- Killing a living thing decreases the population of that living thing
- Hunting is when a human kills an animal for food / recreation in the wild
- An animal is a kind of living thing
- Therefore, hunting / overhunting decreases animal populations

- Hunting / overhunting decreases animal populations
- An animal is a kind of organism
- If a population decreases to zero then that organism is extinct
- Therefore, if hunting decreases the animal population to zero, then that animal is extinct

Hence, if hunting decreases the animal population to zero, then that animal is extinct
Question: Thousands of years ago, several species of large mammals existed in North America. These species became extinct not long after the first human settlement of North America. Which human activity most likely contributed to the extinction of these mammals?
Context: - Killing a living thing decreases the population of that living thing 
- Hunting is when a human kills an animal for food / recreation in the wild 
- An animal is a kind of living thing 
- An animal is a kind of organism 
- If a population decreases to zero then that organism is extinct