Dogs

The Evolution of Dog

How Modern Dogs Came to Be

The first wolves were domesticated by early humans about 15,000 years ago (1). Most dogs have been bred to be companion animals and no longer know how to hunt or adapt to the wolf packs they came from years ago. While the domestic dog still has the basic habitat needs of her wolf cousin, her natural habitat is with her human pack. Some adaptations of dogs are their keen sense of smell, strong, blunt claws, long, slender legs, and long muzzles. A dog may eat raw or cooked meat, organ meats, vegetables, grains and fruits. In areas where both dogs and other large predators live, dogs can be a major food source for big cats or canines (5). It's likely that every carnivorous animal today can trace itself back to Miacis, a slightly bigger, weasel-like creature. Modern dogs evolved from a line of carnivorous mammals called "canids" (1). Some ancestors are the Aelurodon, a "cat-toothed" dog that behaved more like a hyena, the Amphicyon also known as the "bear dog", the Borophagus, one of the biggest of the bone-crushing canids, and the Cynodictis that was once thought to be the first true dog (1). Variation in skeletal morphology in the dog is a complex phenotype, with IGF-1 as a major determinant of small size. Variation in canine pelage, including pattern, length, curl, and texture (smooth versus wire), are controlled by combinations of alleles at only three genes. Common sources of variation are: mutational hotspots, chromosomal fissions, and gene duplications, intense artificial selection, and rapid continuation of new mutations. If a breeder wants a dog with a curly coat, he or she will allow curly-coated dogs to breed and not allow them to breed with straight-coated dogs. In nature, the most well-adapted animals are more likely to survive and reproduce, but in dog breeding, the dogs with the desirable characteristics are allowed to reproduce by the breeders (3). A dog’s paw has four digits that make contact with the ground and on almost every front paw and occasionally on the back ones, there is an inside digit higher up that does not make ground contact (4). This digit is the dewclaw, a vestigial structure that is non-functional or has some function in some breeds (5). Other species in the clade are the Dusicyon, a "foolish dog" that went extinct in the 19th century, the Epicyon, a prehistoric dog that was built more like a big cat, the Eucyon, the immediate predecessor of modern canines, the Hesperocyon, an early ancestor of the modern dog, and the Dire Wolf, a giant wolf of the Pleistocene epoch (1). The fossilized remains of a canine found in the 1970s in southern Siberia's Altay Mountains is the earliest well-preserved pet dog. A Russian team compared the Russian dog fossils with the bones of wild wolves, modern wolves, domesticated dogs, and early doglike canids. Canids have a wide geographical spread, but their fossils are not of great use to date more than some major events and periods in human history (2).


Interactive:

· http://www.pbs.org/wgbh/nova/nature/dogs-around-world.html


Sources:

1) http://dinosaurs.about.com/od/otherprehistoriclife/a/Prehistoric-Dogs-The-Story-Of-Dog-Evolution.htm

2) http://www.dogbreedinfo.com/articles/wolftodog.htm

3) http://www.nature.com/nature/journal/v464/n7290/fig_tab/nature08837_F1.html

4) http://www.pets.ca/dogs/articles/dog-dewclaws/

5) http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1000310