aDNA and domestication Flashcards
(15 cards)
DNA barcoding
- Fast and accurate species identification of non-diagnostic bone
- Minimally destructive, 20mg bone powder
- Bird bone: difficult to identify taxonomically
- Metric traits overlap in closely related species
- Extensive database of reference DNA sequences required
DNA barcoding - walkthrough
- Have an unknown organism
- DNA is extracted
- Barcode fragmented
- DNA is sequenced
- Compared with a barcode database
- Match found
- Species is identified
Why were dogs domesticated
- They are the earliest domesticated species
- And the only domesticated large carnivore
- Not best suited to food production so not a conventional domesticate
- Multiple uses: herding, hunting, tracking, transport, defence
Modern dog breeds
- > 340 distinctive breeds
- Selected for functional, behavioural, aesthetic traits resulting in phenotypic radiation
How to identify the domesticate [dog]
- Conventional approach is the morphometric analysis of remains of large canids
- Overall reduction in size
- Reduction in jaw size and dental crowding
- Problem: little morphological variation between the earliest dogs and wolves
Earliest universally accepted remains of fully domesticated dog
- Canis Familiaris
- Saint-Thibaud-de-Couz
- Dated 11,6000 y.a
Earliest widely accepted remains of domesticated dog
- Bonn-Oberkassel, Germany
- Dated c.14,000 y.a
- Associated with human double burial
Controversies surrounding dog domestication
- Russia, Belgium, and the Czech Republic all have contested remains
- Dates range 31,500-33,000 BP
- E.g. Russia: 33 ka.BP: Short snout, wolf like teeth, liked to Thule Period Greenland dogs, no evidence for human activity
Domestication centre of dogs
If all early fossil specimens are accepted as dogs then:
- Likely multiple centres for domestication
- Dogs were domesticated in the Aurignacian, pre-31,0000 y.a
- They dont necessarily have surviving lineages
What does mtDNA diversity tell us about the domestication origin
- Modern dog and wolf mtDNA was sequenced in the late 1990s
- Gray wold was progenitor of all modern dogs
- 4 main clades suggesting more than one domestication centre
- ORR significant post-domestication hybridization
- Date of domestication determined from the number of point mutations in all dogs using the coyote-wolf split time of 1M years ago to calibrate mutation rates
What’s a Clade?
Group of organisms believed to comprise all evolutionary descendents of a common ancestor
What was shown by domestication studies that extended to Europe, Asia, Africa, and Americas
- Greatest genetic variation observed in East Asian dogs
- mtDNA diversity indicated timing of domestication was 15,000 years ago
Autosomal Sequences
- Diversity of autosomal SNPs shows a distinct pattern from mtDNA studies
- Comparison of breed dogs, wolves, and coyotes
- Dog nuclear DNA does not vary geographically in a consistent pattern
- The individual breeds with the greatest genetic diverstiy come from both China and the Near East
Basal Breeds paradox
- Basal breeds don’t occur in areas with earliest archaeological evidence
- Recently introdued basal breeds in areas outside the range of the grey wolf
- Basal breeds only appear genetically distinctive bc of geographic isolation
- Studies are picking up breed bottlenecks in the past 100-150 years
Why is there no consensus on origins of the dog
- 19th century breeding programmes
- Geographical/genetic isolation of certain breeds
- Admixture/introgression with regional wolf populations
