There are several explanations in the new age community outlining why indigo children appear to be different or special as opposed to other kids ranging from evolution and changes in DNA and being advanced beings of superior genetic code to the notion that children may be of both human and extraterrestrial origin. Children with mixed human and extraterrestrial genes are commonly referred to as star children.
The notion exists that angels are actually aliens as ancient carvings throughout the world depict them as star people that come and give ideas and revelations to the human race and appear to lead to developments in human technology and intelligence that it seems impossible for people to have had at that time in history. These ideas extend to thoughts on pyramid building and abstract thought among humans.
This phenomenon seems to have increased in the 1990's with the growing diagnoses of Asperger's Syndrome, ADD, ADHD, and other psychiatric disorder diagnoses that seem to have been growing since this era. Its said that these children are categorized as having mental health and learning problems as they learn and experience emotions and socialization in a different way. Is this evolutionary, due to environmental pollution, or are these children indeed gifted beings with superhuman alien DNA?