Evolution of the Human Skull

Evolution Human Skull

of the

Authors: Taina, Bill, Kaitlyn S., Evan, Regina

Brain Size

Introduction

Violence

Walking

Pathology

Walking Part II

Index

Dietary Changes

Pathology Part II

Dietary Change Part II

Evolutinary Predictions

Dietary Change Part III

Works Cited

Introduction

Just the way I am

Our presentation discusses this in reference to the human skull and in relation to the radiologic field. We also discuss relevant skull pathologies and modern evolutionary predictions based on recently emerging pathologies.

Changes down to the bone

Morphology and Evolution have almost a symbiotic relationship within the medical field because evolution is studied in the course of generations and that correlates with the amount of time it tales for this to be apparent in bilogical structures. To observe these changes we must look to archaeological findings and plot development stressors against embryonic development. Not only can this help us figure out how we become humans as we are today but it can also help us understand disorders and diseases.

Skull Types

My How We Have Grown

Toumaï

MRD

Unamed

Irhoud 10

Species: Homo sapiens - Age: about 315,000 years old Found: Morocco, North Africa First described: 2017

Species: Homo erectus - Age: 1.77 million to 1.85 million years old Found: Georgia, Caucasus Region of Eurasia First described: 2013

Species: Australopithecus anamensis- (earliest known australopithecin) Age: 3.8 million years old Found: Ethiopia, East Africa First described: 2019

Species: Sahelanthropus tchadensis Age: between 6 to 7 million years old Found: Chad, Central Africa First described: 2002

Development

• Scientists believe that this has occurred in order to maintain posture and balance necessary for walking
• This is demonstrated by this image comparing the modern skull to an ancient skull.
• The foramen located more ventral in the skull of the modern human

Gotta walk before you run

It is believed that early humans began walking on two legs around 6 million years ago

Over time, the foramen magnum of the skull has shifted forward to accommodate the ability to walk

Gotta walk before you run

Researchers have also supported their claim that the foramen magnum is more forward shifted in animals that walk on two legs by comparing the skulls of animals that do not walk on two legs such as rodents to the skulls of animals that do walk on two legs such as kangaroos and primates, and conclude that the foramen magnum was more forward shifted in bipedal animals

They have found that the head sits directly atop the spine in bipedal mammals, but the foramen magnum is positioned more posterior in non-bipedal mammals because the spine is located more behind the head

Dietary Changes

Are we what we eat?

Some scientists believe that diet has changed the shape of the face and skull over time One study showed that the introduction of dairy and softer foods in the human diet after the advent of farming has changed the size and shape of the skull and facial bones compared to earlier humans who hunted and foraged for food

Are we what we eat?

In the study, skulls of humans who consumed milk and softer foods had a narrower mandibular ramus, the point of attachment for the temporalis muscle was lower, and the mandibles were smaller in general of the temporalis muscle, which changed the size and shape of the upper jaw Humans who had to rely on hunting and gathering for their food source had to put more effort into chewing, and the skull reflected this by the presence of larger mandibles and facial bones for attachment of muscles

Are we what we eat?

Some studies also suggest that the softer diet putting less wear and tear on the teeth has contributed to changes in the structure of the teeth over time 7 million years ago, the canines were much larger and pointer as opposed to the shorter, blunter canines of modern humans Also, the molars and incisors were larger in our ancient ancestors

Brain Size

In ancient skulls, the cranium was low and narrow, there was no forehead, and the skull narrowed behind the eye sockets, suggesting there was not as much room for the brain to take up

Skull shape and size may have changed to accommodate the size of the human brain changing over time Seven million years ago, early humans’ brains were only the size of a chimpanzee brain. Since brains do not fossilize, researchers measure the braincase of ancient skulls to gauge how large the brain was .

Methodology

In modern day humans, the brain makes up 2% of their body weight, mainly due to increased capabilities for communication, problem solving, and logical thinking. Therefore the skull has changed to accommodate this Modern skulls have a high forehead, is expanded behind the eye sockets, and the braincase is high and wide The expanded forehead allows room for the frontal lobe, the part of the brain that is responsible for logical thinking

Violence

Kill or be killed

One theory suggest that the human skull may have evolved to withstand being hit in the face and protect it from injury as fighting became more prevalent in modern humansA study showed that when more recent human skulls (around 2 million years old) were compared to our earliest ancestors, the parts of the face that are more likely to suffer fractures in a physical fight became more sturdy, including the nose, zygoma, brow bone, jaw, and more reinforcing under the eye socket

Pathology

Radiography can be used to examine ancient remains and helps us understand what life looked like millions of years ago. Radiography of the skull is also a valuable tool to detect disease and evaluate pathology in the modern human. Xray and CT have both been an invaluable tool in revealing evidence that disease is not a recent phenomenon. Even though the skull has changed immensely over time, pathologic conditions that exist today were also found in ancient skulls.

This is a CT of a half million-year-old Pleistocene child aged around 5-8. This child suffered from a condition called craniosynostosis (a genetic defect that caused the lambdoid suture on the left to fuse but not the right causing pressure on the brain and most likely retardation. The fact that the child even lived to that age is evidence that humans took great care of each other.

The next image is of a 100,000-year-old skull found in China. It is believed to be a birth defect causing an enlarged parietal foramen. Genetic testing has shown it is due to inbreeding. Rampant inbreeding was believed to be due to limited genetic pools, the consequence of small populations.

Although the skull has evolved over time, dental problems have also plagued humans for at least 100,000 years. Skulls found, one in Ecuador aged at 10,000 years and another 100,000 years both showed evidence of impacted canine teeth. This example is an impacted canine from a 35-year-old female who lived around 2700-2400 BC.

Development

There is also evidence that humans would take care of teeth problems with primitive dentistry techniques. This is a man who died in his mid-twenties whose skeletal remains were between 13,820 and 14,160 years old. A sharpened stone such as flint was used to dig out the painful cavity.

Humans not only did their own dental work with primitive tools, but they also went so far as performing an extreme technique called trepaning. This is the act of boring or scraping holes in the skull for health purposes. There is evidence the procedure was done as far back as 7000 to 10,000 years ago. This was done in an attempt to rid the patient of bad spirits but was more likely helping relieve pressure from injury or disease. This is an Incan skull.

Modern Evolutionary Predictions

Researchers believe that modern life might transform the human skull Some doctors have found that patients are presenting with a spike-like growth on their skull One opinion some researchers hold is that the spike forms because of the hunched over posture people assume when looking down at their phones, computers, or books They claim that extra pressure is put on the neck muscles in this position and the body lays down fresh layers of bone

Works Cited