The way our bodies react to mosquito saliva motivates us to avoid being bitten. Which must have had evolutionary benefits, keeping us away from diseases.
I.e. all those people that didn’t mind them and never got itchy from mosquito bites appear to have died out. And mosquitoes really wish that wasn’t true.
I agree. It might take one person a long time to figure that out, if ever, but when you’ve got a few thousand or a few tens of thousands of people, and like 10,000 years, you can narrow it down.