Question

This week we have been learning about the methods archaeologists and paleontologists use to reconstruct the past. Now it’s time to get creative and apply this new knowledge to the present day. This is going to involve a little bit of research and creativity on your part. Pick a room in your house, apartment, dorm, or alternative domicile. If you walked out the door today and your room remained untouched for 100, 1,000 or 50,000 years, what would be left for archaeologists in the future to analyze?

Think about the types of materials that make up your room and how they will degrade over time. Do you have metal, ceramic, glass, and wood in your room? Did you leave chicken bones in your trash or canned soup in the pantry? What types of methods that we employ today, would researchers use to “date” your room? For example if you have ceramic dishes an archaeologist might use thermoluminescence dating to try to figure out when they were made.

Post a paragraph discussing a few of the main things that you think might still be around for archaeologists to find, and include how researchers might identify how old they are. You can insert pictures or drawings in your post if you would like too. In addition, think about what types of issues researchers in the future could have trying to analyze materials from today?

Answer 1

This is a really interesting question with a lot of scope of creativity. I choose to pick my study which has a quaint set-up, which includes a table with an attached cabinet full of books. On my table, I keep my laptop, speakers and the wireless mouse. The room also has a separate cabinet which show cases certain trophies won during my high school activities, ceramic dishes from my grandmother, a teracotta clay pot, my coin collection from various countries, a conch and a coral which I bought during a vacation to a sea beach, and a small container in which my mother carefully kept my first milk teeth when it fell off. My study room also boasts of a small window, with two pots full of flowering Petunia plants. The last day I remember, I was busy with some background research on my laptop, while some chocolate wrappers lied astray on my table. I felt thirsty, and therefore had to fetch a bottle of water before I could resume. So I left my room.....

100 years later..... Archaeologists find there way into my room and come across several things, which they can 'date' to find the exact age of the articles and also of my room. They can use various methods of dating (radiocarbon or luminescent) to find the exact age of the samples collected from the room.

1) Radiocarbon dating: This will help to determine the age of a sample which has organic material. This method uses the properties of a radioactive isotope of carbon (¹⁴C, radiocarbon). The cosmic rays in our atmosphere interact with atmospheric nitrogen constantly generating radiocarbon or ¹⁴C, which then forms carbon dioxide by reacting with atmospheric oxygen. This CO₂ is incorporated by plants during photosynthesis and by animals when they eat the plants. Upon death of these organisms, this carbon exchange comes to a stop. So the  ¹⁴​C that had accumulated starts decaying from this time point by radioactive decay and the resultant ¹⁴​C concentration in a sample decreases. Therefore older samples have less ¹⁴​C content. The half life of 5730 years of ¹⁴​C allows calculation of age to approximately 50000 years ago.

Therefore all samples, which may have an organic or carbon content can undergo this dating method. Using this process, the age of the table, the books, the conch, the coral, and the soil within the pot, can be easily approximated. Precisely my age, can also be guessed from radiocarbon dating using my milk teeth sample.

• Wood from the table, pages from the books, and the soil sample would be rich in cellulose and lignin. Cellulose hardly exchanges carbon with the environment, so it is the best component for carbon dating. The soil sample will be contaminated with the remains of the Petunia plant, which has possibly degraded over the span of 100 years, so the age of the soil and plant cannot be precisely determined.
• Shells, conches and corals from marine organisms are a rich source of carbon, as they are composed of calcium carbonate which is present as aragonite or calcite, or many a times as a mixture of both. Besides, conchiolin, an organic protein found in shells, constitutes about 1-2% of the shell material and is also a potent source of radiocarbon in such samples.
• Soil contains organic material also, but contamination results in disorienting results and approximations. Hence the soil samples can be seived to separate the organic materials from the soil to fine tune the analysis. Again in this case, the petunia plants' age cannot be distinguished from that of the soil.
• Tooth enamel is a good sample to estimate the amount of radiocarbon present and can be an accurate indicator of a person's year of birth. Since there is no turnover or decay of enamel once it is formed, ¹⁴C levels in the enamel typically represent the atmospheric ¹⁴C levels at the time of its formation. Therefore an analysis of my first milk tooth can accurately predict the year when I was born.
• Radiocarbon dating can be achieved either by using 1) a gas proportional counter or a liquid scintillation counter, which counts the number of beta particles being emitted from the sample in a given time period; or 2) accelerator mass spectrometry (AMS) which counts the atoms of ¹⁴C and ¹²C in a sample, thereby directly determining the ¹⁴C/¹²C ratio.

2) Luminescence dating: This determines how long ago the mineral grains in a sample were exposed to sunlight or heat for the last time. Radioactive isotopes of potassium, uranium, thorium, and rubidium can be found in trace amounts in sediments and soil samples. These isotopes slowly decay with time, while the ionizing radiation they emit is absorbed by mineral grains in sediments for example, quartz and feldspar. The ionizing radiation is trapped as charges within "electron traps", which are structurally unstable. If these mineral grains are stimulated using either by light : a) blue or green (optically stimulated luminescence, OSL), b) infrared (infrared stimulated luminescence, IRSL), or heat (thermoluminescence, TL), a luminescent signal is emitted as the energy from the unstable electron traps are released. The intensity of the signal depends on the amount of excitatory ionizing radiation had been absorbed at the time of burial and the inate properties of the mineral.

The ceramic dishes, the trophies and the coin collection are suitable samples for luminescence dating.

• Crystalline minerals, like that preset in the ceramic dishes, emit a weak luminescent signal when heated. Thermoluminescent dating is a good option for such samples.
• The trophies and coins are made up of metal and can serve as samples for OSL. But since trophies and coins usually have a date or year listed on them, I think the archaeologists will prefer absolute chronometric or calendar dating for such items. Such absolute dating can also be done for the food items, such as from the left over chocolate wrappers, to estimate the age of the chocolates or when they were manufactured.

3) Potassium Argon dating: Potassium-40 is the radioactive isotope of potassium, that eventually decays into argon-40. This dating nethod is based on the measurements of the product potassium-40 from potassium into argon-40. The half life of potassium-40 is 1.3 billion years. Potassium is generally found in rocks, clay minerals, micas. The teracotta clay pot showpiece may serve as a suitable sample for such a dating method, and the age of the material of this pot may be approximated by employing this method.

The Researchers or Archaeologists in future may face certain issues in trying to analyze the above mentioned materials.

1) The book pages and the wood of the table are susceptible to termites, which eat up the material and make it porous such that the integrity of the sample is lost. So enough sample cannot be available always.

2) Humic acid and carbonate are the two common contaminants that should be removed before radiocarbon dating. but pretreatment to remove these contaminants also destroy the structural integrity of the sample and the overall material volume for further analysis.

3) Soil samples are rich in organic material, but humic acid contamination can result in dissatisfying results. As previously mentioned, the soil samples need to be seived to enrich the organic components for better analysis.

4) the samples to be used for luminescent dating should be absolutely away from light or heat source, which is sufficient to excite the electron traps to emit photons. Even a brief exposure to light (1-100 seconds) is sufficient to initiate thermoluminescence or OSL, as the dating clock is revised.