When species are extensively hunted, individuals that reach reproductive maturity early make up a larger proportion of the population, because they have a better chance of reproducing. When species face diminished food resources, on the other hand, individuals tend to take longer to reach reproductive maturity. These considerations may help settle whether the primary cause of the gradual disappearance of North America' s mastodons, prehistoric animals related to elephants, was diminished food resources or human hunting, since __. Which of the following most logically completes the reasoning? ['from the location of certain hunting weapons in juxtaposition with mastodon remains, it is possible to determine whether those weapons were used to hunt mastodons', 'it is possible to determine whether the earliest human dwellings constructed from mastodon tusks and bones come from an earlier period than the earliest hunting weapons unambiguously associated with mastodon remains', 'from the remains of mastodons already discovered, it can be accurately estimated when mastodons became extinct', 'the average age at which mastodons reached reproductive maturity can be established from mastodon tusks, of which there are many fossils dating from different periods']