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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4545