Differences in the Behavior of Landraces and Breeds of Dogs - Genetics and the Behavior of Domestic Animals - page 224

Mechanisms for the evolutionary divergence of dogs are reasonably clear.
All the species of the genus Canis are allelomorphic. This simply means that
wolves, coyotes, the jackal (C. aureus), and dogs are karyotypically identi-
cal; that is, they have the same number of chromosomes, the same shape of
chromosomes, and the same mapping of genes on those chromosomes.
Allelic differences are minor differences in the base pairs of individual
genes. Morphological and behavioral differences in allelomorphs must be the
result of heterochrony—changes in the timing of onsets, rates, and offsets of
gene products. Heterochronic shifting of gene products in such a way as to
change development during the juvenile stage (heterochrony), is an explana-
tion that biologists have hypothesized to account for the tremendous pheno-
typic divergence of breeds of dog. However, many divergent morphologies
(such as achondroplasia in dachshunds and basset hounds) are simply point
mutations that show up periodically in any species.
Coppinger and Schneider (1995) have found that various aspects of
behavior appear homologous to juvenile canid behavior. Coppinger and
Coppinger (1982) predicted that breed-specific behaviors would be displayed
against a concordant set of morphological traits such as face length. And
they were wrong.
There is nothing wrong with the neoteny theory in theory, but while the
“snapshot” hypothesis may have conceptual value for the kind of processes
that occur, the predictions of youthful characteristics (either morphological
or behavioral) being ontologically preserved in the descendent adult form
have so far escaped verification. In fact, the reverse is true. One purpose in
proposing such an idea is to attract the attention of other scientists who may
generate data to confirm or refute the idea.
Research on the subject since 1982 has yielded important information.
Global retardation in a developmental stage provides no predictions as to the
form of the character of the descendant. Dogs are not short-faced wolves, as
is commonly thought ( Morey, 1994; Olsen, 1985 ). Differences in skull
morphologies are not the cessation of growth at some intermediate ontoge-
netic juncture of the ancestor ( Drake, 2011 ). Dogs such as the borzoi have
heads that are longer and narrower than the wild types, which also can be
described as neotenic. Arresting development in a growth stage would mean
that the animal would grow and grow, creating skull shapes that were phylo-
genetically bizarre. The brachycephalic (short-faced) dogs don't have heads
that are puppy-proportioned but rather have normal adult wild-type palate
length proportions ( Wayne, 1986 ). Many breeds of dogs have head shapes
that are virtually indistinguishable from the adult allometries of the rest of
the genus. Dog head shape is not a reflection of an ontogenetic stage (paedo-
morphosis), but rather a result of the developmental processes. All members
of the genus start with neonatal heads, which are virtually identical in shape
and size. The borzoi is an exception; the characteristic lengthening of the
skull starts before birth ( Drake, 2011 ). Allometric remodeling of the neonatal