Surely, evidence of everything alive (especially humans) supports Darwin's theory?

[cameron marical]

how is it debatable of the fact that we as life forms evolve without just random mutations but actually genetic differences to better fit there environment. things couldnt just be random like that. its alot like muscles, we need better ones, we develop better ones, we dont, we dont, right?

 

arent humans a good example of that? our different skin pigments? lighter skin, come from a snowier place, wich white reflects sun, and also blends in.

brown, from hotter places, like mexico, and alot of america, to not be as harmed by the sun by just getting darker instead of getting damaged.

black, well im sure they have a reason too. alright maybe thats not a good one to use for an example.

 

same thing, with different wolves. white for snow, dark for forest.

 

and i know, it could just be random mutations wich just happen to fit the best for the present evironment, and those who dont mutate, die, wich forwards that one mutation to become common, but i just think that that sounds too far-fetched to belive that we are as we are by coincidence of gene abnormalities that just happen to be perfect for the environment we live in.

 

what do you guys think?

[Mokele]

We're actually very sure that environment has nothing to do with which mutations show up or don't. For a start, there's no possible mechanism. More importantly, animals with deleterious mutations all the time - consider white alligators, which stick out like a sore thumb.

 

White alligators are also a good example for another reason - most die, and die soon, usually picked off by predators. Selection can be very intense, and even weak selection can push a beneficial mutation to 100% prevalence in a few dozen generations.

 

Mutations also don't show up when needed. An excellent example is the Dodo tree, eaten by everyone's favorite extinct bird until their extinction. Now it's highly endangered because nothing else can eat it without destroying the seed. Clearly, a mutation could solve this problem, but one hasn't happened in 300 years.

[scrappy]

how is it debatable of the fact that we as life forms evolve without just random mutations but actually genetic differences to better fit there environment. things couldnt just be random like that. its alot like muscles, we need better ones, we develop better ones, we dont, we dont, right?...

 

Cameron, it’s also worth mentioning that individuals carry many genes (specifically alleles) that are not expressed as proteins or phenotypes, thus proving a reservoir of code variations for eventual selection. Also there are many phenotypes expressed in individuals that play no role in natural selection. As such, mutations are not always the source of allelic or phenotypic variety that serves evolution. However, if you trace the history of alleles of a gene there could be two things that caused their original formation: 1. mutation, and 2. gene flow (i.e., lateral transfer of genetic material, including whole genes or parts of them, from one species to another*).

 

*If you ever saw the movie The Fly you might get the general hang of it.

[cameron marical]

how do mutations happen in the first place?

[Mokele]

Basically, they're just copying errors. No cellular machinery is perfect, and as a result, errors happen. There's also environmental damage, since DNA isn't a terribly stable molecule.

[scrappy]

Basically, they're just copying errors. No cellular machinery is perfect, and as a result, errors happen. There's also environmental damage, since DNA isn't a terribly stable molecule.

True enough. To expand a bit, I though I'd add this quote on mutation from Daniel L. Hartl and Elizabeth W. Jones (Essenial Genetic/A Genomics Perspective, 2002, p. 520):

 

Mutation is the ultimate source of genetic variation. It is an essential process in evolution, but it is a relatively weak force for changing allele frequency, primarily because typical mutation rates are so low. Moreover, most newly arising mutations are harmful to the organism. Although some mutations may be selectively neutral (in other words, they do not affect the ability of the organism to survive and reproduce), only a very few mutations are favorable for the organism and contribute to adaptation.

 

That is why other non-selective agencies of evolution like random genetic drift and gene flow are also important players.

[cameron marical]

why dont we humans have mutations much?

 

do we?

 

i read that cancer is a mutation. not a very good one though. is this true?

[Mokele]

We have lots - the average human have 10 mutations new to them which affect final protein coding, and countless more that don't. Thing is, most of these mutations either have little effect or are recessive, so are invisible unless you breed with someone with the same mutation.

 

And yes, mutations continue throughout life. If these mutations damage important machinery that regulates cell division and DNA repair, the result can be cancer.

[cameron marical]

why dont we see big mutations like different amount of arms or stuff that often then?

 

thanks for your help man.

[Mokele]

why dont we see big mutations like different amount of arms or stuff that often then?

 

Basically, because it's a complex, interlinked system, and screwing with anything big is likely to be quite, quite bad.

 

Imagine a car, and you modify one random part in a random way. If it's the color or the hubcaps or even the shape of the exterior, it will affect the car, but in a simple way (more drag, less drag, gets hotter on warm days, etc.) But if you randomly modify bits of the engine, it could be disastrous.

 

Developmental genes, which control thinks like limb number, are a lot like that - complex, interacting systems which tend to break down in horrible ways if something goes wrong, often leading to death in the early embryo stage.

 

This doesn't mean that there can't be changes, just that the odds of a mutation being good are pretty low. This is borne out by evolutionary history, where you see a lot of little changes all the time, but it's only rarely that you see major changes in body form.

[Kyrisch]

Further, however, is always that fact that it does happen. There are stories all the time about babies with eight limbs and mermaid feet and cows with bizarre deformities on farms. It's just much rarer, and often disastrous enough to, as iNow said, cause early death.

[cameron marical]

why then, do species all seem to have that one mutation, i know, natural selection kills off the weak, and leaves the ones with the good mutation, but that means that multiple organisms of the same species would have to have that same or similiar mutation, and then mate, and those kin would have to mate with others that have similiar mutations, but not their relatives, because that causes mutations in its own{does that mean that inbreds are more likely to have a good mutation too}, and the odds just stack up dont they?

 

so how can one species all change like that? like the white wolf in snowy climates, or brown in forests, those odds are just too high, arent they? its beleiveable to say that the ones with the good mutation live and the bad normal ones die, leaving only mutated ones, but that means that theyed have to find another of the same species with the same mutation, if the mutation is recessive and not dominate.

 

so lets say 5 cubs are born{ill go with wolves}, well out of those 5 cubs, 2 come out dark and eventually die, so 3 cubs, need to find others to mate with that have the same mutation as them, and more of that mutation than anything else{like parents with that mutation}, and now this has to be done like 30-40x. {judging by quick rounding in my head and population limit for extinction is about 100, or things get inbred and mutations are bad and they all die}

 

really? that sounds pretty unlikely to me, though i could be wrong.

thanks.

[Mokele]

What you're missing is that, in many cases, the mutation will be 'hidden' due to a recessive gene. It's like albinos - an organism that looks normal may have one copy of the albino gene, but if it breeds with another like itself (with a hidden copy), a fraction (25%) of the offspring will be albino. If the albino breeds with another animal with one hidden albino gene, 50% of the offspring are albino.

 

The key is that there is a large amount of standing variation in any population, mostly 'hidden' in this manner. Occaisionally, the mutations get expressed, and the offspring is selected for or against, but in the absence of strong selection in either direction, there will be quite a lot of variation just laying in wait for selection.

 

Another important key is that either-or traits are quite rare in nature. You're more likely to see traits vary continuously (such as variation in body size, or literal shades of grey in coat color), with selection favoring one extreme or possibly the middle. In these situations, where there's no binary expression, its a lot easier to see how speciation could happen. Consider variation in neck length, with selection for long necks leading to giraffes.

[Tsuyoiko]

Just to expand a bit on what Mokele says, the changes are cumulative. Continuing with your wolves, you won't get all white wolves in a couple of generations. But if an even slightly lighter coat makes the wolf cubs less susceptible to predators, it might mean that lighter wolves have 10 surviving cubs instead of 9, those cubs go on to have their own cubs. Maybe one or two of those are lighter still, so they have 11 surviving cubs etc etc. Eventually, after several hundreds or thousands of years you will get white wolves. I'm over-simplifying, but I think that's roughly how it works.

[scrappy]

Just to expand a bit on what Mokele says, the changes are cumulative. Continuing with your wolves, you won't get all white wolves in a couple of generations. But if an even slightly lighter coat makes the wolf cubs less susceptible to predators, it might mean that lighter wolves have 10 surviving cubs instead of 9, those cubs go on to have their own cubs. Maybe one or two of those are lighter still, so they have 11 surviving cubs etc etc. Eventually, after several hundreds or thousands of years you will get white wolves. I'm over-simplifying, but I think that's roughly how it works.

Or, in other words, cumulative selection and random pressures on the wolf's genome, however they are interpreted, favored the propagation of the white-fur genotype.

[cameron marical]

Or, in other words, cumulative selection and random pressures on the wolf's genome, however they are interpreted, favored the propagation of the white-fur genotype.

 

due to snow, ya.

 

what about things like muscle gain or sun taning, could that be classified as adaptations? is that what they are? when something needs more muscle or whatever, it will make more muscle to cope with its environment. could things like that{muscle gain, darkened or lightened skin color, bone density gain, etc...} just add up with variations of environments and ecosystems to eventually lead on to speciation? i know that things like skin color changes are due to changes in melanin {i think, might be something else} from light quantites received, but i still consider it like muscle gain, an adaptation. am i wrong?

 

thanks.

[Mokele]

Muscle gain due to exercise isn't actually passed on to your kids, nor is tanning. However, different people have different ability to tan or build muscle, and different natural levels of muscle or melanin. So if being dark-skinned or muscular is an advantage, individuals who start at a higher baseline (due to genetics) will have an advantage, even if everyone can 'improve'.

[cameron marical]

the body size doesnt get passed down? i thought it was the same, isnt it fact that if 2 obese people have a child, that child is more likely to be obese? that doesnt mean that they can work it off of course, but that would be the same as muscle wouldnt it?

 

how could something like a higher baseline be passed down due to genetics not be the same thing as what im saying?

maybe i misinterperted.

[Mokele]

The issue is that everyone starts out with a certain natural size, muscle mass, tan level, etc. You can alter any of these, but what gets passed on to your offspring is your natural level, not the improved version.

[scrappy]

the body size doesnt get passed down? i thought it was the same, isnt it fact that if 2 obese people have a child, that child is more likely to be obese? that doesnt mean that they can work it off of course, but that would be the same as muscle wouldnt it?

 

how could something like a higher baseline be passed down due to genetics not be the same thing as what im saying?

maybe i misinterperted.

It helps to remember that organisms do not evolve, only their populations. However, in the case of obesity, a child of two obese parents could be genetically predisposed to obesity...just like a cub of two white wolves.

 

As Mokele has already pointed out, a lot depends on whether not the obesity allele (variation of a gene) or the white-fur allele is dominant or recessive.

[cameron marical]

so say my grandparents were both obese born on both sides of my family, yet my parents were all skinny, due to working it all off or getting lucky and not getting the "fat" gene, would that mean that i would be more prone to be obese?

 

when do gene or allele frequency's get disregarded after being passed down so many generation?

[Mokele]

so say my grandparents were both obese born on both sides of my family, yet my parents were all skinny, due to working it all off or getting lucky and not getting the "fat" gene, would that mean that i would be more prone to be obese?

 

If they worked it off, yes, because you'd have the gene from your parents.

If they luckily escaped the gene, then they could not pass it on to you, so you would have no more risk than normal.

[cameron marical]

i see. thanks. ok, now that thats cleared up, i have some more.

 

this is completely off topic and possibly should be in another post, but here goes it.

 

why cant people today re-form the abiogenisis process? i watched a couple videos on it, and it seems like people have it all mapped out, so why hasnt anyone done this yet? whats stopping them?

[Kyrisch]

i see. thanks. ok, now that thats cleared up, i have some more.

 

this is completely off topic and possibly should be in another post, but here goes it.

 

why cant people today re-form the abiogenisis process? i watched a couple videos on it, and it seems like people have it all mapped out, so why hasnt anyone done this yet? whats stopping them?

 

We could under simple laboratory conditions compel some simple self-replicating molecule to come into existence, but it wouldn't prove anything because the boundary conditions would be so simple as to no longer relate to the kind on early Earth. On the other hand, we don't have the resources to recreate the vast laboratory that was early Earth. In short, the event is too complicated to model simply, and too complex to model fully.

[cameron marical]

We could under simple laboratory conditions compel some simple self-replicating molecule to come into existence, but it wouldn't prove anything because the boundary conditions would be so simple as to no longer relate to the kind on early Earth. On the other hand, we don't have the resources to recreate the vast laboratory that was early Earth. In short, the event is too complicated to model simply, and too complex to model fully.

 

i see. and its really too complicated to just form this simple rna strand, and then just wait to see if it mutates even a little bit over time? or maybe mutate it yourself and speed up the evolution process? well, i guess that isnt that simple either, but still.

 

thanks.