Okay a short request, I need a few cases of a family or person to have some kind of beneficial mutation. Titanium bones or IR-eyes or something like that... less drastic things are okay too.
Thanks...
O and i need some good links to scientific papers for someone.
Edit;31 10 08
| Quote: |
| Any beneficial mutations (I just gave examplesi thought up, so heres try 2). I know evolution is slow but there must have been SOME beneficial mutation, like some people that are immune to HIV. |
Last edited by Klaw 2 on Fri Oct 31, 2008 11:13 am; edited 2 times in total I don't really understand the request.
How would you measure a beneficial mutation in a human, since the world is pretty much set-up for the normal human phenotype. You could argue that a particularly tall person had a beneficial mutation since they could reach higher fruits on apple-trees. In real life, however, it is more likely to be a handicap.
You are not going to get drastic mutations such as the ones you mention for the simple reason that evolution does not work like that.
What sort of scientific papers do you want?
| Bikerman wrote: |
| I don't really understand the request. |
Ditto.One could argue that the genotype (not phenotype) for sickle cell anemia is an evolutionary step to protect humans from Malaria.
In high malaria areas (africa) people with the genotype for sickle cell (SC/sc) do not exhibit the disease sickle cell, but are immune to malaria. People with the sickle cell phenotye (SC/SC) exhibit sickle cell disease and are immune to malaria (bad). and people without the genotype for sickle cell (sc/sc) are in danger of malaria infection.
This example argues in the favor of evolution in that the genotype for sickle cell is selected for (to protect against malaria) in areas with high rates of infection. And also explains why african americans are more prone to the disease.
Any beneficial mutations (I just gave examplesi thought up, so heres try 2). I know evolution is slow but there must have been SOME beneficial mutation, like some people that are immune to HIV.
kmkramer,
yes, I think that is well established now. Good example.
Klaw2,
on the one hand you say that evolution is slow (correct) and on the other you mention evolved immunity to AIDS (a disease which is about 1 generation old). Sorry, that is simply not going to happen.
It could be that there are people who are naturally resistant to AIDS (in fact there is some suggestion that this is the case), but there has not been sufficient time for those people to pass on their genes to new generations and it is arguable that there has not been sufficient selection pressure to favour that genotype in any case. I would predict that if the disease continues to run rampant in many African states then we will begin to see significant levels of resistant individuals in a couple of generations but I, for one, am hoping that the disease is brought under control well before that happens.
Steve Jones (British geneticist) recently argued that evolution in humans has effectively stopped. I'm not sure I agree with him entirely, but he does make some valid points;
http://www.timesonline.co.uk/tol/news/uk/science/article4894696.ece I read/heard somewhere that some people are imune to aids because of the black plague
People have plenty of advantageous genes, but I think studies showing novel advantageous mutations in people are probably few and far between.
By the way, evolution is not necessarily slow. Adaptation can occur really fast even under surprisingly weak selection, and neutral forces like drift and flow can result in rapid evolution, too. Evolution resulting from mutation is slow, but selection acting on mutations may produce responses fairly rapidly.
| Gagnar The Unruly wrote: |
| By the way, evolution is not necessarily slow. Adaptation can occur really fast even under surprisingly weak selection, and neutral forces like drift and flow can result in rapid evolution, too. Evolution resulting from mutation is slow, but selection acting on mutations may produce responses fairly rapidly. |
Yes, depending on how well correlated the beneficial mutation is with other beneficial traits.
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The thing that has me most confused about this thread is the notion of time. ^_^; i mean... if you were to ask me to name one beneficial mutation that humans passed on through evolution, i might shrug and say "the large brain".
But while that's technically correct i don't think that's what you're looking for. It sounds like you want to take the phenotype as it is now and ask what beneficial changes have happened... in which case i'd have to answer "none... because now is now, and we can't change from what we are now - beneficially or otherwise - until... later." ^_^;
The other thing i'd point out is the curious selectivity in what counts as a beneficial mutation and what doesn't. i assume no one here argues that resistance to some virus or bacteria could mutate into existence, and that would be beneficial. i also assume that no one disputes that an extra toe is a mutation, but that no one thinks it's particularly beneficial. All fine and good so far... but what about people who can metabolize heavy trans-fats extremely well? They can eat all the cheap fast-food and insta-food they like, and never get sick or overweight. Isn't that beneficial? That would relieve them of the burden of having to watch what they eat for the sake of their health and appearance... making it easier to look good (which improves their sexual selection rate), etc. It's not adamantium bones... but it ain't that bad, eh?While sickle cell anemia is the classic example of human genetic mutation, skin color could also be a good example. People indigenous to the tropics have much darker skin than do people far north of the equator. The explaination I have heard is that the darker skin color protects the skin from harmful UV light. Upon migration to the far north, the need for this trait diminishes and random mutations lead to different skin colors. Here is a link to a wikipedia article: http://en.wikipedia.org/wiki/Human_skin_color#Genetics_of_skin_color_variation | Voodoocat wrote: |
| Upon migration to the far north, the need for this trait diminishes and random mutations lead to different skin colors. |
Partially, but there is actually a strong selector for fair skin in northern (and far southern) climates: blocking too much of that light inhibits the body's capability of producing vitamin D. With the reduced sunlight of these regions, dark skinned people have trouble getting enough vitamin D.Peace.
On the general note of evolution in humans, couldn't we argue evolution is now greatly reduced in humans because of our ethics to protect the weak, disabled, and our scientific/technological knowledge which allows to extend the lives of those who would die e.g. due to inherited genetic disease. In other words, since the weak aren't dying and breed with the strong, then natural selection isn't occuring.
Same thing with the ability to travel globally: Isolation is reduced greatly thanks to aeroplanes, so speciation is less likely to occur.
What do you think?
It is a valid argument to some extent, but not entirely. Certainly there is less 'natural weeding out' in modern human society. There are other, I think stronger, arguments why evolution may have slowed (even stopped?) in humans.
You may find the following by Steve Jones interesting.
http://www.guardian.co.uk/science/2002/feb/03/genetics.research It sounds to me like a bunch of silly arguments are being made by people who want to sell books.
One point needs clarification here. Natural selection is NOT the same thing as evolution. Natural selection is a process in which individuals of a certain traits are more likely to survive or reproduce than individuals with other traits. Evolution is genetic change over time. To the extent that that trait is heritable, natural selection will lead to evolution by natural selection. Also, it's very important to remember that evolution will still occur even in the absence of natural selection, due to other forces that produce evolution and that are always present (unlike natural selection).
For example, lets pretend that selection is acting to favor orange people. There is a plague that kills pale people, but never kills orange people. Lets consider three possible circumstances:
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1) Two people are orange because they have a gene that makes them orange. Everyone else is pale because they lack the 'orange' gene.
2) One person is orange because they have the 'orange' gene, and another person is orange because she happens to eat a lot of carrots, but she lacks the 'orange' gene. Everyone else is pale.
3) Noone has the orange gene, so everyone is pale except two people, who eat a lot of carrots. |
In case 1), the survivors of a plague that kills all pale people will be genetically orange. Their offspring will be orange, and the population will evolve (the orange gene increases in frequency)
In case 2), one survivor has the gene and the other doesn't. Evolution will happen (the gene will still increase in frequency), but not as fast as in case 1)
In case 3), the survivors orange because of what they ate, and not what their genes were. Therefore, their trait was due to 'plasticity' and not genetics.
To the extent that a trait is controlled by plasticity and not genetics, natural selection will not result in evolution. Natural selection can also be relaxed. Lets say that only half of the pale people are killed off in the cases given above. Selection would be weaker, and evolution would be slower than if all of the pale people were killed off and only orange people survived.
What humans have done (at least those living comfortable lifestyles) is both increase plasticity and decrease the strength of natural selection, particularly selection acting on genes related to disease resistance. We have medicines to treat disease, so susceptible people have a similar chance to survive as resistant people (plasticity). We also have eliminated a lot of diseases by our health and sanitation practices (reduced strength of selection). Both of these processes can, and probably do, reduce the strength of selection, reducing rates of evolution by natural selection. However, there are two important points to make: 1) this is only the case for a minority of the world population, and 2) evolution by natural selection results in a LOSS of genetic diversity.
Point 2) is very important. The 'scientists' in the Guardian article talk about the homogenizing consequences of weak selection and high rates of gene flow in human populations. However, this does not mean that genetic variance is lower. People may appear more similar to one another, but the overall genetic variation of the human population will increase. Furthermore, genetic variants will become more broadly distributed. This makes humans more, not less, capable of adapting to sudden changes in selective forces. Not that it matters, as we can respond plastically to most environmental changes, making us less reliant on adaptation by natural selection (generally, lots of people have to die for evolution by natural selection to occur).
Unfortunately, I think that many of the authors cited in the Guardian article are guilty pseudoscience. They make arguments founded upon biased assumptions based on their own biased perceptions, and then use their perceptions to validate their arguments. It's typical pseudoscientific circular reasoning. It's also unnecessary, as we have plenty of evidence of how human phenotypes have changed over time. It's also possible to track genetic changes in human populations to see exactly how much change is happening. Genetic signatures can even suggest what kind of change is happening. A study like this would be possible in Iceland, where the human population is perfectly censused (it may already have been done). Wouldn't it be interesting if natural selection is still playing a role in Iceland? It's as likely as not, and we have no way of knowing without looking.
There are also a few facts that shouldn't be ignored. First, regardless of the reason (plasticity vs. adaptation), humans are now faster, smarter, stronger, fitter, and better than ever before, on both local and global scales. Second, our technology gives us a chance to respond plastically to whatever changes in our environment do occur, and this is an improvement over relying on adaptation. Third, there is no reason to believe that our genetic variance now lower than it was historically -- we have in no way 'weakened' as a species. Fourth, most of the world still lives in a state of misery, with high birth rates and high death rates. Natural selection is still a problem faced by many people on Earth. Double post. Sorry! 
| Gagnar The Unruly wrote: |
| It sounds to me like a bunch of silly arguments are being made by people who want to sell books. |
Actually that's my fault for linking to the Guardian article - it hardly discusses Jones' thesis at all. I should have linked to the Times article
http://www.timesonline.co.uk/tol/news/uk/science/article4894696.ece
In fact I should link to Jones' seminar speech but I haven't got the link handy.
Jones does tend to court publicity a bit but he does know of which he speaks (he is Professor of Genetics and Head of Biology at UCL).
