The cerebellum a part of the brain once recognized mainly for its role in coordinating movement underwent evolutionary changes that may have contributed to human culture, language and tool use. Scientists studying how humans evolved their remarkable capacity to think and learn have frequently focused on the prefrontal cortex, a part of the brain vital for executive functions, like moral reasoning and decision making. But recently, the cerebellum has begun receiving more attention for its role in human cognition. Researcher investigated the evolution of the cerebellum and the prefrontal cortex by looking for molecular differences between humans, chimpanzees, and rhesus macaque monkeys. Specifically, they examined genomes from the two types of brain tissue in the three species to find epigenetic differences. These are modifications that do not change the DNA sequence but can affect which genes are turned on and off and can be inherited by future generations.Compared to chimpanzees and rhesus macaques, humans showed greater epigenetic differences in the cerebellum than the prefrontal cortex, highlighting the importance of the cerebellum in human brain evolution. The epigenetic differences were especially apparent on genes involved in brain development, brain inflammation, fat metabolism and synaptic plasticity the strengthening or weakening of connections between neurons depending on how often they are used. The epigenetic differences identified in the new study are relevant for understanding how the human brain functions and its ability to adapt and make new connections. These epigenetic differences may also be involved in aging and disease. Previous studies have shown that epigenetic differences between humans and chimpanzees in the prefrontal cortex are associated with genes involved in psychiatric conditions and neurodegeneration. Overall, the new study affirms the importance of including the cerebellum when studying how the human brain evolved.

A genome by itself is like a recipe without a chef full of important information, but in need of interpretation. So, even though we have sequenced genomes of our nearest extinct relatives the Neanderthals and the Denisovans there remain many unknowns regarding how differences in our genomes actually lead to differences in physical traits. Researcher have the naked DNA sequence, and can really do is stare at it and hope one day able to understand what it means. Motivated by such hopes, a team of researchers have devised a new method to harvest more information from the genomes of archaic humans to potentially reveal the physical consequences of genomic differences between us and them. The process by which genes are activated or silenced, which determines when, how and where DNA's instructions are followed. Gene expression tends to be the genetic detail that determines physical differences between closely related groups. Starting with 14,042 genetic variants unique to modern humans, the researchers found 407 that specifically contribute to differences in gene expression between modern and archaic humans. In further analysis, they determined that the differences were more likely to be associated with the vocal tract and the cerebellum, which is the part of our brain that receives sensory information and controls voluntary movement, including walking, coordination, balance and speech. With such a large number of variants to examine, the researchers relied on a technique called a "massively parallel reporter assay" to test which sequences actually affect gene regulation. That virus is then put into a cell. If that variant affects gene expression, the reporter gene produces a barcoded molecule that identifies what DNA sequence it came from. The barcode allows the researchers to scan the products of a large number of variants at once. Essentially, the whole process imitates an abridged version of how each variant would play out in a cell in real life and reports the results. In total, the researchers found 407 sequences that represented a change in expression in modern humans compared to our predecessors. Among that list, genes that affect the cerebellum and genes that affect the voice box, pharynx, larynx and vocal cords seem to be overrepresented. This would suggest some kind of rapid evolution of those organs or some kind of a path that is specific to modern humans. Even with those unknowns, this technique by itself is a significant advance for evolutionary research.