Logical Reasoning

PT5 · S1 · Q19 A tree’s age can be determined

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A tree’s age can be determined by counting the annual growth rings in its trunk.

Given that ...

The tombs were made out of freshly cut logs (and trees will stop growing rings once they're dead)

How could it be that ...

Archaeologists can determine the relative ages of ancient tombs at Pazyryk?

Evaluate

Our task seems to be to just make sense of this method of using annual rings to judge the relative ages of tombs.

It's a little paradoxical. Say that we cut down a 50-year-old tree to build a tomb. The wood will have 50 rings. We'll make the tomb right away (it's made from freshly cut logs).

Next to this tomb is one made from a tree that was cut when it was 30-years-old.

Okay, so which tomb is older? We wouldn't really have any way of knowing from just knowing the ages of the trees.

Say that you cut down a 30-year-old tree to make a tomb in 1930. It would be an older tomb than a tomb made from a 50-year tree in 1940. In other words, the age of the tree doesn't have any clear connection to the age of the tomb.

Unless, we knew that all trees were starting from the same reference point. If we knew that all the trees were planted in 1900, then a tomb made of a 30-year-old tree would be from 1930, and a tomb made from a 50-year-old tree would be from 1950.

Goal

Maybe we need to know that all the trees in Pazyryk Valley started growing at the same time?

We need some way of getting from "age of tree that made the tomb" to "age of the tomb".

19.

Which one of the following, if true, contributes most to an explanation of the archaeologists’ success in using annual rings to establish the relative ages of the tombs at the Pazyryk site?

  1. The Pazyryk tombs were all

    Unrelated to Goal

    It's not clear how any of the story in this answer would translate into a way that archaeologists can figure out the age of a tomb based on the age of the tree that was used to make it. This just tells us that stuff inside the tomb was well preserved.

    2% picked this

  2. The Pazyryk Valley, surrounded by

    Unrelated to Goal

    It's not clear how any of the story in this answer would translate into a way that archaeologists can figure out the age of a tomb based on the age of the tree that was used to make it. This says that these trees were distinct from other valleys' trees. But it doesn't say how we could look at the rings from one of these trees and figure out the age of the tomb.

    29% picked this

  3. Correct

    Each log in the Pazyryk

    Why this is right

    This is very confusing, but this telltale sequence of twelve rings would allow archaeologists to figure out "relative ages". Given that all the trees show that sequence of rings somewhere in their set of rings, we can judge the relative ages of the trees/tombs by looking at how many rings come after the telltale sequence. Let's say there's a telltale sequence of rings that are represented by four capital R's: RRRR Consider these trees, listed from innermost (earliest) ring to outermost ring: TREE 1: r r r r r R R R R r r r r TREE 2: r r R R R R r r The RRRR is the same time period. Tree 1 and 2 were both alive during the RRRR time period. Tree 2 lived two more years (because there are two more r's after the RRRR), and then was cut and made into a tomb. Tree 1 lived four more years (because there are four more r's after the RRRR) and then it was cut and made into a tomb. So a tomb made from Tree 2 is two years older than a tomb made from Tree 1, because Tree 2's tomb was built two years after the RRRR phase, whereas Tree 1's tomb wasn't built until four years after the RRRR phase.

    Skill tested: Paradox · how this choice captures the argument's function is the move to repeat next time.

    54% picked this

  4. The archaeologists determined that the

    No Impact

    This feels tempting, because it's talking about ages of trees, but that doesn't tell us the relative ages of the tomb. A tomb made in 1920 is five years older than a tomb made in 1925, but how would knowing the age of the tree used to make those tombs help? It's possible that the tomb in 1920 was made from a 90 -ear-old tree, and the tomb in 1925 was made from a 450 year old tree, or vice versa. There's no way to get from the age of the tree to the relative age of the tomb.

    13% picked this

  5. All of the Pazyryk tombs

    Unrelated to Goal

    It's not clear how any of the story in this answer would translate into a way that archaeologists can figure out the age of a tomb based on the age of the tree that was used to make it. It's just telling us that we could use the artifacts to determine that the tombs are at most about 2300-years-old. But we need a way where the tree rings tell archaeologists the relative ages of the tombs, i.e. which tomb is oldest / youngest.

    2% picked this

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