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Fear of Snakes May Have Driven Pre-Human Evolution
Krishna Dagli writes "An evolutionary arms race between early snakes and mammals triggered the development of improved vision and large brains in primates, a radical new theory suggests. The idea, proposed by Lynne Isbell, an anthropologist at the University of California, Davis, suggests that snakes and primates share a long and intimate history, one that forced both groups to evolve new strategies as each attempted to gain the upper hand. Early primates developed a better eye for color, detail and movement and the ability to see in three dimensions — traits that are important for detecting threats at close range. Humans are descended from those same primates. "
Snakes...ON A PLANE
Humans are descended from those same primates.
And lawyers/politicians/managers are descended from snakes.
At least its an explanation of the uneasy feeling I get when I see Darl Mcbride.
liqbase
Genesis 3:14-15 The LORD God said to the serpent, "Because you have done this, Cursed are you more than all cattle, And more than every beast of the field; On your belly you will go, And dust you will eat All the days of your life; And I will put enmity Between you and the woman, And between your seed and her seed; He shall bruise you on the head, And you shall bruise him on the heel."
1. Dream up a far-fetched 'theory' that Joe public can understand and involves strong emotions ....
2. Seek publicity
3.
4. Profit!
-- Cheers!
Conventional wisdom is that our depth perception and improved color vision supported an arboreal fruit-eating lifestyle.
It's not obvious why our lineage would co-evolve with snakes any more than any other mammalian lineage would.
BTW, "improved color vision" is relative. Birds have receptors for four colors rather than three. Early mammals lost two of the four, which is why your dog is "color blind". Our lineage re-gained a third, though not the same as either of the two that our ancestors had lost. There was an article about this in Scientific American a month or two back.
Sheesh, evil *and* a jerk. -- Jade
Did the primates have no other predators? As I recall, binocular vision is a characteristic of predator, not prey. (How far do I have to run or jump to catch dinner?) Motion detection and wide-field vision are a characteristic of prey, not predator. (Is something about to run or jump on me? Maybe a moderator with points?)
@HbFyo0$k8 tH!$
I *am* a psychologist / scientist that studies vision, and I can happily report that this material is a) not new [see the bogus theoretical ramblings of Mineka on the subject] and b) not in any way factual.
Why should the threat of consumption from snakes (snakes! of all things!) have driven us to evolve incredibly good eyesight? Why not hearing? Why not some more obvious and simple snake defense mechanism (like, immunity from snake poison?) At no time in our evolutionary history did snakes actually represent a dominant predatory force (To deal with this, some "experts" claim generalization from dinosaur tails. Right). Just because it has the word "evolution" in it doesn't mean it's right.
This idea, and almost every instantiation of this idea, is total crap, and should be treated this way.
...a snake participates in an arms race, I'll never know.
That's quite far-fetched. Snakes and primates do not strongly compete for the same food source and do not really have a strong predator/prey relationship. In fact, they can get along quite well as long as they stay out of each other's way.
The primates' evolutionary developments might have other, much more direct reasons. Color perception is directly related to gathering food (red and yellow fruit vs. green leaves. Btw, picking strawberries is quite a pain in the ass if you're colorblind). Depth perception is pretty much a necessity when jumping from tree to tree - natural selection manifests quite quickly and painfully here. Being able to perceive movements
I've misplaced the link, if I ever had it (I just recall hearing about this from my wife the evolutionary biology teaching fellow) but there's currently a species of primate (bonobo?) that has different behaviors for different kinds of predators. They scurry up into trees for land-based predators, they go down under cover for large birds, and do something in between (I forget what) for snakes.
And they have different calls for each of these kinds of predator.
Well, they've developed another one for humans with rifles. And they give the call if they just see hunting dogs.
So yeah -- adapting to predators is a top-level priority. Although in that case they're benefitting from previously-evolved capabilities, presumably, given the speed of adaptation.
To err is human. To forgive is good system design.
Within the context of the original post (the evolving to see in 4 dimensions thing), it suggests to me that he meant seeing all 3 spacial dimensions. Stereoscopic vision is not the same as that. It just means your brain is capable of recognizing angles on objects and interpreting them for you as some level of depth. People with poor depth perception don't necessarily have anything wrong with their eyes. They see the same thing everyone else does, their brains just don't interpret the angles properly.
You can prove quite easily that you can only see two dimensions of space. Simply place a cube on a table, lower and center your vision so it's pinpointed right in the center of one side, and note that you see a square, not a cube. Without the angles to suggest depth, you're not capable of perceiving three dimensions at all.
If you haven't foed me yet, what are you waiting for?
To my knowledge - which is admittedly a year or so old - basically there are three relevant points.
1. Most people have 3 color receptors that they actually use, while some are colorblind to varying degrees including a relatively high number are red-green colorblind having effectively one RG and one B receptor. HOWEVER, where (what wavelength) the "R" "G" and "B" receptors is is NOT exactly the same for each person. So it is very possible that a perfect match for one person is not a perfect match for another especially for colors that are a complex mixture of wavelengths (eg most real-life pigments in sunlight) Note that generally matching the amount of the same pigment should generally be very, very close - to demonstrate this effect you mostly need to be combining very different wavelengths that "should" be the same added together.
The take-home geek message is that you can use an RGB monitor to match every color you can see - IF the monitor's RGB match yours. Otherwise it's not perfect. (Also see point 3)
Have two receptors very close together eventually becomes indistinguishable from just having one as they approach being in the same spot.
2. Some people are known as "tetrachromats" All examples I've heard about have been the mothers of red-green colorblind men. Essentially they have an extra receptor between R & G. This means that they can determine that two colors don't match in situations where everyone with three receptors would think they matched.
3. Apparently we may also have a 4th (or 5th, depending on pt 2) receptor in the ultraviolet range. However, most of the light in this range is blocked by the alchohol in our eye fluids, so this receptor is mostly pretty useless. However, this doesn't mean we don't see SOME color with this receptor right at the edge where it's not blocked by the alchohol - it's just not a very large part of our sight.
These colors definitely don't exist in monitors, which I personally and nonscientifically think is why I love staring at the LED on a PS2.
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The only thing stranger than the content of this article is the fact that it is being hosted on foxnews.com.
- Picasso
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And we wonder why there is a debate between Darwinism and Creationism.
No, we don't.
There is a debate because creationists have manufactured a debate. There is internal debate among biologists about some of the mechanisms of evolution and natural selection, but that doesn't require creationism in the slightest.
Those who espouse creationism do so out of a bond to a cult. "If it contradicts what is literally in my Bible, it is false." That is an aspect of a cult: to deny the evidence when faced with it. (There's also the whole personality-driven thing, in which Jerry Falwell, Ralph Reed, Pat Robertson, and their demons play a major part.)
Now, it's your chance to respond, "That is just what Darwinists do!" As if stating it as fact makes it fact.
The funny thing is, Darwin didn't create the theory of evolution. It existed for years before Darwin boarded the Beagle. He came up with the concept that is the core of current evolutionary theory, though: that evolution is driven by natural selection. "Natural selection" is merely the idea that some phenotypes within a population are better adapted at survival than others, within the current environment. When there is little selection pressure, many phenotypes may survive, allowing genetic diversity within a population. When the environment changes, certain phenotypes may provide better adaption to the environment. When two different phenotypes provide survival traits, you may end up with a divergent population, resulting in two species where there used to be one.
Most modern biologists accept this as the driving force behind evolution. There are details that are argued, and there is always points of debate, but the fundamental theory is laid down more-or-less as Darwin painted it.
. . . but are in actuallity mere theory and speculation.
That pretty much removes you from any serious debate. The Theory of Gravity is just a theory, but I don't see you jumping off a very tall cliff with no parachute any time soon. You should go figure out what a "theory" is in the scientific sense before making stupid statements like this.
The way science works is this: if you have an theory that fits the facts, and accurately makes predictions (which is required for testability), that theory survives. Once that theory fails a prediction, the theory is either modified or discarded. Hopefully, there are competing theories to take its place that provide a more accurate prediction mechanism.
The theory of evolution through natural selection has survived a long, long time. It is probably one of the most-tested theories ever. One example: it predates modern genetic theory, and yet the implications of evolution on genetics (the predictions) are borne out by modern genetic research.
The problem with the creationists' appeal to a divine intervention is simple. For it to be a viable scientific theory, it must make predictions that can be tested for accuracy. There is no known method to accurately test for God. You might assume his existence, but you cannot test for him, the the best of my knowledge.
The arguments of the intelligent design crowd invariably reduce to a simple logical mistake: we don't know how it happened, so it must've been God who did it. And when science, using its proven epistemology, pushes back the boundaries of knowledge, the ID crowd responds, "Oh, yes, well, we didn't quite mean that. We meant this other thing that you can't prove." It happened with "irreducible complexity" (which is nothing but the long-disproven "Only God could create the eye" argument gussied up with the terminology of microbiology), it happened with the catastrophists (who use catastrophism to prove the Biblical flood), and will most likely occur with the next pseudo-scientific attempt to subvert education.
Ultimately, that's what this is about: the ability to control the next generation through education. If they are taught to think for themselves, to reason about problems instead of appealing to
Microsoft is to software what Budweiser is to beer.
How come snakes are the ancient symbol for medicine that we still use?
--
make install -not war
Would you like them on a plane?
Would you like them on a train?
Would you like them on a boat?
Would you like them in your coat?
Would you like them on the road?
Would you like them in a commode?
I would not like them, Samuel J,
I do not like snakes any way.
Regarding your idea of evolution, I'll paraphrase you:
"The idea the evolution was a conscious process, and almost every instantiation of this idea, is total crap, and should be treated this way."
You, like millions of others, make a mistake in thinking evolution is a conscious process. With genetic manipulation it may become that way in humans, but otherwise it is not. It isn't like the proto-humans/early humans sat around and said "You know these snakes are a deadly threat. We shall form a comittee and decide on how best to evolve to defeat them.". If that had happened we would have snake venom immunity.[1]
IF snakes were a deadly threat, than whatever provided an advantage in escaping the threat would have sufficed. If better vision provided "good enough" advantage for the being with those genes to pass on their DNA then that would happen (with regard to that threat). It could well be that several advantages produced a set of genes that provided multiple avenues of threat avoidance. Particularly if these advantages were useful for more than snakes.
Evolution is explanatory, not proactive. Yet. Sadly, scientists working in the field often use stupid and ridiculous statemets such as "in response to" when they should be saying "as a result of...". The headline for the article here on
If conceived of today evolution would be termed an "emergent phenomenon". The primary principle of evolution is "good enough". If it works, it works - that is all that is required. There is no planning, no intentional process.
Regarding snakes being a threat
1) Venom immunity would not have sufficed. What good is immunity to venom if the wounds get infected and you die from infection? A Committe would have produced venom immunity and then we'd have died out from secondary snake bite infections. A clear example of the phrase "to each and every problem there is solution that is simple and obvious. Said answer is also wrong."
Hearing would have been a likewise poor choice given the sensitivity and limited range of perception it would have produced. Early humans occupied multiple niches and thus were open to many predators of a wide range of "features".
My Suburban burns less gasoline than your Prius.
Some people are known as "tetrachromats" All examples I've heard about have been the mothers of red-green colorblind men. Essentially they have an extra receptor between R & G.
Actually, it's more interesting than that. There are variant genes for the red & green cones that result in the cones absorbing a slightly different spectrum of light. The genes for this are on the X chromosome. A tetrachromat is a woman who has differing genes on her two differing X chromosomes that are somehow both active, leading to either her red cones or her green cones being split between the two variant alleles and allowing for finer detail in distinguishing shades of red or green.
Why I say it's more interesting is that this shows us that beyond the perceptual, cognitive differences between perception of color that we grow up with within our cultures, humans actually have differing physical hardware for perceiving color. We really don't see the world with the same eyes.
Apparently we may also have a 4th (or 5th, depending on pt 2) receptor in the ultraviolet range. However, most of the light in this range is blocked by the alchohol in our eye fluids, so this receptor is mostly pretty useless.
Actually, it's just that our blue cones and our rods have sensitivity in the near UV range. It's the lens of the eye that blocks UV; there's no alcohol in the vitreous humour. People who have cataract surgery that replaces their lens can sometimes see UV in a very limited fashion.
You can read more about aphakia and UV sensitivity here.
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You can find an absolutely fascinating study of how the symbols of our creation myths (primarily Genesis, but others are explored fairly well) seem to reflect our actual evolutionary history in Carl Sagan's Dragons of Eden: Speculations on the Evolution of Human Intelligence.
While it includes some later-disproven assertions (dinosaurs being killed off by a nearby supernova, mainly), most of it is brilliant and engrossing for anyone interested in topics like this.
He postulates that Genesis is really the story of the evolution of human intelligence being selected for because it was necessary for us to defeat the reptiles which preyed on our ancestors. We defeated the serpents -- there are no more legged "dragon" type creatures which every human civilization remembers in legend. However, the price we paid was a separation from the animal kingdom, self-consciousness (the realization that we are naked), and most interesting to me, pain in childbirth because of our big brain-holding heads.
Another interesting bit from the book: In every single culture in the world, the sounds "ssssssss" or "sssshhhhhhhhhh" mean "Everybody Shut Up!", as in, "Quiet! Snake!".
It's a good, quick read. I enjoyed it on a Lufthansa flight from Philly to Frankfurt a few years ago. Highly recommended.