Human brains are definitely different from other animals. Yes, of course. But, there raises the question that how humans differ from primates and all other animals genetically and neurologically. And how human brains are so highly developed and evolved which makes humans – the most intelligent? Recently, the journal Science published a report about this study on August 25, 2022, by Yale university researchers. The National Institutes of Health and the National Institute of Mental Health funded this study. This study helps us even more distinct features from our ancestral primates.
The Findings of How Humans Differ From Primates
The researchers found the phenomenon that makes us human which may also be the factor for neuropsychiatric disorders. The researchers focused on the dorsolateral prefrontal cortex (dlPFC), a brain area unique to primates which is responsible for higher-order intelligence. They analysed gene expression levels in hundreds of thousands of cells obtained from the dlPFC of adult humans, chimps, macaques, and marmoset monkeys using a single-cell RNA-sequencing approach.
Researchers’ Explanation of the Study
Nenad Sestan, the lead senior author of the study says that they have identified the dorsolateral prefrontal cortex (dlPFC) as the main part of the human identity. But, they don’t know how this makes humans unique and distinct from other primate species.
For the explanation, the researchers first examined if there are any cell types that are only found in humans or other non-human primate species. They discovered 109 shared primate cell types but also five that were not shared by all species after grouping cells with comparable expression characteristics. These included a kind of microglia or brain-specific immune cell, found solely in humans and another shared by humans and chimps.
The researchers discovered that the human-specific microglia type remains throughout development and maturity. That indicates that the cells are involved in brain maintenance rather than disease combat.
Sestan stated that humans live in a very different environment with a very different lifestyle than other primate species. Glia cells, especially microglia, are highly sensitive to these variances. The microglia found in the human brain might be an immunological response to the environment.
The gene expression related to neuropsychiatric disorders
The study of microglia revealed another human-specific gene expression called FOXP2. These findings attracted researchers as FOXP2 variations have been related to verbal dyspraxia, a disorder in which individuals struggle to produce words or speech. Various research has linked FOXP2 to other neuropsychiatric disorders such as autism, schizophrenia, and epilepsy.
Sestan and his team discovered that this gene expresses primate-specifically in a subpopulation of excitatory neurons and human-specifically in microglia.
Shaojie Ma, a postdoctoral associate in Sestan’s lab and co-lead author says that FOXP2 had piqued the interest of many scientists for decades. But they still don’t know what distinguishes it in humans from other primate species. And they were quite enthusiastic about the FOXP2 results since they open up new approaches for research into language and illness.
The findings of this study are going to direct the new approach to the advancement of neuropsychiatric diseases.