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Fear of Snakes May Have Driven Pre-Human Evolution 553

Posted by Hemos
from the snakes-on-a-plane dept.
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. "
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Fear of Snakes May Have Driven Pre-Human Evolution

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  • by countach (534280) on Monday July 24, 2006 @09:01AM (#15768825)
    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."
  • Conventional wisdom (Score:5, Interesting)

    by Black Parrot (19622) on Monday July 24, 2006 @09:09AM (#15768876)
    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.
  • Why snakes? (Score:5, Interesting)

    by triskaidekaphile (252815) <xerafin@hotmail.com> on Monday July 24, 2006 @09:12AM (#15768897) Homepage
    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?)
  • This Idea = Bogus (Score:5, Interesting)

    by Anonymous Coward on Monday July 24, 2006 @09:18AM (#15768936)
    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.
  • by arivanov (12034) on Monday July 24, 2006 @09:24AM (#15768987) Homepage
    I had the same thought at first.

    At second - another thought. Birds of prey. Keeping alive from them requires similar improvements in vision. It also requires much more.

    Current primates do not cooperate to defend against snakes. At the same time they cooperate even on interspecies level to keep track and warn the pack about forest eagles. There is some extremely good footage narrated by David Attenborough on that (forgot in which one of his movies). The most important characteristic of primates is their socialness. In fact the size of a primate brain for the lower primates is directly proportional to the group size (once again quoting Attenborough).

    So the primary driver in primate development should be the predators which improved their pack social cohesion and group communication. Eagles, tree mammal predators from the polecat family and to some extent cats.

    Not snakes.

  • Bullshit (Score:3, Interesting)

    by dargaud (518470) <slashdot2NO@SPAMgdargaud.net> on Monday July 24, 2006 @09:25AM (#15768991) Homepage
    Why are there such bullshit theories regularly sprouting in the news ? Either the summary is (very) bad, or the theory itself is. It's so obvious that there are _many_ factors guiding the evolution of several _sets_ of species like that. And snakes don't eat primates (except for a few exceptions). They only bite when threatened or scared, so I don't see how this could be a leading evolutionary factor.
  • Re:2D-3D? (Score:2, Interesting)

    by LiquidCoooled (634315) on Monday July 24, 2006 @09:26AM (#15769000) Homepage Journal
    I can already see in four dimensions.
    Your memory stores information about the passing of time and so you can see what something used to look like and how it looks now.

    For an often strange example, go and visit your childhood neighbourhood and you will see all the things that have changed since.
  • Far-fetched. (Score:5, Interesting)

    by Ihlosi (895663) on Monday July 24, 2006 @09:29AM (#15769024)
    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.



    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 ... well, primates are somewhere in the middle of the road here. They don't perceive ultra-slow movements as well as a prey animal would, nor do they have the ability to perceive quick movements that a pure predator needs.

  • by AndersOSU (873247) on Monday July 24, 2006 @09:29AM (#15769028)
    FTFA,
    predatory birds evolved much later than snakes, after primates developed steroscopic vision.
  • by CurtMonash (986884) on Monday July 24, 2006 @09:35AM (#15769081) Homepage
    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.

  • by hey! (33014) on Monday July 24, 2006 @09:36AM (#15769088) Homepage Journal
    My mind leapt to Genesis as well.

    The thing is, the snake is by no means a uniformly malign figure in mythology. Quite the opposite; they are often beneficent. The snake has other symbolic potentials, with its ability to shed its skin (rebirth) and to form a circle by biting its tail (eternity).

    Chinese dragons are conspicuously snake-like, and share the common mythical snake role as bringers of wisdom. In fact Genesis, if you read it closely, is clearly a compilation of myths. It is clear that in the source material for the temptation story, the snake plays exactly the bringer of wisdom role in the story ("Now the serpent was more subtil than any beast of the field which the LORD God had made." Gen 3:1). But with irony that is a particular characteristic of Jewish scripture, that gift is a source of misfortune.

    Stories of dual natured gifts are not uncommon in folklore and myth. The point of these stories is pretty much the same: life is full of pain and toil, then you die. But on the other hand if you could choose otherwise, there would be a price you might not be so happy to pay: without death children are not born, illness and suffering does not end. Wisdom is a particular source of pain, but as the generations of scribes and their successor Talmudists, it's also a source or pleasure and comfort. There is no wisdom without toil and suffering.

    Our way of looking at these stories, Genesis in particular, has been diminished by religious ideology. To the point that those of us raised in the Judeo-Christian tradition think nothing is more natural than to hate and revile snakes. The snake figure in Genesis was never equated with Satan until a much later date. "Satan" comes from the Hebrew word for "obstacle" or "adversary". Read carefully: the snake's part in the story puts enmity between him and humanity, but it does not unambigiously put him in the role of The Enemy; he could equally be seen as a tragic figure that nudged humanity down an alternative path of pain and enlightenment.

    In any case, to bring this back to the topic at hand, it is certainly not the case the myth and religion can be used to show an atavistic revulsion to snakes that may have an evolutionary basis.
  • by digitalhermit (113459) on Monday July 24, 2006 @09:37AM (#15769101) Homepage
    Of course it may only be coincidence that pre-Christian civilizations worshipped snakes... These civilizations saw the annual re-birth of the snake (via shedding its skin) as somehow divine. It may also be coincidence that the bull (horns, cloven feet) was also worshipped by pre-Christian civilizations. Or not so coincidental. Nothing like making the god of the old religion the icon of evil, eh?

    Of course, this didn't always happen. In many cases the beliefs and rituals of the previous civiliation were modified by Christianity. It's not just coincidental -- almost all civilizations/religions have a feast time at the end of winter, end of harvest, during the winter. There are *human* reasons for this. Most times it's either for rationalizing the unknown or just an excuse to feast. So we have Christian feasts that coincide with the Saturnalia and other ancient ceremonies. Maybe when we sit down for a Christmas dinner some ancient god nods and thanks us for remembering. Maybe when we recognize the Resurrection of Christ some primal force awakens and pushes the new plants out.

    But back to snakes. The story of Genesis is old and borrows heavily from previous traditions. To condemn the snake by selecting one reference is wrong though, as the snake/serpent is considered wise throughout other books in *YOUR* Bible (E.g., John 3:14). Read your Book!

  • by OhHellWithIt (756826) on Monday July 24, 2006 @09:48AM (#15769172) Journal
    That struck me, too. From TFA:
    "Primates went a particular route," Isbell told LiveScience. "They focused on improving their vision to keep away from [snakes]. Other mammals couldn't do that. Primates had the pre-adaptations to go that way.

    Natural selection doesn't work that way. Pre-human primates focused on staying alive. It could be that the ones who were better at detecting snakes survived and the others didn't, but we humans are the first species that seem to be capable of directing the evolution of our descendants (for better or worse).

    I wish that people who wrote about evolution would learn to use phrasing that conveys how natural selection works, instead of attributing it to the intelligence of the species in question. I know, it's a Fox News article, but I've even seen Daniel Dennett make that mistake in his writing.

  • by lbmouse (473316) on Monday July 24, 2006 @10:07AM (#15769312) Homepage
    The only thing stranger than the content of this article is the fact that it is being hosted on foxnews.com.
  • Fox News Reports (Score:3, Interesting)

    by jeffsenter (95083) on Monday July 24, 2006 @10:37AM (#15769514) Homepage
    Folks this is coming from Fox News' science department. I wasn't aware Fox News had a science department and after reading the story I am still unaware of any reporting on science by Fox News.

    Snakes being a major force in the evolution of mammals including humans? I want to see some pretty strong evidence first.
  • Draggons (Score:1, Interesting)

    by Anonymous Coward on Monday July 24, 2006 @10:42AM (#15769553)
    I remember hearing an interesting theory about this somewhere (some documentary). It has been hypothosised that the presense of draggons in the mythologies of many human cultures is due to a sort-of hard wiring in the brain to fear certain threats to early man. The biggest threats that our pre-historic ancestors faced were from snakes, birds of prey, and large cats. The imagery associated with dragons is basically a composite of those three groups. Like birds of brey, draggons fly and have sharp tallons. They are scaled like snakes and move like large predetory cats.
  • by Ill_Omen (215625) on Monday July 24, 2006 @10:44AM (#15769572)
    According to the article, you're thinking way too far in the future. The time period this scientist is talking about are from a period in mammal evolution before most primates' modern day predators existed. Snakes, however, did exist and likely hunted the small mammals.
  • by tetranz (446973) on Monday July 24, 2006 @12:33PM (#15770425)
    Someone told me this long ago ... I don't know if its true but ...

    Someone in the Pacific during WWII made a lot of money by having a snake in a big glass bowl or something. He would get someone to hold their hand on the outside of the glass and then make a bet with them that they couldn't kept their hand there while the snake attacked them (safely) from the inside of the glass. I guess the rules were that they had to keep their eyes open and looking at the snake. He very seldom, if ever, lost the bet. Everyone, no matter how big and tough or unafraid of snakes they were, would involuntarily pull their hand away suggesting some sort of inbuilt fear of snakes.
  • by Valdrax (32670) on Monday July 24, 2006 @01:24PM (#15770833)
    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. [guardian.co.uk]
  • 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 [amazon.com].

    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.

  • ?

    Dude, we live 100 years and don't seem to care what happens 25 years down the line.

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