While exploring Nevada's Gypsum Cave in 1930, Seneca and Abenaki archaeologist Bertha Parker made her most famous discovery: the skull of a now-extinct ground slot (_Nothrotheriops shastensis_) alongside human-made tools. Parker's crucial finding was the first ________ humans in North America as far back as 10,000 years ago.

Which choice completes the text so that it conforms to the conventions of Standard English?