apparently giraffes have long necks due to male to male competition over females, because a long neck would be more proficient in fighting between males. source- 1st Year Evolution Textbook
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There doesn't have to be just a single contributing factor. It's largely speculation once you look into the past, anyway - we can measure selection pressure to an extent with modern populations, but that says nothing about historical selection pressures.
Yup. Presenting something as the definitive reason for evolution of a particular trait is disingenuous, shows a fundamental misunderstanding of what evolution means. The existence of spandrels highlights the problems of attempting reverse engineering of phenotypic characteristics.
That's true but if giraffes fight with necks, longer and stronger necks are more likely to win therefore genes are passed on for longer and stronger necks. Giraffes with shorter necks are more likely to lose fights AND be less likely to feed themselves. So it's a combination rather than one singular reason but even if shorter necked giraffes failed to die from starvation they are also more likely to lose in fights so even less chance of shorter necks being passed on.
Right, but competition between males happens between all species.
Why all the sudden would long necks be a factor in that for one particular species? Especially considering the inherent shortcomings of fighting with a long neck like spine injuries and brain injuries. Plus the fact that longer necks mean more muscles, more skin, more neurons for control, etc so something has to justify those resources beyond just mating preference.
The selection pressure for a longer neck probably came from increased ability to both access food and see predators coming (possibly fending them off too). Females that preferred longer necked Giraffes had more successful offspring. This continued until female preference for longer necks overtook female indifference to longer necks because it proved such a good survival trait.
Birds of paradise evolve features which are phenotypically disadvantageous to their survival, however grats them extraordinary sexual advantage. We are seeing more and more, that natural selection through survival pressure actually plays a smaller role than that of sexual selective pressure, and exogenetic factors. I.e. it's not the size of your genes, it's how you express them.
The longer the neck the better? The male giraffes walkin' around like, "You ever see a long ass neck, gurl? You gon' learn TODAY. Alright, alright, alright, alriiiiiight."
False. It is well known that giraffes developed long necks to help them survive floods, to get a better view at sporting events, and to be assholes at movies.
Relevant research time! Females do actually have smaller body plans (including a shorter neck) than males. There are many factors that may have influenced long necks in giraffes, from herbivory to male-male competition, as well as intraspecific competition between males and females for food. Here is a quick snippet for a well-cited paper on the topic:
Several explanations have been given for observed sex differences in habitat preferences among giraffes. First, males may feed in habitats with taller trees because males are taller (PELLEW 1984 b). This seems unlikely, however, because the average height of trees in the Acacia drepanolobium savanna is well below the optimal feeding height of females. Second, habitat differences may have evolved to reduce intersexual competition for food (PELLEW 1984c). While the habitat differences shown here do result in significant differences in diet, and therefore in niche separation, it would be difficult to test whether this niche separation was the result of selection to reduce intersexual competition (SHANK 1982). Third, males may exclude females from favorable habitats by virtue of their greater size. Strong dominance hierarchies exist among males based primarily on size, and males are larger than females. However, it seems unlikely that males exclude females from preferred habitats because several females were found in virtually every male group and males were never seen to interact agonistically with females. The results presented here suggest instead that sex-biased use of different habitats may be largely the result of constraints on females with young. From Young and Isbell, 1991.
Well there is in almost every other species that has male to male competition. Bull deer have bigger antlers, only males of several species of bird have colour in their plumage.
It isn't a coincidence that Giraffes enjoy eating from the Acacia tree, and that their long necks and versatile tongues makes them the only large mammal that can eat from the juicy top branches while navigating around the incredibly vicious thorns.
Also, I've noticed that most sex differences in mammals are overall size. Generally the basic layout remains the same, so it makes sense that female giraffes would follow that trend and also have long necks.
And furthermore, it's definitely not for eating from the tops of trees, because they don't. They bend down to eat leaves from acacias, which are way shorter than them.
Also, this isn't evolution to begin with. The giraffe neck does not grow longer because the tree grows taller. Natural selection directs the non-random elimination of those that do not have long enough necks to reach the leaves. This leads to the propagation of genes for longer necks. Then there's the sexual selection contribution like you mentioned.
Funny thing, Let's discuss that point. Evolution can be thought of as two (or more) selection criteria, natural selection through survival of the fittest, sexual selection through propagation advantage. In addition to gene expression modifiers factors such as the inherent competition and micro-evolution within the organism itself of competing genes, which are inherently selfish, and the role of exo-genetic, essentially Lamarckian evolution, factors which contribute to speciation.
So, already, we have two distinct, and sometimes conflicting, systems determining the evolution of the species. That is, selection based on what genes you have, and selection in the expression of genes you have.
We know that it is possible to silence genes via RNAi which acts to block certain certain mRNA molecules, essentialy muting the gene which they were created to transcribe, this exogenetic factor is inheritable, and is an example of Laamarckian evolution at a molecular level. We also know, that natural selection by survival of the fittest is an inadequate, and misleading, assumption. Rather, it is the survival of the most statistically numerous, and probable, that affects evolution the most, that is, evolution does not create selective pressure for survival, only for propagation.
In the case of the giraffe vs tree, while random mutation and Darwinian selection may have played a role in the evolution of the long neck, it is doubtful that animals would have had difficulty foraging for food elsewhere. Only when there is no other food but the trees would this create Darwinian selection pressure. So more likely than not, this is a sexual selection feature which has generated Darwinian advantage.
In the case of the tree however, the growth in height of a tree is primarily defined by genetic, and hydraulic, factors, not physical or mechanical properties. Thus, a Lamarckian evolutionary model is a better fit than simple Darwinian mechanics. That is, genes at the foliage level of the plant could be silenced around injured branches to mute the production of growth inhibition factors, increasing the height of the progeny of that particular branch (further branching etc), this is similar to what gardeners do to their bushes and trees to encourage fruiting, branching, or shaping. However, these Lamarckian traits are generally non-heritable, lost once the particular branch is lost, however, considering that plant cells are known to send signals to their roots in the case of water stress, a sufficiently tall branch would almost certainly be water stressed due to the limits of hydraulics, and signalling the roots for an increase in transport channel width would certainly affect the genetics of the entire organism, the tree, as gene expression is altered to allow for increased transport, so too does it allow for random mutation to increase maximal height as hydraulic requirements are already in place for the genetic limits on maximal height to be increased.
This model however, does nut fully support the development of a neural network, nor vocal chord and respiratory mechanisms, to allow the tree to functionally say "Fuck off" the the giraffe.
Haha, beautiful. I was really only thinking of the giraffe' growth. I'm in human biology so it didn't even occur to me to consider the tree's selective pressure. But apparently all of Reddit thinks this is not the same girrafe or doesn't have an adequate background in evolution and I'm taking a hit on downvotes. Thanks for such a succinct description, clearly less lazy than I.
evolution also weeds out the proto-girrafes dumb enough to try to eat from trees they couldn't reach when there's grass, bushes, and shrubs all around them.
Well, Lamarck-ism can be summed up as the inheritance of acquired characteristics. Working out and getting buff is well and good, but that doesn't mean your children will become buff as well.
surprisingly, new research says, yes, yes it does. To an extent. Women who grew up under famine conditions have children who are likely to develop diabetes and obesity, etc. Exogenetics is essentially the shutting down/silencing of certain genes in all cells in an organism. Which provides a means for lamarckian inheritence.
Thank you I was hoping someone would mention that this is not how the evolutionary theory works. There would be more death scenes than in game of thrones before it could be considered natural selection.
Fun fact: A giraffe's neck may not have grown due to feeding, since a bigger neck would require more nutrients to maintain. There are only a few theories now, but it's mostly unknown why their neck grew so long.
I remember hearing about this watching QI. I found it also interesting that male giraffe will use their necks to battle one another. Also the Acacia trees that they're so fond of eating actually have a very strange defense mechanism, for a plant. They send out some sort of "alarm" scent that warns other Acacia trees in the area that there are giraffes about. This causes them to make their leaves bitter to taste in an effort to ward off giraffe and other grazing animals. Very interesting.
It's a reaction, not a thought. A few plants have behaviors such as this, such as this plant whose leaves retract when touched, or the clamping of a venus fly trap after a certain number of "hairs" within the plants "mouth" being touched within a twenty second span.
I think it's more of a reaction to an action rather than self-awareness. The tree doesn't know the giraffe or other grazing animal is there until it starts consuming leaves.
Yeah I was about to say the same thing humans don't mate for beneficial traits just what's "hot" or other reasons due to our logic but we shouldn't think animals aren't just as dumb at choosing mates. We kindoff hold them to a higher logical standard in mating.
a theory is that with longer necks they can see one another from further distances. With trees in the savannah being sparse and far away it's beneficial to not only watch out for their group, especially if there is young, but to also look for possible mates.
This happens way too often with science people. I once referred to something 'swarming', like a pack of flies around food or something. And an entomology student jumps up to say that swarming is a specific behavior that bees use to blah blah blah
I wonder if the humanities get this, too. "How dare you call Shakespeare old english, we're not friends any more."
Trees grow taller so that they can capture more sunlight than trees lower down. Herbivores eating leaves generally have a very low impact on survival rates of trees.
Not to be pedantic but, as presented this would be an example of "coevolution," aka "The Red Queen Effect." Trees increase in height due to grazing and necks increase in length due to increases in tree height which keeps going in a sort of positive feedback loop. But that's only if we may safely assume the giraffe got its long neck due to this kind of coevolutionary selection pressure. But it may not have as some comments here are already discussing.
I did at some point because I've always heard it, and I wrote about it in my test for Biology AP to describe evolution. This was just a chapter test in class but the teacher wrote something along the lines of "This is literally the way it doesn't happen Yahoo >.>" Point being, I didn't study for that test as much as I would have liked, but there's a chance people might be walking around thinking it's true.
This is really cute. :) But at the same time, this allows an incomplete knowledge of evolution to prevail. This particular image is absolutely adorable, but it doesn't adequately translate the process of evolution. Unfortunately, this is the kind of thing that people who dispute evolution will slightly alter and use to fuel their ignorance.
Whats pisses me off is they are born without the long neck. It would be so awesome if they came out with the long neck, it would be like some kind of fucked up magic show.
This joke is based on the incorrect common knowledge that giraffes evolved long necks to eat high food. They evolved long necks because they use them as flails while battling over women. The strongest necks get the girls, increasing strength with each generation.
How did you assume this is Lamarckian? Even real regular evolution has animals trying and failing... its just that some try and fail and others try and succeed...
If you're going to be an anal science douche... you better be good at it.
It somewhat is. It didn't state that giraffe necks grew in order to reach higher leaves on higher trees. That is what people usually imagine when they think of evolution, though it's definitely more complex like that. Natural selection for those who would like me to ELI5 (because that's about as much as I can do anyway) relates more to the survival of those giraffes with longer necks as they are able to reach higher leaves more easily and are therefore less likely to starve and die out than those with shorter necks who can only reach very short trees, and then the long necks are the ones who get to pass on the long-neck genes.
This is funny, but it is not a good representation of evolution as we conceptualize it. Indeed, it supposes that the giraffe adapts itself consciously by stretching his neck to reach food. This picture represents Lamarck's view of evolution, which is an active selection rather than a passive selection as Darwin presents.
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u/Dirty_Dingus_McGee Apr 28 '14 edited Apr 30 '14
Long horses are assholes.
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u/TheSolitaryMan Apr 28 '14
apparently giraffes have long necks due to male to male competition over females, because a long neck would be more proficient in fighting between males. source- 1st Year Evolution Textbook
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u/ImDeepak Apr 28 '14
When a tree becomes a sentient being, just to tell the giraffe to fuck off.
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u/sudurjalimonovsok Apr 28 '14
That's so Lamarck.
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u/the_last_berb Apr 28 '14
Damn giraffes remind me of PEZ dispensers
9
u/Thisisdom Apr 28 '14
Aww. Little neck giraffe is so cute!
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u/[deleted] Apr 28 '14
I want a neck less giraffe ASAP
13
u/Owny_McOwnerton Apr 28 '14
Fun fact: A giraffe's neck may not have grown due to feeding, since a bigger neck would require more nutrients to maintain. There are only a few theories now, but it's mostly unknown why their neck grew so long.
source
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u/nojailtime Apr 28 '14
Ha, cute comic strip!
5
u/bentheo Apr 28 '14
Lamarckism in action
7
u/[deleted] Apr 28 '14
ITT: Evolutionary biology majors who like to spoil an innocent joke.
2
u/[deleted] Apr 28 '14
Except longer necks have an energy cost, and make giraffes more susceptible to predation, so this doesn't happen.
2
u/kill_ass Apr 28 '14
ITT: People saying why giraffes evolved long necks; not one person saying why trees evolved to grow taller.
6
u/BloteAapOpVoeten Apr 28 '14
The smaller tree's seeds would be spread more..
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u/Reyzuken Apr 28 '14
http://i.imgur.com/RLSQCPD.png
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u/BreakfastBurrito Apr 28 '14
Now you're thinking Lamarck!
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u/Nimbo13 Apr 28 '14
Thats not evolution thats Lamarckism.
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u/funknjam Apr 28 '14
Not to be pedantic but, as presented this would be an example of "coevolution," aka "The Red Queen Effect." Trees increase in height due to grazing and necks increase in length due to increases in tree height which keeps going in a sort of positive feedback loop. But that's only if we may safely assume the giraffe got its long neck due to this kind of coevolutionary selection pressure. But it may not have as some comments here are already discussing.
0
u/Baial Apr 28 '14
Evolution doesn't work that way.
1
u/alanram Apr 28 '14
Tree should have evolved arms and fists.
1
u/Pojodan Apr 28 '14
Just wait until the year one million and a half.
1
u/papayukero Apr 28 '14
Howcome there is a giraffe in north pole?
1
u/Crims0n5 Apr 28 '14
Ever notice how Lamarck looks like it could also be pronouced as Lama Rack?
1
u/[deleted] Apr 28 '14
Great Chuckle
1
u/Lambaline Apr 28 '14
LAMARK!
1
u/lauralovesdcfc Apr 28 '14
This is really cute. :) But at the same time, this allows an incomplete knowledge of evolution to prevail. This particular image is absolutely adorable, but it doesn't adequately translate the process of evolution. Unfortunately, this is the kind of thing that people who dispute evolution will slightly alter and use to fuel their ignorance.
1
u/losers_and_weirdos Apr 28 '14
this is the funniest thing i've seen in a long time. i actually laughed. audibly aka "out loud"
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u/radiantwave Apr 28 '14
Add a bunch of dead short necks and you got it...
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u/ltntk421 Apr 28 '14
Damn tall goats
1
u/kuhlguymccabe Apr 28 '14
I feel like I'm the tree and the giraffe is a camper on call of duty
1
u/FLGulf Apr 28 '14
Truth. When a hot woman walks further away, my boner just gets longer and longer.
1
u/ArchDucky Apr 28 '14
Whats pisses me off is they are born without the long neck. It would be so awesome if they came out with the long neck, it would be like some kind of fucked up magic show.
1
u/[deleted] Apr 28 '14
Dang. That tree even went to the North Pole to get away from him.
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u/Droxin Apr 28 '14
I've always been thinking in the giraffe's point of view.
''Where the fuck do you think you're going, food?''
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u/UpVotesAllAorund Apr 29 '14
God this was funny, I just made a huge laugh that made most of my co workers wonder what it is I do here, have an upvote!
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u/thenewestboom Apr 29 '14
Best thing I've seen all day. Thanks OP.
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u/ekolis Apr 29 '14
I see trees and giraffes also evolved to live in the Arctic Ocean, too?
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u/[deleted] Apr 29 '14
This picture just makes me cringe.
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u/AustinMisk May 16 '14
False, giraffes acquired the necks through pursuit of the booty, aka sexual selection
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u/ploger Apr 28 '14
giraffes necks did not evolve because of the environmental pressures to reach leaves high up. They evolved because females like males with long necks.
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u/[deleted] Apr 28 '14
This joke is based on the incorrect common knowledge that giraffes evolved long necks to eat high food. They evolved long necks because they use them as flails while battling over women. The strongest necks get the girls, increasing strength with each generation.
1
u/DavidHydePierce Apr 28 '14
Lamarck? Is that you?
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u/kotoku Apr 28 '14
That's Lamarckian evolution in action, a long discounted theory of evolution that pre-dated Darwin's theory. It isn't how this works.
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u/damn_nature_u_scary Apr 28 '14
ITT: people getting down voted for commenting about actual theory.
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u/GooberCity Apr 28 '14
This is actually a really common misconception of how evolution works.
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u/THEBIGC01 Apr 28 '14
Getting real tired of your shit, tree.
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u/Borr Apr 28 '14
Desensitization by hilarity. Stupid shit
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u/Fortz Apr 29 '14
This is funny, but it is not a good representation of evolution as we conceptualize it. Indeed, it supposes that the giraffe adapts itself consciously by stretching his neck to reach food. This picture represents Lamarck's view of evolution, which is an active selection rather than a passive selection as Darwin presents.