Sorry, Mike, but one can’t really assume that earlier people were as smart and rational as present ones. First, if we recognize changes in organisms which benefit them in the environment more than their peers will usually allow them to procreate more effectively, then those humans who are more able to deal with life will probably produce more offspring. If the ability to think is of value, then we might guess that the average IQ has been moving up. albeit very slowly, over the last few thousand years.
Second, while reason is valuable, it has to be based on facts. We know vastly more now than we did a few millenia ago. Therefore, we are likely to be far more effective in our thinking than they were.
Occam