PT6.S3.Q17 - Samples from the floor of a rock shelter...

tamjg1564

I picked C initially but I am confused as to why and how A is the correct answer and how that information could be deduced?

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dubatt

Hey @tamgutic, So we're told (1)these sample from the floor in the rock center are dated by analyzing the carbon they contained, (2) the samples that specifically are associate with human activity form a consistent temporal series which starts from the present and goes back in time (for example the consistent temporal series of my sister when going back in time is 21 years before the present). Finally (3) there is a correlation ( a relationship) between the depth of these samples and this consistent temporal series. The oldest and deepest sample ( Let's say Sample A) is 19650 years old ( according to the depth). Now we know that there is a relationship between the depth and the temporal series. We also know that the temporal series we were given are for samples which are associated with human activity. However, the skeptics are not convinced ( despite the correlated depth and time series) that these samples could date to human activity because it is too early ( perhaps humans only came around 19000 years ago). So the skeptics offer an alternative explanation: the old carbon from nearby percolating groundwater coal deposits contaminated these samples ( keep in mind that these samples are the oldest and the deepest they found). So we are looking for an answer that makes the skeptics alternative explanation less likely to be true. A does just that!

'A' states that there is no likely tool/process of contamination from the groundwater that would contaminate these really deep samples and not contaminate the ones on the top layer. If this is true, then the upper layer of samples should also have been affected and perhaps with a similar time series. Since this is not the case, it is less likely that that the deep samples were contaminated.

'C' since our task is to weaken the skeptics argument this answer fails at doing that. First of all we do not know what "human activity" is so how can we assume that the humans were using these samples for fuel? Second, if there is no evidence of human activity this does not weaken the Skeptics who are arguing that there was no human activity.

claire.crushesthelsat

help For A, it's saying if deeper levels are affected, then upper levels are too. But the stimulus says the skeptics thought the deepest level measurements were wrong, and it doesn't say anything about the upper levels...so why do we care about the upper levels to disprove the skeptics? I'm missing something.

LivinLaVidaLSAT

@"claire.crushesthelsat" Science stimuli can sometimes be hard to wrap your head around. If, according to the skeptics, coal deposits are giving false dates for the deepest and oldest levels, the same would have to be true for the middle and upper levels. The skeptics only mention having an issue with dates of the deepest and oldest levels. What about all the other sample levels/dates? This coal deposit issue should also make the upper level appear older than it is as well. However, we're told the upper level corresponds to the present time. I hope that helps.