Nobody is quite sure where heredity fits into autism. There seems to be some genetic component because it looks to be running in families.

There may be more than one gene involved and they may interlock. Also it may be a situation where genetic vulnerability may have to align with some external factor for full blown autism to be seen. There may also be another set of genes which may provide a protective effect. These may be separate controller genes that switch on or off the susceptibility genes or they may independently control the formation of the neurological structures and biochemical functions in a way that disallows autism.

A lot more research and experimentation needs to be done on autism. I think medical science is just now coming to grips with this disease. It has only been recently that the medical community has started to define what autism is. Without being able to clearly define what is, and what is not autism, and to start to categorize various different forms it is pretty hard to do much research. Autism may be a complex of separate but interactive issues.

The possibility of spreading diseases by allowing functionality is, has been, a big issue. Some of it comes down to what we define as a disease. White skin is clearly an adaptation to allow people to live in climates where they don't get much sunlight. Ironically while all humanity clearly had dark skin at some earlier time some claim that dark skin is the 'mark of Cain' and an affliction. It isn't clear how the starting point of all humanity can be seen as a genetic liability, possibly a disease, but it goes to show how life spits out random mutations independent of design or purpose and it is society that defines what is and what is not a disease.

I was watching TV and a piece said that all the people with blue eyes can track their heredity back to one person that had a mutation that cause blue eyes. Are blue eyes a disease? Depends. If your the first person with blue eyes and they think your possessed by a demon and stone you to death I would say it is a disease. On the other hand if everyone in your tribe thinks your special and makes you king based on your blue eyes I would say it is useful and advantageous variation.

You can see this with malaria and sickle-cell trait. If malaria is wiping out wide swaths of the population having the recessive form of sickle-cell gene, which makes you much less likely to die of malaria, is a very good thing. The sickle-cell trait is a blessing. The down side is that if you cross two people with the recessive gene a quarter of their kids will have full blown sickle-cell anemia, a debilitating disease.

Diabetes is suspected to have started as a adaptation allowing people to function longer on less food. In lean times the genes are a blessing. But the same people put into an environment where food, particularly starchy and fatty foods, are in hyper-abundance those same genes are a curse.

This is the problem with the harder forms of genetic controls, particularly eugenics. Someone comes along and in the moment decides they know what is the best form. But they largely, if not completely, ignore their own biases and the simple fact that they are stuck in the here and now and completely unaware of what is coming.

Every aspect of the human body and its variations is a potential adaptation to a past, present or a future situation. I don't want to go to far, to the point where we all stand under a rainbow with joined hands and sing Kumbiah, but variation and mutation is natures way of making sure someone survives. It pays to have many different tools in your genetic toolbox.

To some extent accommodating what might be seen as defects allows those defects to survive and flourish. We could test everyone each year and anyone who doesn't have at least 20/20 vision we shoot. In a few generations everyone has good eyesight. But at what cost? Where does it start and stop. Exactly what constitutes being sufficiently defective to not be worthy of reproduction? And how far are you willing to push it.

I suggested that within the close-knit and tightly controlled society of the Amish there are a lot of societal controls on reproduction. I'm not sure how far they would go to keep a profoundly autistic child from reproducing. I suspect they would reject the use of force but even if they don't go that far social controls are pretty strong.

I suspect that with so many other complicated issues there will always be a large grey area and a lot of what constitutes best practice will depend on the individual cases. I see little advantage to promoting the reproduction of persons with profoundly debilitating genetic defects. But defects are often social labels assigned by people in a particular time and place so I also loath the idea that society could step in and both arbitrarily and violently declare someone unworthy of reproduction.

In it's own faltering and error prone way society will have to work this out.