Does natural selection justify evolution?

[Martian]

At first Natural Selection theory looks brilliant.But how can you measure if natural selection is really true?Its logical to claim that giraffes got tall because shorter giraffes died of starvation but how could you scientifically prove this thing?
I always thought that pure Luck is the Key reason why some organisms live and why some others not.A tall giraffe might die on childbirth while a short giraffe could survive.The hight of the neck plays no role to this.
Perhaps Life has the ability to "learn" some things and adapt?

[Himster]

At first Natural Selection theory looks brilliant.But how can you measure if natural selection is really true?Its logical to claim that giraffes got tall because shorter giraffes died of starvation but how could you scientifically prove this thing?

Starvation is not the most common means that a species disappears. Much more likely long necks were seen as attractive by females, short necks were not selected.

I always thought that pure Luck is the Key reason why some organisms live and why some others not.A tall giraffe might die on childbirth while a short giraffe could survive.The hight of the neck plays no role to this.
Perhaps Life has the ability to "learn" some things and adapt?

Not luck, it's adtaptation to the changing enviroment.

[Martian]

Yeah but how can you be sure that female giraffes found long necks more attractive?I find it very logical that giraffes adapted to their environment in order to eat leaves that were at the top of a tree.How this happened?

[Himster]

Yeah but how can you be sure that female giraffes found long necks more attractive?I find it very logical that giraffes adapted to their environment in order to eat leaves that were at the top of a tree.How this happened?

The simple answer is: we don't know, the exact circumstances are unknown, we do know laws of attraction, we know how mammals select today, it is perfectly reasonable to speculate based on what we know.

What we do know is it happened.

[Prince of Darkness]

Yeah but how can you be sure that female giraffes found long necks more attractive?I find it very logical that giraffes adapted to their environment in order to eat leaves that were at the top of a tree.How this happened?

Short necks can't be more attractive than long ones because the short necks didn't survive.
Theories evolve from facts.
This thread should be in the Athaneum, btw.

[Martian]

Isnt it a bit odd to have a theory and adjust it in a way that fits every situation?You have an animal trait and when you dont understand how this trait emerged you pick up the sexual selection which is convenient because it cannot be proved that really sexual selection made this trait emerge

[Himster]

Isnt it a bit odd to have a theory and adjust it in a way that fits every situation?You have an animal trait and when you dont understand how this trait emerged you pick up the sexual selection which is convenient because it cannot be proved that really sexual selection made this trait emerge

It is proven that sexual selection determines genetic traits today, there are of course other factors at work, but it is the most influential and we know it always has been by looking at the fossil records. The causes could be manifold, but observing modern giraffes we easily see that long necks do not help when it comes to eating, they prefer the moist leaves in the center of the tree and short grass. Where the long neck does some into play is where males compete for mates. The two males cross necks and swing as hard as they can to get their "Horny" heads to connect with the upper cranium of his opponent. The longer the neck the greater chance of victory and the greater chance reproduce.

[Theseus1234]

I always thought that pure Luck is the Key reason why some organisms live and why some others not.A tall giraffe might die on childbirth while a short giraffe could survive.The hight of the neck plays no role to this.
Perhaps Life has the ability to "learn" some things and adapt?

No. Giraffes evolved long necks because they could use them to reach the tall acacia trees, a previously untouched niche. Because of this, giraffes which are unable to reach the leaves will pretty much die and those who can will have a stable food source since giraffes are practically the only animals to eat those leaves.

[Elfdude]

Natural selection places adaptive pressures on the evolution already occurring due to the natural instability and chemical properties of DNA. As the DNA mutates in it's replication (some creatures have reductions on this mutation others have DNA that mutates awesomely fast) natural selection decides whether the traits of the new DNA are beneficial or not in the long term.

For example people with brown eyes see less glare than those with blue eyes. This advantage is only apparent in a very sunny area because for the most part brown and blue eyes work the same. So in a population with 500 blue eyed and 500 brown eyes, if we imagine that the brown eyes give a 10% advantage (due to slightly increased ability to spot food, longer eye health, cultural preferences etc), each generation the brown eyed people will grow at a 1% faster rate than the blue eyed people. Lets pretend that the world they live in is pretty harsh and they're managing a 1.0% and 1.1% growth rate on average.

Now, we'd still have a big population of brown eyed and blue eyed people in the first generation and even in the 50 years there's only really a 50 population difference between the two growth. But! Resources aren't unlimited. It'd be nice to imagine a village of 1000 people growing in 50 years to ~1700 but there was a reason that village had a 1000 people in the first place. Lets imagine that the carrying capacity of the land can only support 1200 people at maximum. Now lets add in the natural death rate of the people in the land at .1%.

Now we've got some real evolution happening. At a 1200 maximum population this will result in massive amounts of deaths as growth rate occurs. Naturally the brown eyed people will push the blue eyed people out of the gene pool. However if we pretend that the two groups are against each other (lets say for racism) suddenly one population group could eliminate all (of course some genetics are recessive and will hide) of another population's genetics. Naturally this could happen via a natural disaster (called bottle necking).

Anyways, the totality of this effect over a 100 years is nothing, in a 1000 years depending on random events it could have changed something drastically (for example human sexual selection has lead to humans today who are up to about 6-12 inches on average than their ancestors during roman times), or nothing really at all (depends on the stability of the environment and the competition the species has). Like I said, a few differences. However as the natural death rate approaches the growth rate of the blue eyed people the population will be significantly biased towards brown eyed genetics. This is what they mean by natural selection. Nothing is selecting anything, and the traits themselves are only barely more beneficial than other traits. Some traits are even only beneficial to animals because of their own personal behavior or culture, a peacock's tail actually reduces it's survivability but because it's required for sexual reproduction it ensures that surviving males are tough and cunning leading to better genetics in the long term. A human's brain in intermediate stages offers very little physical advantage over smaller brains, however it would offer significant advantages in communication (both sexually and within the social unit).

It's key not to mix up the process of natural selection (which is the biasing of traits for success) and evolution itself. Evolution will always occur because of our DNA (in simple terms), unfortunately as we can tell with a machine there's more ways to make something not work than to make it work. Natural selection is simply the difference in utilitarian advantages/disadvantages that lead to a population's success or failure.

edit for giraffe evolution

Also giraffes are one of two surviving species from a line that includes the Okapi

Spoiler Alert, click show to read: 

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Basically they're a deer like creature who evolved very dexterous tongues to eat the leaves of thorny plants. In Africa this is a huge amount of untapped food resource which evolutionary pressures lead towards a larger creature in general. As the creatures got larger they were unable to stand up on their hind legs anymore giving those with longer necks the ability to reach the food they required. The Acacia trees do have creatures which take advantage of the lower stalks. The tops from about 8-9 feet + however typically are untouched. This puts the giraffe species in a sink or swim moment. For the carrying capacity of the environment to tolerate more creatures utilizing the tops of the trees is a requirement.

What would've happened if the giraffes didn't evolve? Likely another creature would've capitalized on the resource. Dinosaurs on the other hand developed long necks for a different reason. It was so they could reach more food from a safe location. Sauropods were far to large to be able to move easily in forested areas but most of their food was from the forest (keep in mind grass hadn't evolved yet) they needed to be able to get into it and get into it deeply. Thus rather than creating tall necks sauropods got long low to the ground necks that could reach dozens of feet into the forest and devour it. Forests were also the hunting grounds of many predators meaning getting stuck in them was a giant dino's worst nightmare. Thus long necks are simply more effective and thus invariably appear.

[Darth Red]

More like an Athenaeum thread to me as well. Moved.

[Colonel Cleg McLeg]

It can also be observed in nature. Have a look at this little horror story, for instance. Evolution in action, and it ain't pretty.

[chamaeleo]

At first Natural Selection theory looks brilliant.But how can you measure if natural selection is really true?Its logical to claim that giraffes got tall because shorter giraffes died of starvation but how could you scientifically prove this thing?

Perhaps Life has the ability to "learn" some things and adapt?

Natural selection is very often the result of the persistence of slightly advantageous traits across several generations, until the proportion of your population which inherited that trait becomes dominant.

Classic example:
http://en.wikipedia.org/wiki/Peppered_moth

For your giraffes: nothing so drastic as "starving to death" need occur. Since evolution happens over multiple generations, all you need for one lineage to succeed is a slightly better success rate. For instance, if a lineage w a 10cm neck length advantage eats about 3% more leaves on average days and 10% more leaves during drought periods (when competition for lower branches is tight), each mother's offspring will not only inherit the advantageous neck-length...but will also receive energetic benefits from Mama's better milk supply: making them stronger, faster growing, and more resistant to disease. Net effect: more offspring survive to breeding age, who then continue the trend.

I always thought that pure Luck is the Key reason why some organisms live and why some others not.A tall giraffe might die on childbirth while a short giraffe could survive.The hight of the neck plays no role to this.

Actually, neonates w super-long necks might die more often during birth due to complications. Humans w our overly large heads are ourselves balancing birth success rates w the need for big-ass craniums.

Across multiple generations, even a slight advantage becomes a logarithmic, positive feedback loop.

Why then doesn't neck length increase, ad infinitum? At some point, the giraffe must be able to escape predation...in which case, neck length is a disadvantage. What we have, is a species performing a constant balancing act: always struggling to find the optimal neck length. Introduce more predators, necks shorten...remove predators, necks lengthen. Such is evolution: except for species extinction, it never really stops.

[Georgy Zhukov]

But how can you measure if natural selection is really true?

http://en.wikipedia.org/wiki/Peppered_moth_evolution
BEATEN BY THE GUY ABOVE

[Copperknickers II]

At first Natural Selection theory looks brilliant.But how can you measure if natural selection is really true?Its logical to claim that giraffes got tall because shorter giraffes died of starvation but how could you scientifically prove this thing?

Well, you look at fossils, and you measure your moths and your bacteria in the short term and measure small changes. You are correct that noone has sat down and chronicled a species evolving a completely new feature or into a new species, but that's because it takes millions of years. The theory and short-term evidence tell us how it could happen, and the modern animals and fossils tell us that something has made it happen, so its literally a case of putting two and two together to create evolutionary theory.

[Colonel Cleg McLeg]

You are correct that noone has sat down and chronicled a species evolving a completely new feature or into a new species

What, a carnivorous mouse three times the size of any other species isn't a good enough example for you?

It can also be observed in nature. Have a look at this little horror story, for instance. Evolution in action, and it ain't pretty.

[cpdwane]

According to QI (the most reliable source in the world, obviously!) Giraffes actually evolved their longer necks due to sexual selecion. It's because when the males compete for a female they try and beat the competition into submission by bashing their necks into each other's, and wrapping themround each other until one submits. The longer necks are an advantage because they give the longer necked Giraffe more ability to beat the other one.

[Prince of Darkness]

According to QI (the most reliable source in the world, obviously!) Giraffes actually evolved their longer necks due to sexual selecion. It's because when the males compete for a female they try and beat the competition into submission by bashing their necks into each other's, and wrapping themround each other until one submits. The longer necks are an advantage because they give the longer necked Giraffe more ability to beat the other one.

I think longer necks are more clumsy to control.
Btw, does longer penis also fit this theory?

[Tacitursa]

You are correct that noone has sat down and chronicled a species evolving a completely new feature or into a new species

Thats not correct

http://www.sciencedaily.com/releases...0305150917.htm

http://www.newscientist.com/article/...n-the-lab.html

[Sphere]

Thats not correct

But thats just micro evolution. If sum up small changes over millions of years you cannot get large changes, obviously.

Really there's no use, attack childhood indoctrination or you will never be able to undermine these belief systems. In their mind they have linked the love for their family/friends/community with the notion that evolution isn't true. For them to accept the fact of evolution, they have to accept that their parents/ministers/community are deluded liars and everything they think is good in the world is a falsity. If you put yourself in their shoes you can easily understand why they are desperate to hold onto what seems like a silly belief to us who aren't invested in such a way.

They have an emotional bond, not a logical one, and that is why no type of evidence can break it.

[Tacitursa]

But thats just micro evolution. If sum up small changes over millions of years you cannot get large changes, obviously.

Yes you can , thats exactly how large changes occur. There's no difference between micro and and macro evolution both happen in the same way for the same reasons. Macroevolution is just the result of alot of microevolution. You cant just bake a cake , you need the ingredients first.

I dont think the problem lies with religious people having an emotional bond, Millions of religious people fully accept evolution including the pope. Some religious people are just very poorly educated and ignorant and dont understand what micro evolution actually is.

In their mind they have linked the love for their family/friends/community with the notion that evolution isn't true. For them to accept the fact of evolution, they have to accept that their parents/ministers/community are deluded liars and everything they think is good in the world is a falsity

I think its more of the oposite. They are trapped in there wackjob community and constantly reinforce each other that the rest of the world are liars. It's just ignorance. If you removed a creationist from there community and surrounded them with rational educated people it wouldnt take much for them to see sense.