Sen. Rand Paul, R-Ky., grilled a medical expert who opposes the lab leak theory for COVID-19's origins during a hearing on Tuesday.

Paul questioned Dr. Robert Garry, a professor at the Tulane School of Medicine, during his appearance before the Senate Homeland Security Committee. The senator criticized Garry for a lack of "open-mindedness" when it comes to the origins of COVID-19.

"So, just in the last few minutes, Doctor Garry has told us that this couldn't have come from bats. It had to go through an intermediate host. That may well be true, but arguing against that is they tested 90,000 some-odd animals and there is no animal host that's been found," Paul said.

"But what he also doesn't tell you is the animal host could be a laboratory animal. It could be passed serially through that. And that's one way of quickly adapting and pushing natural selection to adapt a virus toward humans," he continued.

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Rand Paul

Sen. Rand Paul grilled a medical expert who opposes the lab leak theory for COVID-19 during a congressional hearing on Tuesday. (Reuters/Nathan Howard)

"Doctor Alina Chan has written extensively about this, how this virus didn't show up clunky and poorly transmissible, this virus showed up immediately, very transmissible in humans, as if it had been pre-adapted in a lab," he added.

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Paul went on to target Dr. Anthony Fauci and others.

"I know of no other example in modern scientific history or publications where a publication has come forward pronouncing with such authority that the lab leak is implausible and is not a laboratory construct, while privately saying this is no friggin' conspiracy theory, it looks like it did," Paul said.

Dr. Anthony Fauci on CBS

Paul once again went after Dr. Fauci during Tuesday's Senate hearing on the origins of COVID-19. (CBS)

"We know that it went back and forth with Dr. Fauci, with editors who say we want the statements to be stronger, we want the conclusions to be stronger…because we're making a political point here. That's where we should have known we were off track, that these people were politicians and that they were pushing an idea because, as Doctor Collins finally admitted in one of the emails, this is about the business of science with China," he finished.

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Garry countered that there was evidence that COVID-19 had spilled over into the public at least twice at the Wuhan food market, where it is alleged to have originated.