Gr 11 Human Evolution

The U.N. released a big report this week that says among other things, that more than a million species of plants and animals are facing extinction. This is something we need to act on, so to raise awareness, we went out on the street to ask people if they were worried about one endangered species in particular - 'Homo Sapiens.' Homo Sapiens, of course, are humans. So we asked humans if they care about the extinction of humans, and this is what we got back.

Humans are Primates

Primates are adapted for an arboreal (tree-dwelling) life in a forest environment and possess the following features:

Forward facing eyes (binocular vision)
Larger brains (improved cognition)
Opposable thumbs (capable of power grip and precision grip)
Finger pads with nails instead of claws (improved tactile sensitivity)
Skull adapted for upright posture (downward facing foramen magnum)
Rotating hand / forelimb (capable of pronation)
Flexible shoulder joints (shoulder blades on dorsal side of the thorax)

Watch me first

Australopithecus to Homo sapiens

An example of how fossils provide evidence of evolution can be established by comparing hominin skeletons

Australopithecus is an early hominin ancestor that first appears in the fossil record approximately 4 million years ago
Comparing these fossils to the bone structure of modern man (Homo sapiens) demonstrates key evolutionary changes

These evolutionary trends:

Outline the trends illustrated by the fossils of Ardipithecus radius, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens

Evolutionary Trends

By comparing the different types of hominin fossils, we can identify key evolutionary trends:

More downward facing foramen magnum (caused by a transition to bipedalism)
S-shaped curvature of the spine (an artifact of an increasingly erect posture)
Lower and broader pelvis (bipedalism has changed the hominin birthing patterns and behaviours)
Change in relative lengths of arm and leg bones (arms have become relatively shorter and legs longer due to walking upright)
Increased size of heel bone and alignment of big toe (changes in feet to become greater weight-bearing structures)
Flatter faces, with reduced brow ridges and jaw protrusion (head is no longer the most anterior part of the body)
Larger cranial capacity with increased brain size and greater encephalisation (greater intellectual prowess)
Smaller teeth and jaws more V-shaped (reflecting changing dietary requirements with less emphasis on tough vegetation)
Marked reduction in body hair (improved hunting and cultural practices have lead to the development of warm clothing)
Shift in muscle groups (particularly the gluteal and hamstring groups, in order to accommodate new mode of locomotion)

Fossilisation is an exceptionally rare occurrence that requires an unusual combination of special conditions
Most living things tend to decompose rapidly (or be scavenged) following death
Fossilisation tends to favour hard body parts (bone, teeth, shells, etc.) and exposed fossils will soon be weathered / destroyed
Only a small percentage of fossils have been discovered - fossilisation favours species that were long-lived and widespread

Individual fossils may not be representative of species (e.g. Homo floresiensis - 'Hobbit' man)
Very few complete skeletons have been discovered, and so paleoanthropology is an inductive (data-poor) science
Many conclusions have been drawn on limited data and are frequently re-interpreted in the light of new discoveries

Brain Size

A change in habitat in Africa ~2.5 million years ago may have prompted the emergence of Homo species from forest to savannah
This necessitated a change of diet to include meat (more protein), which increased the skull capacity and brain size of hominids
Improved diet quality provided energy to support greater brain function and learning capacity (positive correlation)
Activities resulting from improved cognition (such as group hunting and cooking food) enabled hominids to eat a wider variety of food

Genetic and cultural evolution

Genetic evolution involves physical changes in the human genome which become inherited (passed on through reproduction)

It involves the transfer of genes from one generation to the next (slow transfer)

Cultural evolution involves changes in human thinking and can be passed on by communication / social interaction

It involves the transfer of ideas / information either within or across many generations (fast transfer)

Changes in genotype (genetic evolution via natural selection) have lead to cultural evolution in humans by promoting intelligent behaviour
- Larger brain sizes have promoted increased learning capacity / greater cognitive ability
- Prolonged gestations have promoted social interaction / familiy networks
- Bipedalism has promoted extensive migration and improved socialisation tendencies
- Shorter finger bones and reduced reliance on forelimbs for locomation have promoted increased tool manipulation
Evolution of culture (e.g. art, science, language) has been more rapid and recent than genetic evolution (which requires many generations)
Further cultural evolution (through genetic engineering) may hasten changes in our genetic evolution
Certain products of cultural evolution (e.g. medicines) may reduce genetic evolution via natural selection
Other products of cultural evolution (e.g. pollution) may increase genetic evolution (increased mutagenic rate)

VIDEOS

Full Documentary-how scientists do their work

Virtual Simulation

https://www.classzone.com/books/hs/ca/sc/bio_07/virtual_labs/virtualLabs.html

I really like Playing with skulls

My time as a student studing Biological Anthropology at The University of Toronto (2011)

Google Sites

Report abuse