I went to school in the 80’s and they still taught that.
An animal that is restricted to feeding within 5 feet of the ground will suffer just as much competition from these creatures as one that feeds at 20 feet. The only difference is that the one feeding at twenty feet *only *suffers competition from these creatures. That’s a massive reproductive advantage right there.
You seem to have some idea that novel adaptations only proliferate if they are perfect in every sense. Nothing could be further form the truth. So long as the adaptation offers any advantage at over those creatures that lack it, it will proliferate.
It seems like they can all be attributed to obtaining food in the upper levels of trees. They may not have been due to that, but there is no obvious difficulty in attributing them all to that.
thank you. it goes back to the difficulty in attributing any evolutionary change to a simple benefit.
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It’s not an assumption, it’s an indisputable fact.
No, there demonstrably isn’t. Do a Google image search of “browse line” if you want photographic proof of that point.
Can you share them please. I would really like to know how anybody reached that conclusion.
Sure.
Makhabu. S. W. 2005 "Resource partitioning within a browsing guild in a key habitat, the Chobe Riverfront, Botswana"Journal of Tropical Ecology 21
Young,T.P & Isbell, L.A. 1991 “Sex differences in giraffe feeding ecology: energetic and social constraints.” Ethology 87
du Toit, J.T. 1990 "Feeding-height stratification among African browsing ruminants. Africab Journal of Ecology 28
Really, this is something that is so well confirmed by research that I would love to know how anybody reached an alternative conclusion. It doesn’t appear to make any sense. If there are a dozen large mammal specie sin addition to insects competing for food at ground level, and only one large mammal and the insects at the upper levels, then there must be more food available in the upper levels.
Perhaps we’re missing the obvious explanation for giraffes’ long necks. If you’ve ever watched lionesses hunt, you’ll notice that they depend on biting the victims neck to bring the prey down and deliver the kill. Watch this video of a giraffe successfully fending off a pack of hungry lions - its survival is purely a factor of its long legs and having the neck up so high out of the lions’ leaping range.
I’ve been told that a number of times.
Except that adult giraffes are killed by predators at exactly the same rate as any other animal of similar size (see Sinclair, Mduma & Brasheares “Patterns of predation in a diverse predator–prey system” Nature 425).
So if the giraffe attained its ridiculous proportions as a means of limiting predation it has been a complete and utter failure.
I’m almost certain I was also taught that the appendix had no function. Don’t we now believe that it stores bacteria for digestion?
Not for digestion, but there is some evidence that it serves as a reservoir of normal gut flora that can’t be scoured by illness or poisoning. Kind of like a seed bank of gut flora.
The sun is a mass of incandescent gas
A gigantic nuclear furnace
Where Hydrogen is built into Helium
At a temperature of millions of degrees
…except that the sun isn’t gas, it’s plasma. TMBG have kindly come out with a new song (“The sun is a miasma of incandescent plasma”), but sadly the new one isn’t as catchy as the original.
Oh man - not only was I taught about brontosauruses (brontosauri?) in school in the 1970s but I discovered recently that they’ve been called apatosauruses since 1903. WTF, school system/childrens’ books publishers? The Flintstones have a lot to answer for, I guess.
Blake, evolution isn’t about “keeping up with the Joneses.” Just because elephants and ibexes have their adaptations to limit predation that are no less successful than the giraffes’ set of adaptations doesn’t mean that the giraffes’ stature isn’t successful in its own right.
The neck is the end-game in animal predation. The prey always seems to have a chance until the neck is bit. Makes sense a giraffe would want to be taller rather than shorter if everybody’s trying to bite your neck.
The problem is that we now have an argument from ignorance. You’re arguing that it must be true precisely because it can *never *be been disproved. The original hypothesis was fine: that a giraffes proportions were a means of avoiding predation. However when we find out that, despite the numerous disadvantages the posture gives, giraffes are just as heavily preyed on by generic predators you want to say that we can’t prove it isn’t true.
The problem is that we have absolutely no evidence that it is true. We know that the posture provides a significant feeding advantage, so positing that it also helps evade predation is in violation of Ockham’s Razor.
Can we have a reference for this please? Because lions, wild dogs and hyaenas are the main predators of giraffe sized animals, and while lions mostly kill by smothering either the neck or muzzle *after * the animal has been brought down, hyaenas and dogs tear at the prey inflicting numerous injuries to kill, often by disembowelling. Can we please see your reference that the prey have a chance until the neck is bit?
Since even the lion’s use of the neck is applied when the animal is already lying on the ground, what advantage do you believe the posture of the giraffe gives?
No, it doesn’t. Because necks mostly get bitten after you have been brought down, and all animals are the same height when they are lying.
How about the definition of “siphon”? It turns out the Oxford English Dictionary has been wrong for the past 100 years!
Well, without the locks (or if the locks were to fail) Gatun Lake would empty into the Atlantic or Pacific. That almost 1.4 quadrillion gallons of water 85 feet above sea level would create quite a bit of mayhem and chaos as it plunged to the sea.
Thanks to our wonderful, awe-inspiring, fairytale telling book publishers history (taught in non college levels) has become a complete joke. You could sift through a high school U.S. History book and find gross errors in every chapter.
Our wonderful country decided to proclaim a day Mr. Sleezeball Columbus…why?
Columbus’ own diary tells story to his murdering, raping, and torturing of the indigenous people that crossed his path.
Instead of teaching the kids the truth these books search to tell an amazing, falsified story to “make history entertaining.”
This book could get you started in terms of historical errors - apparently publishers don’t believe in primary sources.
That won’t work as a definition for a planet. There is an asteroid with a moon, and the asteroid is only 15.7 km in diameter and very irregularly shaped. Not what most people think of as a planet.
You also run into the problem that Mercury and Venus don’t have moons.
You get an even weirder problem. Mars’ moons are captured asteroids. One of the moons, Phobos, is being moved in toward Mars by the same tidal forces that are making our moon move further from the Earth. Eventually, Phobos will crash into Mars. There are chains of craters on Mars that look like they might have come from former moons that met the same fate as Phobos. This causes a problem for defining a planet as something that has a satellite, because it means Mars might not have had moons at some point in its history (or might not have them sometime in the future). That would mean that Mars is sometimes a planet and sometimes not, which is just weird. Worse yet, it happens with no real change in Mars itself.
Blake, I’ve gotta run, but for now I’ll just say watch the video if you haven’t. The totality of the giraffe’s defense against the pack of lions consisted of being tall. And it survives. I think the survival advantage is patently obvious, not conjectural at all.
And since when does Occam’s Razor say that an adaption can have only one advantage?
Wow, that’s better than how I learned heat transfer as a kid. It was basically conduction, convection, and infrared. I’ve actually seen that (heat being radiated as infrared and only infrared) alot of place. (Including I think Mr Wizard.)
The giraffe obviously gets an advantage from being tall. But what advantage would a long neck bring? 6 feet tall followed by a 3 foot neck versus 6 feet tall followed by a 1 foot neck, still leaves the neck in the same place relative to the ground.
blake, thank you for providing support for your argument. i will look at this material. your statement above about proliferation is not anything that i said. it still seems like everyone is missing the main point. evolution does not occur to achieve some goal. pointing out advantages of evolutionary adaptations doesn’t make them a cause. the occam’s razor argument is not science. it is method for making best guesses, it is not conclusive in any way. if your materials show that there is more food available at the 20 ft. level than at ground level, then i will not contend otherwise. but if you read the referenced source materials, you will see that giraffes spend a lot of time feeding at ground level, with difficulty. why would they do that if there so much food up in the treetops? also, if you follow back through the chain, these arguments are about a section called ‘things i have noticed’. i never put them down as indisputable facts, so i am happy to discuss these things, and if i am mistaken i will change my mind. but neither you nor anyone else has even attempted to dispute my main point, evolution is a series of accidents, it does not serve a predetermined purpose. and i will add, there is no way to indisputably conclude anything about the evolution of giraffes. there is next to nothing in the way of fossil evidence. we don’t know what environment giraffes evolved in. where is your argument if they evolved on treeless plains? finally, whether or not there is more food in the treetops available to giraffes is determined by measurement, not supposition by you, me, darwin, or anyone else.
unless someone claims that evolution is based on the achievement of a goal, or that science is based on supposition instead of measurement, there isn’t much more to discuss. but i will still investigate the references concerning availability of food.
I don’t really have a dog in this fight, as I really prefer the browsing-line theory, but have you ever seen a giraffe? Saying that it’s killed by predators at the same rate as any other animal of similar size is like saying that refrigerators get thrown about by enraged humans at the same rate of any household appliance of similar size. Sure, it happens, but not that much. Sinclair, Mduma and Brasheares say “A threshold occurs at prey body sizes of approximately 150 kg, above which ungulate species have few natural predators and exhibit food limitation”. Giraffes weigh more like 1000 kg. So they’re way out of the category where predation is the main thing to worry about. Hey, actually, this argument supports the browsing-line theory!
High School science taught Newton’s laws of motion as absolute facts.
College physics introduced a lot of gray into it. The laws still hold true… BUT an hour later the teacher was still talking. 
My eyes glazed over and I had a headache.
I lost interest in Physics. Because I liked the absolute, black & white rules. When I found out there’s a hundred shades of gray I lost interest. I did enjoy chemistry because most of that was black & white rules. You balance a chemical equation the same way every time.