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Questions about Evolution

Any topic related to science can be discussed here.
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MedMae
Posts: 167
Joined: March 14th, 2008, 9:46 am

Re: Questions about Evolution

#21 Post by MedMae » October 6th, 2008, 6:52 pm

Latest post of the previous page:

Beki wrote:I thought that something became a different 'species' when the genetic code had diversified enough that any offspring were infertile. You know, like horses and donkeys mating to produce sterile mules.

Is that not right then?
Thats one of the requirements used to define different species and when speciation has occured.

However there are 2 buts.

But 1.
It's not that simple.

But 2.
Species are an entirely artifical concept.
Complexity is just simplicity multiplied to a point which exceeds a particular level of comprehension. - Theowarner

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Paolo
Posts: 1474
Joined: September 13th, 2008, 9:15 am

Re: Questions about Evolution

#22 Post by Paolo » October 6th, 2008, 7:24 pm

I'm not sure I'd go as far as "entirely artificial", but they certainly aren't the clearly delimited categories that we might want them to be.

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jaywhat
Posts: 15807
Joined: July 5th, 2007, 5:53 pm

Re: Questions about Evolution

#23 Post by jaywhat » October 7th, 2008, 10:35 am

A bit (very small) in today's Guardian (p12) which says 'this is as good as it gets'. Or as bad!
Human evolution is slowing, say Prof Steve Jones of University College, London. Alterations to the genetic blueprint are less likely in a world that is an ethnic melting pot. We are apparently living in utopia.

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Paolo
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Re: Questions about Evolution

#24 Post by Paolo » October 7th, 2008, 12:11 pm

Selection pressures are reduced in the Western world (they are still very high in other parts of the world, particularly some regions in Africa), so beneficial mutations do not currently confer any advantage over neutral, or (with modern medicine) many negative mutations. We may be becoming more homogenous as a species, but, mutations continue to accrue in the genome of the population, albeit in a diluted manner. At some point in the future, if (or quite likely when) selection pressures increase again, this large pool of diverse mutations could potentially fuel a rapid rate of evolution, leading humans to adapt (and possibly speciate) at a faster rate than might be expected. Of course, this is all conjecture!

MedMae
Posts: 167
Joined: March 14th, 2008, 9:46 am

Re: Questions about Evolution

#25 Post by MedMae » October 7th, 2008, 12:35 pm

I'm not convinced there is a reduced selection process going on or if it's just changed. For example in western society there is clearly a reduced significance on physical capabilities, but there is still going to be a high selective process going on in relation to cognitive abilities. Not just in intelligence but abilities to endure stress and concentrate.
Complexity is just simplicity multiplied to a point which exceeds a particular level of comprehension. - Theowarner

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Alan H
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Re: Questions about Evolution

#26 Post by Alan H » October 7th, 2008, 12:51 pm

Has anyone read the articles in today's papers reporting what Prof Steve Jones has said about the slow down in human evolution?

The Scotsman

The Herald

The Times
Alan Henness

There are three fundamental questions for anyone advocating Brexit:

1. What, precisely, are the significant and tangible benefits of leaving the EU?
2. What damage to the UK and its citizens is an acceptable price to pay for those benefits?
3. Which ruling of the ECJ is most persuasive of the need to leave its jurisdiction?

Nick
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Re: Questions about Evolution

#27 Post by Nick » October 11th, 2008, 10:26 am

I'm hazy about this, but it may stretch back to Malthus. The proposition is that it is the less able who breed more, and therefore that humanity is on a downward path. I'm not competent to examine thoroughly, though I'm inclined to think it is too pessimistic, but it would be an interesting starting point, to attack or defend as appropriate.

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Paolo
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Re: Questions about Evolution

#28 Post by Paolo » October 11th, 2008, 11:43 am

MedMae wrote:I'm not convinced there is a reduced selection process going on or if it's just changed. For example in western society there is clearly a reduced significance on physical capabilities, but there is still going to be a high selective process going on in relation to cognitive abilities. Not just in intelligence but abilities to endure stress and concentrate.
Intelligence is likely to be a negatively self-selecting trait. It is hard to pick intelligence from education (and socioeconomic status) in our society, but intelligent/well educated people (most importantly women) generally don't start reproducing until later in life (if they choose to all). It tends to be the less intelligent/educated who start breeding at an early age, continuing to do so for longer, having more children in total, many of whom repeat the process. Being less intelligent/educated is actually a beneficial trait for passing on genes.
Nick wrote:I'm hazy about this, but it may stretch back to Malthus. The proposition is that it is the less able who breed more, and therefore that humanity is on a downward path. I'm not competent to examine thoroughly, though I'm inclined to think it is too pessimistic, but it would be an interesting starting point, to attack or defend as appropriate.
I think that the concept of a "downward path" is rather deterministic, since it applies that we are/have been/should be on an "upward path" - but towards what? Evolution is about breeding, not brains. The "less able" are those that don't breed, when we are talking in evolutionary terms. Someone might have an IQ of 72, no education, have no job and do nothing for society, but if they have ten kids (even if they are taken into care immediately) they are evolutionarily more successful than a Nobel Prize winner who has no kids.

I'm not sure I entirely agree with Steve on this, I can see where he's coming from, but use of the mean age of fathers does not reflect any pattern of the data. I'd like to see the raw data on this (or at least the range, standard deviation, median and a Kurtosis value), because the reduced average age could be due to be the result of a negative skew towards very young fathers (or even a binomial distribution of some young and some older fathers). Such a skew would shift the value of the mean, without it reflecting where the bulk of the data lie. Also, it would be interesting to see if the range of the data is greater than it was historically, since it may include a wider range of ages of men, so although the mean is lower, there could be more older men reproducing that there were historically. I also think that the narrow temporal range weakens the observation, since it wouldn't take much social change to shift the pattern.

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Alan H
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Re: Questions about Evolution

#29 Post by Alan H » October 12th, 2008, 5:08 pm

Paolo wrote:I'd like to see the raw data on this (or at least the range, standard deviation, median and a Kurtosis value), because the reduced average age could be due to be the result of a negative skew towards very young fathers (or even a binomial distribution of some young and some older fathers). Such a skew would shift the value of the mean, without it reflecting where the bulk of the data lie. Also, it would be interesting to see if the range of the data is greater than it was historically, since it may include a wider range of ages of men, so although the mean is lower, there could be more older men reproducing that there were historically. I also think that the narrow temporal range weakens the observation, since it wouldn't take much social change to shift the pattern.
This happens so often, doesn't it? All we ever get is an occasional 'average' value of something, be it house prices, salaries or whatever. But this tells us little of the shape of the distribution and the shape is very important. I long to see an article in the media that gives mean, median, modal value, std dev and Kurtosis. Without, it's impossible to come to any firm conclusions about the data. I won't hold my breath, though. [/rant]
Alan Henness

There are three fundamental questions for anyone advocating Brexit:

1. What, precisely, are the significant and tangible benefits of leaving the EU?
2. What damage to the UK and its citizens is an acceptable price to pay for those benefits?
3. Which ruling of the ECJ is most persuasive of the need to leave its jurisdiction?

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Alan C.
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Joined: July 4th, 2007, 3:35 pm

Re: Questions about Evolution

#30 Post by Alan C. » October 14th, 2008, 8:35 pm

There is a book coming out in January Why Evolution Is True.
See PZ Myers review here.
I hope Jerry Coyne will forgive me that my frequent thought as I was reading his new book, Why Evolution Is True was, "Wow, this sure is easier to read than that other book.
Abstinence Makes the Church Grow Fondlers.

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