D.3b: Hominid Evolution

23/09/2013 § Leave a comment

This is the strangest blog I’ve ever written for this class.

There are two types of evolution. Jon talked about it last Thursday and I didn’t believe him but he was telling the truth. There is cultural evolution which are new methods, inventions or customs that can be passed on easily. Then there is genetic evolution, which involves natal selection between inherited differences.

/looks at DBQ – You’ve got to be kidding me.

Rediscovering biology

Page 319, hominid skull comparison

1. Well, I don’t have a skull of which I could measure its cranial capacity but the formula for the volume of a sphere is V = 4/3πr^3 and I hope that quenches your thirst for this answer.

2. If you have a bigger head, you’d have a bigger skull, and you’d need more protein and calcium to support your bigger skull since you literally have more bone mass. And this doesn’t just involve the bone mass, a dietary change would be necessary to support the brain itself. PROTEINS, GUYS.

3. Degrees of prognathism, in order of most protruding to least protruding:  Australopithecus afarensis, Australopithecus africanism, Homo habilis, Homo erectus, Homo neanderthalensis, Homo sapiens – you win again, humans.

4. The sagittal crests found on each skull looks like the keel of a boat which is – I’m guessing – the bottom edge of the boat. On H. sapiens, the crest is much more flat compared to that of its previous ancestors, i.e. H. erectus, whose sagittal crest is more pointed. The size of the crest and the jaw seem to be in the same location and of the same length. When the crest flattened on H. sapiens, the jaw did as well.

5. Just as the jaw gets less protruded and the forehead begins to recede more, the brow ridges on each skull start to shrink until they completely disappear. With H. erectus, the brow ridges were quite distinct. H neanderthalensis had slightly smaller brow ridges and by H. sapiens, there were no brow ridges at all (thank god).

6.

a) …I am actually offended that you (the tiger textbook) asked me to do this and will postpone doing 6a until I’ve regained any trace of respect for you (the tiger textbook).

b) Aren’t molars for chewing food and breaking it down – they’re at the back of our mouths for a reason so that we chew our food well so it can be digested more easily. Hominids went from eating mainly plants – they were vegetarians, but as they evolved, they started having to hunt and kill larger animals – so then they became omnivores and wouldn’t need such big teeth (meat is easier to eat than raw vegetables/greens?).

7. THE CEREBRAL CORTEX IS LOCATED AT THE FRONTAL LOBE OF THE BRAIN. So first the forehead isn’t round, it’s slanted upwards put starts to recede and become more rounded. A slanted forehead doesn’t give much space for the CEREBRAL CORTEX but when the forehead become more rounded, there’s more space for that baby! AND SO NOW OUR NEURONS GET DOPAMINE KICKS AND EVERYONE IS HAPPY.

8. H. habilis really gets me b because its foramen ovale is, like, three-quarters of the way across it’s skull – it’s really far up into the bottom of the skull and then with H. erectus, the foramen ovale starts to recede just a little bit until it’s about halfway on the bottom of the skull. This is probably to help us balance our skulls on the spine of our necks so that we can hold our heads up vertically.

9. First of all, let’s not discriminate against domestic animals, they can do 46093200000 other things we can’t and they have soft fur. Obviously our dogs and cats can’t rotate their shoulders while we can but primates need their limbs to climb trees or hunt for other animals (probably not cats and dogs) and if we weren’t able to rotate our limbs, they’d be pretty useless for thrusting or throwing spears or sticking daggers into carcasses (I don’t know).

10. As hominids evolve, the angle of the jaw starts off flat and then starts to depress with H. erectus. This enables them to use mostly the bottom jaw to chew (I know from experience, ahahaha) and I assume that it would be easier to chew this way instead of with the protruding jaw like that of A. afarensis, good god.

11. The pelvis would become shorter, the backbone – or at least the lower back – would eventually reduce into the pelvis, and the rib cage would … shrink too? Hominids flatten out so that we can stand up straight, basically. AND HUNT.

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