Biomolecules and Dating Methods

Question 1

Answer 1

Ancestry, genetics and migration in Britain • Based on genetics of ~2000 Britons with grandparents within 80 km • 17 geographical groups – Flow of Anglo Saxon genes – Little trace of Viking

Question 2

Answer 2

Eulau, Germany • Late Neolithic (Corded Ware culture): 2700- 22/2000 BC Family buried together Violence: projectile points, perimortem fractures, defence injuries to forearms

Question 3

Answer 3

Dendrochronology Master Chronology - can be dated back to 11kya. West European master chronology of oaks. Used to calibrate radiocarbon dates but can also be used for direct dating.

Question 4

Answer 4

Bronze Age tomb from Qatna, Syria. Patches of purple dye made from sea creatures. Very rare to find preserved dye- showed what colour clothes and remnents of them would have been. Found via Analysis of lipid residues • Do not dissolve easily in water (hydrophobic).

Question 5

Answer 5

Oldest door in Britain • Westminster Abbey Chapter House • Dendro dated to AD 924 - 1030

Question 6

Answer 6

Middle Awash Herto AMH 154-160ky by Ar-Ar (Clark et al. 2003; Nature) ‘oldest modern human’

Question 7

Answer 7

DNA -Deoxyribonucleic acid. Mostly in cell nucleus, some in mitochondria • Very specific • Degrades easily; survives best in cold and dry conditions • Can be subject to contamination!!

Question 8

Answer 8

Our history of milk drinking. Lactase persistence allele ( 13910*T) frequency is less in Southern Europe so more people are lactose intolerant there.

Question 9

Answer 9

Ancient DNA • Preservation • Contamination • Expense • Mitochondrial DNA (from mother only) • Nuclear DNA (from all ancestors)

Question 10

Answer 10

Maize starch residues from Peru • Associated with lithics and coprolites from Late Archaic period (3000 – 1800 BC)

Question 11

Answer 11

Proteins

• In hair (keratin), bone (collagen), skin, dentine, fingernails …
• Contains: – Carbon – Hydrogen – Oxygen – Nitrogen

Question 12

Answer 12

Carbohydrates • Simple (monosaccharides) and complex polysaccharide) sugars • Very soluble in water • Under-represented bioarchaeologically • High in foods such as sugars and cereals

Question 13

Answer 13

Bones • The organic component of bone (approx. 20 %), made up of proteins (carbon nitrogen, oxygen, hydrogen …) • (The mineral component is hydroxy apatite). Diet can be seen in bone collagen through carbon and nitrogen isotope make up.

Question 14

Answer 14

Plants use C3 in cold conditions. Plants use C4 for photosysnthesis in hot conditions. C3 filters out 13C a lot, and C4 filters out 13C a bit- they retain 13C as they need to avoid warerloss. Tissue will represent what kind of plants you eat due to the presence of 13C.

Question 15

Answer 15

Radiocarbon dating

• Used for dating carbon-containing materials, e.g. bone collagen, wood, seeds, hair, shell, leather
• Destructive – mgs to grams required
• Only calibrated back to ca. 20 kya
• Maximum limit of 40 – 60,000 years
• A radioactive isotope of carbon ( 14C) is formed in the upper atmosphere
• Incorporated into plants (and hence foodchain) by photosynthesis
• While an organism (e.g. plant) is alive, 14C is constantly being replenished; however once it dies, the amount of 14C decreases
• Time for half of the 14C atoms left to decay Half life of 14C is 5,730 yrs Originally thought to be 5,568 yrs; for historical reasons this is still used to calculate the radiocarbon date

Question 16

Answer 16

Uranium-thorium dating is a radiometric dating technique commonly used to determine the age of calcium carbonate materials such as coral.

Question 17

Answer 17

A varve is an annual layer of sediment or sedimentary rock. Similar to dendrochronology, varve layers can be counted and a mastetr chronology created back to 52,800 years.

Question 18

Answer 18

Calibration curve for radiocarbon dates using dendrochronology, u-series dated corals, and varves.

Question 19

Answer 19

Dendrochronology

• Dating limit currently approx. 10kya
• Seasonal growth in wood
• Counting rings gives age (of tree! Not date)
• Width of annual rings in wood varies according to climate, local conditions Dating wood (often very precisely) by matching patterns of annual growth

Ring porous (image) = oak, ash, elm or diffuse porous = birch, maple, cherry

Question 20

Answer 20

Outer ring = sapwood - required for accurate felling date

Inner core = heartwood

Outer edge = bark

Question 21

Answer 21

Potassium-Argon and Argon-Argon dating

• 40K decays to 40Ar (half life 1250 million years)
• Argon is a gas: when a rock is molten (e.g. volcanic eruption) all argon should be released. When solidifies, 40Ar is trapped in rock as 40K decays
• Therefore by measuring the accumulation of 40Ar in a volcanic layer, can date time passed since the eruption - can date artefacts between layers of volcanic ash.

Need to measure current abundance of parent and daughter isotopes, either: 40K and 40Ar (K-Ar dating) or 39Ar and 40Ar (Argon-Argon dating)

Question 22

Answer 22

U series dating

• Radioactive isotopes of Uranium decay to various radiogenic (and insoluble) isotopes, e.g. thorium, protactinium

Dating of stalagmites and flowstones

• The daughter isotopes (Th, Pa) will only start to accumulate once the carbonates have precipitated; therefore can measure relative amounts and date when flowstone formed

Question 23

Answer 23

Thermo- and optically stimulated luminescence dating

Measuring luminescence which builds up in crystal lattices due to exposure to background radiation

This luminescence is released on heating/light; then it builds up again

Date: how long since last heating/light

Materials: fired pottery, burnt flints, aeolian sediments

Question 24

Answer 24

Analysis of lipid residues

• Do not dissolve easily in water (hydrophobic)
• Waxes
• Oils
• Fats
• Sterols