Why does a giraffe have a long neck?

[GoSeminoles!]

Ok, the theory is that a giraffe developed a long neck and long legs to reach the tender leaves on the top of the tree. Can someone give me a more exact description on how the neck and legs got longer? I need a little bit more than just a generic answer saying long necked giraffes were selected over short necked giraffes. I need to know why some giraffes had longer necks and why some had short necks. Also, how did longer necks get longer over time?

From TalkOrigins:

Giraffes: Branched off from the deer just after Eumeryx. The first giraffids were Climacoceras (very earliest Miocene) and then Canthumeryx (also very early Miocene), then Paleomeryx (early Miocene), then Palaeotragus (early Miocene) a short-necked giraffid complete with short skin-covered horns. From here the giraffe lineage goes through Samotherium (late Miocene), another short-necked giraffe, and then split into Okapia (one species is still alive, the okapi, essentially a living Miocene short-necked giraffe), and Giraffa (Pliocene), the modern long-necked giraffe.

...Giraffe neck lengths. Baby giraffes start out with necks whose relative length is similar to those of other ungulates; it is as they grow that they acquire the relatively long necks that the species is noted for.

An interesting piece suggesting the neck's evolution was driven by sexual selection.

 

[UniversalAxis]

The same logic of suggesting that the added weight of the giraffe's body would give it an advantage in territorial contests, and thusly breeding advantage, is the same advantage which would lend itself to fending off preditors.
A lion or other carnivore is much more likely to kill a smaller giraffe than one which could protect itself properly.

 

[napajohn]

what many of you fail to realize is that there is a natural selection that act upon the trees as well..why are some trees tall and others are not..this is a case of what came first tall trees or giraffes reaching for that tree..THE EVIDENCE and i mean EVIDENCE that go against this can be seen in the so called giants that exist today..most often a case called acromegaly is treated..not trumped as an advantage..often many like Andre the Giant die an early life..so you can speculate all you want but the evidence of natural selection on necks growing are so not supported ...there are issues such as differences in how the blood pressure changes are to be handled for one as well as the
explanation as to how the socalled shortnecks lived if the long necks were favored and survived..thats way the darwinian mechanism is so challenged by many scientists today.

 

[UniversalAxis]

Tragedies like Andre the Giant are perfect evidence of what happens when an individual is the subject of a major genetic mutation which the current species cannot support; but, somewhere in the genetic code of men is the possibility for great physical growth. One need only look at the similarities between a person with Lincoln's Disease or Giantism, which are currently fatal to some individuals, to see the capability and frequency of these genetic mutations. Moreover, look at one such a Manut Bol, the basketball player, or the guy from China, Yao, who both stand over seven feet tall. This is one end of the genetic spectrum, and in the case of the latter basketball players, both men are fit and healthy. Perfect examples of genetic expression. But even beyond that, should natural selection favor that genetic disposition, I.E. to be tall, that trait could become dominant within a group of individuals.
I don't suppose that you have ever heard of Secraterat? The supernatural, yet real race horse which won the Tripple Crown. Moreover, Chihuahuas have not always existed. Nor have German Shpherds, Doberman Pichers, or any other breed of dog. They are all descended from wolves which were tamed by man long ago. This is verifyable. New breeds of Dog have arisen due to human selection. Breeding for specific traits has long been a source of biodiversity. Are you aware that modern Corn cannot reproduce successfully without Human help? No other animal in the world can aid corn, except humans. We have created new breeds in almost every animal and plant which we have used for an extended period. We have forced evolution. But nature forced it first.

 

[kingreaper]

what many of you fail to realize is that there is a natural selection that act upon the trees as well..why are some trees tall and others are not..this is a case of what came first tall trees or giraffes reaching for that tree...

Its a simple evolutionary arms race, those giraffes which are tallest can reach the most trees, those trees that are tallest can be reached by least giraffes, both selection pressures operate simultaneously

THE EVIDENCE and i mean EVIDENCE that go against this can be seen in the so called giants that exist today..most often a case called acromegaly is treated..not trumped as an advantage..often many like Andre the Giant die an early life...

Yeas, largescale mutations such as uninhibited growth are often deleterius, however being slightly taller is advantageous in some situations (imagine if mates were picked solely based on their basketball prowess)

so you can speculate all you want but the evidence of natural selection on necks growing are so not supported ....

What support do you want?

there are issues such as differences in how the blood pressure changes are to be handled for one as well as the .

As the adaptation of longer necks occured adaptation to handle the extra blood pressure required happenned simultaneously, not in one individual but in many generations (better able to handle blood pressure= fitter)

explanation as to how the socalled shortnecks lived if the long necks were favored and survived...

IIRC this is known as allotropic speciation, there were different niches, as the long-necks ate the tall trees the short-necks probably ate shrubbery, and a longer neck would quickly become deletrious in eating shrubs

thats way the darwinian mechanism is so challenged by many scientists today.

many= about 100 probably

 

[Hydra009]

what many of you fail to realize is that there is a natural selection that act upon the trees as well..why are some trees tall and others are not..

Because trees evolve, too. Some species grow to be very tall and some are shorter.

this is a case of what came first tall trees or giraffes reaching for that tree..

Obviously, tall trees came first. If there were no tall trees, there would be no benefit for long necks in giraffes.

THE EVIDENCE and i mean EVIDENCE that go against this can be seen in the so called giants that exist today..most often a case called acromegaly is treated..not trumped as an advantage..often many like Andre the Giant die an early life..

Let me get this argument straight, because being execessively tall/large can cause health problems in humans, that means that comparably large animals like giraffes cannot exist. I think you might be wrong about that...

so you can speculate all you want but the evidence of natural selection on necks growing are so not supported ...there are issues such as differences in how the blood pressure changes are to be handled for one as well as the
explanation as to how the socalled shortnecks lived if the long necks were favored and survived..

Interestingly enough, this claim has been thoroughly refuted by Darwin himself. http://www.talkorigins.org/indexcc/CB/CB325.html

thats way the darwinian mechanism is so challenged by many scientists today.

Oh, really. Pray tell, how many scientists reject evolution today?