Kary Mullis, the inventor of the polymerase chain reaction, died last week. PCR, a method of making exact copies of a DNA molecule at exponential scale, is the reason molecular biology is the basis of a business that runs to 12 digits in dollar size. It is the reason “DNA” is an everyday concept to us, a piece of jargon that is in the newspaper literally every day and can be explained on some level by almost anybody.

PCR is the technology that has led us into an era of pioneering in human-origins research, has transformed genealogy and criminal investigation, and has created a disturbing spectre of personal eugenics and human (or post-human) enhancement. There is talk this week of a possible cure for the Ebola virus, and good candidates for a vaccine exist: to say that this could not have happened before PCR is probably an understatement.

His own reward directly from Cetus was a $10,000 bonus

As Mullis was fond of pointing out, he came up with the idea for PCR in 1983 while employed by a private company, Cetus Corp., which sold the associated patent for $300 million. His own reward directly from Cetus was a $10,000 bonus. Although he invited and revelled in the label “cranky eccentric” at a level that suggests it may appear on his grave marker instead of “Kary B. Mullis,” he was not angry about this. He was known to the public as the surfer-scientist — when he got the phone call about his Nobel Prize, fleeing for the nearest beach was the first thing he did — and had a laudable laid-back attitude toward the deal he had made, as readers of his now-classic memoir Dancing Naked in the Mind Field will know. (If you’ve read and liked Richard Feynman’s memoirs, you can think of Dancing Naked as more thoroughly left-coast Feynman. They are in countless ways the same person, but when Mullis moved to California, he went truly native.)

Mullis was allergic to the academic environment and had dropped completely out of science when a buddy snapped him up for Cetus. They gave him a budget for the fancy scientific equipment he had always adored, and didn’t put much pressure on him about monetizable specifics. (Later, he complained, the middle managers descended upon the shop and began to obtrude. He fled.) He got the chemistry Nobel in 1993, and plenty of other baubles with cheques pinned to them. Like many Nobelists, he would say “the Nobel gave me freedom,” and he didn’t ask for much else.

PCR seems so fundamental to civilization and its future now that to describe Mullis as a “Nobelist” may underrate him. In Dancing Naked he talks about having anticipated the prize — something those who have won it rarely do for the record. His claim to PCR was so clear, and its importance so self-evident, that he and his friends were certain he would get it. But he was warned that the committee might wait until he was ancient. His thesis supervisor, Joe Neilands (1921-2008), a Canadian chemist at Berkeley who seems to have worked to tame Mullis a little, told him “it was probably OK that I admitted loving surfing and women, but … Surfing, women, and LSD might be too much.”

In fact, science as a social institution probably has regretted giving the outspoken Mullis the prize while he was still young. In later life he became a free-range skeptic, condemning everything from global warming theory to nutrition research. Like a few other scientists of less distinction, he was concerned about the lack of a purely experimental foundation when it came to the relationship between HIV and AIDS, and became associated with the “HIV denialist” crowd. This was the sort of thing the “Nobel gave him freedom” to do, and in the case of HIV it caused real harm, although not, I think, in amounts that can counterbalance the benefit of PCR.

In later life he became a free-range skeptic

The retrospective question about a discovery such as PCR, which came to Mullis in a flash of insight during a drive up the coast, is always “Would someone else have bagged it two weeks later?” In the inevitable legal and historical priority fighting over Mullis’s discovery, there was some prior art: other researchers had written down ideas quite like PCR. But Mullis has won the war decisively. His passion for “bench” science, for experiment, made the clear difference: the famous car journey took place sometime in May, and Mullis had actually demonstrated PCR technique with his own hands by the end of December.

This was a result of the same instinct that turned Mullis into a climate and HIV crank later. He wanted someone to tell him how to do the bench experiment showing that carbon in the atmosphere would warm the Earth, or that HIV infection is the cause of AIDS, and nobody could do so to his satisfaction. When I heard of Mullis’s death my first reaction was that he was somebody who had changed the world on at least the level of a Boyle or a Huygens, a great 17th-century polymath. I had forgotten (or half-forgotten) that Mullis was personally obsessed with that era and those people: he could, and did, talk for hours about the creation of the Royal Society and the spirit expressed in its motto, “Nullius in verba” — Latin for “on no one’s mere word,” more or less.

• Twitter: colbycosh