Calvin says they are studying the first Americans that crossed the land bridge in about 11,000 BC according to Sangres.com. They used a spear and a sprear throwing stick called atlatl. The bow and arrow didn't show up until 1,200 years ago.
They hunted probably "mammoths" (and not mastodons which are older relatives apparently but lived contemporaneously during the last ice age).
There is of course some controversy as to whether they were the first people. Reuters reports that some think the first folks here were here 15-25,000 years ago.
