The Pyramids

We’ve covered a lot of stuff throughout the semester. But call me cliché, I still think the pyramids of giza take the cake on  being the most intriguing and impressive. It all comes down to the organization, time, and engineering to construct these massive works to such high precision. There are a couple categories that most impress me.

1. Flatness of stones. This cannot be overstressed. I’ve worked in a machine shop (precision metal and materials cutting) for a year and a half now, and it amazes me how much it takes to make something flat. For us, we use a mill that uses a spindle with a metal blade that rotates at thousands of RPM. To move, this thing requires precision ground surfaces (made by other perfect machines) so that it may cut a straight, flat surface. Did I mention these machines don’t cut stones of any sort? Stones are brittle: they’d crack under any sort of pressure, and are therefore very, very difficult to make. The Egyptians cut granite to very high precision flatness: if a straight edge is taken to the surface and a sheet of paper is slid through to detect imperfection, the paper would not go through. The paper’s thickness is 0.002″… SUPER THIN. Well, how do we cut granite these days to that precision? Grinders, High RPM skilsaws with specially engineered blades, etc. technologies NOT available to the Egyptians. How did they do it? Most recent theories support evidence of using a large, copper blade saw, some sand, and some water. With just these tools, the ancient Egyptians could cut 15 foot, 70 ton slabs of granite with surfaces that had flatnesses with a precision to 0.002″. Granted, I bet it took a long time and a lot of copper (since copper is softer than granite), but they still got the job done. Simply baffling.

2. Ability to organize the project and people for 10-20 years (Khufu). That is the definition of endurance, I don’t care who you are. Creating just Khufu required thousands, maybe tens of thousands of people to construct. A pyramid isn’t just something you and your buddies set out to do over the weekend, this thing required years of architectural designing, scheduling, logistics, workforce training, etc. For the Egyptians to even design this thing without standard measuring conventions or even apparatuses to make measurements and have these pyramids turn out the way they did? Incredible.

The construction of the pyramids is nothing short of one of the greatest, most impressive things mankind has put on this earth with its bare hands.

Early Development of Modern Humans

Early development of modern humans (known as Homo sapiens sapiens) has been an area of intense research for almost 100 years. In his book “Descent of Man” published in 1871, Charles Darwin first hypothesized that modern humans may have had a single origin. When archaeologists eventually discovered and began categorizing early human remains in Africa in the early and mid-20th century, the debate changed from one of sheer speculation to a more evidence-based movement. From the 1920’s through the 1980’s, archaeologists primarily used anatomic changes in skeletal fossils to slowly and progressively developed a human “family tree” of sorts. Though this type of archaeological research has been helpful in retracing mankind’s history, it lacked scientific certainty due to its reliance on the interpretation of recovered artifacts such as tools, art, and human remains. Consensus in many important areas had been lacking. With the advent of accurate and inexpensive DNA testing beginning in the 1990’s, this research field has exploded. DNA analysis of ethnic populations and ancient remains has led to dramatic new findings, resulting in the development of timelines, migration maps, and lineages showing connections between early human populations at a confidence level that many thought would be impossible just two decades ago.

Of these findings is Pääbo’s sequencing of the Neanderthal genome. Pääbo’s group published a study that turned previous perspectives on the modern human-Neanderthal relationship upside down. The team used samples from the Vindija cave in Croatia, preparing 9 DNA extracts from 3 bones to compare to human genome sequences. Modern human sequences came from 5 geographically diverse sources: one San from Southern Africa, one Yoruba from West Africa, one Papua New Guinean, one Han Chinese, and one French from Western Europe. The results gave completely new perspectives on old unanswered questions. One of these long standing questions regards the actual time the Neanderthal and modern human populations diverged. Their research shows that Neanderthals and modern humans split between 270,000 and 440,000 years ago, which is compatible with other paleontological and archeological predictions. It was also found that Neanderthals shared more derived alleles with non-African modern humans than Africans and that no variation in the derived alleles was apparent when comparing the Neanderthals to individuals within these two subsets. From this, it was determined that Neanderthals contributed 1% to 4% to the non-African modern human genome compared to a negligible contribution to African humans, a drastically different result from those reported by all previous mtDNA studies. This implies a great deal about the expansion of modern humans out of Africa. First, it can be inferred that a large group of modern humans separated from their forbears and migrated out of Africa. The fact that Neanderthals share the same amount of derived alleles with all non-Africans implies that the interbreeding between the migrating homo sapiens sapiens and the Neanderthals occurred before they (modern humans) inhabited other parts of the globe. This admixture then was most likely to have occurred somewhere in the Middle East.

Pääbo’s team’s sequencing of around 70% of the Neanderthal genome illustrates an entirely new picture of the early human migration patterns: a picture that archeological studies alone couldn’t have hoped to predict. Neanderthals migrated out of Africa around and split with the – what would become – modern humans around 400,000 years ago. They continued their migration north into and eventually inhabited most of the Middle East and Europe. Modern humans first successfully arose from Africa around 60,000 years ago. As they began to move across the Arabian Peninsula and made their way into the Middle East, they encountered Neanderthals and subsequent gene flow transpired. From here, the bulk of the modern humans began making their way eastward into Asia and eventually across the Bering Strait into the Americas while others continued north into Europe. For whatever reason, not many Neanderthals followed the modern humans that continued eastward (and none made it into the Americas), nor did they mate significantly with those who traveled into Europe as Pääbo’s discovery implies. By 30,000 years ago, the Neanderthals had completely vanished, and the modern humans emerged, becoming the last hominid species to occupy the planet: and we are still the only hominids around today.

Stonehenge: How’d they get ’em there?

The last lecture, we began discussing Stonehenge in some significant detail. I wanted to take an opportunity to talk about some of the leading theories as to how the stones actually got there (I hope we don’t discuss all of these today in class).

The transport of the bluestone and sandstone was not a trivial task: these mulit-ton blocks had to be carried to the various sites from over 100 miles away! How did they do it that long ago? From wicker baskets to, of course, alien technology, there are a wide variety of ways people believe these stones were transported such great distances.

Let’s just get this one out of the way: Ancient aliens. Easily enough, aliens came around these parts and helped us construct Stonehenge. It is thought by the famous Erich von Däniken that the aliens may have used Stonehenge either as a landing pad for alien spaceships or an observatory for alien happenings in the sky. He also theorizes on the idea that Stonehenge represents our solar system.

Some geologists support the idea that glaciers actually did most of the moving, not humans. As glaciers flowed out and carved out the Preseli hills, 200 miles from Stonehenge, perhaps they deposited the bluestone much closer to the site than previously thought. However it is unclear whether or not the ice sheets were able to transport the stones far enough as to reduce the technological requirements for transporting the stones further. In other words, if you can transport the stones 25 miles, chances are you could probably transport them 100 miles. Another question: how likely is it that the glaciers deposited the EXACT number of stones for ancients to make a circle out of them?

A more recent theory posits that large rock or wooden ball bearings along with wooden tracks were used to transport the stones. Such an idea came about due to the large, stone balls found near the Stonehenge site. It has been calculated that the Neoliths could have moved the stones up to 10 miles a day, only taking two weeks to get the stones from the mountains to the actual site. An initial attempt using student volunteers, wooden balls, planks, and concrete slabs shows this method to be quite feasible. However, a more authentic attempt using materials of that age as well as oxen will provide a better idea on this method’s feasibility.

A recent theory, brought to attention in 2010 by an engineer, suggests that it was large wooden cradles that encapsulated the stones and transported them across land and water.  The engineer, Gary Lavin, believes that 5 men and perhaps some oxen rolled these baskets along the plains, then floated them across bodies of water when needed. But why wicker baskets? Archaeological evidence shows that the people of that time were already weaving such baskets and other objects at the time of Stonehenge’s construction. Lavin created a prototype out of willow and alder was able to successfully transport a 1-ton rock for some amount of distance on both land and in the water. Future efforts will include the transport of 5-ton stone blocks (keep in mind the heaviest stones were around 150 tons).

Radiocarbon Dating

I found many of the technological methods Archaeologists use throughout the duration of their explorations to be fascinating (I’m a Physics major, so I’m pretty geeky like that…). I contemplated using this opportunity to take one of these rather involved pieces of technology (such as LIDAR) and go into depth as to how it works exactly, but I figured that would put anyone unfortunate enough to stumble upon the blog post to sleep. Instead, I’d like to talk about probably one of the most well known tools in archaeology, radiocarbon dating.

 

As mentioned in class, it all starts with the nucleus of a carbon atom, and more particularly, some sort of isotope. What is an isotope? An isotope is a variant of an element (elements are characterized by the number of protons they have in their nuclei) that has a different number of neutrons from the number of protons in the nucleus. There are three naturally occurring isotopes of carbon: carbon-12 (the carbon we all know and love), carbon-13, and carbon-14. The dashes after the carbon indicate the total number of protons and neutrons in the nucleus; for carbon, there are always 6 protons in the nucleus so you can do the math to find the number of neutrons. Carbon-12 and carbon-13 are both stable isotopes, while carbon-14 is unstable and decays. When I say “decay” I mean that it lets go of some of the matter inside of it, and this happens because it is energetically “favorable” to do so, i.e. the nucleus wants to be in the lowest state of energy and undergoing beta decay (lets off an electron) allows it to do that. This part is rather complicated: but in short, a neutron is actually comprised of a proton, an electron and another particle called an electron anti-neutrino (not important in our case). Any who, the neutron lets off an electron, which means that the extra neutron in the carbon atom turns into a proton, which now gives the element 7 protons, making it a nitrogen atom! If you don’t quite get this part, that’s ok, just FYI.

 

Cool, now that we know about the decay of carbon-14, how do we use it? First off, we know that the half life of carbon-14 is 5730 years (plus or minus 40 years). This means if I took a big chunk of radioactive carbon-14 (probably not a good idea), half of it would be gone in about 5730 years (way after I’m dead). We also know that while someone is living, he/she/it is ingesting carbon-14 naturally, and when dead, no longer ingests that carbon-14. Here starts the decay process. So, one can naturally deduce that you could probably tell how old something is by taking the ratio of carbon-14 to regular carbon-12 (carbon-13 only accounts for 1% of naturally occurring carbon, so we can neglect it).

 

This process only allows us to date things in a specific time frame, accurately however. Why is this? It involves one function: the exponential function. The rate of any radioactive decay is proportional to e^(-kt) where k is the decay constant, and t is time. If we plot this on a graph as a function of t, you’ll notice a couple things: 1. The slope of the graph is steep at t=0 and2. The slope of the graph really flat for large t. what can we say about that? Think about if we’re trying to measure the ratio of the carbon-14 to carbon-12 for small t (where the graph is steep). We can see that there is a very wide range of carbon values during a very small amount of time: this makes measuring the exact chronology of living events almost impossible if there are any measurement errors! Now let’s take some very large t, where the curve is very flat: now we have the opposite problem. If there’s any small error in the calculation, this could mean the difference between 50,000 and 200,000 years, which is of no help.

 

I hope you’ve enjoyed this slightly more in depth look at radio carbon dating. There are a lot of other factors and a ton of research that goes into this subject as well, so research on your own if you’d like!