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20 March 2017

Environmental Adaptations: How Climate Shaped Our Noses

In the animal kingdom, we humans and our great ape cousins are fairly unique in our diversity. Take our facial features, for example; in most species; these features are fairly set, with little variation from one animal to the next of the same species. In humans this is simply not the case; depending upon heritage, there can be significant differences in the physical characteristics of human populations around the globe. You do of course also see variation within a single population, but particular features are often similar throughout the group. The prevailing theory as to why this is concerns the climate, with previous hypotheses suggesting that our noses are shaped depending upon locate climate to which our ancestors adapted in order to regulate the moisture content and temperature of air as it enters our respiratory system.

A more recent study conducted in 2015 casted doubt on this theory however, as the research team found that our nasal cavity is fairly ineffective at performing this function as compared to other, non-human primates. As such, they argued that rather than responding to the climate, our noses had in fact been shaped passively as a result of adaptations to other facial features.

Aiming to clarify the matter, an international team of anthropologists has now come together to conduct their own analysis, published in the journal PLOS Genetics. They compared features such as nostril distance in relation to atmospheric conditions including temperature, relative humidity, and absolute humidity. This marks the first time such a study has been conducted using measurements from living humans as opposed to skeletal remains.

“Many people have tested the question with measurements of the skull, but no one had done measurements on live people.” said Dr Mark Shriver from Pennsylvania State University, who was heavily involved in the research project.

In order to properly understand the adaptations made by our bodies in regards to climate, the team also had to understand the role that genetic drift may have played in the shaping of such features. To this end, the faces of 476 volunteers were scanned into a computerised system; the volunteers all came from one of four geographical locations, namely West Africa, East Asia, South Asia, and Northern Europe. The scans were then turns into 3D digital models, which allowed the team to measure the variations of various characteristics including the protrusion of the nasal tip, the base width of the alar, and the width of the nostrils. They then applied a statistical test to each feature to determine the likelihood of genetic drift.

Following these tests, the team were able to identify two traits which have seemingly been shaped as a result of natural selections, those being the width of the alar, and the nostrils.

The next step involved taking note of the birth locations of the parent of 140 female volunteers. The volunteers were then assigned a value based upon the climate of the given region, with particular emphasis placed on both temperature and humidity. The results seem to show a clear correlation between the width of the nostrils and the given region’s average temperature and absolute humidity.

“It all goes back to Thompson's Rule,” said Dr Shriver, in reference to the famed British anatomist Arthur Thompson.

“In the late 1800s, he said that long and thin noses occurred in dry, cold areas, while short and wide noses occurred in hot, humid areas.”

To summarise, whilst this new research certainly adds weight to the argument that climate played a large role in the shaping of particular human features, the theory is far from proven. The research team have themselves admitted that other factors likely played some role in the shaping of our noses, and hope to conduct additional studies in the future incorporating a wider variety of ancestries, in order to fully ascertain the various influences that shaped our faces. 

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.