It turns out that the the standard figure of 98.6 F for average body temperature came from a statistical study conducted by a German doctor in the mid-19th century.
But according to the article below" ... researchers questioned whether that data truly represented average body temperature in the modern age ... (and after doing a study) the researchers found the average human body temperature has decreased by 0.03 degrees centigrade, or about 0.05 degrees Fahrenheit, per birth decade (over the past 157 years)."
"Today, a temperature of 97.5 may be closer to 'normal' than the traditional 98.6."
But why would this be happening?"While it's unclear what drove the decline in body temperatures, the researchers did offer a few possible explanations. Namely, the researchers pointed to advancements in heating and air conditions, which help maintain constant temperatures; reductions in chronic inflammation; and improvements in dental care, medical care, and sanitation."
In other words, aside from the modern prevalence of A/C, maybe it's just because on the whole we're not as sick as earlier generations were, and our average body temperatures have adjusted accordingly.
Of course studies like this one are always subject to question, as to reliability of technique used, accuracy of data collection, etc. So I did a little webchecking, and did find similar studies supporting this thesis, including one done at Stanford Medical School. So maybe there's really something to it.
The thought I came away with from this is that the body really is a dynamic, evolving thing, and that maybe some of its "standard" metrics, like 98.6 F, may not be as written in stone as much as we may have been thinking they were. https://www.advisory.com/daily-briefing/2020/01/16/body-temperatures