In the year 2000, about one half of 1% of kids in the U.S. had a diagnosis of autism.

Today, just 25 years later, the rate is nearly six times that, something like one out of

every 35 children. Those numbers have Health and Human Services Secretary Robert F. Kennedy

Jr. freaked out. From KERA in Dallas, this is think. I'm Chris Boyd. RFK is hardly alone in his

concerns, and many people want more research into what causes autism.

But many scientists who've been trying to answer that question for a long time are concerned

that Kennedy's pledge to find the environmental toxin that causes autism makes the enormous

unverified assumption that there is an environmental toxin to blame,

despite growing evidence that as many as 500 genes are linked to a heightened risk.

Dylan Scott is senior correspondent at Vox, where you can read his article,

RFK Jr. is looking in the wrong place for autism's cause.

Dylan, welcome back to think.

Thanks for having me, Chris. So there are unquestionably

more kids walking around today with a diagnosis of autism than before. Do we know if that's because

a greater percentage of children today have autism than a generation or two ago or because the way

we diagnose autism has changed?

So that is the $64,000 question. And the answer is frustratingly complicated. So I think, you know,

as I was reporting this story, I read a lot of studies. I talked to a lot of researchers. And here is how I would synthesize the story. Over the past 30, 40 years, we have developed a more, a broader understanding of what autism can mean. You know, back in the 80s, when autism first became, you know, a diagnosis of

its own into the 90s even, you know, we usually reserved an autism diagnosis for people who were

severely debilitated, who, you know, required, had very limited language, required a lot of support

just to get, you know, go about their lives. And, you know, we had other

diagnoses for people who had had milder forms of the, of these similar, you know, struggles with

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