In my opinion, New Scientist is the best of the current crop of science magazines for the general public, although, in all honesty, the competition is not very challenging.New Scientist has published Darwin's dangerous idea: Top 10 evolution articles. Most of them are fairly respectable. The main exception is an article on epigenetics [Rewriting Darwin: The new non-genetic inheritance]. That article is an embarrassment.
One of the best articles is Evolution: 24 myths and misconceptions. I've already posted my kudos at: Evolution: 24 myths and misconceptions. One of the nicest things about the series of articles is their description of random genetic drift as an important player in evolution; for example, Evolution myths: Natural selection is the only means of evolution.
Which brings me to the last article in the top ten list: Freedom from selection lets genes get creative. Here's what it says about random genetic drift.
Natural selection, first identified by Charles Darwin in On the Origin of Species, occurs when genetic mutations cause changes in the body and behaviour of an animal that affect its ability to survive and pass on its genes. Some mutations will have positive effects, others may kill an animal outright or somehow affect its offspring's ability to survive and reproduce. Harsh climates, sparse food and relentless predators destroy many individuals, leaving only those that survive best under exactly those pressures. As a result, the more intense the pressure of natural selection, the tighter the fit between a species and its niche.Close, but it doesn't quite merit a cigar. Drift does not "kick in" when selection pressure is lifted. Drift occurs all the time. It even competes with natural selection.
So, what happens when the pressure is off? You might think there would be little impetus to adapt, so that species would pretty much stay the same. Not so, says Deacon. Animals still change because genes mutate all the time. The constant rewriting of DNA supplies the raw material from which natural selection picks its winners and losers, and when selection is relaxed, the process of weeding out is less ferocious. Instead, a process called genetic drift kicks in as mutations proliferate and animals with a much wider variety of traits are able to survive and reproduce. Some of the classic traits of a species may be lost, while others can arise for no reason other than that it simply doesn't matter if they do.
And while it's partially true that, "the more intense the pressure of natural selection, the tighter the fit between a species and its niche" it's also true that intense "pressure" increases the chance of extinction.
It seems strange that popular journals can publish articles about evolution that disagree with each other and nobody (editors?) seems to notice.
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ReplyDeleteIt seems strange that popular journals can publish articles about evolution that disagree with each other and nobody (editors?) seems to notice.
ReplyDeletePut the ideas out there, and let natural selection pick the winners.
I don't think that people don't notice. Its just that your average reader doesn't care enough to analyze things to any extent, or simply doesn't retain enough article-to-article to really hit on the "conflicts".
ReplyDeleteUnfortunately, creationists occasionally notice, and then claim that the errors (conflicts) in those articles represent some sort of scientific uncertainty about the accuracy of evolutionary theory.
Bryan
PS: Happy new year
Another minor gripe is the way they imply that selection is one-dimensional. As if one species is under intense selection because food is sparse and there are lots of predators, but another is under little selection because food is plentiful and predators few.
ReplyDeleteOf course in reality, thousands of different traits will be subject to all different levels of selection simultaneously.
Of course in reality, thousands of different traits will be subject to all different levels of selection simultaneously.
ReplyDeleteIt's a jungle out there.
Interesting to note that drift weakens severely the efficacy of natural selection and the probability of any particular beneficial gene becoming fixed in a population.
ReplyDeleteRegarding drift and selection, it reminds me of Hodgkin's analogy in distinguishing diffusion from electrochemical diffusion: diffusion is like fleas hopping, and electrodiffusion is like fleas hopping in a breeze.
ReplyDeleteThe statistical mechanics of drift are always operating, but may be obscured by winds of selection.
It is funny that Jablonka would present epigenetics contribution as the overturning of the "selfish gene" crap, which is such hopeless and unscientific crap to begin with.
ReplyDeleteIt's also funny that "bad" epigenetics is surfacing that is quite like the soft, "bad genetics", that has been around for so long...now we will not only identify a gene for, say political preference, but also a gene methylation for it...
These aberrations and overhyping not withstanding, it is clear that the phenomenologicla horizon of heredity is being expanded by epigenetics, and there are "mildy" lamarckian implications (environmnetal modificataion of heredity and "inheritance of acquired traits" albeit without the adaptaionims and progressism that characterized lamarckism) . Of course, this is no true "lamarckism", but let us not forget that a fairly stupid "antilamarckism" has led to flat denial of some hereditary phenomena that we now know is completely true, down to the molecular detail.
I don't see what the big deal with epigenetics is. And I find it disappointing that talk circulates of some new Synthesis of epigenetics, when the primary alterations to the modern synthesis should come from paleobiology and evo-devo. I think Jablonka may be tooting her own horn here.
ReplyDeleteRichard Lewontin has some cynical thoughts on the import of epigenetics here:http://www.scoop.co.nz/stor
ies/HL0807/S00077.htm
In his words: "[People]...are always looking to suggest that they have an idea which will overturn our whole view of evolution because otherwise they’re just workers in the factory, so to speak. And the factory was designed by Charles Darwin. You want to become famous, you make a big noise about some of your latest theory."