It's usually intelligence that gets discussed in this way, almost always in the context of racist, sexist, or otherwise inequality-justifying theories about some groups being naturally smarter than others, but there's been a similar periodicity in thinking about other things, like personality traits. (Gender differences in cognitive style, interests, and personality are some of the things that are now widely believed to be present at birth; see Cordelia Fine's book Delusions of Gender for a lot more about these ideas' ubiquity and the still-ambiguous nature of the evidence they're supposed to be grounded in).
Right now, I want to talk about how this idea has gotten established in two different subcultures to which I belong: the autism community* and the gay community.
Autism and homosexuality have somewhat similar recent histories in US culture: both either are, or have been, considered mental disorders, both were thought in the 1950s and early '60s to be caused by some warping of the normal bond between mother and child (either, as with autism, too much distance between them, or with male homosexuality, not enough), and papers from the 1960s, '70s and '80s document various attempts to "treat," with aversion therapies that would now be considered abusive, children showing signs of either one. (One researcher even worked on both projects: O. Ivar Lovaas, who has done famous, if controversial, work adapting Applied Behavior Analysis (ABA) for use with autistic children, has also co-written several articles about "feminine boys," and using ABA to normalize their behavior).
Homosexuality was removed from the DSM in 1973, but there are still people who consider it (or anything deviating from straight, married monogamy, really) a pathological condition, and therapists who specialize in trying to turn gay people straight.
In contrast to that idea --- that gay people can change, and therefore should change --- the gay-rights movement has embraced the idea that sexual orientation is inborn. (And most mental-health professionals, including groups like the American Psychological Association, the American Psychiatric Association, the American Counseling Association, the National Association of Social Workers, and the American Medical Association, pretty much agree with them that no sexual orientation is inherently pathological, and that you can't change a person's sexual orientation through therapy).
The picture is somewhat different for autistic people. Not only is autism still considered a disease, and a pretty serious one, by almost everybody, but the idea of innateness, when it comes to autism, doesn't have the same implied corollary of "... and therefore you should accept us the way we are" that it has in reference to sexuality.
No, the shift from "psychogenic" to "biogenic" theories of autism happened for two reasons: first, and probably most important, the evidence (what little there was in the early '60s) didn't fit well with the psychogenic model**, and fit better with the biogenic one; another factor was activism by parents, who were fed up with being blamed for their children's condition, and who called for more research into potential biological causes.
Here, Boston University law professor Daniela Caruso, who has written an article on the history and legal impact of autism advocacy in the US, describes the relationship between the nascent field of biomedical research into autism and the beginnings of the US's major autism-advocacy groups:
It was only in 1964 that Bernard Rimland put forth an alternative explanation of the syndrome, based not on psychodynamics but rather on neurobiology. In 1965, Rimland founded the American Society for Autism (ASA) which is, to this day, a major center of advocacy.
Following Rimland's work, activism in the name of autism began to flourish thanks to both grassroots efforts and power houses. Some groups - most visibly Cure Autism Now (CAN) and the National Alliance for Autism Research (NAAR) - coalesced around genetic research and investigation of toxic substances potentially related to the surge of autism. It is no coincidence that such movements emerged in a context of burgeoning environmental activism. Many other capillary initiatives focused instead on the reality of living with autism by developing information centers for parents of newly diagnosed children, and starting awareness campaigns aimed at educating the public about this poorly-understood phenomenon.
(See also: this post, which discusses another article on the history of autism advocacy in the US. I also found another recent article about the role of parent activism throughout the history of autism, but I can't get at the full text of it).
I also found this snippet in Rimland's book itself (that part of it I could see on the Internet, anyway; I don't own the book), discussing why he thought so many researchers were reluctant to consider the possibility that autism had a biological basis:
In discussing the obvious prejudice against the hereditary viewpoint, Nolan Lewis (1954) points out, "It would seem that most of the prejudice against genetic inheritance stems from a feeling in the realm of wish fulfillment, based on the idea that acceptance of genetic factors would create an attitude of therapeutic hopelessness." Williams (1956) cites this point among others in his attempt to penetrate the prejudice against heredity. He notes that hopelessness is by no means justified by the evidence, and cites the ready correction of diabetes, phenylketonuria and hypothyroidism as examples.
So, that's kind of interesting --- that, at the outset, there was reluctance to adopt a conception of autism as innate and biologically based because of worries that that might mean it was impossible to eradicate through treatment --- but the answer to that wasn't, "so let's not try to make them non-autistic, let's just try to integrate them into society to the best of our, and their, ability", it was "don't be silly, of course we can make them non-autistic!"
I'd also want to point out that the two competing narratives of autism came from the same source: medical professionals, whether psychoanalysts or biomedical researchers. This is in contrast to the two competing narratives of homosexuality, one of which came from medical professionals and the other of which came straight (heh) from the people they were trying to describe. It wasn't until much later that autistic people's own viewpoints were even known to exist, much less taken into account by medical professionals and policymakers.
So, while as far as I know most autistic people do think they were born autistic, that idea doesn't have the same liberatory subtext for autism that it has for sexual orientation. (Indeed, the switch over to a mainstream view of autism as innate and biologically based had already happened when research into "extinguishing" autistic behaviors was at its peak.) The biggest thing it did was to free parents from guilt at having caused the autism, which is important and was definitely needed, but it left the position of the autistic people themselves unchanged.
*I'm using that phrase --- instead of "the autistic community" --- because I am mostly talking about parents. I've made this distinction before: the autism community, which includes parents/caregivers, healthcare workers, autism researchers, and educators; and the autistic community, which is the autistic people themselves. Sometimes the latter group is included in the former, but mostly it is not, and sometimes the two groups are at odds with each other.
**See Chapter 3 of Rimland's 1964 book, Infantile Autism, for a discussion of what those findings were and how they conflicted with the psychogenic model of autism.