I believe the thing that separates humanity from other the domesticated species on this planet is that we never ask ourselves who or what it is that domesticated us. Even those who profess to have a personal relationship with some mythological deity whom they hold responsible for our current predicament become extremely reticent when you ask them for its cell phone number. That said, before can I begin to describe what domesticated us, I I have to define exactly what it means to be domesticated especially for those readers who vanity is such that they find the notion that we share anything in common with Canis lupus or Felix catus to be too distasteful to consider.
verb /dəˈmestiˌkāt/
domesticated, past participle; domesticated, past tense; domesticates, 3rd person singular present; domesticating, present participle
- Tame (an animal) and keep it as a pet or for farm produce
- – mammals were first domesticated for their milk
- Cultivate (a plant) for food
- Make (someone) fond of and good at home life and the tasks that it involves
- – you’ve really domesticated him
The defining characteristic of the process of domestication is artificial selection. The objective of which is to produce a specie with characteristics better suited to whatever its purpose may be. In example, household pets have to be selected for a friendly demeanor toward humans and cows have been selected to grow fast and produce copious amounts of milk.
Many species have been artificially selected but there is a very limited number that are considered truly domesticated. According to the evolutionary biologist Jared Diamond animal species must meet the following six criteria to be considered for domestication.
I would point out that humanity as specie meets all of these criteria. We are omnivorous, capable of breeding in 12 years, thrive in captivity, are eager to please, etc. etc.
Domesticated species that have been raised for many generations become substantially altered in both appearance and behavior. Dogs are very different from wolves. Recent studies begun in the 1950’s by Dmitry Belyeav in the breeding of the silver fox Vulpes vulpes has established that numerous morphological changes such as depigmentation, floppy ears, rolled and shorter tails with fewer vertebrae, dwarf and giant varieties, the ending of the yearly estrous cycle, lower corticosteroid levels, and higher blood serotonin levels all occur in concert with the deliberate selection of more docile and malleable animals. Click here for more information.
Hypothalamic hormone interactions are not amenable to overly simplistic description but cortisol is generally viewed as a stress related hormone. Individuals under high stress produce more cortisol and it’s presence facilitates the production of adrenaline which triggers fight or flight behaviors. Higher serotonin levels in the mid-brain and hypothalamus also correlate with the reduced aggressiveness of the domesticated animals. The lower cortisol and higher serotonin levels appear to be related to the animal’s reduced adrenal response and correlates to change in appearance such as mottled or spotted colored fur. The overall effect of all of these changes is to delay the onset of fear response from 6 weeks to 9 weeks and even later in the domesticated fox. The technical term for biological changes that delay the onset of adolescent characteristics into adulthood is pedomorphosis and results in an adult that retains many of the characteristics of the juvenile of the specie.
Pedomorphosism is the retention of juvenile characteristics well into maturity. Developmental biologists have determined there are two distinct ways this can occur, neotony and progenesis. In neotony the physiological development of an animal is slowed or delayed. In progenesis sexual development occurs faster. Both of these processes result in an adult capable of reproduction that retains juvenile physical characteristics.
Mickey Mouse's "evolution" in the 20th century is an example of Neotony
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The evolutionary biologist Steven J Gould has stated that the fundamental “evolutionary story” of humans is based on our specie “retaining to adulthood the originally juvenile features of our ancestors.”
Human beings are members of the Great Apes and our closest living relatives are the chimpanzee with which we share a common ancestor some six million years ago.
For reference purposes here is a picture of an adult chimpanzee:
It is fairly evident from that while we are similar in many ways to the adult chimpanzee pictured above, the differences between our two species makes it fairly unlikely that anyone would confuse the two if they were both invited to a party. Notice the small eyes set below a thick wide brow ridge, the long limb to torso length, the large prognostic jaw and teeth, the chimpanzee’s stooped posture, thick fur body and facial hair, and of course the chimpanzee’s much thicker skull and commensurately smaller brain. Now take a look at a juvenile chimpanzee.
Notice anything familiar? The large cranium to body size? The flat facial physiognomy? The lack of prognostic jaw? Weaker muscle tone? Diminished adrenal response, etc. etc.
OK, how about this:
Again this is an adult chimpanzee:
And this is George Burns: (Photo courtesy of Sheila Smart Photography Click here to see more her excellent work)
"If you live to be one hundred, you've got it made. Very few people die past that age."
Those of you who are still following along should be able to see that physiologically adult human beings are very similar to pre-adolescent chimpanzees and that as we age members of our specie tend to look more and more like chimpanzees. This is exactly what pedomorphosis looks like and it is a well know physiological effect of domestication.
So in summary human beings look like a domesticated chimpanzee because we share a common ancestor “only” six million years ago and we are domesticated and they are not. If you still find that you cannot accept this, well then… “Good night Gracie.”
Now the defining characteristic of domestication is the artificial selection of a specie for a specific purpose. So the next question becomes who or what domesticated us and for what purpose?
The answer to this is located here and it may surprise you.