There is enough research to show that testosterone is still much higher in modern societies than in tribal communities. Likely linked to the abundance of calories in modern societies.
There's also a very wide range for "healthy" testosterone levels. Turns out endocrinology is more complicated than looking at one value and saying higher is gooder. Fertility is not directly linked to testosterone levels or even meaningfully so: when my wife and I were trying for a kid, my doctor actually suggested that despite my T-levels being a bit low he would suggest delaying any treatment for that until after our family planning was complete, my testosterone levels weren't affecting my fertility (tho other complications can arise) but increasing them actually would have had a chance of impacting it negatively.
FWIW we have a healthy son now.