Science Watch
- 1. How X-Rays Work
- 2. Foreign Animal Species
- 3. The Road to Domestication
- 4. Demon Gene (Genetic technology)
The Road to Domestication
Dr. Stephen Zawistowski, Ph.D., ASPCA
“Many have forgotten this truth, but you must not forget it. You remain responsible, forever, for what you have tamed.”
—Antoine de Saint-Exupéry, The Little Prince
Domestication is among the most visible yet poorly understood biological events to impact a species. While we are all familiar with dogs, cats, horses and other domesticated species that live closely with humans, where they came from, how they were changed and how they are related to “wild” dogs, feral cats and mustangs is less familiar and can complicate our attitudes and treatment of them.
Domestication is a process that takes place over time and multiple generations. All species are not domesticated in the same way, and, at any given time, different species may be in different stages of the domestication process.
Domestication generally changes a species in several key ways. First, individuals of the species tend to be more easily socialized to people. This certainly facilitates the general desire to maintain the animals in close proximity, whether for companionship, work or convenience. The social structure exhibited by the wild ancestor species may be modified, as in the transformation of the intraspecific pack orientation of the dog to the interspecific bonding of dogs to human families. While an individual member of a wild species may be tamed, allowing or tolerating a high degree of close human proximity or contact, it will retain instinctive behavior patterns, and will not directly pass its tameness on to its young. Selecting the individuals who are easiest to approach, tame and socialize and least likely to show instinctive patterns of attack or flight, is one of the first stages of domestication—whether intended or not.
Increasing and Multiplying
A second change is the species’ enhanced reproductive potential. Domestication typically is motivated by economics, which means the production of more individual animals. Wild species reproduce in accordance with social structure, the seasons, the availability of food and the presence of predators. In comparison, domestic species may begin breeding at a younger age, breed more frequently, be nonselective in mates, i.e., accept those provided by humans and have larger numbers of young.
Once a species is easy to handle and breed, it’s possible to identify and select individual animals who exhibit desirable traits and breed them for a specific purpose or appearance. The extent of variation in a domestic species, as in breeds of dogs, for example, is a function of both the genetic variation that was present in the original population of wild ancestors and of mutations that may be identified and used in breeding programs. Over time, accumulated differences between the wild and domestic forms may preclude crossbreeding and/or the production of fertile offspring, though this is not always the case. For example, wolves, coyotes and domestics dogs, all members of the genus Canis, remain interfertile.
In some instances, domestic animals have “leaked” back to a free-living or wild state. Mustangs, for example, are the descendants of horses brought to the New World by explorers and settlers. Pigeons are the progeny of ancestors brought to America as a ready source of food in colonial days. Over time, populations of these animals began to readapt to a free-living, wild existence. The descendants of a domestic species living in such a fashion are called feral.
Wary and Wise
Among the most common changes seen in feral animals is a reacquired wariness of humans. This is likely a function of both limited or no opportunities for socializing when young and gradual genetic changes in the population. Unfortunately, the enhanced reproductive rate that accompanied domestication tends to remain. When an increased reproductive rate is coupled with limited natural predators, populations may increase to the point of threatening the local environment. Past efforts to manage these populations typically relied on lethal control, but successful management of feral cat colonies through Trap-Neuter-Release programs or of wild horse herds with immunocontraceptive techniques have shown that killing is not necessary. We must always remain cognizant of our responsibilities when we modify a species.
Whether species change as a result of natural or of artificial (human-directed) selection, the process is dynamic and ongoing. Thus wild, domestic and feral are descriptors that indicate the current position of a species along a continuum of change.
Dr. “Z” is senior vice president of ASPCA Animal Sciences and Animal Watch science advisor.
Courtesy of
ASPCA
424 East 92nd St.
New York, NY 10128-6804
(212) 876-7700
www.aspca.org
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