Tuesday, October 4, 2011

Archaeology: What's Hot Now: Stable Isotopes for Dummies

Archaeology: What's Hot Now
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Stable Isotopes for Dummies
Oct 4th 2011, 10:02

The following is a vastly over-simplified discussion of why stable isotope research works. If you are a stable isotope researcher, the imprecision of the description will drive you mad. But it is a fairly accurate description of the natural processes which are being used by researchers in so very many interesting ways these days. A more precise description of this process is provided in the article by Nikolaas van der Merwe called the Isotope Story.

Forms of Stable Isotopes

All of the earth and its atmosphere is made up of atoms of different elements, such as oxygen, carbon, and nitrogen. Each of these elements has several forms, based on their atomic weight (the number of neutrons in each atom). For example, 99 percent of all carbon exists in the form called Carbon-12; but the remaining one percent carbon is made up of slightly different forms of carbon. Carbon-12 has an atomic weight of 12, which is made up of 6 protons and 6 neutrons. The 6 electrons don't really count towards the weight, because they're so light. Carbon-13 still has 6 protons and 6 electrons, but it has 7 neutrons; and Carbon-14 has 6 protons and 8 neutrons, which is basically too heavy to hold together in a stable way, so it is radioactive.

All three forms react the exact same wayâ€"if you combine Carbon with Oxygen you get Carbon Dioxide, no matter what the number of neutrons. In addition, Carbon-12 and Carbon-13 forms are stableâ€"that is to say, they don’t change over time. Carbon-14, on the other hand, is not stable, but instead decays at a known rateâ€"because of that, we can use its remaining ratio to Carbon-13 to calculate radiocarbon dates, but that’s another issue entirely.

Constant Ratios

The ratio of Carbon-12 to Carbon-13 is constant in earth’s atmosphere. There are always 100 12C atoms to one 13C atom. During the process of photosynthesis, plants absorb the carbon atoms in earth’s atmosphere, water, and soil, and store them in the cells of their leaves, fruits, nuts, and roots. But as a result of the photosynthesis process, the ratio of the forms of carbon gets changed as it is being stored. The alteration of the chemical ratio is different for plants in different parts of the world. For example, plants that live in regions with lots of sun and little water have relatively fewer 12C atoms in their cells (compared to 13C) than do plants that live in forests or wetlands. This ratio is hardwired into the plant’s cells, andâ€"here’s the best partâ€"as the cells get passed up the food chain (i.e., the roots, leaves, and fruit are eaten by animals and humans), the ratio of 12C to 13C) remains virtually unchanged as it is in turned stored in bones, teeth and hair of the animals and humans.

In other words, if you can determine the ratio of 12C to 13C in an animal's bones, you can figure out what kind of climate the plants it ate during its lifetime came from. The measuring takes mass spectrometer analysis; but that’s another story, too.

Carbon is not by a long shot the only element used by stable isotope researchers. Currently researchers are looking at measuring the ratios of stable isotopes of oxygen, nitrogen, strontium, hydrogen, sulfur, lead, and many other elements that are processed by plants and animals. That research has led to a simply incredible diversity of human and animal dietary information.

More on Stable Isotopes

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Archaeology: What's Hot Now: El Castillo (Kukulkan or the Castle)

Archaeology: What's Hot Now
These articles that had the largest increase in popularity over the last week // via fulltextrssfeed.com
El Castillo (Kukulkan or the Castle)
Oct 4th 2011, 10:02

El Castillo (Kukulcan or the Castle), Chichen Itza, Mexico

El Castillo (Kukulcan or the Castle), Chichen Itza, Mexico

Jim Gateley (c) 2006

A close up of the balustrades on the north face of el Castillo, where the sundial aspects of the monument are seen during the equinoxes.

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Archaeology: What's Hot Now: World History Timelines

Archaeology: What's Hot Now
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World History Timelines
Oct 4th 2011, 10:02

World History Timeline - Timeline of World History

By , Guide

Most of the history of the ancient world has been collected by archaeologis

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Monday, October 3, 2011

Archaeology: Yana Rhinoceros Horn Site

Archaeology
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Yana Rhinoceros Horn Site
Oct 3rd 2011, 09:07

The Yana Rhinoceros Horn Site, or Yana RHS, is a 27,000 year-old site above the Arctic Circle in Siberia, if you can imagine. And it might hold the key (or one of them) to the first colonization of the Americas.

Location of the Yana Rhinoceros Horn Site in Siberia
Location of the Yana RHS site in eastern Siberia. Base map: Norman Einstein

Located on the Yana River 1200 kilometers west of the Bering Strait, the site is the oldest site within the Arctic circle--and I fully admit the notion of being in the arctic circle at all is daunting, let alone without polar fleece. Found within the site are redeposited mammoth, bison and horse bones showing butchering marks; stone tools including scrapers and a hammerstone; and bone tools including a beveled foreshaft.

The site is pretty old, not to mention pretty cold: but its location in eastern Siberia may represent evidence that human migration into Beringia during the early parts of the Last Glacial Maximum was possible.

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Archaeology: What's Hot Now: Pigs

Archaeology: What's Hot Now
These articles that had the largest increase in popularity over the last week // via fulltextrssfeed.com
Pigs
Oct 3rd 2011, 10:02

Pigs were first domesticated in central Asia, at least as long ago as 9000 years, and perhaps a couple thousand years older. They were part of the original suite of domesticates, including sheep, goats, wheat and barley, that were spread into Europe via the Linearbandkeramik. Archaeological sites with evidence for early pigs include Hallam Çemi, Çayönü Tepesi, and Neval Çori in eastern Turkey.

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Archaeology: What's Hot Now: Aztec Empire

Archaeology: What's Hot Now
These articles that had the largest increase in popularity over the last week // via fulltextrssfeed.com
Aztec Empire
Oct 3rd 2011, 10:02

Important Archaeological Sites of the Aztec Empire

Tenochtitlan - Capital city of the Mexica, founded in 1325 on a swampy island in the middle of Lake Texcoco; now underneath the city of Mexico city

Tlatelolco - Sister city of Tenochtitlan, known for its huge market.

Azcapotzalco - Capital of the Tepanecs, captured by the Mexica and added to the Aztec hegemony at the end of the Tepanec War

Cuauhnahuac - Modern day Cuernavaca, Morelos. Established by Tlahuica ca AD 1140, captured by Mexica in 1438.

Malinalco - Rock cut temple built ca 1495-1501.

Guiengola - Zapotec city on the Isthmus of Tehuantepec in Oaxaca state, allied with the Aztecs by marriage

More Aztec Empire Articles

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Archaeology: What's Hot Now: Anthropology Definitions

Archaeology: What's Hot Now
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Anthropology Definitions
Oct 3rd 2011, 10:02

The study of anthropology is the study of human beings: their culture, their behavior, their beliefs, their ways of surviving. Here is a collection of other definitions of anthropology from anthropologists.-Kris Hirst

Anthropology Definitions

[Anthropology] is less a subject matter than a bond between subject matters. It is in part history, part literature; in part natural science, part social science; it strives to study men both from within and without; it represents both a manner of looking at man and a vision of man-the most scientific of the humanities, the most humanist of sciences.-Eric Wolf, Anthropology, 1964.

Anthropology has traditionally attempted to stake out a compromise position on this central issue by regarding itself as both the most scientific of the humanities and the most humanistic of the sciences. That compromise has always looked peculiar to those outside anthropology, but today it looks increasingly precarious to those within the discipline.-James William Lett. 1997. Science Reason and Anthropology: The Principles of Rational Inquiry. Rowman and Littlefield, 1997.

Anthropology is the study of humankind. Of all the disciplines that examine aspects of human existence and accomplishments, only Anthropology explores the entire panorama of the human experience from human origins to contemporary forms of culture and social life.-University of Florida

Anthropology is Answering Questions

Anthropologists attempt to answer the question: "how can one explain the diversity of human cultures that are currently found on earth and how have they evolved?" Given that we will have to change rather rapidly within the next generation or two this is a very pertinent question for anthropologists.-Michael Scullin

Anthropology is the study of human diversity around the world. Anthropologists look at cross-cultural differences in social institutions, cultural beliefs, and communication styles. They often seek to promote understanding between groups by "translating" each culture to the other, for instance by spelling out common, taken-for-granted assumptions.-University of North Texas

Anthropology seeks to uncover principles of behavior that apply to all human communities. To an anthropologist, diversity itself-seen in body shapes and sizes, customs, clothing, speech, religion, and worldview-provides a frame of reference for understanding any single aspect of life in any given community.-American Anthropological Association

Anthropology is the study of people. In this discipline, people are considered in all their biological and cultural diversities, in the present as well as in the prehistoric past, and wherever people have existed. Students are introduced to the interaction between people and their environments to develop an appreciation of human adaptations past and present. Portland Community College

Anthropology explores what it means to be human. Anthropology is the scientific study of humankind in all the cultures of the world, both past and present.-Western Washington University

The Human Experience of Anthropology

Anthropology is the study of humans in all areas and in all periods of time.-Triton College

Anthropology is the only discipline that can access evidence about the entire human experience on this planet.-Michael Brian Schiffer

Anthropology is the study of human culture and biology in the past and present.-Western Kentucky University

Anthropology is, at once, both easy to define and difficult to describe; its subject matter is both exotic (marriage practices among Australian aborigines) and commonplace (the structure of the human hand); its focus both sweeping and microscopic. Anthropologists may study the language of a tribe of Brazilian Native Americans, the social life of apes in an African rain forest, or the remains of a long-vanished civilization in their own backyard - but there is always a common thread linking these vastly different projects, and always the common goal of advancing our understanding of who we are and how we came to be that way. In a sense, we all "do" anthropology because it is rooted in a universal human characteristic -- curiosity about ourselves and other people, living and dead, here and across the globe.- University of Louisville

Anthropology is devoted to the study of human beings and human societies as they exist across time and space. It is distinct from other social sciences in that it gives central attention to the full time span of human history, and to the full range of human societies and cultures, including those located in historically marginalized parts of the world. It is therefore especially attuned to questions of social, cultural, and biological diversity, to issues of power, identity, and inequality, and to the understanding of dynamic processes of social, historical, ecological, and biological change over time.- Stanford University Anthropology department website (now moved)

More Definitions

This feature is part of the Guide to Field Definitions of Archaeology and Related Disciplines.

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