Natural Selection

[timf1234]

Your thought, explanation will be greatly appreciated.

Is the long neck of giraffe is the result of giraffe trying hard to reach high branches of tree to feed itself or is it that nature just randomly produced short neck, medium neck, long neck and anything in between and it happened to be that long neck survived due to its match with the natural envirnment.

Another way to put it, is the improvement in health due to rigorous athletic practice heritable? could the benefit of 10 or 20 years of swimming practice can be passed on to its off spring?

IS the reconfiguration of human mind due to extreme religious belief heritable?

In contrast, when human design something the second time it has learned from its mistakes that he did the first time. There is a learning feedback is going on. But it seems to me that there is no learning process the method of raw nature. Natural selection is extremely inefficient and wasteful. It is just trial and error minus the learning feedback. It is sheer luck (happening) that out of thousand slight variation only few will render better result.

To survive Monkeys were forced to stand erect so that it can see over the bushes to notice the predators. As a result homosapient walk erect straight up. But this can't be heritable, could it be?

In a sense evolution is very dumb.

Please explain.

 

[MG1962]

Another way to put it, is the improvement in health due to rigorous athletic practice heritable? could the benefit of 10 or 20 years of swimming practice can be passed on to its off spring?

Humans are a poor example to use because we manipulate our environment to the point were a specific attribute is not required to improve survivablilty

However.........Lets look at the Polar Bear. With the reducing ice flows, the bears are having to swim further to access food. Many reports suggest quiet a few bears are turning up drowned. But the occasional bear is going to be a better swimmer than others.

As numbers dwindle, those that are stonger swimmers are going to breed because they have survived, so whatever it is about their make up that makes them stronger swimmers could potentially be passed down down through successive generations.

 

[plumjam]

To survive Monkeys were forced to stand erect so that it can see over the bushes to notice the predators. As a result homosapient walk erect straight up.

Makes you wonder how the non-standing-erect monkeys we see behind bushes today managed to survive.

 

[Ziggurat]

Is the long neck of giraffe is the result of giraffe trying hard to reach high branches

This idea is commonly known as Lamarckian evolution. It is wrong. Herritable traits are passed on through genes. A giraffe does not change its genes by stretching its neck.

 

[Jackalgirl]

Understand that the biggest hurdle (IMO) to understanding natural selection is comprehending the time scale involved.

What happens is this: a random mutation occurs. If it conveys an advantage in an individual and that individual survives to breed and if that mutation is transmitted to its offspring (and if its offspring are not all killed, etc.), then over a very very long period of time that advantage may be conveyed to the majority of the population. The time it takes for this to happen depends largely, of course, on the life span of the individual (and can change in a moment if the environment changes). For primates, this can be a really long time.

As MG1962 points out, it's even harder to understand in humans because we complicate the matter because of culture. Culture -- traditions (such as shared rituals, etc), language, and technology -- allow us to manipulate our environment (and ourselves) in such a way as to "leapfrog" the whole evolutionary process. Instead of gradually, over vast periods of time, evolving a thick pelt so that we can better survive in cold climates, we kill something with a thick pelt and make a coat. That's a simplistic way of describing it, but hopefully it gives you the idea of how very much culture confuses the picture. We are so used to intelligently devising a solution to an environmental problem that we assume that any other solution we observe in nature must have somehow been designed. Even scientists will say "such-and-such animal evolved x trait in order to survive", as if the animal decided to evolve or evolution somehow "decided" to occur so that that animal could fill an environmental niche.

Evolution is not "dumb" or "smart". It is simply the process of random mutation and natural selection over time.

I highly recommend that you check out talk-origins.net archive. Excellent stuff there. There is also a pinned topic in the Science forum called "Evolution: The Facts" you might find of interest.

 

[Gord_in_Toronto]

Makes you wonder how the non-standing-erect monkeys we see behind bushes today managed to survive.

Only if you are completely ignorant about Darwin's Theory of Natural selection and the Theory of Evolution as it is currently understood.

 

[plumjam]

Only if you are completely ignorant about Darwin's Theory of Natural selection and the Theory of Evolution as it is currently understood.

Got any explanation which goes beyond speculative imagination driven by theory? You know, evidence.

 

[shadron]

Makes you wonder how the non-standing-erect monkeys we see behind bushes today managed to survive.

Sometimes it makes sense to be small enough to look under the bushes at they's little feets.

 

[I Ratant]

Giraffes are specialized deer/antelope.
An environmental niche, food in high trees, was exploited by variations of the basic form which passed on their genes.
"Giraffids evolved from a 3 metre (10 ft) tall antelope-like mammal which roamed Europe and Asia 30-50 million years ago.[4] The earliest giraffid was the Climacoceras, which still resembled deer, having large antler-like ossicones."

 

[TX50]

This idea is commonly known as Lamarckian evolution. It is wrong. Herritable traits are passed on through genes. A giraffe does not change its genes by stretching its neck.

I always feel that Lamarck gets a bad press, being associated with just that
small aspect of his theory. By the standards of his time he was an important
promoter of the idea of evolution and adaptation (the prevailing view then
was that species were immutable and individually created). Charlie Darwin
himself was a proponent of the inheritance of acquired characteristics.

 

[cj.23]

Yep,as everyone has said, this is Lamarckianism (a superseded pre-Darwin theory of Natural Selection) not Darwinian Natural Selection.

Jackalgirl gives a good account - but with giraffes it is a bit difficult. The Darwinian hypothesis: Imagine giraffes only eat food from very tall trees. Those giraffes with short necks do not get as much food, as they can't reach, so they die off in times of famine more. Giraffes with a genetic mutation that gives them long necks however survive, so they pass on the genes by hereditary methods to their kids, and more giraffes with long necks are born. The process stops when you reach optimum neck length for tree height - and adaptive advantage.

In Lamarckianism it is as you described. One of the worst disaters in modern scientific history happened when a Soviet scientist called Michurin and his ally Lysenko had the USSR accept Lamarckianism as true and try to employ it to agriculture. Long story, but Google will find it.

However, athe risk of completely confusing you, the genetic theory (the Darwinian -Mendelian synthesis) is not the whole story. Various other factors apply, and some seem Lamarckian - see New Scientist issue 2664, "Rewriting Darwin: The new non-genetic inheritance" on neo-Lamarckism, focussing on possible epigenetic inheritance of acquired characteristics - this article will give you the basics if you are really interested, but if you are not familiar with Natural Selection and the gentic theory it won't get you far --http://en.wikipedia.org/wiki/Epigenetic_inheritance

Dawkin's The Selfish Gene is a good place to start learning this stuff - very readable. If you want to take epidgenetics in to account just replace "gene with replicator" as Dawkins himself said. I'm not sure how deep your understanding of evolutionary theories is, so I hope I have not confused you. Do ask if you have specific questions - lots of much clever people than me on here, and hopefully some biologists

cj x

 

[cj.23]

I always feel that Lamarck gets a bad press, being associated with just that
small aspect of his theory. By the standards of his time he was an important
promoter of the idea of evolution and adaptation (the prevailing view then
was that species were immutable and individually created). Charlie Darwin
himself was a proponent of the inheritance of acquired characteristics.

Very true! Darwin's theory on how characteristics were passed on is nothing like what we understand today, as he seemingly never read Mendel's letter to him outlining his discoveries.

cj x

 

[timf1234]

I want to thank all of you who replied to my question and explained. Yes, it helped.


Ziggurate wrote: <quote>A giraffe does not change its genes by stretching its neck. </quote>

I think that is the answer I was looking for.

then the next question comes in...

since genetic mutation takes place randomly then evolution can take two step forward and then a step backward as well. Yes, I can see that overall there will be forward pressure. But it feels like to me that 3.5 billion years is not sufficient to evolve human being. I wish, similar to half-life of radio-active atoms, they had some statistical data, probability distribution on spontaneous genetic mutation. rate of genetic mutation could have been used to compute the duration it would take for an ameba to evolve to human being.

Is it correct to say that anything species learn either mentally (knowledge in the brain) or its body learns (growing stronger muscle) during its life time is not heritable.

 

[Gord_in_Toronto]

Got any explanation which goes beyond speculative imagination driven by theory? You know, evidence.

Why yes I do. And it has been presented to you many times on this Forum. The evidence has convinced just about every scientist in the World. However, for some reason you seem to feel it is not your problem that you don't understand.

 

[cj.23]

Is it correct to say that anything species learn either mentally (knowledge in the brain) or its body learns (growing stronger muscle) during its life time is not heritable.

Sort of - it's like my friend DC's lament --"you live and learn, then die and forget it all". In a species like humans knowledge is transferable by education etc, though one has to make the effort to acquire it - hence my lament about one of my mates internet usage - "He had at his fingertips the learning of the ages. He chose to dedicate his life to looking at breasts."

cj x

 

[Subduction Zone]

We are learning more and more about evolution every year, it is sure that it has occurred, and is still occurring and that it is the mechanism that gave us life as we know it today. For example one of the first keys was the fossil record. Even 100 years ago it was complete enough to show that creationism was not the answer. Since then we have added substantially to it. Every fossil found has supported the evolutionary theory and no other. Now that we are beginning to understand genetics we are beginning to understand the how. For example not every change in a specie has to be done by creating new genes. In the genetic code there are all sorts of genes that are "turned off". They have done experiments to "turn on" some of these genes and have found features not found in the current specie. With chickens they have developed teeth, a longer tail from its dinosaur past, scales, and hairy feathers. But until they find out how a specie evolves it is going to be a bit to early to say how long it takes.

 

[temporalillusion]

since genetic mutation takes place randomly then evolution can take two step forward and then a step backward as well. Yes, I can see that overall there will be forward pressure. But it feels like to me that 3.5 billion years is not sufficient to evolve human being. I wish, similar to half-life of radio-active atoms, they had some statistical data, probability distribution on spontaneous genetic mutation. rate of genetic mutation could have been used to compute the duration it would take for an ameba to evolve to human being.

Terms like "forward" and "backward" imply a direction to evolution that isn't really there. There's simply directionless change. The shaping takes place through natural selection; selection will determine if the change is negative, positive, or neutral.

I'm not sure exactly what you are looking for with regards to statistical data, but there's something like 175 mutations in each generation of human... you have 175 mutations from the genetic code you got from your parents. Obviously the vast majority of those would be neutral, otherwise either the race would die out in a few generations, or there'd be too much change from one generation to the next.

Trying to come up with the # of incidents of genetic change (because mutation isn't the sole source of this) to get from a single celled organism to a person, not sure if they've done something like that.

Is it correct to say that anything species learn either mentally (knowledge in the brain) or its body learns (growing stronger muscle) during its life time is not heritable.

Pretty much, though the ability to do these things are themselves determined genetically and are selectable. So while how strong an animal gets in its life may not be passed on, how strong it is able to get would be. Same with knowledge, while the specific piece of knowledge might not be directly passed on, the capability to learn it would be. Instincts are examples of patterns that arose and were passed on because they lent survival advantages.

 

[Subduction Zone]

temporalillusion, I would not quite use the term directionless change. The direction of change is determined by the environment or changes in the environment that the specie lives in. For example submitting a population of bacteria to anti-biotics will induce a change into a resistant specie. But you are right in that an animal does not purposefully evolve into a giraffe.

 

[drkitten]

But it feels like to me that 3.5 billion years is not sufficient to evolve human being. I wish, similar to half-life of radio-active atoms, they had some statistical data, probability distribution on spontaneous genetic mutation. rate of genetic mutation could have been used to compute the duration it would take for an ameba to evolve to human being.

Well, they do have some experiments and calculations of the sort you ask for, albeit not for the full amoeba-to-human (which is a misrepresentation anyway, since you'd be looking at the evolution of the most recent common ancestor of an amoeba and a human, and we don't really know much about what that would have been, genetically speaking).

But they've done smaller-scale analyses of things that are more amenable. One of the most famous is presented here; the eye can evolve from, literally, bare skin, in less than 400,000 generations. Since most animals have a generation time of a year or so, that means less than a half million years --- there's time for the eye to evolve from scratch 1500 times since the beginning of life on earth.

 

[shadron]

Is it correct to say that anything species learn either mentally (knowledge in the brain) or its body learns (growing stronger muscle) during its life time is not heritable.

Yes - in order to be heritable, a change must be made to the DNA (no other change will do) of the egg/sperm cells of the individual. I know of nothing which changes the DNA of any cell, except in a generally bad, quasi-random way by inhibiting the normal chemistry, of any cell, barring human bio experiments.