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. "

Re:Conventional wisdom

[dreamchaser]

Addressed somewhat in the article (yes I actually read it).

Scientists had previously thought that these traits evolved together as primates used their hands and eyes to grab insects, or pick fruit or to swing through trees, but recent discoveries from neuroscience are casting doubt on these theories.

Re:2D-3D?

[Roody Blashes]

You don't see in 3 dimensions now, you MOVE in 3 dimensions and you SEE in 2. If you could see in 3 dimensions you'd be awfully confused, because you'd be able to see every side of every object in your field of view.

Theoretically, this would not be possible anyway given our current configuration and understanding of light. To be able to see in 3d, you'd have to somehow pick up light that was being deflected away from your eyes, or that was blocked by foreground objects in your field of vision.

Re:2D-3D?

[AndersOSU]

I'm pretty sure you knew this, but seing in three dimensions means having stereoscopic vision, and the benifits of much improved depth perception.

Re:Why snakes?

[swv3752]

The big cats, particularly the cave lion and sabertooth tiger preyed on early man. There have been a number of skulls of early man found with holes in the cranium consistent with the fangs of the big cats. Of course this article is talking about time before there was big cats. There would have been crocs and proto-birds. The crocs and birds would have driven motion sensing. Our motion sensing is so strong that we flick our eyes aboutconstantly to create a pseudo-motion so that we can see properly.

Re:This Idea = Bogus

[hey!]

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?)

Because evolution does not provide an organism with what it needs to survive and reproduce. The organism takes what it gets from the mutation lottery and does the best it can.

However, I agree, it seems very unlikely that snakes could be an explanatory factor in the development of stereo vision. After all, there's no reason to think snakes particularly predated on early primates is there? Squirrels, for example, are prime candidates for tree dwelling snakes the hunt in the tree rather than drop on prey. But rather than stereo vision, they have eyes on either side of their heads which provide greater coverage. If snake predation necessarily produces stereo vision, then we would expect all kinds of animals subject to snake predation to have it; if it does not necessarily produce stereo vision, then I'm not sure the idea has any meaning.

Tetra and quinta? chromatic humans

[arete]

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.

Re:I knew that already...

[operagost]

I forgot to add something else to the thread.

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.

In Genesis 2, God says that he will "greatly increase" woman's pain in childbearing. Clearly, children were being conceived and born in Eden. Also, Eden is the definition of Utopia, and no trace of illness or suffering are to be found. Perhaps you do not find eternal life to be palatable, but the entire Judeo-Christian theology revolves around it (save for the Sadducees, whose position Jesus soundly refuted).

Re:Snakes on Staff

[Anonymous Coward]

Wrong. http://en.wikipedia.org/wiki/Caduceus

The symbol predates Moses by several hundred years.