I have found that definitions of neoteny that I provide to friends often don’t easily stick in their mind.  To ask someone to think of an automobile accelerating is easy.  It is not too difficult to ask people to make a picture in their mind’s eye of an accelerating automobile changing its model year to acquire future features while speeding up, decelerating to change shape to look like an older model.  But it is more difficult to ask them in their mind’s eye to perform this animation while considering a long succession of automobile models, each succeeding vehicle behaving a little different from the one before, different in a fashion where its ability to change model year with speed is enhanced or compromised with time.  Minds’ eyes sometimes can use a little training.

Neoteny, one of six heterochronic dynamics described by Gould (1977), is the biological process that prolongs ancestor embryo, infant and childhood features and displays them in the physical bodies and behaviors of descendant adults.  The classic examples are our ancient chimpanzee-like forebear infant features of small jaw, small teeth, big head, relatively large brain, upright stature, vertical skull positioning, playful disposition, curiosity, social dependency and displays of affection all prolonging to stay engaged later and later in childhood over the course of successive generations until these features appear not only in the young, but in adults.

Gould lists over 30 contemporary human features formed from ancient forebear infants.

Imagine that your great grandmother loved and played harmonica until she was six.  Your grandmother enjoyed playing until she was ten.  Your dad played until he hit puberty, then quit.  Then you, grown up, play harmonica a little bit each day.  You might say harmonica playing displayed a neotenic trajectory over the course of four generations.  It has been estimated that neoteny has influenced human evolution over the course of maybe 100,000 generations.

Acceleration is the opposite of neoteny.  With acceleration, ancestor adult features withdraw, instead of prolonging, to appear in the childhoods of descendants.  If mammoths were originally warm-weather elephant-like creatures, and they needed more hair and aggression to survive difficult winters, then they may have taken elephant adult-like tendencies to have more hair and aggression and placed those tendencies in younger members of the species, until eventually over the course of generations both adults and children displayed more hair along with crusty dispositions.

Though with humans the drift in a neotenous direction occurred over the course of many generations, studies have been conducted on foxes that show radical changes in look and disposition in a mere 20 years.

“Belyaev, who was in charge of a huge fox-fur farm in Novosibirsk, wanted to develop a strain of foxes that would more readily tolerate contact with people.  Of a study population of 465 foxes, he selected the 10 percent who were most calm and curious toward people and displayed the least fear or aggression.  He bred among this group and continued selecting for succeeding generations.  After only twenty generations he had ‘naturally tame animals that…would search for their keepers, climb on them… sit on the windowsill waiting for someone to approach, roll over to get their tummies rubbed, and let people carry them around and give them their shots.’ They would wag their tails that turned up at the end, like dogs.  They barked like dogs, as foxes almost never do in the wild.  These surprisingly speedy and diverse changes were produced by inducing neoteny, so that the foxes reached sexual maturity while continuing to behave like immature animals…Belyaev’s tame foxes came into heat twice a year, instead of once, just as dogs can breed twice a year and wolves only once.”  (Katharine M. Rogers, First Friend:  A History of Dogs and Humans (New York:  St. Martin’s Press, 2005), p. 20.)

In addition, after 20 years these foxes started licking the hands and faces of familiar people, their annual molting in some cases stopped, ears drooped like dogs and piebald coat coloration emerged. (click here)

A number of authors have described how differences in dog breeds can be ascribed to the degree that a breed has been influenced by neoteny or the prolongation of ancestor wolf cub features to appear in the adult of dog descendants.  Selecting specific tame behaviors featured by the very young resulted in physiological transformations that included animal size, skull shape, coat variation, dog age and more promiscuous mating strategies.

In Mexico, there is a salamander-like creature called an axolotl.  It has external gills and spends its whole life in the water.  Change the axolotl environment, remove the water, and the axolotl, over a generation, will adjust to become indistinguishable from the North American salamander.  The North American salamander lives on land and uses lungs.

The larval or embryonic stage of the salamander is the axolotl.  This creature can evolve or adjust maturation to offer descendants a choice of a larval version (living in the water) or an adult version (living on the land).  Both forms reproduce.  The axolotl features neotenous characteristics of the salamander.  Or, you might say that the salamander exhibits acceleration regarding axolotl features.  The absence or presence of water determines which form this axolotl/salamander takes, an environmental effect.

This blog explores the power of neoteny and acceleration to explain evolution and transformation at a biological, social, ontogenetical and personal scale.  What I am calling an orchestral theory of evolution has to do with the adjustments of maturation rate and timing.  Although at these four scales the process is driven by the influences of social structure and the environment upon testosterone and estrogen, which impact rate and timing, I am also suggesting that adjustments in the rate and timing of systems over time, at other scales, may follow the same process.

This work also considers that though testosterone and estrogen do not inform rate and timing at the molecular biological or cosmic scales, the evolution of systems at these scales may be impacted by an identical or similar dynamic.


This entry was posted on Monday, December 14th, 2009 at 9:09 am and is filed under Biology, Neoteny, Ontogeny. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
1 Comment so far

  1. Andrew on December 24, 2009 6:04 pm

    An interesting quote from http://8e.devbio.com/article.php?id=223

    “The most obvious physiological changes involved corticosteroids. In wild foxes, the levels of corticosteroids, hormones involved in adaptation to stress, rise sharply between the age of 2–4 months, reaching adult levels by 8 months of age. The domesticated wolves had their corticosteroid surge significantly later. The domesticated foxes have a much lower adrenal response to stress, and they have more serotonin in their blood.”

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