While scientists still don't know exactly what causes autism, there are two new studies that suggest that while heredity is still considered a major factor for triggering autism spectrum disorders, environmental factors and conditions in a mother's womb may also trigger the disorder. Dr. Gary Goldstein recently told CBS News that… “we've identified lots of vulnerability genes, but not everybody who has them gets autism,” says Goldstein, who works at the Kennedy Krieger Institute in Baltimore. One study, published in the July 4th issue of Archives of General Psychiatry, found surprising evidence when it came to their research. Upon studying 192 pairs of twins—both fraternal and identical—where one was affected by autism, they found that not unsurprisingly, 77 percent of the male identical twins and 50 percent of the female identical twins had autism, which can be attributed to the fact that identical twins share the same genes. However, what surprised them was the fact that of the fraternal twins, 31% and 31% of males/females, respectively, were found to have the disorder. Why is this surprising? Because fraternal twins share only as much genetic material as any other sibling. But what they do share is the same womb. Click here to read more.