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The Domestic Dog Divergence of dogs Why has the divergence timeline of domestic dogs changed over time? - Better fossil evidence, leading to better DNA samples (eg nuclear and mtDNA). mtDNA is more stable and provides better DNA samples - Better DNA sequencing techniques - Timeline ha...

The Domestic Dog Divergence of dogs Why has the divergence timeline of domestic dogs changed over time? - Better fossil evidence, leading to better DNA samples (eg nuclear and mtDNA). mtDNA is more stable and provides better DNA samples - Better DNA sequencing techniques - Timeline has been reduced from 135000 years to 30-40000 Wolf vs dog characteristics - Dogs are considered the same species as wolves but they have differing characteristics. - Wolves have no floppy ears and are typically larger, dogs have larger eyes, wider faces, shortened snout, curled tails, and mature slower - Wolves form no strong attachments to humans and are typically better problem solvers - Although there are significant physical differences between different domestic dog breeds, dogs are always more related to other dogs than they are to wolves (eg a husky is more related to a pug than it is to a wolf) Dogs have shorter braincases than wolves Wolves have larger incisors (front teeth) It is thought that at the beginning of the divergence, wolves and dogs looked very similar  Wolf skulls were found at the entrance of a hominid dwelling dated 125,000 years ago- it is unknown if they were decorative or if a previous relationship was present The Goyet dog (seen left) is 32-35000 years old and looks very dog like (short snout, smaller braincase, crowded teeth) compared to wolves present in the same period. Indicates early evidence of domestication Originally discovered in Belgium Mitochondrial DNA Studies mtDNA is used in many phylogenetic tree studies DNA is either stored in the nucleus (nuclear DNA) or in mitochondria (circular DNA, essentially bacterial DNA). Due to the presence of many mitochondria, there are numerous mtDNA copies in a single cell. mtDNA is much more stable than linear nuclear DNA, and mtDNA is only from the mothers eggs (shows maternal lineage) Dog Divergence mtDNA studies of canids revealed: - Domestic dogs interbred with wolves various times, so they are still considered the same species - Since mitochondria are maternally inherited - wolf mitochondria indicate a female wolf was bred by a dog (Likely the reverse also occurred) - North American Dogs probably evolved from Eurasian wolves - Dogs came to the Americas about 12,000 B.P. (before present), in the Paleolithic period across the Bering Strait Dingo origins - Thylacine was the largest known carnivorous marsupial and had a canid-like face (present in Tasmania and Australia) - It became extinct in 1936, likely due to competition with the dingo (canid) - Dingo likely made it to Australia with seafarers 4000 yrs ago, and was an early domestic dog variant - They now live in the wild, but are descended from domestic dogs (feral dog) - - Since there were no land bridges during the origin time of the dingo, it was thought that they moved in with the seafarers (too far to swim, ~50km) - “the Dingo was a highly valued companion to the Aborigines - they lived, ate and hunted with their human keepers. They were their bed warmers, camp cleaners, hunting companions and guard dogs. The Aborigines took puppies from wild litters each breeding season, but upon reaching maturity most of these dogs reverted to the wild lifestyle. Puppies were often suckled by the women of the tribe.” mtDNA studies of dingos mtDNA study of 211 dingoes, 676 dogs, 38 wolves revealed: - Seafarer’s dogs were from East Asia and were derived from a small group of dogs - Remained isolated in Australia from dogs for a considerable time, making them feral - Today, dogs and dingoes interbreed (are not a separate species) - Both dingoes and dogs are derived from a wolf ancestor Dog domestication What does domestication mean? The process of adapting wild plants and animals for human use with control over the reproduction and care - Archeological records show that numerous domestic dog ancestors were domesticated near the fertile crescent, due to the advent of agriculture - This occurred before sheep, goats, cattle were domesticated - Unknown if speciation caused domestication, or vice versa - Possibility that other Hominid species domesticated dogs in the past, around 30-40000 years ago (as we were living beside them at that time) Wolf domestication - theories Commensal theory: one species benefits but the other does not, although there is no harm (wolves would benefit from human scraps, no effect on humans) - Some wolves would be brave enough to collect scraps from human settlements, and aggressive ones would be killed or driven away by the humans - Since wolves are social creatures (hunt in packs with pack structure, raise young collectively, and communicate), this would have aided their domestication. - Arguments against this theory: it would have been harmful to have wolves near human encampments, and humans probably wouldn't have left enough scraps to attract wolf packs Other theory: humans stole wolf pups from wolf packs, which would build an intense bond between the human and wolf Acceptance - Changes in DNA sequence allow for a more open relationship with humans (this is called domestication) - Acceptance is when a behaviour change occurs, no change in DNA sequences (eg red foxes- bred in captivity for fur) Silver fox experiment Completed by Dr. Dmitiri Belyaev at the Institute of Cytology and Genetics in Novosibirsk, Russia Hypothesized that humans kept the tamest of animals to live with them, and this would have led to domestication (led to changes in physiology and behaviour) Used a melanistic form of Vulpes vulpes (silver fox) and selected the tamest. The tamest were then bred amongst themselves which continued for generations Created a population of foxes that were very tame compared to wild populations. Their physical forms changed as well; had floppy ears, curled tails, and white patches. Wild vs Domesticated Neural crest cells play major roles in the development of bone, cartilage, and melanocytes (which produce melanin for colouration), and they also form areas of the brain. It is believed that selection for specific changes (eg behaviour and docility) will simultaneously select for physical changes as they are both influenced by the neural crest cells. Morphological changes: - Fur colour/texture - Ear shape - Tail length and curvature - Eye colour - alterations in craniofacial structure Genetic changes - Genes involved in neural crest cell formation Archaeological Evidence Oberkassel, Germany - Domestic dog mandible near grave, discovered in 1914; found with 2 human skeletons - 14,200 years old, from the very end of the ice age - Further analysis revealed a red powder on the human skeletons and dog mandible, indicating that it was buried there on purpose (burial ritual evidence) Natufian burial site - Human was buried with a dog, 12000 years ago - Conclusive evidence of domestication, as Natufians used dogs to hunt - Petroglyphs in Saudi Arabia - Petroglyphs depict domestic dogs (eg the Canaan breed) - Curled tail represents a domestic dog - First depictions of humans and dogs - Other images depict humans and dogs hunting together (up curled tail means dog) North America - Wolf skulls found near Fairbanks, Alaska have shortened facial regions - Thought to represent “tamed wolves” - Dated to end of Last Ice Age ~8000 BC Ancient Egypt - Dogs were in households (fully domesticated; had collars) - Tons of evidence of their domestication (eg included in tombs and burials) - Royalty were often entombed with their dogs, and mummified dogs have been found - Anubis, the Egyptian god of the dead, guarded the world of the afterlife and is thought to have the head of a jackal Ancient China - Remains of dogs found; from 6000 - 7000 years ago - Dogs were used for hunting, food sources, companions, religious roles - Dog bones were also used as oracle bones (eg for telling the future thru rituals) Ancient Mesoamerica - Had similar relationships with dogs as Chinese people - Dogs were source of protein for large population Assyrian Empire - ~2500 years ago, Mastiff-like dogs were used to hunt lions - Also used for hunting in general and guarding Ancient Greece - Large shaggy dogs guarded sheep - Wore spiked collars as wolf protection - Guard dogs walked the town walls at night - Tracking dogs pursued criminals