How correct are our dates?

Our aim?
What we are aiming to achieve is a tightly-grouped (precise) collection of shots in the centre of the bullseye (accurate).
A little further
Now we move the target right to the back of the range, way beyond the limits of the spotlight and into the impenetrable darkness. We take our bow and arrow and fire off our first shot… and… thunk! Ok, we have a result. We try again. The first thing we discover – our arrows scatter widely. The precision is not good. But is the bullseye within the spread of our arrows? If nothing has changed, it should be. But what if there is a sidewind further down the range that we don’t know about? A wind blowing from left to right. All our arrows would be pushed to the right. No matter how often we shoot at the target, none will be close to the bullseye. If we knew about the existence of the sidewind, we can adjust our shots. But what if the sidewind wasn’t constant, and changed in strength from day to day?How did we go? How accurate were we?We feel pretty good about our equipment. For our method, however, we are starting to make some significant assumptions. This is how we use models and theories to map environments and conditions of the past in order to arrive at a result. Is our result correct? Only if all of our assumptions have been correct.A colleague then arrives, steps up with a different bow and she takes a shot. Thunk! But her arrow strikes quite some distance from our shots. We ask her to take another shot and she makes a few adjustments and does. Thunk! Ah, this time her arrow seems to strike more closely to where our shots went.Many methods
Any analogy can be stretched – and we may be guilty of that here. The point is that we don’t know exactly what the target date is. We can only report our results, based upon our equipment, our methods and the assumptions that we are making. Along with a margin of precision. (We’ll look at some of these assumptions and margins when we consider our three dating methods later this week.)We try to take as many measurements as we can with the same equipment and method. We try to use as many different dating methods as we can on the same target. Then we compare the results. If three completely different methods all return a date range very close to each other, then that would appear to be a confirmation of the date. If three completely different laboratories and scientists using the same method return a date range very close to each other, then that would also appear to confirm the date. All teams would include their margins for error in their reported results. However – reverting back to our analogy – all six results may be experiencing the same unrecognised side wind.We asked Mathieu why it was important to use different dating methods.This is an additional video, hosted on YouTube.
Your task
Congratulations for working your way through that analogy.So, what do you think?Select the comments link below and let us know if this has surprised you or confirmed what you already knew. Perhaps it is a topic that you have not given much consideration to before now. Take a moment to let us know.References
Grün, R. (2006). “Direct Dating of Human Fossils”. Yearbook of Physical Anthropology, 49: 2-48.Aitken, M.J. (1990). Science-based dating in Archaeology. Longman Inc., New York.A Question of Time: How We Date Human Evolution

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