Bonds hit 59 HR from the ages of 40-42, which included one year where he basically missed the whole season with an injury of some sort (I forget the details).
ARod is 39 now. I think he can break this record if he stays healthy and keeps passing tests.
Even at age 42 (his last year) Bonds still hit 28 HR in 126 games, 1.045 OPS and led the league with a .480 on-base percentage. Guy was crazy-good, I don't care what drugs he was on.
Different eras ... then and now.
Bonds was basically openly juicing in his 40s (wasn't suspicious when sluggers looked big.)
And MLB didn't start effectively testing players until 2013.
in 2013, there were 4,661 home runs hit in MLB
in 2014, ... 4,186 homers
between the years 1998-2007 (when Bonds retired) there were about 5,500 home runs hit each year in MLB