Posted on 07/20/2006 6:58:11 AM PDT by PatrickHenry
The ability to spot venomous snakes may have played a major role in the evolution of monkeys, apes and humans, according to a new hypothesis by Lynne Isbell, professor of anthropology at UC Davis. The work is published in the July issue of the Journal of Human Evolution.
Primates have good vision, enlarged brains, and grasping hands and feet, and use their vision to guide reaching and grasping. Scientists have thought that these characteristics evolved together as early primates used their hands and eyes to grab insects and other small prey, or to handle and examine fruit and other foods.
Isbell suggests instead that primates developed good close-up eyesight to avoid a dangerous predator -- the snake.
"A snake is the only predator you really need to see close up. If it's a long way away it's not dangerous," Isbell said.
Neurological studies by others show that the structure of the brain's visual system does not actually fit with the idea that vision evolved along with reaching and grasping, Isbell said. But the visual system does seem to be well connected to the "fear module," brain structures involved in vigilance, fear and learning.
Fossils and DNA evidence show that snakes were likely the first serious predators of modern mammals, which evolved about 100 million years ago. Fossils of snakes with mouths big enough to eat those mammals appear at about the same time. Other animals that could have eaten our ancestors, such as big cats, and hawks and eagles, evolved much later.
Venomous snakes evolved about 60 million years ago, raising the stakes and forcing primates to get better at detecting them.
"There's an evolutionary arms race between the predators and prey. Primates get better at spotting and avoiding snakes, so the snakes get better at concealment, or more venomous, and the primates respond," Isbell said.
Some primate groups less threatened by snakes show fewer signs of evolutionary pressure to evolve better vision. For example, the lemurs of Madagascar do not have any venomous snakes in their environment, and in evolutionary terms "have stayed where they are," Isbell said. In South America, monkeys arrived millions of years before venomous snakes, and show less specialization in their visual system compared with Old World monkeys and apes, which all have good vision, including color.
Having evolved for one purpose, a good eye for color, detail and movement later became useful for other purposes, such as social interactions in groups.
Isbell is currently working on a book about primate origins, including her snake hypothesis.
It sounds sketchy to me, too. However, the article does have the disclaimer that it's only a hypothesis at this point.
She, in my humble opinion, is incorrect. Dinosaurs were chomping on small mammals since they started to differentiate from reptiles.
Nothing except that the theory of evolution has shown to be consistent everywhere it has been tested in the zoological realm.
We have nothing but supposition to assume a particular star is held to the rest of Milky Way by gravity, other than the fact that other stars tend to obey gravitational theory. Do you think we try to prove the Gravitational Law works for every new star that's discovered?
Evolution is known to be such a ubiqitious concept that it's not a stretch to assume it generally works, as is done with any well-established theory in science.
Well, a couple of our more recent responses are the 12 gauge shotgun and night vision goggles. Let's see the snakes match those.
I fix because I care...
Just because you have an idea about how the teeth came to be, that does not mean your idea is a fact. There is very little known about this fish and its history, so you are way overstating your case. That is why adding the word "presumably" is a reasonable modification.
The only ones concealing anything are the creationist sources of disinformation, which hide the fact that evolution can and does explain eyes and limbs and more.
What are your feelings on the current situation in the Middle East?
I spent a miserable research summer watching squirrel monkeys (new world), and their compound was swarming with flies. The monkeys would sit quietly and when a fly went by they would simply pluck it from mid-flight with their fingers (then eat it). That's not shabby hand-eye coordination.
How simple and easy - no thought required!
Why don't we do the same with ALL sciences? Why bother studying astronomy? Let's just say everything revolves around the Earth - then we don't have to worry about pesky things like scientific research.
Why bother studying medicine? If someone gets sick, we can just say: "It's God's will".
See how easy life could be?
There are theories that our fear of spiders is innate.
Fair enough - but it's a reasonable presumption.
1) What is the Theory of Evolution (in your own words)?
2) What are the problems with the Theory of Evolution?
Note, if you do not answer these questions we'll just have to assume you have absolutely no idea of that of which you speak, and can therefore be dismissed as the ignorant troll you probably are.
Thanks for the ping!
Wow!!!
See any herps?
Sounds like an unproven, non-universally-accepted hypothesis you've got there.
It all comes down to "Evolutionary Pressures".
This reminds me of an article I read on fear & learning in monkeys a while ago.
Basically, monkeys aren't born with fear of snakes; they only start fearing snakes when they see another monkey fearing snakes.
However, if a monkey sees another monkey fearing, say, flowers... the only thing that that monkey learns is that some monkeys are crazy.
The conclusion of the article was that fear of snakes and other dangers were instinctive & genetic, but it was dormant by default and had to be "triggered" by external stimulus before it could be expressed. This fits in with a lot of genetic-influenced behavior we see (e.g., alcoholism; little kids don't steal from their parents' liquor cabinets--they have to take their first drink before becoming alcoholic).
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