Evolutionary biology does not make a mention of mermen. It does not talk about men turning into amphibious beings, capable of navigating water at will.

But. We might be getting a glimpse into the future of human adaptability at this moment in Rio. We might be witnessing the zenith of physical prowess, the Sistine Chapel of sport performance.

By all stretches of the imagination, and by all acceptable definitions of normal body proportions, Michael Fred Phelps II is an aberration. An irregularity in the conveyor belt of creation, a singularity unlikely to be repeated.

From having a set of paddles for palms to a disproportionately long torso coupled with comparatively shorter legs allowing for a reduction in drag force and aiding in propulsion, Phelps is clearly in possession of an extraordinary body. Perhaps the comparisons he evokes with fish are erroneous.

Phelps is not a fish. He is the huge gush of water and dread that bears down upon that fish. Simply put, Phelps is a shark.

The gold standard

“Nixon took us off the gold standard, Phelps has helped put us back on it,” was Sportscenter Anchor John Anderson’s reaction on-air when he found out that Michael Phelps had won his 21st Olympic gold in the men’s 4 X 200 m freestyle relay.

Anderson’s statement made it sound like a formality, which was probably the best response given the situation. Why? Because it was a formality. It was always going to be one. Was there ever any doubt?

Retirement and trouble

Yet, this was a man who had retired, who in his own words was “finished”. When Phelps had hung up his trunks after the London Olympics four years ago, he had everything – the records, the medals, the legacy that he had never dreamt of as a kid at seven, when he had taken up the sport with the purpose of beating Attention Deficit Hyperactivity Disorder (ADHD).

What do you give a man who has everything? Athletes struggle, push and fight through pain to win a gold that gets framed on the most visible wall in their homes. Phelps had 18 of those after London.

The image of Phelps as the supreme athlete had become a larger-than-life portrait, looming over Michael himself. Coach Bob Bowman had described Phelps as a private person and the spotlight became too bright for him. He struggled to cope with it and he wanted out.

For Phelps, swimming had always been a release of energy, a necessary exertion. By his own admission, he had to get away from the anger he had been directing towards his father, who left he was only nine.

“It was a massive waste of energy,” says Phelps. That energy was manifested in the most exquisite of ways when the man from Baltimore won eight – count 'em – gold medals at the Beijing Olympics in 2008, setting one Olympic and seven world records along the way.

Then, Phelps was arrested for driving under the influence (DUI) of alcohol in September 2014, his second such offence in ten years. USA Swimming banned him for six month and barred him from participating at the 2015 World Aquatics Championships.

Swimming, the only thing that had kept the demons at bay, was now taken away from him. For the first time in the public eye, Phelps’s aura of invulnerability was shattered. He had to re-build himself mentally in order to stand a chance at Rio. The swimming world had moved on while Phelps had stopped.

Comeback and triumph at Rio

Behaviour therapy, marriage and subsequent fatherhood saw Phelps come back in style at the US National Championships where he won three gold medals, setting the fastest times in 2015 for those events.

After winning three events at the US Trials for Rio 2016, Phelps became only the second American swimmer to qualify for a fifth Games, after Dara Torres.

In the 200m butterfly, Phelps finished a modest fifth in the initial heats before qualifying second in the semifinals. In the final, he was not to be beaten as he edged Masato Sakai by four-hundredths of a second.

Incidentally, Phelps had finished fifth in the 200m butterfly at the age of 15. He broke the world record the following year at the World Aquatic Championships. At 15 years and nine months, he became the youngest swimmer ever to set a world record.

With two events remaining – the 100m butterfly and the 200m individual medley – Phelps can go past Ethiopia, that country of legendary runners, who also have 21 gold medals. His tally would see him at 39th on the all-time Olympic medal tally by nation, ahead of the Czech Republic, Mexico and Portugal. And yes, his total medal tally would tie with, or beat, India's 26.

The statistics are nothing short of mindboggling. Out of a total of 79 medals in competitive swimming, only 3 are bronze. The majority, as you might imagine, are gold – 64 of them. Yet, the statistics only tell a part of the story.

For it is extremely difficult to us to comprehend the man behind the medals. After all, one can only imagine the magnitude of pain that was stored within Phelps if it was the catalyst for what was to follow. All those golds can't even begin to express it.