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./
Recently published research has found that children with autism had elevated levels of the plastic bisphenol A (BPA) compared to the children in the control group.  BPA is a contaminant in the food supply from its use in the plastic lining of cans and in other food packages such as plastic drink bottles. It may also be found on the slick surface coating of some types of register receipts.
This is a significant step compared to “we don’t know what causes it or how to stop it,” because BPA is something that could be avoided by prenatal women and people with autism. It is also good news because it may also be possible to reduce the risks of exposure to BPA by increasing intake of the plant phytoestrogen, soy genistein, or methyl donors such as vitamin B12 and folate and choline. 
/Disclosure: This information is provided for educational purposes and is not intended to provide individual health guidance. Please see a health professional for individual health care purposes./
Proper methylation of DNA regulates which sections of DNA are active and will be used to direct metabolic activities in the body and which sections are turned off. Some people have metabolic defects in their ability to methylate normally. Problems in the normal methylation cycle may be more common for people on the autism spectrum and in some other genetic conditions like Down’s Syndrome.
The following website has a book available to read online that includes information about metabolic differences that have been found to be more common for people on the autism spectrum. Methylation differences in metabolism are discussed in Chapter 2 of the book Autism: Pathways to Recovery, by Dr. Amy Yasko. In the chapter coffee and Ritalin are described as methyl donors, and it is suggested that they might be helpful for some people for that reason. Defects in the normal ability to methylate DNA is impaired in some people which may leave their immune systems over active with autoimmune symptoms or underactive and more susceptible to actual threats. [dramyyasko.com/resources/autism-pathways-to-recovery/chapter-2/]
A book available online, thanks to the author Dr. Amy Yasko. She mentions in the opening paragraph of Chapter 1 that the U.S. population grew by 13% in the 1990s and the number of people with autism grew by 172% in the same time frame. Read more: [dramyyasko.com/resources/autism-pathways-to-recovery/chapter-1/] *She is a Ph.D. professor in genetics rather than an M.D. Medical Doctor.
In 1975 the rate of autism was 1 in 5000. Approximately one child of every 88 born in the year 2000 were found to have autism and the rate was 1 in 68 – one infant out of every 68 children born in 2002 were found to have autism. [aplus.com/a/scientist-claims-half-of-children-will-have-autism-by-2025]
There may not be a ‘cure’ for autism but there are nutritional strategies that help manage some of the more common metabolic differences if parents and health professionals are allowed to acknowledge the existence of the differences.
/Disclosure: I am not recommending coffee for children or infants. This information is provided for educational purposes and is not intended to provide individual health guidance. Please see a health professional for individual health care purposes./