Different human head shapes11/5/2023 To do this, they took advantage of the fact that modern humans and Neandertals have interbred, and that some populations (like Europeans) still contain many Neandertal-derived genetic variants. It took some time to get our distinctive head shape, but why?Ī paper published last week in Current Biology by Philipp Gunz and colleagues, “Neandertal Introgression Sheds Light on Modern Human Endocranial Globularity,” attempts to identify genetic variants that might underlie our skull shape. This shape didn’t appear immediately in our species we know that 300,000-year-old modern human fossils from Morocco have elongated crania much like older human species. Modern humans’ crania are globular-shaped, rather than elongated. One of those traits is the unusual shape of our crania (skulls). It is very easy for us to spot differences between our fellow humans-skin color, hair color and texture, body shape, facial features, and so on-but less easy for us to readily see those traits which unite us compared to all other human and hominin groups in the past. They find introgressed Neandertal alleles that associate with reduced endocranial globularity and affect the expression of genes linked to neurogenesis and myelination. In a study published in Current Biology Gunz, Tilot and colleagues combine paleoanthropology, archaic genomics, neuroimaging, and gene expression to study biological foundations of the characteristic modern human endocranial shape. scan of a modern human the cranium was cut open virtually to reveal the inside of the braincase. Left: Computed tomographic (CT) scan of a Neandertal fossil (La Ferrassie 1). Just blame it on the resonant properties of your skull.Figure 1. Would it show us an injury? Well, it might if the skull changed dramatically, which could indicate a head injury.”Īnd, more trivially, he says, perhaps it could explain why you really can’t stand that one singer everyone loves. “What if we could cheaply and easily run broadband noise through someone’s skull and look at how it filtered-and then do it again later. Īlthough the research is just preliminary, Gordon says there might be some intriguing therapeutic uses of this new insight. The findings appear in the Journal of the Acoustical Society of America. “The skull itself, because it’s such an intimate and personal thing, is going to shape your experience of the world, perceptually.” And those ups and downs actually correlated to each volunteer’s ability to perceive certain frequencies in the bone-conduction hearing test. With those filtered samples, they were able to see the unique spectral fingerprints each volunteer’s skull left on the white noise, amplifying some frequencies and damping down others. through the skull, from behind the ear, and recorded what came out at the forehead. Then they did a “bone conduction” hearing test, where vibrations are transmitted directly onto the skull, from behind the ear.įinally, they projected white noise like this. “We were shocked. My first version of the draft had exclamation points all over the place, but we eventually removed those from the final copy.”įirst, Gordon’s team gave 30 volunteers a hearing test-the standard type, where different frequencies of tones are played at varying loudness. Some frequencies can appear tens of decibels louder or quieter than average-based on the resonant properties of a person’s skull. But while studying this process, he also found there’s actually a lot of variability in the way people hear. Mike Gordon, a psychologist at William Paterson University in New Jersey. So anything and everything you hear is going into our ear and then going into this little bony chamber.” “It’s like its own tiny little acoustics chamber, if you will. It turns out there’s a similar process at play in your cochlea, deep inside your ear-where a tiny bony cavity houses the organ that allows you to hear. Certain concert venues, like Boston’s Symphony Hall, are known to beautifully reflect the sounds of an orchestra.
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