Muscles once thought 'uniquely human' have been discovered in several ape species, challenging long-held theories on the origin and evolution of human soft tissues. The findings question the anthropocentric view that certain muscles evolved for the sole purpose of providing special adaptations for human traits, such as walking on two legs, tool use, vocal communication and facial expressions.
The study was published in Frontiers in Ecology and Evolution, the study highlights that thorough knowledge of ape anatomy is necessary for a better understanding of human evolution. This study contradicts key dogmas about human evolution and our distinct place on the 'ladder of nature.
Our detailed analysis shows that in fact, every muscle that has long been accepted as 'uniquely human' and providing 'crucial singular functional adaptations' for our bipedalism, tool use and vocal and facial communications is actually present in the same or similar form in bonobos and other apes, such as common chimpanzees and gorillas.
Long-standing evolutionary theories are largely based on the bone structures of prehistoric specimens, also on the idea that humans are necessarily more special and complex than other animals. These theories suggest that certain muscles evolved in humans only, giving us our unique physical characteristics. However, verification of these theories has remained difficult due to scant descriptions of soft tissues in apes, which historically have mainly focused on only a few muscles in the head or limbs of a single specimen.
There is an understandable difficulty in finding primate, and particularly ape, specimens to dissect as they are so rare both in the wild and museums. They also conducted anatomical research on several bonobos that died of natural causes, looking for the presence of seven different muscles thought to have evolved only in our species.
Diogo discovered that these seven muscles were present in apes in a similar or even exact form. Similarly, both the laryngeal muscle arytenoideus obliquus and the facial muscle risorius thought to have evolved for our uniquely sophisticated vocal and facial communication, respectively were present in at least some chimpanzees and gorillas.
These findings open crucial new directions for research and question our understanding of human evolution. The picture emerging from this research is that the origin and evolution of human soft-tissue are clearly more complex and not as exceptional as first thought.
The author concludes that most theories of human evolution give the impression that humans are markedly distinct from apes anatomically, but these are unverifiable 'just-so stories.' The real evidence shows we are not so different overall. This study highlights that a thorough knowledge of ape anatomy is necessary for a better understanding of our bodies and evolutionary history.