Is Domestication Inherently Unhealthy?

There was a discussion on a radio program the other day I found fascinating. It involved Darwinian evolution and focused on an experiment begun by Dmitri Belyaev and domesticating silver foxes. This has been written about many times, and is highlighted in Richard Dawkins' excellent book on Darwinian theory, The Greatest Show on Earth. The method of this experiment was simple--all foxes were classified in one of three ways: Class I would flee and/or bite a handler that tried to hand-feed and stroke the animal; Class II would accept the handler but show no positive response; and Class III would approach the handler, wag its tail and show other positive behaviors. Only Class III foxes were bred, and within 6 generations Belyaev had tame animals. The truly remarkable part of this experiment were the unexpected changes that took place (seen in the top image to the right): the silver coat changed to black and white piebald, teeth became smaller, bones less robust, faces became rounder, ears flopped over, tails curled up, and females went into heat every six months rather than on

ce a year like the typical vixen. In effect, the foxes had become more dog-like and development had stopped at a juvenile phase: Belyaev's foxes had become Peter Pans of the canine world.

What really grabbed my attention was the explanation for why these physical changes are tied to behavior. Domestication experiments in both foxes and Norway rats show that structural changes occur in the zona fasciculata of the adrenal cortex, the area responsible for glucocorticoid (think prednisone) release--in a larger sense the flight-or-fight response. Makes sense right? If an animal has a weaker flight response it should be easier to domesticate. Where it really gets interesting is when we look at where these cells come from. The adrenals originate from the neural crest in embryonic development. These cells also differentiate into other tissue like craniofacial bone and cartilage (faces and ears), teeth, bone, heart valves, and some neural tissue.

This correlates very closely with Chinese medical theory. Centuries before we had any understanding of embryonic development the Chinese came up with their system. Within this system, six pairs of organs are said to be responsible for all the physiological processes in the body--one of which is the Kidney. This should not be confused with the (small 'k') kidney; the actual organ. The Chinese concept of Kidney includes the bean-shaped organs but also encompasses many other functions not typically associate with the western definition of the kidney. This Chinese Kidney is responsible for many things--Jing, or Essence being one, which can be thought of as constitutional or genetic health. In addition to urine production, the Kidney also controls aging, bone growth, teeth, hair, and reproductive function. Interesting, huh?

All of this is important to the health of our animals. If, as the research indicates, domestication leads to a weaker adrenal-pituitary axis, might this explain some of the medical problems that seem rampant in our pets? There are the obvious, like dental issues that might arise from smaller teeth, or ear infections in floppy ears. But what of Cushing's or Addison's disease, both directly related to the adrenal/pituitary axis? How about conditions like inflammatory bowel disease and skin allergies? Both are overreactions of the immune system and commonly treated in Western medicine with steroids like dexamethasone and prednisone. What if in normal/wild systems the adrenal cortex pumps out just enough steroid to keep things in check--a feedback loop grown weaker with domestication? This is very much along the line of the research and treatment protocol of Dr Alfred J Plechner's Endocrine-Imbalance-Syndrome.

Of course, the horse is out of the barn and we aren't going back to tying a wolf up in the back yard or roping a mustang to ride. But it might give owners and breeders a little pause when choosing an animal: maybe a little attitude is preferable to an animal that rolls on its back every time you look at it sideways.

This radio program ended with a discussion on what might be going on with our own species. Our ancestors had larger teeth and thicker bone as well as coarser facial features. Through the centuries, have social groupings like cities and events like war culled the most aggressive humans from our gene pool? Are human adrenals becoming weaker as we become more "domesticated"? If so, then the choices we make in diet, lifestyle, and medical care might be as important for the health of ourselves as that of our pets.