Lecture 8 Flashcards
What does neolithic mean
the ‘new stone age’. Neolithic used ground or polished stone tools and weapons, and manufactured pottery.
They lived in settlements (period from which tools and pottery became more sophisticated and evidence of manufacturing in the same location and people settled in those locations- more recent) - more settled farming cultures
What does paleolithic mean
the ‘old stone age’. Characterised by archaeological remains that included stone tools- tools are less sophisticated and less evidence of settlements- not much evidence of pottery in those places
What does mesolithic mean
archaeological cultures that fall somewhere between paleolithic and neolithic
What does Neolithic describe
The transition from hunter gatherers to more settled farming cultures and people that settled in places for longer rather than constantly moving around
When did domestication begin
Neoliphic period begun after the last ice age which finished around 10-15 thousand years ago.
Farming emerged as an innovation after those ice sheets had melted.
Where did domestication happen
In many places.
Different organisms were domesticated in different places. There were some organisms that were domesticated at the same time in multiple areas e.g. Pigs in Europe and China and Millet in West Africa and East Africa and in China.
Earliest archaeological evidence of agriculture across Europe
Agriculture spread from the Near-East about 12KYA and reached NW Europe by about 5KYA
Darker colours suggests the agriculture is older, lighter colours means its more recent
Agriculture is spread from the near East from 12,000 years ago into the rest of Europe where it happened much later (5000 years ago)- quick transition, 7000 years but it happened earlier in the South East.
When did the human population rapidly grow
Population was relatively stable until 10KYA, and then grew around 1000-fold
This was as a consequence of the switch to domestication leading to the rapid expansion in population size. Invention of farming meant we had better access to food
How domestication occurred - cattle
Troy (2001) looked at mtDNA (~200bp) in 392 cattle from breeds across Europe including 4 aurochs from Europe
European aurochs are not an ancestor of modern European cattle but it was initially suggested that they were
They classified the amount of mitochondrial DNA variation and built haplotype networks. What these networks show is each circle represents a different mitochondrial haplotype.
The size of the circle shows how common it is in each location. Branches indicate other haplotypes that are connected to it and the branch length tells you how similar it is
South East Europe has all 4 haplotypes, consistent with it being the origin of domestication
Orox are extinct but are genetically distinct from modern breed of cattle so they are not the main ancestor for modern cattle.
Asian and European cattle must have domesticated separately due to their distance on the mtDNA tree
What did the 2009 Bovine HapMap project show
It looked at 37,000 SNPs in nearly 500 cattle from 19 breeds
Included Bos indicus and Bos taurus are genetically distinct. Hybrid breeds fall in between, as expected
They also looked at the amount of genetic variation in the different breeds- compare it to humans and to one another
Patterns of genetic diversity (Ѳ), suggest that Bos taurus was derived from smaller populations than Bos indicus
Angus and Holstein Bos taurus have 40% more variation than humans. Brahman (Bos indicus) are a lot more diverse- measure diversity.
What did recent studies of aurochs show
- An aurochs (from close to Sheffield) mtDNA genome has now been sequenced
- Same haplotype as earlier aurochs mtDNA sequences
- Now possible to sequence entire aurochs genomes- can then do ABBA BABA type tests-
- Distinct from European modern breeds – consistent with Near East Origin.
- BUT: ABBA-BABA tests show they contributed to UK breeds
Signatures of selection in cattle genomes
Can look in the genomes- can take cattle breeds from around the world- find parts of the genome that have clearly undergone positive selection.
Absence of horns - safer for farmers and other animals
Double muscling: more meat on animal
Milk composition, body size, coat colour
We can see the legacy of the subsequent human selection on different phenotypes
Other examples of domesticates telling us about human history
Pigs were independently domesticated in Europe and China, with gene flow occurring between wild and domesticated populations
Sunflowers were domesticated in NE America rather than introduced from Mexico
Rice was domesticated more than once in different parts of China. Today there are two main variety of rice: Japonica variety was domesticated first, and Indica rice was created by crossing Japonica to wild rice- reveal when are where domestication happened by comparing domesticated species to their wild relatives
Adaptations to Agriculture- Lactase
Lactase is the enzyme required to digest lactose, the main sugar in milk.
In most mammals, lactase levels are reduced after weaning (probably costly to produce lactase)
That was historically true for human populations
In populations where cows and sheep and goats were first domesticated, lactase persistence had arisen as an adaptation and reached high frequency in those populations
In humans, the ability to tolerate lactose into adulthood is because lactase is still produced (lactase persistence- more common in Western Africa, Europe etc.)
Lactase persistance has arisen multiple independent times in different places- different colours representing the different mutations. The ability to tolerate lactose into adulthood is because these mutations enable lactase to still be produced into adulthood.
Lactase persistence is caused by dominant alleles in the lactase (LCT) gene; these alleles are common in populations where there is a history of drinking milk
Once the domestication happened- went from hunters to farmers. Adaptation from diary to milk. Evolution of lactase persistence
LCT persistance alleles in different populations
We can see whether there’s genetic evidence for lactase persistence
There are different derived LCT persistence alleles in different populations
E.g. 13910T in Europeans, 14010C in Africans but they show signatures of positive selection
e.g. EHH tests in African populations for 14010C allele (red) and ancestral allele (blue)
There were similar patterns for 13910T allele in Europeans
Data support the idea that there has been (recent) convergent evolution of alleles that enable humans to have a milk- rich diet in populations that adopted diary-based agriculture
