Why Do We have Chins?

Humans are strangely obsessed with how they look, and when we talk about looks, the first thing that typically pops up is someone’s face. Although there is the whole rest of the body too, the face is often the predominant factor when considering someone’s appearance.

George Clooney is well known for having a distinct, “powerful” chin. It’s not only him, either, many people have chins that other people would long to have. However, why do we have a chin in the first place? Does it have any specific purpose or is it just there?

In the past, there were many hypotheses about chins and the purpose of their placement on the bottom of the human face. One hypothesis that became very popular – and subsequently accepted – was that humans have chins to support the forces that our face experiences while we chew our food.

Lately, however, this theory has been debunked. “The development of the chin doesn’t seem to have anything to do with resistance to bending stresses,” said Nathan Holton, an anthropologist at the University of Iowa.

Chins: A Study

Go on and try to find any other animal with a chin. I bet this stumped you. Even our closest cousins, the apes don’t have a chin. Their chins, in fact, turn slightly inwards. Anthropologists haven’t found chins on Neanderthals, to whom we might, at least, be distantly related.

There have been many hypotheses about chins, why they exist, and what’s the purpose of their placement on the bottom of the human face? One hypothesis that gained a fair bit of traction was that humans have chins to support the forces that our face experiences while we chew our food.

Lately, however, this theory has been debunked. “The development of the chin doesn’t seem to have anything to do with resistance to bending stresses,” said Nathan Holton, an anthropologist at the University of Iowa.

To ascertain the reason, we have chins and disprove the above assumption, Holton examined X-ray images from the Iowa Facial Growth Study using measurements from 18 females and 19 males. He tracked jaw development and bone distribution, which are said to play a vital role in protecting against various types of stresses that a human face experiences.

It is true that chins become more prominent as a person ages, but researchers didn’t find any link between chin development and force resistance. Interestingly, Holton also said that jaws are better at resisting certain types of forces at the age of 3 as compared to adult jaws with a fully developed chin.

Some have also proposed that the chin helps with another distinctly human trait – speech. The chin helped cushion of the force which we picked up speaking. But speech doesn’t put force that requires cushioning.

Sexual selection

Another hypothesis was that chins were sexy. Sexual selection is when a trait aids an individual in attracting another individual of the same species. The lion’s mane is a perfect example of a trait due to sexual selection. A big mane tells the lioness that the lion has great DNA. Similarly, a strong protruding chin would have helped a human male attract a female.

This doesn’t hold up either when one considers that both human sexes have chins. In sexually selected traits, only one of the sexes will have the trait, like the lion having the mane. It is rare for both sexes to have a sexually selected trait.

Shrinking Faces

Ever since the jaw-protection hypothesis was nullified, a concrete reason hasn’t been found for the existence of chins on human faces. However, Holton is of the view that the Homo genus (which includes humans, Neanderthals, and our other ancestors) have evolved in such a way that their faces have generally become smaller.

Humanoid faces have become smaller over time and the lower portion of the face is the last to stop growing, which is why this part looks more prominent and longer as we age. This is also why we have a ‘chin’, since it simply doesn’t stop growing.

Our faces becoming smaller than our distant ancestors is one of the most important reasons for chins.

The older Homo species were used to living in the wild, so their bodies were adapted based on those conditions. As time passed, humans became more ‘domesticated’, meaning that there were fewer encounters with unpredictable conditions of nature and dangers of the wild. This resulted in hormonal changes associated with reduced violence and stress on the body. As the overall size of the body decreased, the nasal cavities did not have to grow much to let in more air to ensure the survival of the body. As a result, the face did not have to grow as much to support what would have been a bigger nose.

‘Thus, noses became shorter and chins slowly came into existence,’ says Holton.

A Useless Byproduct

Evolutionary biologists Stephen Jay Gould and Richard Lewontin called the chin a ‘spandrel’, a useless byproduct of evolution. In their paper, “The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme” they suggested that not every trait has a use. The chin might have emerged as a mere byproduct without any use, while our faces got smaller and our jaws became the way they are.

If the chin is useless or simply a byproduct, then why study it? Chins are uniquely human. Many of the other features us humans have, other animals have too. The evolution of the chin might reveal something solely about our human history. As self-titled odd creatures of the planet, understanding why we have a chin might reveal to us what makes us human.

References:

  1. Evolutionary Anthropology
The short URL of the present article is: http://sciabc.us/eX9gb
Help us make this article better

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

.
Science ABC YouTube Videos

  1. What is Quantum Entanglement: Explained in Simple WordsWhat is Quantum Entanglement: Explained in Simple Words
  2. Can We Harness Electricity From Lightning?Can We Harness Electricity From Lightning?
  3. Are Giant Insects Larger Than Humans Possible?Are Giant Insects Larger Than Humans Possible?
  4. What are Glial Cells: Definition, Types, Functions of Glial Cells | Role in PsychologyWhat are Glial Cells: Definition, Types, Functions of Glial Cells | Role in Psychology
  5. Why Don't They Have Parachutes For Passengers In Commercial Planes?Why Don't They Have Parachutes For Passengers In Commercial Planes?
  6. Methusaleh: The oldest tree in the world | What's the mystery of trees' immortality?Methusaleh: The oldest tree in the world | What's the mystery of trees' immortality?
  7. 7 Scientifically Inaccurate Things They Show in Movies: Most Common Movie Mistakes and Myths7 Scientifically Inaccurate Things They Show in Movies: Most Common Movie Mistakes and Myths
  8. Why Venus and Mercury have no Moons?Why Venus and Mercury have no Moons?

Tags: