Gainsay
Definition: contradict or deny
There’s an Old English interpretation of “gain” as meaning “against.” So, “gainsay” is to literally “say against.”
Why I Looked It Up
One need not gainsay the scientific endeavor to call attention to the remarkably large amount of equine excrement in many of its manifestations…
The author was talking about the idea that there are biological roots to political position. I think he was trying to make the point that you can disagree with this point without disagreeing with all science… I think?
Postscript
Added on
From Messy: The Power of Disorder to Transform Our Lives:
After the fact, who can gainsay the call handler who says the ambulance hit the target rather than missing it by a second or two?