[gowld]

I suspect the reason autism has such a constellation of symptoms isnot because the cause is complex, but because the environment (human brain and body) is complex. Imagine there was "cardboard box spectrum disorder", caused by keeping a child in a 4x4-ft box for their first 5 years. They'd develop a host of comorbid symptoms, in varying intensities, based on how the child developed coping mechanisms and workarounds to it's confinement, even though the actual cause is quite simple.

For autism, the "cardboard box" is something to due with the pattern of connections in the developing brain, and pattern has wide ranging impacts on many brain functions, which then influence physical functions , which cause feedback loops back to and inside the brain.

[InclinedPlane]

Case in point: girls and boys are diagnosed with autism at wildly different rates. But how much of this is due to actual differences in the incidence of autism versus the differences in the way girls and boys are socialized resulting in different appearances of symptoms?

This is true of many behavioral and cognitive conditions. The symptoms and severity of things like schizophrenia vary significantly from culture to culture (in some cultures schizophrenics hear benign or even kind voices versus here in the western world where the voices tend to be harsh and violent).

[projectramo]

Good point. However, this example could go either way.

Suppose everything you said is true, but in addition to all that, there is a set of symptoms caused by -- making this up -- endocrine disruptors in our drinking water. When pregnant women drink too much, they get some subset of symptoms from a set that overlaps 80% with the cardboard box symptoms.

Now we have two different causes for different symptoms. In addition, you can get the strange case where:

patient A, symptoms X, condition G

patient B, symptoms X, condition H

patient C, symptoms Y, condition G

patient D, symptoms Y, condition H

Although most of the time, condition G will have similar symptoms and condition H will have similar symptoms.

That's why it is so useful to have a marker.