July 18, 2005
Lose Tusks, will Travel
Posted by scott at July 18, 2005 12:13 PM
Problem: While big, burly tusks make you real popular with the ladies, it also makes you really popular with naked apes with boomsticks.
Solution: Drop the tusks. Since you're the only male around, it won't much matter what the chicks think:
The tusk-free gene, which is found in between two and five percent of male Asian elephants, has increased to between five percent and 10 percent in elephants in China, according to Zhang Li, an associate professor of zoology at Beijing Normal University.
Apparently controversial even in China, the finding will need more testing before firm conclusions can be drawn.
eMail this entry!
Hmmm - to bad this wasn't a new gene at work - it would've been nice to see evolution handling a problem introduced by man...
Ron - You don’t have to look far to see man’s influence on evolution. From specialized moths to bacteria to the eradication of biodiversity throughout all habits, for better or worse man has thrown many problems at the animal kingdom and evolution has responded.
Scott, no matter what I click, I can't seem to find a trackback link.
Back on topic... I'm with Roth. I've seen some moths that evolved to take advantage of a particular niche - that niche being a building where I once worked. About a third of the moths I saw there were the exact same color as the building.
But the question is did the moths adapt or evolve? That's a key difference. If you're talking about the B Bistulara (I think I'm getting the right species spelling there, but I do tend to screw it up) moth, I can't say that this was a new gene or an existing gene and the population shifted. I'll see what I can do on researching the topic and then try and sweet talk Scott into posting findings...
I think we would notice if the elephants were taking to breaking off their own tusks to avoid predation (which would be adaptation) as opposed to the ones being born without tusks surviving to produce more offspring with the no-tusk genes (which is evolution).
Actually, in the article, they stated that the mutation had previously existed in 2-5% of the population, leading me to believe it wasn't specifically an evolutionary change - the increase in the gene in the population would appear to due to selection - in this case, folks with rifles shooting them for their tusks.
The part that's unclear based on what the article said is when the gene first appeared. If it appeared after the influence of mass-hunting for ivory, then it would be considered evolution. If it's always been there, it isn't.
A similar case involves salmon. Normally, the chinook (okay, I think it's the chinooks - it could be another species of salmon) mailes are large and easily distinguishable. However, there are 'runt' males that are called jacks. During the mating process, the females let the males jockey for position to fertilize their eggs - leading to fish fighting and the like. Since the jacks are small, they let the others fight and sneak in and fertilize the eggs when no one's looking. However, this appears to have been happening before the influence of man. Interestingly enough, each group of the population changes in it's overall percentage based on it's previous percentage - when there are more normal males, there's more fighting and the jacks benefit. When the percentage of jacks increases, the normals then increase because they can easily fight off the jacks and do the fertilizing themselves.
The sudden appearance of new genetic strains is called mutation, not evolution. Evolution is a process, mutation is one of the by-broducts. Saying the appearance of new genetic expressions is evolution is like saying a computer is science.
Actually, I'd say it's the other way around - without mutation, you've no evolution. Whether or not the mutation leads to evolution depends on whether or not the specific mutant, or mutants, have a better chance at survival. If they don't, they didn't evolve, the devolved and likely died (which is the case with the vast majority of phenotypically-expressed mutations). If they did happen to have a better chance at survival, and conditions existed that selected for that trait, then I'd say you get evolution.
And some people say that without computers, you would have no science.
As I said before, evolution is the selection process, nothing more and nothing less. It can take place with or without mutations, such as when it results from recessive genes becoming dominant under sufficient selection pressure.
I disagree with both the example and the point - not trying to be harsh or anything like that.
Science existed long before there were computers and is, in fact, independent of computers. They certainly help, especially in organizing data, crunching numbers, etc., but science isn't beholden to computers.
The specific example you have here of recessive genes becoming dominant is a bit cloudy. If the recessive gene just becomes more prevalent and the dominant managed to basically non-existant, that isn't evolution - that's selection. Unless a new gene is introduced, there is no evolution. That's a basic tenet of evolution. You are correct, evolution is a process. It's a process by which mutations occur in a species genome that give the individuals within that species a better chance of passing on their genes. If they don't pass on their genes, that individual might have evolved, but the species didn't. If the changes are of a sufficient number or impact, then a new species is introduced.
However, again, no new gene (i.e., mutation), no evolution.
Ron – Don’t you have a degree in this stuff?
Evolution – Change within a line of decent over time. A population is evolving when some forms of a trait are becoming more or less common, relative to the other kinds of traits. The shifts are evidence of changes in the relative abundance of alleles for that trait, as brought about by mutation, natural selection, genetic drift, and gene flow. *Biology concepts and applications, 3rd edition, Cecie Starr, 1997 Wadsworth Publishing* – probably wrong format of citation.
Biological evolution is a process of some traits becoming dominant over others due to many environmental and random factors, not solely defined by the creation of new genes or traits (mutations). Maybe it changed since 1997… but I think you‘re wrong on this one, my friend.
Yes, I do have a degree in this. And I actually disagree with the above definition, but will admit that folks do define evolution as changes in alleles, regardless of the mechanism. The problem is that this leads to confusion between Darwinian evolution and, the current best example, Punctuated Equilibrium.
In Darwinian evolution, natural selection is the pressure and changes in phenotypic expression (traits, as defined above) can result in evolution. Unfortunately, phenotypic expression doesn't necessarily mean genotypic (as the genes may still be present in the population). It also doesn't explain speciation (the process that brings about new species).
In order for speciation to occur, the genotype of the population must change or else all you have is a different phenotype (think breeds as an example). Historically, differing phenotypes have been classified as different species - something that is currently regarded as an incorrect view of classification. We now do genetic testing to determine whether or not we have a new species or just a variation on a currently existing species. This leads me to Punctuated Equilibrium. This theory states that while mutations occur at a steady rate in a population, there is typically no real reason for those changes to continue (and, in fact, most of them tend to die off rather quickly - they exist in a single individual and die there) unless and until some pressure acts from the outside that causes the individuals with those mutations to survive, thusly replacing or displacing the current population, or allowing them to occupy a new environment. Then, the two populations accumulate enough mutations that they can't interbreed, resulting in new species.
So, in this specific example and the following posts/arguments, I'm both right and wrong. I believe I'm right in that no mutation=no evolution. However, I'm potentially wrong in calling this an adaptation and not evolution. It could very well be evolution - but I think that this remains to be seen. The true test will come down the road - if the tuskless elephants replace or displace the tusked ones, then we have seen what I would call a true evolution. Until then, I'd argue that it's adaptation.
Hopefully, this clears what I'm saying up a bit. So to T and Roth, I did present too narrow of a view, and for that I apologize - I was wrong. I should've gone back and explained my view much more thoroughly which should've not lead to the arguments...
You know, I just remembered having a nearly identical argument here once before, and Ron handed me my head then too.
I hate when my wetware system spontaneously reverts to a previous version.
I didn't think I handed anyone their head - I do tend to be rather direct. As Scott, Johshua, and I have discussed before - we're all rather reasonable when we're in the flesh, as it were (no puns, please).
I think part of the problem on subjects that I have some measure of expertise in is that I can sometimes get too far into the details and am arguing the potential implications and not specifically the case at hand, trying to correct misperceptions, etc. I'll try to work on that so don't hand folks their heads...
Go ahead and be direct, this is how I learn. Eventually.