Huge Weight off the Shoulders!

May 15, 2009

I’m still in Jordan but I finally got that pesky thesis finished and into the multiple revision process. I’ll have to say I am fairly happy how it turned out. There were a few times when I wasn’t too sure if it was going to come together. Now, I don’t mean get it finished on time because the submission deadline isn’t actually until June 15th. I was worried about how to effectively portray all the variables I needed on one graph. However, thanks to the great help of a friend in my lab, the Computational Archaeology Lab at McGill, I was able to figure it out.

Since it’s been a while, before I tell you about the graph I better review the thesis. The whole point is to test current descriptions of the prehistoric transition from chipped stone to ground stone technology on the southwest coast of British Columbia, Canada. Specifically, I am looking at whether or not the concept of phase (prehistoric periods of time for which all sites get grouped together) has an impact on interpreting archaeological change. So, I analyzed the above mentioned transition using prehistoric periods and then again without them, using strictly carbon-14 dates, to see if there was a difference in the temporal and spatial pattern of change. The tricky graph I mentioned was the final one, placing all the assemblages (75 of them) on one graph that had time and space (coordinates) represented as continuous axes as well as including the proportion of chipped stone, ground stone, and faunal tools for each assemblage. That makes 6 variables for one graph…and voila….kind of

composite_plot _2

What we came up with is this graph. It is a basic scatterplot with the Y-axis being time, the X-axis being space, and the assemblages coloured using an RGB composite where Red = ground stone proportions, Green = faunal tool proportion, and Blue = chipped stone proportion. This gives every assemblage a unique colour based on the combination of the three colour proportions. There were two tricky parts. First, the spatial axes is actually two variables, the latitude and longitude. Luckily our sites are positioned on a fairly east/west axis so we reclassified them as the distance from the mouth of the River. Zero kilometers is the river mouth and everything East is inland up the river while everything to the West is in the delta or coast islands. You can see the division between deltaic sites and coastal island sites clearly on the graph between 30 and 50km W. The other tricky part was the legend but thanks to some helpful colleagues we got it figured out properly. What the graph shows is a pattern that goes against the current descriptions of the transition and suggests that continuous axes of time and space are more appropriate than archaeological phases for understanding change through time. I’m sure more info is needed but that will have to come later.

For now, enough technical mumbo jumbo. I’ll get you up to speed on the work here in Jordan very soon!

Triangular Confusion

March 8, 2009

What a week! I am fully enjoying a very slow Sunday after an insanely frantic week. Thankfully the payoff was well worth every minute of stress.

Yesterday was the final day of the first (and hopefully annual) McGill Anthrograd Conference. Myself and two other friends put together a two day event at McGill that brought together the wide range of research that the grad students are conducting. It was a phenomenal success thanks to the many hours of hard work from all of the volunteers. We even had the local archaeology lab band Megalith end the evening last night with an hour and a half show. With so many wonderful volunteers the conference organization was only minimally responsible for the ferocity of this week on my nervous system. Most of the suffering was induced by me also presenting my MA thesis in the first session on Friday evening. But I managed to get my primary analysis done and the results proved to be much more thought provoking than I expected. The project is examining the transition from predominantly chipped stone tool technology to ground and polished antler, bone, and stone tool technology on southwest coast of British Columbia over roughly the past 9000 years. Now the end points of this transition are well established and my initial question was why did this transition happen. But before I could as why did things change I needed to understand the nature of this change through time and space. What I stumbled upon is that very little detailed work had been done on the broader temporal and spatial patterns of the transition and most people conclude/assume that there was a gradual or incremental increase in ground stone technology at the expense of chipped stone technology through time. The result of this observation is my thesis: Is the temporal and spatial distribution of the observed technological change on the southwest coast of British Columbia over the past 9000 years gradual and spatially uniform? Here’s my answer to the temporal component:

Ternary Plot

What you see here is a ternary  plot on which each point is an assemblage and its position represents the proportions of chipped, ground, and faunal tools. If the change through time is gradual or incremental we would expect the gray-scale (which represents the age of an assemblage) to get gradually lighter as it extends out from the bottom left corner. Clearly this is not the case. Once you get more than 10% ground stone there is no discernible pattern through time or by phase. I think we need to reconsider the dynamics between the two endpoints of this transition.

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