Sentence Correction (SC) | The analysis, published by several researchers

The analysis, published by several researchers at Yale and Stanford,shows that the recently discovered individual belonged to a previously unknown human lineage, a group that split off from other Native Americans just after — or perhaps just before — they arrived in North America.

A. shows that the recently discovered individual belonged to a previously unknown human lineage, a group that split off from other Native Americans just after — or perhaps just before —they arrived --here "They" (Plural) incorrectly refers to "A group" (singular)