Skulls and evolution

The trend of properties changes in gorilla, Homo erectus, Homo sapiens, and cro-magnon as we go from ancestral primates to modern human.
Feature
Details
Brain case
·         The brain case size increased in the order: Gorilla < Homo erectus < Homo sapiens < cro-magnon.

·         The cranial ridge became less sharp, rounder. It was flat and smooth in cro-magnon while it was sharp, long, and protruding in gorilla.

·         The brow ridge reduced in size and changes in form: it was large, protruding in gorilla, gradually reducing in the H. erectus and the H. sapiens, then absent in the cro-magnon.
Teeth
·         Reduction in the size and prognathism of the teeth.

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·         Carnies were large, long, and sharp in gorilla, then turned smaller, shorter, flatter, and more like incisors in others.
Palate
The overall shape of the gorilla’s teeth was U-shaped and wide. The shape of cro-magnon was more evenly curved and more narrow.
Forehead (compared to face)
The forehead was low, small, receding and sloping. It became higher, larger and less sloping as we go from gorilla to cro-magnon.
Location of eye sockets (orbits)
Front of skulls.
Snout
The snout became smaller, shorter and narrower from gorilla to cro-magnon.
Cheekbones (zygomatic bones)
The face was wider and flatter.
Foramen magnum (where the backbone attachs)
It was located at the bottom of the skull.

Hominids first walk upright at the stage of Homo erectus because their foramen magnum is located at the bottom of the skull.
Carnivore: Leopard
Omnivore: Siberian wolf

Herbivore: Sheep

Feature
Details
Explanation
Canine teeth
Reduce in size from a carnivore to an omnivore. An herbivore has no canines at all.
Carnivores and omnivores need canines to strike, attack, and kill their prey, while herbivores have no need to subdue their food.
Molars
The herbivore has flat molars with sharp ridges on the top while the carnivore and omnivore have pointed molars.
Carnivores and omnivores need pointed molars to rip and shred meat. Herbivores have sharp ridges to snip off leaves from branches. Omnivores eat both meat and plant, so they have all kind of teeth.
Eye sockets (orbits)
·         The carnivore and omnivore have their eyes at the front of the head, allowing for overlapping fields of vision.

·         The herbivore has its eyes on the side of the head, allowing for greater visual field coverage.
·         Carnivores and omnivores have smaller field of view but better depth perception, which they need to catch prey.

·         Herbivores are often preys for other animals, they need a wider field of view to detect them earlier and have a chance to flee.
Masseter muscle attachment points
Large in the herbivore, smaller in the carnivore and the omnivore (in proportion to its skull size).
The masseter muscle is used to swing the jaw from side-to-side; this is necessary for the grinding motion of chewing.
Temporalis muscle attachment points
Small in the herbivore, large in the carnivore and the omnivore (in proportion to its skull size).
The temporalis muscle is used for operating the jaw to create a slicing motion needed for shearing meat off bone.

Dolphin.
Dolphins breathe through a blowhole, thus the blowhole of a dolphin corresponds to the nose of a terrestrial mammal skull.
Dolphins grab and kill their prey with their teeth and swallow them whole or in large pieces. This is because the teeth of dolphins are pointed and sharp unlike humans’ or herbivore’s teeth.

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