Month: September 2022

DEEP CLUES. “These differences in the ratio of slow-twitch to fast-twitch myosin fibers can inform our understanding of muscle function and preceding evolutionary pressures.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

THE INDEFATIGABLE TONGUE. “A recent study by Sanders et al. (2013) showed that human tongue musculature has a greater percentage of slow-twitch fibers than tongue musculature from chimpanzees. Authors of that study correlated this evolutionary innovation in muscle physiology of the human tongue with the ability of the human tongue to slow down and produce more specific and longer contractions during speech, relative to how the tongue behaves in chimpanzees during vocalizations.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

THE ARTICULATE LIP. “Some mimetic musculature in humans is also used during speech. Human lips act in part as ‘articulators’ during speech, refining the sounds that come from the larynx into specific, meaningful speech units.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

FAST VS SLOW. “Burrows et al. (2014) demonstrated that humans have a greater percentage of fast-twitch fibers than slow-twitch fibers, and the relationship holds true for both the closely related chimpanzees and the distantly related rhesus macaques. However, humans have a significantly higher percentage of slow-twitch myosin fibers than either chimpanzees or rhesus macaques.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

FAST-TWITCH TOPHEAVY. “In other words, our minority of slow-twitch fibers was far greater than the minority of slow-twitch fibers in chimpanzees and macaques. The distribution of slow-twitch fibers in human is roughly 15–20%, whereas in chimpanzees and macaques it is only 2–7%.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

SOCIAL FACIAL MASK. “Overall, these qualitative case studies add to the growing body of evidence that primate mimetic musculature form and evolution are adaptive to social, communicative pressures. We know that mimetic musculature in extant species is adaptive to social variables (such as group size and dominance ‘style’), but future studies may be able to extrapolate our current knowledge to taxa represented only in the fossil record.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

SO ENDS this section on the evolution of the human face, driven by the type of musculature and the social pressures for communication. The superficial beauty of the human mask captivates us all, but the effects are just skin deep. Below is a structure welded by forces over long periods of time, designed for a social function. We are easily misled, as was the intention, if ever there was one. View in LinkedIn

Galena close up. View in LinkedIn