An international team of researchers has found via study that a groove in the brain, which they have named the ‘superior temporal asymmetrical pit’ (STAP) appears to be unique to humans as it is barely noticeable in primates. The team suggests their finding may help better understand the evolution of our species. Medical scientists and doctors have known about the STAP for some time, but until now, it was not known just how unique it is. It is on average just 4.5-centimetres long and is deeper in the right hemisphere than it is in the left. No one knows why the groove exists, but its location offers clues—it is likely associated with communication, the researchers note. To learn more about the STAP, the researchers looked at brain scans of 177 people and 73 chimpanzees—analyses revealed that while clearly present in all the human scans, it was barely present in any of chimps.
The team notes that in the right hemisphere, the groove is in a part of the brain involved in facial recognition and in figuring out the motives or feelings of other people. In the left hemisphere, the groove runs through a part of the brain very clearly associated with language skills. The human brain is approximately three times as big as a chimp's, yet finding functional differences in brain structure has been difficult to pinpoint. One structure that has been seen to be different is Broca's area, which is known to be important to speech. It is smaller in chimps which would seem to make sense as their speech capabilities are far less complex. The researchers note that the STAP is prominent in people of all ages, from those still in the womb to the elderly. That suggests, that the groove is involved in inherited traits—traits not present in other primates.