TRAs and their allies like to argue that 'sport isn't fair anyway' and that there will always be people who have a competitive edge...
... so let's see...
The competitive edge that Michael Phelps' physical advantages gave him over his closest male competitors at the peak of his career measured less than 0.5%.
Phelps' edge over the top female swimmers of his era was 9-13% - which is the usual performance gap between females and males in swimming.
At the 2004 Olympics, Phelps won the 200m butterfly with a time of 51.25 seconds. The second place man had a time of 51.29 seconds. That's a performance gap of 0.08%.
Phelps beat the 8th place male finisher by 2.56%.
By contrast, Phelps' winning time in the 2004 men's Olympic 100m butterfly was 12.56% faster than the winning time of the female swimmer who won the same event that year in the women's category.
There have been many elite female swimmers over the years like Sylvia Poll, Claudia Poll, and Missy Franklin who have physical features such as unusually tall height (the three are 6'4, 6'3 and 6'2 respectively), large feet, and enormous shoulder width and long arms resulting in vast wingspan that together have given them natural advantages over their competitors too. But all around the world at every level of swimming, from junior club level to the Olympics, males consistently outperform females by about 10-12%. And swimming, along with running, is a sport where the male-female gap is the lowest. In some sports, the gap is 50% - and in particular activities like throwing a ball or a punch, the male advantage is 160%-350%.
The performance gaps between the male and female competitors in the 100m butterfly finals at the 2004, 2008 and 2012 Olympics were as follows:
2004
1st place: Male>Female +12.62%
2nd place: Male>Female +12.77%
8th place: Male>Female +13.83%
2008
1st place: Male>Female +12.16%
2nd place: Male>Female +12.87%
8th place: Male>Female +12.88%
2012
1st place: Male>Female +9.31%
2nd place: Male>Female +10.55%
8th place: Male>Female +10.97%
...
time and time and time again the only universal competitive edge is male over female.