Passage Summary: Researchers found that some chimps act more like a distant group of relatives than their own close family. Because their behavior doesn't match their genetic grouping, the researchers think they learn these behaviors from their social environment instead.

Conclusion: These chimp behaviors are likely determined by cultural factors rather than genetics.

Reasoning: A group of East African chimpanzees was found to be behaviorally more similar to West African chimpanzees (a different subspecies) than to other groups within their own East African subspecies.

Analysis: The argument relies on the assumption that if genetics were the primary driver, behavior would align with subspecies lines. To strengthen this, we need to bolster the 'culture' explanation or further weaken the 'genetics' explanation. An answer that shows the environments of the similar-behaving groups are different would be particularly strong, as it would rule out environmental adaptation as a cause, leaving culture as the most likely culprit. Alternatively, confirming that the groups are indeed genetically distinct despite their similar behaviors would help.