Re: pesticide allergy


wkambic@xxxxxxx wrote:
On Fri, 21 Jul 2006 12:33:59 -0400, Hunter <HHamp5246@xxxxxxx> wrote:

How many people die every year from snakebite here in the US... I
think it's something like... none.

It's more than "none" but fewer than those hit by lighting, IIRC.

If you don't go grabbing at them the chances are they won't bite. If
they do, you aren't going to die... you are going to the hospital.

In a weird cosmically coincidental sort of way, this article is on
Yahoo top news:
<http://news.yahoo.com/s/space/20060721/sc_space/fearofsnakesdroveprimateevolutionscientistsays&printer=1;_ylt=AozhmXkTSNwJ7gxk4TcIU.r737YB;_ylu=X3oDMTA3MXN1bHE0BHNlYwN0bWE->

Mary

Fear of Snakes Drove Primate Evolution, Scientist Says

Ker Than
LiveScience Staff Writer
LiveScience.comFri Jul 21, 10:32 AM ET

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.

To avoid becoming snake food, early mammals had to develop ways to
detect and avoid the reptiles before they could strike. Some animals
evolved better snake sniffers, while others developed immunities to
serpent venom when it evolved. 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.

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.

"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."

Harry Greene, an evolutionary biologist and snake expert at Cornell
University in New York, says Isbell's new idea is very exciting.

"It strikes me as a very special piece of scholarship and I think it's
going to provoke a lot of thought," Greene said.

Isbell's work is detailed in the July issue of the Journal of Human
Evolution.

Snake Gallery | Cobra's Deadly Aim | Flying Snakes

A new weapon

Fossil and DNA evidence suggests that the snakes were already around
when the first mammals evolved some 100 million years ago. The reptiles
were thus among the first serious predators mammals faced. Today, the
only other threats faced by primates are raptors, such as eagles and
hawks, and large carnivores, such as bears, large cats and wolves, but
these animals evolved long after snakes.

Furthermore, these other predators can be safely detected from a
distance. For snakes, the opposite is true.

"If you see them close to you, you still have time to avoid them,"
Isbell said. "Primate vision is particularly good at close range."

Early snakes killed their prey using surprise attacks and by
suffocating them to death-the method of boa constrictors. But the
improved vision of primates, combined with other snake-coping
strategies developed by other animals, forced snakes to evolve a new
weapon: venom. This important milestone in snake evolution occurred
about 60 million years ago.

"The [snakes] had to do something to get better at finding their prey,
so that's where venom comes in," Isbell said. "The snakes upped the
ante and then the primates had to respond by developing even better
vision."

Once primates developed specialized vision and enlarged brains, these
traits became useful for other purposes, such as social interactions in
groups.

Seeing in 3D

Isbell's new theory could explain how a number of primate-defining
traits evolved.

For example, primates are among the few animals whose eyes face forward
(most animals have eyes located on the sides of their heads). This
so-called "orbital convergence" improves depth perception and allows
monkeys and apes, including humans, to see in three dimensions.
Primates also have better color vision than most animals and are also
unique in relying heavily on vision when reaching and grasping for
objects.

One of the most popular ideas for explaining how these traits evolved
is called the "visual predation hypothesis." It proposes that our early
ancestors were small, insect eating mammals and that the need to stalk
and grab insects at close range was the driving force behind the
evolution of improved vision.

Another popular idea, called the "leaping hypothesis," argues that
orbital convergence is not only important for 3D vision, but also for
breaking through camouflage. Thus, it would have been useful not only
for capturing insects and finding small fruits, but also for aiming at
small, hard-to-see branches during mid-leaps through trees.

But there are problems with both hypotheses, Isbell says.

First, there is no solid evidence that early primates were committed
insectivores. It's possible that like many primates today, they were
generalists, eating a variety of plant foods, such as leaves, fruit and
nectar, as well as insects.

More importantly, recent neuroscience studies do not support the idea
that vision evolved alongside the ability to reach and grasp. Rather,
the data suggest that the reaching-and-grasping abilities of primates
actually evolved before they learned to leap and before they developed
stereoscopic, or 3D, vision.

Agents of evolutionary change

Isbell thinks proto-primates-the early mammals that eventually
evolved into primates-were in better position compared to other
mammals to evolve specialized vision and enlarged brains because of the
foods they ate.

"They were eating foods high in sugar, and glucose is required for
metabolizing energy," Isbell said. "Vision is a part of the brain, and
messing with the brain takes a lot of energy so you're going to need a
diet that allows you to do that."

Modern primates are among the most frugivorous, or "fruit-loving," of
all mammals, and this trend might have started with the proto-primates.
"Today there are primates that focus on leaves and things like that,
but the earliest primates may have had a generalized diet that included
fruits, nectar, flowers and insects," she said.

Thus, early primates not only had a good incentive for developing
better vision, they might have already been eating the high-energy
foods needed to do so.

Testing the theory

Isbell says her theory can be tested. For example, scientists could
look at whether primates can visually detect snakes more quickly or
more reliably than other mammals. Scientists could also examine whether
there are differences in the snake-detecting abilities of primates from
around the world.

"You could see whether there is any difference between Malagasy lemurs,
South American primates and the African and Asian primates," Isbell
said.

Anthropologists have tended to stress things like hunting to explain
the special adaptations of primates, and particularly humans, said
Greene, the Cornell snake expert, but scientists are starting to warm
to the idea that predators likely played a large role in human
evolution as well.

"Getting away from things is a big deal, too," Greene said in a
telephone interview.

If snake and primate history are as intimately connected as Isbell
suggests, then it might account for other things as well, Greene added.

"Snakes and people have had a long history; it goes back to long before
we were people in fact," he said. "That might sort of explain why we
have such extreme attitudes towards snakes, varying from deification to
"ophidiphobia," or fear of snakes.
Gallery: Snakes of the World Deadly Aim: Cobras Really Do Shoot for the
Eyes Flying Snakes: New Videos Reveal How They Do It Millions of Years
Ago, Snakes Were Hip Top 10 Deadliest Animals Birds of Prey Original
Story: Fear of Snakes Drove Primate Evolution, Scientist Says

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