I skimmed the The End of Illness (David B. Agus) while waiting at a Brisbane Queenstreet bookstore that has taken up the slack for the massive Borders Books that shuttered recently. I was looking for health wisdom. One statistic was quite new to me--that sitting at a desk all day after a strenuous morning workout can be as damaging to your health as smoking (statistically speaking). However, I had to put down the book and discount that tidbit of "insight" after I surveyed the chapter on "Rotten Eggs" which describes what Agus calls his egg theory. After explaining how subtle environmental factors for a chicken egg can profoundly affect it's state, Agus proceeds to exaggerate the link between embryonic environment and its affect on development of the human brain. Agus falls into the banal statistical trap of assuming correlation and causation are equivalent. According to Agus, a child born within 18 months of another child to the same mother develops autism with 3 fold greater likelihood. He assigns the cause to the change in the uterine environment for the embryo due to recent childbirth and the brother/sister recently living there. However, a much more plausible argument is that closely spaced births and the environmental effect of being a little brother/sister to a mother juggling two breast-feeding children have a much more profound influence on mental development. Subtle changes in a mother's behavior have been associated with autism since the 70's. And mothers of 2 children close in age may adjust their care for the second child, using what they learned with the first, and perhaps rationing breast milk in different ways than they would if they only had one child suckling every 2 hours. The manufactured nature of baby formula (perhaps with trace heavy metals and volatile organic chemicals) might also have an effect on neural development. Not to mention that the mother will likely be more confident with the second child, with so recent a memory of the birth and care of a child. And confidence can have unexpected affects on the actual development of a child, I'm sure. The parents may become more aloof, less responsive to familiar personality quirks of their baby. Tehy may even devalue those unique personality trates that make their second baby who he is, simply because they've seen something similar recently. The baby cuteness instincts may not work as well the second time around, if recent in parents' memory. Parental emotional connection to a child must certainly affect their brain development, much more strongly than the recent presence of another child in the womb. Just being the second child (younger brother/sister), close in age, surely has a profound impact on development due to the natural rivalry. Unfortunately, a younger brother is shackled with the jealousy and lack of power that an older brother might have -- like a prisoner and a gate keeper. The older sibling has physical and mental power but a lack of recognition (parents often go to great lengths to assure both children that they have equal "rank")--and power without status is the hallmark of a sociopath. That leads to another commonly accepted concept that should be debunked--autism and aspergers being a "spectrum" disorder separate from narcisism, sociopathology, etc. Spectrum really isn't the right term for a mental illness. Mental illness is multidimensional not a linear quantity or scale or spectrum--complex system metrics would be more applicable.