Differences make us unique, and may have helped with survival
Modern humans may have multiple ancestors. Sub-Saharan Africans may be the only modern race without a mixture of ancestors. European and Asian populations have been found to typically have a small percentage of genes from Neanderthal people and more recently genes similar to Denisovan people have also been discovered particularly in people with native Australian and Melanesian ancestors. [1, 2, 3]
Today or yesterday is Autism Awareness Day, making it a good day to appreciate differences. Mixing with other peoples may have helped early African travelers adapt to lower levels of sunlight and colder climates. Lighter skin tone would allow more production of vitamin D even in areas with less sunshine.
The term autism spectrum helps suggest how much difference there can be between people with autism symptoms. The condition is not well understood. Some individuals may have increased skills in some areas of life but may have other difficulties with communication or social interaction. Underlying metabolic differences may be present that could be modified by diet if the genetic difference is identified. The type of bacteria in the the intestines may also be involved, which also could cause symptoms that might be helped by diet or use of probiotic supplements.  More research is needed - a phrase that gets overused. Searching for a cure to a genetic issue may not help as much as searching for ways to manage the changes that exist for each individual on the autism spectrum.
The increased rate of autism may also involve differences in the prenatal environment. Research into the frequency of defects in the methylation cycle in mothers may lead to better understanding of how we could help prevent the genetic changes in infants that can cause symptoms associated with the autism spectrum. Adequate levels of methylation can help protect genes from changing form. If the mother has an inadequate ability to methylate her own genetic material or vitamin B12 or folic acid, then the infant may also be more at risk of genetic changes occurring. A diet and environment that contains more toxins may leave a person with a limited ability to methylate more at risk for genetic changes occurring. [Methyl donors] [Methylation and BPA] [Elevated levels of BPA found in children with autism] [Genetic Screening for defects in the methylation cycle, a book link]
More research is needed into prevention and management of autism rather than looking for a cure to something that isn't really a disease. Antibiotics might help if intestinal bacteria are unhealthy but underlying genetic changes are also involved.
/Disclosure: I am a nutritionist. Disclaimer: Information presented on this site is not intended as a substitute for medical care and should not be considered as a substitute for medical advice, diagnosis or treatment by your physician. Please see a health professional for individualized health care services./