Q20 - Sociologist: Climate and geology

[dtangie23]

I got this question wrong on my first attempt. When reviewing, I came up with the following. Please let me know if I am on the right track. Thanks.

drastic shift in climate --> migrations --> ideas necessary for rapid advances in civilization

The contrapositive would state:

~ideas necessary for rapid advances in civilization --> ~migrations --> ~drastic shifts in climate

Answer choice (C): population settled --> climate stable

~migrations = population settled
~drastic shifts in climate = climate stable

[giladedelman]

Yes, you're right on the money! Since we're told that drastic climate shifts always result in migrations, it must be true that a settled population -- i.e., one that doesn't migrate -- lives somewhere where the climate doesn't shift drastically, i.e., is fairly stable.

(A) is incorrect because although we know climate can cause migration, we have no idea whether it's the primary cause.

(B) is incorrect because 1) we only know about the results of drastic shifts in climate, and 2) even those drastic shifts merely bring about a necessary condition for human progress, not a sufficient one.

(D) is totally unsupported.

(E) is tempting, but as I said earlier, all we know is that migrations bring about something that's necessary for advances; they don't guarantee those advances.

Good work!

[zainrizvi]

I was a bit confused by the usage of only. A part of me thought that it would constitute as a scope shift. How can we properly infer that the population remains settled ONLY if its fairly stable. Is it because if its a drastic shift, they ALWAYS move? Is it is because of that word we can use such certainty?

[noah]

Right - if the climate isn't fairly stable, what do we know will happen?

It's basically the contrapositive of the given:

~ stable climate --> migration
~ migration --> stable climate.

And, as you suspect, the "always" in the stimulus ensures we can consider that sentence a conditional.