Summarize Argument
The author concludes that warmer winters caused northern cardinal populations to increase in Nova Scotia, which was previously beyond the cardinals’ range. This is based on a correlation between warmer winters and increasing northern cardinal populations.
Notable Assumptions
Based on a mere correlation, the author believes warmer winters caused the northern cardinals to expand their range into Nova Scotia. While the inverse relationship (i.e. that cardinal populations caused warmer winters) can’t be true, the author assumes there’s no third factor that could’ve caused the cardinals to migrate.
A
Bird feeders, an important source of nutrition to wintering birds, became far more common in Nova Scotia after 1980.
Warmer winters didn’t cause northern cardinal populations to expand. Instead, a proliferation of bird feeders made winters more manageable for wintering cardinals, hence why their populations increased.
B
Because of their red plumage, northern cardinals are easier to spot than most other songbird species are.
This suggests that northern cardinals would be liable to predation. However, that doesn’t explain why their populations increased in Nova Scotia.
C
Some songbird species other than the northern cardinal also became more common between 1980 and 2000.
Perhaps warmer winters benefitted those songbirds, as well. We’re trying to weaken the link between warmer winters and increasing songbird populations.
D
According to field observations, the populations of migratory birds fluctuated less during the period from 1980 to 2000 than the populations of nonmigratory birds.
We don’t care what happened before 2000.
E
Birds that prey on songbirds became more common in Nova Scotia between 1980 and 2000.
If those same predatory birds decreased after 2000, we would have a weakener. But this doesn’t tell us that those predatory birds decreased.
Summarize Argument: Phenomenon-Hypothesis
The anthropologist hypothesizes that cooking was probably the development that enabled humans to get enough calories from their food to support a larger brain. This is based on the observation that humans developed larger brains around the same time as starting to control fire, and the observation that it’s hard for people to get enough calories by eating raw food.
Notable Assumptions
The anthropologist assumes that humans began to cook around the time they began to control fire.
The anthropologist also assumes that there isn’t another reason why people who eat raw food have more difficulty getting enough calories—for example, that they are not eating significantly less than people who eat cooked food.
The anthropologist also assumes that there isn’t another reason why people who eat raw food have more difficulty getting enough calories—for example, that they are not eating significantly less than people who eat cooked food.
A
Cooked foods contain the same number of calories as raw foods.
This weakens the anthropologist’s hypothesis, as it rules out one possible mechanism for how cooking food increases the number of calories available from that food—that is, that cooking could add more calories to the food.
B
Raw meat contains more calories than a similar quantity of raw vegetables.
This is irrelevant, because the argument only compares raw food to cooked food. Comparisons between different types of raw food don’t help us support the anthropologist’s hypothesis.
C
The human body is able to extract a similar number of calories from cooked food and raw food.
This weakens by effectively ruling out the cooking of food as a mechanism for humans to get more calories from less food; instead, this would mean that cooking food makes no difference to how many calories humans can get from it.
D
The human body uses more calories to process raw food than it uses to process cooked food.
This strengthens the anthropologist’s hypothesis by providing a mechanism for humans to get more calories from cooked food than raw food.
E
Domesticated plants and animals are richer in calories than their wild counterparts are.
This is irrelevant, because we don’t have any information about when humans started eating domesticated plants and animals in relation to when they started using fire. Without a timeline, this can’t help us.