What does the author refer to?

What does the author refer to?

The passage below is from ‘the Blank Slate’ by Steven Pinker.

http://evolbiol.ru/blankslate/blankslate.htm

Even his [=Chanon] most controversial claim, that killers had more wives and offspring, has been replicated in other groups, though there is controversy over the interpretation. It is instructive to compare Tierney's summary of a book supposedly refuting Chagnon with the author's own words. Tierney reports:

Among the Jivaro, head-hunting was a ritual obligation of all males and a required male initiation for teenagers. There, too, most men died in war. Among the Jivaro leaders, however, those who captured the most heads had the fewest wives, and those who had the most wives captured the fewest heads.

I'd like to ask two questions regarding the underlined parts.

First, what does 'the author' refer to?
It seems refer to Chagnon in a way, but also Tierney in another.

The reason for my confusing seems to the next underlined part.

If 'the author' is Chagnon it conflicts with the first sentence of this passage; killers had more wives and offspring.

If the author is Tierney, this quote 'refutes Chagnon with the author's own words' and can make sense.

But I'm not sure.

Hope for your replies.
Regards.