#8 - Fossilized bones from the hominids Australopithecus

[jmaclan01]

I'm a bit confused studying from the superprep book because the explanation uses "H. erectus is known to have eaten meat" as a premise needed to conclude answer A. Wouldn't the premise "the lower the ratio of strontium to calcium in fossilized hominid bones, the more meat the hominid had in its diet" alone be enough to determine the correct answer is A?

[BethRibet]

Hi Jmaclan,

Thanks for the question. The reason the premise you quote is required is that based on the other facts presented only, there would still be the option that both species are not meat-eaters. There may for instance, be some threshold point at which the ratio of the two minerals would indicate that there must be meat being consumed, such that presumably even vegetarian species might still have both calcium and strontium in their bones. However, knowing that H. erectus did eat meat, and that A. robustus had a ratio of calcium and strontium consistent with more meat consumption than H. erectus would tell us that A. robustus must be a meat-eater.

As an analogy, suppose you were presented with the premise: "The more fashionably dressed you are, the more money you have." Then you were told: "Jane is more fashionably dressed than Joe." It's still possible that both Jane and Joe are cash-poor at the moment, or had their wallets stolen, for instance. We only know that Joe does not have more money than Jane. But if we add the premise: "Joe has some money", then we know that Jane can not be broke, since whatever the threshold is for having at least some money, she must have passed it, being more fashionably dressed than Joe, who does have money.

Hope this helps!

Beth