X-Message-Number: 4545
Date: 24 Jun 95 14:34:26 EDT
From: Jim Davidson <>
Subject: Dogs and Humans

Dogs and humans are both examples of a type of predator called a "corsairial
hunter."  The term "corsair" refers to the ability to pursue prey over great
distances using greater stamina to wear down the animal.  Humans are probably
better than dogs at this type of hunting, but both are successful.


Humans and dogs also hunt in packs, using verbal and non-verbal communication to
move around a herd and join together in picking off likely prey.  Much of human
language skill is probably due to the need to communicate in the field.  Cave

drawings from over 30,000 years ago support the contention that humans hunted in

packs.  There are even cave drawings which suggest that humans hunted with dogs.

Dogs have extremely effective forelegs where tearing and holding prey is

concerned.  Although many breeds of dogs have lost vital characteristics through
in-breeding, close derivatives of the original wild dogs of Europe, such as the
border collie, have quite capable claws.  These claws can grow to an extensible
length of an inch or more unless trimmed regularly.  Though lacking an opposing
thumb, they have a vicious "dew claw" which seems almost useless until one
scrapes your neck.

Dogs use their fore legs for batting and clawing their prey, their teeth for
finishing the kill.  They also use their teeth for clinging to prey, and can
support the entire weight of their bodies by their jaws.  Indeed, this ability
to cling by the teeth may explain much of the reinforcement of their necks and
heads.  As a prey animal writhes and kicks, the clinging dog is accelerated and
decelerated, back and forth, up and down.  The resulting whiplash must be quite
fierce.

Back in the days of the australopithecines, humans had much stouter necks as
indicated by muscle attachments.  We also had much thicker skulls and
correspondingly smaller brains.  By evolutionary standards, the 2 million or so
years separating us from the australopithecines isn't that much time.

Why do modern humans have thinner skulls?  Perhaps the development of language
and tool use led to an evolutionary advantage for larger brains.  The smarter

humans with the larger brains didn't need as much protection for their heads for
reasons Mike Darwin has considered (not swinging in the trees or climbing to
great heights) but also because they did much more cooperative hunting in packs
and tribes, keeping the cranial insults to a minimum.


What about the shared characteristic of limited tolerance of ischemia?  Dogs and
humans may have very similar circulatory and endocrine systems, given their

similar hunting methods.  Consider the marathon runner, the closest contemporary
analog to the corsairial hunter.  The marathon person has an incredible ability
to shed heat, an incredible ability to process water into sweat and urine, an
incredible ability to keep the brain supplied with blood so it can direct the

vigorous activity of the legs and feet (and balancing arms).  Perhaps as part of
the adaptation that permits the body to maintain a continuous blood flow to the
extremities for a long period of time, certain other characteristics of veins
and tissues had to be compromised.

Compare the human to the cougar.  The cougar lies in wait, then uses a burst of

speed to bring down its prey.  Thus the evolution of the cat did not require any

compromising of circulatory and heat transfer systems to sustain long periods of
activity.

Indeed, if you have an appetite for cat, you can wear them down, too.

Jim


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