. Their mutation rate seems to be high enough for both fit and unfit to be maintained."
Dr. David Lipson of San Diego State University, concluded: "Earlier work showed that opposing food utilisation strategies could coexist in complex environments, but this is the first explanation of how trade-offs, like the one we studied between growth rate and efficiency, can lead to stable diversity in the simplest possible of environments."
Yes, as a matter of fact, *I* do.
It means you'd better answer correctly when your wife asks "Does this outfit make my butt look big?" or -- you'll either get killed outright, or else never get a chance to propagate your jeans genes.
Darwin award, indeed.
Cheers!
gotta watch it, grey .. some people have NO sense of humor.
Hmmmmm, so the creationist prediction that stasis is very much underrated is......accurate?
That's what the "fittest" means: those most fit to survive under the circumstances. This "fitness" may be a genetic predisposition, innate qualities, size, color, etc., or even something learned...but whoever or whatever has it will have a greater chance to survive under specific circumstances.
Variation within a populations is a measure of the fitness of a population, not just an individual. A stress that could wipe out a hypothetical “super fit ultimate competitor” bacterial population with almost no variation would only decimate a population with more variations, because some variations would be or become resistant to the stress.
Well, yeah, but that’s how their society worked.
I recently read about a compilation of all known examples of pre-Alexander Greek art. In those which were intended to represent the ideal of beauty, young boys/men outnumbered females by 14:1.
Which is as if you walked down the magazine rack today and 95% of the covers had young males on them rather than young females, instead of the other way around. Sex sold in ancient Greece, as today, but it was a very different kind of sex. Obviously changes a society quite dramatically.
This changed later, BTW. The Hellenistic Greeks and the Romans had much more appreciation for female beauty.
Another Greek ephebophile issue.
The high point of Greek culture and art coincided exactly with the maximum popularity of ephebophilia.
Which makes it pretty unlikely their addiction to homo sex caused their eventual collapse.
The common conservative belief that Greek/Roman homosex caused their societies to collapse does not, unfortunately, fit the timeline.
LOL! I do have a sense of humor. And grey is correct, for the term “fit” doesn’t mean the biggest, meanest ‘badass’ - it means those best able, by any means, to survive.
And you don't get chromosomes unchanged from a grandparent or great grandparent. The chromosomes you inherited from mom are almost exactly a 50/50 inheritance split between her mom and dad - and the chromosomes you inherited from dad are almost exactly a 50/50 inheritance split between his mom and dad.
Recombination frequency is measure in “centimorgans” which correspond to a % chance that a crossover event will happen between two chromosomal markers (mixing and matching mom and dad's DNA along the chromosome to make reproductive cells). It is about a 1% chance to have a cross over every 15,000 nucleotides.
The human genome is on 46 chromosomes and consists of 3 billion base pairs. That makes the scale of 15,000 nucleotides pretty small.
Correct and amend my remarks....
“and the chromosomes you inherited from dad are almost exactly a 50/50 inheritance split between his mom and dad.”
Other than the Y chromosome in males - that you get from your father much the same as he got it from his father; with only a small section that does recombination with the X chromosome he got from his mother.
..... um.......
And of course the X chromosome in women that they got from their father; that also only underwent a very small amount of recombination with the Y and is therefore almost exactly what he got from his mother.
A fitness partition function -- now that's an odd thought.
Cheers!
The attraction to young men did not "cause" a demographic death spiral of the type Mark Steyn laments in America Alone (a possible "cause/effect") but it might have "caused" God to get pissed at their culture and arrange for them to get their ass kicked.
(E.g. think of Old Testament judgements, there was often a time lag baked in. cf Jeremiah 44.)
Cheers!
| 0 | 0 | 0 | 1 | 2 | 1 | 0 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 0 | 0 | 3 | 1 | 2 | 2 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 3 | 0 | 2 | 1 | 1 | 0 | 1 | 0 | 1 | 2 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 2 | 2 | 0 |
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| 2 | 1 | 0 | 2 | 1 | 1 | 2 | 2 | 2 | 1 | 2 | 1 | 2 | 1 | 1 | 2 | 1 | 2 | 0 | 2 | 2 | 2 | 2 | 1 | 1 | 1 | 2 | 1 | 2 | 1 | 1 | 2 | ||||||||||||||||||||||||||||||||
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There is no need to find an “integer solution to one quarter of 46” because chromosomes DO NOT PASS DOWN INTACT as an “integer”.
Recombination during meiosis, also called chromosomal crossover, makes sure that no mother or father passes on, intact, a copy of their mothers chromosome 21 but their fathers chromosome 20, etc. Each and every chromosome (excepting the X and Y as I previously mentioned) is a 50/50 mix of grandparent DNA when passed down.
No, it isn’t. That’s why I didn’t respond to that part.
http://biology.clc.uc.edu/courses/bio104/meiosis.htm
“Meiosis is a special type of cell division that produces gametes with half as many chromosomes. The opposite process would be syngamy or fertilization, which is the union of the egg and sperm to restore the 2n number.”
This is familiar to everyone who ever saw a cell nucleus in division, but these gametes are the basis for sexual reproduction.
Genetic info can and does cross over, but it’s similar to mutation rates, with a higher frequency — still small. For all practical purposes, the integer model shown above is correct. Meiosis isn’t like shuffling all the genes on every chromosome or blending out the differences.
http://en.wikipedia.org/wiki/Recombinant_frequency
“At the beginning of normal meiosis, a chromosome pair (made up of a chromosome from the mother and a chromosome from the father) intertwine and exchange sections or fragments of chromosome. The pair then breaks apart to form two chromosomes with a new combination of genes that differs from the combination supplied by the parents. Through this process of recombining genes, organisms can produce offspring with new combinations of maternal and paternal traits that may contribute to or enhance survival.”
The human genome is 3 billion base pairs.
How many crossover events would you expect during one round of recombination of the “average” chromosome?
Chromosomes are from 50,000,000 to 300,000,000 base pairs. So the smallest would have a 1% chance * (300,000,000/15,000 = 20,000).
A 1% chance 20,000 times is going to be a significant number of crossover events - resulting in the chromosome being a mix of paternal and maternal DNA.
Every time. Not as rare as a mutation.
As such it is immaterial to talk of finding an integer solution to 46/4 to determine grand-parental contribution to an individual. It just doesn't go down like that at all.
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