Evolutionary Trends, hominid evolution Flashcards
Order of evolutionary ancestry
Hominins
Australopithecines
Homos (erectus, neanderthalensis)
Homo sapiens (modern humans)
Define adaptation
Structure, physiological process or form of behaviour that makes an organism better able to survive and reproduce in a particular environment
Adaption to skull?
Reduced prognathism- skull on vertebrae, reduction of teeth size, flat profile
Foramen magnum-
hominins: centrally underneath skull, skull balanced in vertebrae, limited muscles required.
Apes: Foramen magnum – Posteriorly positioned foramen magnum under the base of the skull, pushes the centre of gravity in front of the pelvis
Adaption of the spinal column
-Hominins ‘s’ shaped spine - low Center of gravity. S shape curvature brings vertebral column directly under weight of skull. Improves balance in upright position. While the lumbar vertebrae is thick & wedge shaped from front to back supporting the upper body weight.
Gorilla- C shaped - high Center of gravity. C shaped curvature of the spine projects centre of gravity forward of the pelvis/ for improved balance in the quadrupedal position.
Adaption of Jaw?
A- protruding jaw
H- flat allowing for skull to balance on top of spine because weight in front of foremen magnum = weight behind
Adaption of pelvis?
Hominins: bowl shaped and broader supporting abdominal organs, transferring weight, helping with childbirth and pregnancy and providing muscle attachments for large gluteal muscles
Gorilla- elongated flat pelvis Allows hind limbs to move under centre of gravity which is in front of the pelvis.
Adaption of hip and femur
- head of femur large and fits into acetabulum (hip socket) of the pelvis because pelvis is broad. femurs converge towards the knees ensuring:
Weight distribution and creating the carrying angle. Remaining close to the central axis of the body when walking = stability, rotation from lower leg and foot, stride instead of swaying walk
Gorilla: Hip joint located behind head/ trunk
femur positioned vertically so no carrying angle
Hominin: pelvis shape makes hip sockets further apart and femur sit in acetabulum So joint is more forward = carrying angle
Adaption of knee?
Hominin knee - bicondylar angle bringing feet in line with Center of gravity when walking
= weight transferred from femur to outer hinge so outer ligament is larger and stronger than inner ligament
no energy required to stand
Naturally resistance to knee bending backwards
Adaption of foot?
Ape- opposable big toe + knuckle walking
Hominin- lost opposablity; big toe pushes off
Structured to transfer weight equally
Two arched ( longitudinal and transverse)
Adaption of centre of gravity
- longer human legs= lower centre of gravity
- lower centre of gravity = increased stability when moving bipedally or standing erect
What is muscle tone?
Partial contraction of skeletal muscles and is an essential element for maintaining upward stance.
Human brain vs ape brain?
H- more dev. Cerebral cortex (more convulsions and SA )
- average 1350cm cubed
A- 400 to 500cm cubed
What are endoclast?
Impressions inside skull made from rock or some other solid materials
Define prehensile
Grasping; refers to the digits of a hand or a foot that can grasp an object. Prehensibility is the ability to grasp objects
Origin, location and cranial capacity of Australopithecines afarensis ‘lucy’
Australopithecus afarensis East Africa 3.9 mya- 3 mya Cranial capacity of 375-550 O
Origin, location and cranial capacity of Australopithecus africanus?
South Africa
3.0- 2 mya
Cranial capacity: 420-500
Origin, location and cranial capacity of Paranthropus robustus?
East and South Africa
2.5- 1.1 mya
Cranial capacity: 500-545
Origin, location and cranial capacity of Homo habilis?
Eastern Africa
2.4- 1.5 mya
Cranial capacity of 500-800
Origin, location and cranial capacity of Homo erectus?
Asia and europe
1 mya- 300 000ya
Cranial capacity of 1000-1250
Origin, location and cranial capacity of Homo neanderthalensis?
Europe and Asia
230000- 28000 ya
Cranial capacity of 1450
Origin, location and cranial capacity of archaic Homo sapiens?
Africa Asia and Europe
300000 ya
Cranial capacity of 1100-1400
Location, origin and cranial capacity of modern Homo sapiens?
Everywhere
160000 ya
Cranial capacity 1350
Define binomial system
The system of naming organisms using the generic (genus) and (species) names to describe a species