Autism and Evolution


    Commonly described as impaired communication and social interaction disorder, Autism spectrum disorder is a serious developmental disorder that impairs the ability to communicate and interact normally.

    Autism spectrum disorder impacts the nervous system.

    The range and severity of symptoms can vary widely. Common symptoms include difficulty with communication, difficulty with social interactions, obsessive interests and repetitive behaviors.

    Early recognition, as well as behavioral, educational and family therapies may reduce symptoms and support development and learning.

    Social Challenges

    Typically developing infants are social by nature. They gaze at faces, turn toward voices, grasp a finger and even smile by 2 to 3 months of age. By contrast, most children who develop autism have difficulty engaging in the give-and-take of everyday human interactions. By 8 to 10 months of age, many infants who go on to develop autism are showing some symptoms such as failure to respond to their names, reduced interest in people and delayed babbling. By toddlerhood, many children with autism have difficulty playing social games, don’t imitate the actions of others and prefer to play alone. They may fail to seek comfort or respond to parents’ displays of anger or affection in typical ways.

    Research suggests that children with autism areattached to their parents. However the way they express this attachment can be unusual. To parents, it may seem as if their child is disconnected. Both children and adults with autism also tend to have difficulty interpreting what others are thinking and feeling. Subtle social cures such as a smile, wave or grimace may convey little meaning. To a person who misses these social cues, a statement like “Come here!” may mean the same thing, regardless of whether the speaker is smiling and extending her arms for a hug or frowning and planting her fists on her hips. Without the ability to interpret gestures and facial expressions, the social world can seem bewildering.

    Many persons with autism have similar difficulty seeing things from another person’s perspective. Most five year olds understand that other people have different thoughts, feelings and goals than they have. A person with autism may lack such understanding. This, in turn, can interfere with the ability to predict or understand another person’s actions.

    It is common – but not universal – for those with autism to have difficulty regulating emotions. This can take the form of seemingly “immature” behavior such as crying or having outbursts in inappropriate situations. It can also lead to disruptive and physically aggressive behavior. The tendency to “lose control” may be particularly pronounced in unfamiliar, overwhelming or frustrating situations. Frustration can also result in self-injurious behaviors such as head banging, hair pulling or self-biting.

    Communication Difficulties

    By age three, most children have passed predictable milestones on the path to learning language. One of the earliest is babbling. By the first birthday, most typically developing toddlers say a word or two, turn and look when they hear their names, point to objects they want or want to show to someone (not all cultures use pointing in this way). When offered something distasteful, they can make clear – by sound or expression – that the answer is “no.”

    By contrast, young children with autism tend to be delayed in babbling and speaking and learning to use gestures. Some infants who later develop autism coo and babble during the first few months of life before losing these communicative behaviors. Others experience significant language delays and don’t begin to speak until much later. With therapy, however, most people with autism do learn to use spoken language and all can learn to communicate.

    Many nonverbal or nearly nonverbal children and adults learn to use communication systems such as pictures, sign language, electronic word processors or even speech-generating devices.

    When language begins to develop, the person with autism may use speech in unusual ways. Some have difficulty combining words into meaningful sentences. They may speak only single words or repeat the same phrase over and over. Some go through a stage where they repeat what they hear verbatim (echolalia).

    Some mildly affected children exhibit only slight delays in language or even develop precocious language and unusually large vocabularies – yet have difficulty sustaining a conversation. Some children and adults with autism tend to carry on monologues on a favorite subject, giving others little chance to comment. In other words, the ordinary “give and take” of conversation proves difficult. Some children with ASD with superior language skills tend to speak like little professors, failing to pick up on the “kid-speak” that’s common among their peers.

    Another common difficulty is the inability to understand body language, tone of voice and expressions that aren’t meant to be taken literally. For example, even an adult with autism might interpret a sarcastic “Oh, that’s just great!” as meaning it really is great.

    Conversely, someone affected by autism may not exhibit typical body language. Facial expressions, movements and gestures may not match what they are saying. Their tone of voice may fail to reflect their feelings. Some use a high-pitched sing-song or a flat, robot-like voice. This can make it difficult for others to know what they want and need. This failed communication, in turn, can lead to frustration and inappropriate behavior (such as screaming or grabbing) on the part of the person with autism. Fortunately, there are proven methods for helping children and adults with autism learn better ways to express their needs. As the person with autism learns to communicate what he or she wants, challenging behaviors often subside. (See section on Treatments.)

    Repetitive Behaviors

    Unusual repetitive behaviors and/or a tendency to engage in a restricted range of activities are another core symptom of autism. Common repetitive behaviors include hand-flapping, rocking, jumping and twirling, arranging and rearranging objects, and repeating sounds, words, or phrases. Sometimes the repetitive behavior is self-stimulating, such as wiggling fingers in front of the eyes.

    The tendency to engage in a restricted range of activities can be seen in the way that many children with autism play with toys. Some spend hours lining up toys in a specific way instead of using them for pretend play. Similarly, some adults are preoccupied with having household or other objects in a fixed order or place. It can prove extremely upsetting if someone or something disrupts the order. Along these lines many children and adults with autism need and demand extreme consistency in their environment and daily routine. Slight changes can be extremely stressful and lead to outbursts

    Repetitive behaviors can take the form of intense preoccupations, or obsessions. These extreme interests can prove all the more unusual for their content (e.g. fans, vacuum cleaners or toilets) or depth of knowledge (e.g. knowing and repeating astonishingly detailed information about Thomas the Tank Engine or astronomy). Older children and adults with autism may develop tremendous interest in numbers, symbols, dates or science topics.

    Autism and Evolution

    Neuroscientists and Neurogeneticists has thrown more light on this developmental issue in children and hopefully, more remedy and treatment options will be developed soon.

    Genomic regions that set humans apart from other primates carry many autism-linked mutations

    Scientists suggest that mutations in genetic regulatory elements may be important in both autism spectrum disorder and human evolution.

    Small regions of the genome where humans have diverged from chimpanzees contain a variety of mutations implicated in autism and other neurodevelopmental disorders, as reported by Harvard Medical School researchers at Boston Children’s Hospital.

    Published online Sept. 22 in Cell, the genomic analysis—the most comprehensive of its kind to date—opens a new approach to understanding both cognitive/behavioral disorders and the still-mysterious genetic changes that made human language, culture and civilization possible.

    In the last decade, comparative genomic studies have identified small regions of the human genome that are shared with many species but that changed relatively rapidly during the evolutionary divergence of humans from chimpanzees, our closest living relatives. There are about 2,700 such sequences in the genome, known as human accelerated regions or HARs.


    “Since human intellectual and social behaviors are so different from other species, many labs have figured that changes in HARs might be important in the evolution of these traits in humans,” said neurogeneticist Christopher A. Walsh, HMS Bullard Professor of Pediatrics and Neurology at Boston Children’s and senior author of the Cell paper.

    “But we hypothesized that if important HARs were damaged, it might also cause defective human social and/or cognitive behavior,” said Walsh, who is also chief of the Division of Genetics and Genomics at Boston Children’s and a Howard Hughes Medical Institute investigator. “We found that this is indeed the case.”

    Altered gene regulators in the brain

    With first author Ryan Doan, HMS research fellow in pediatrics at Boston Children’s, Walsh and colleagues used multiple genetic techniques to examine HARs and patterns of mutations within HARs in diverse, healthy human populations (using existing databases) and in two populations of children with autism spectrum disorder.

    In addition to protein-coding genes, they surveyed noncoding DNA sequences, which regulate gene activity, and tried to identify which genes these sequences regulate. They also looked for evidence of HAR activity in the brain.

    “We found that most HAR regions contain enhancer or regulatory DNA,” said Doan. “More than 40 percent of those HARs had some sort of regulatory activity in the brain—much more than we would expect by chance.”

    In all, the investigators identified about two dozen mutations in HARs that appear to have important roles in brain structure and function. Some HARs, for example, contained regions regulating neurodevelopmental processes that have diverged between humans and chimpanzees, such as synapse development.

    Autism and brain evolution

    The researchers then looked at genomic sequence data from 2,100 American children with autism spectrum disorder from the Simons Simplex Collection.

    They found that these children were 6.5 times more likely than healthy siblings to harbor a de novo (non-inherited) duplication or deletion of a HAR. In all, they estimated that these mutations within HARs contributed to 1-2 percent of the autism spectrum disorder cases by giving children too much or too little of the gene or regulator.

    “This work brings together the study of evolution and the study of neurological disease.” –Christopher A. Walsh

    The team also looked at children with autism spectrum disorder from 218 Middle Eastern families in which parents were related to each other, usually as first cousins, increasing the likelihood of recessive disorders.

    The children with autism spectrum disorder had 43 percent more recessive mutations in HARs when compared with unaffected children. In all, the researchers estimated that 5 percent of these children had recessive mutations in HARs that were related to brain function and likely to be disease-causing.

    “The evidence for recessive mutations in HARs was greatest for those HARs that are active in the brain,” said Doan. “This suggests that HARs that are active in brain development are the ones that are contributing to autism.”

    The fact that many of the HAR mutations linked to autism spectrum disorder affect noncoding DNA sequences, especially gene enhancers, suggests that autism spectrum disorder sometimes results from disordered levels or patterns of gene expression in the brain that might be amenable to intervention, according to Walsh.

    “We know from animal models that intensive environmental stimulation can increase gene expression, and that intensive training is often helpful for children on the autism spectrum,” he said. “Noncoding sequences control levels of gene expression, which suggests that a lot of the gene is still good—if there were just a way to turn it on.”

    But the evolutionary implications of the study are what most fascinate Walsh and his colleagues.

    “This work brings together the study of evolution and the study of neurological disease,” said Walsh. “Studying the kinds of mutations in HARs that cause neurodevelopmental disorders like autism spectrum disorder may tell us about the sorts of changes that led to us having a different brain than other animals’. Chimps are social creatures, but they’re different from humans. They don’t live in compact cities of a million people. That requires extraordinary social behavior.”

    The study was supported by the Paul G. Allen Family Foundation, the National Institutes of Health (T32NS007484-14, 1R21NS091865-01, RC2MH089952, R01MH083565, 1S10RR028832-01), a Nancy Lurie Marks Postdoctoral Fellowship and the Howard Hughes Medical Institute.

    Treatment and management of Autism

    Objective scientific studies have confirmed the benefits of two methods of comprehensive behavioral early intervention. They are the Lovaas Model based on Applied Behavior Analysis (ABA) and the Early Start Denver Model. Parents and therapists also report success with other commonly used behavioral therapies, including Floortime, Pivotal Response Therapy and Verbal Behavior Therapy.

    Check back next week for other symptoms and detailed discussion of these modern treatment options.

    Adapted from a Boston Children’s news and

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