Unit 4, Chapter 11: Human Evolution and Migration

Based on the information provided by and the structure of the Edrolo VCE Biology 3-4 Textbook (AI was not used to present any of the information)

Identify the Class, Order, Super Family, Family, Genus and Species that Humans Belong to

Class: mammalia

Order: primates

Super Family: hominoidea

Family: hominidae

Genus: homo

Species: homo sapiens

Identify 5 Key Characteristics of Mammals

• Variety in teeth (incisors, canines, premolars, molars)

• 3 middle ear bones to aid hearing

• 1 single lower jaw bone attached directly to the skull

• Hair or fur in varying amounts on the body

• Mammary glands to produce milk for offspring

Identify 5 Key Characteristics of Primates

• Binocular vision with forward-facing eyes

• Prehensible hands and feet (typically with 5 digits)

• Larger craniums than other mammals relative to body weight

• Flexible spines

• Larger degrees of rotation around hips and shoulders

Identify 5-7 Key Characteristics of Hominoids

• Increased cranium size (larger and more complex brains)

• Typically smaller arm to leg ratio

• Shorter spine between ribs and pelvis (making it easier to sit upright)

• Broader ribcage and pelvis (making it easier to sit upright)

• Lack of a tail

• Y5 molar teeth in the lower jaw

• Shoulder blades and joints that allow arms to swing behind head

Identify 5 Key Characteristics of Hominins

• Bipedalism

• Smaller canines due to changed diet

• Ability to speak and communicate basically

• Ability to form large/complex societies

• Increased cognitive abilities (abstract concepts, language)

Identify 6 Structural Effects of Bipedalism

• Centralised foramen magnum

• S-shaped spine

• Broader ribcage

• Bowl-shaped pelvis

• Non-prehensible feet with two arches

• Increased carrying angle of the femur

Identify 4 Species of the Genus Homo in Order of Evolution

• Homo habilis

• Homo ergaster

• Homo erectus

• Homo hiedelbergensis

• Homo neanderthalensis

• Homo sapiens

Describe Changes in Brain Size throughout Hominin Evolution

Although not perfectly linear, the general trend of hominin evolution is the gradual increase in brain size in subsequent hominin species compared to that species recent ancestor/s, indicated by cranium volume of fossilised remains.

Identify 2 Possible Contributors of Increased Brain Size

• Changed diet to incorporate fruit and animal products followed by control of fire to cook food.

• Changed environmental challeges/stressors such as climate change or migration.

Summarise Changes to the Cerebrum of Hominin Brains

The cerebrum in hominin brains has become more folded, increasing surface area and numbers of neurons and connections between brain cells, enhancing cognitive ability.

Identify 3 Pros to Larger Brains

• Lowr predation vulnerability

• Group care and shared mothering

• Cooking and stable food production

Identify 3 Cons to Larger Brains

• Higher energy needs

• Higher complexity of childbirth

• Larger diet

Identify 7 Skull Structural Changes throughout Hominin Evolution

• More centralised foramen magnum

• Shrinking of the sagittal crest

• Less prominent brow ridge

• Flattening of the face

• Less protruding chin

• More domed skull

• Smaller teeth

Explain Evolutionary Change in Hominin Arm Length

When our ancestors began moving primarily on the ground, in contrast to an arboreal lifestyle, forelimbs were no longer required to be in continual contact with the external environment during locomotion. With less need for available contact points, arms were more commonly used for carrying objects and manipulating tools and became shorter and better suited for bipedalism.

Explain Evolutionary Change in Hominin Leg Length

As well as reducing the intensity of the rising and falling motion when walking, hominin legs have gradually become longer as we have adapted to bipedalism, allowing for a longer, more efficient stride length.

Explain Evolutionary Change in Pelvis Shape

A shorter and more bowl-shaped pelvis provided hominins with the support for the upper body required when walking upright. Further changes to pelvis shape have also been influence by the changed demands of childbirth as cranium volume increases.

Identify 3 Factors Contributing to the Incomplete Human Fossil Record

• Complete decomposition of individuals rather than fossilisation or fossilisation of only small fragments

• Many rock layers remain inaccessible to paleontologists

• Comparitively small population sizes and short span of existence for many unique hominin species

Describe the Coexistence of Homo Sapiens and Neanderthals

• Modern humans and Neanderthals are predicted to have lived in the same regions of Europe and Asia 40,000 - 100,000 years ago.

• mtDNA evidence suggests that Homo sapiens and Neanderthalensis were seperate species that shared a recent common ancestor ~400,000 years ago.

Suggest 2 Pieces of Evidence for Interbreeding between Neanderthals and Homo Sapiens

• nuclear DNA studies show around 1-4% of the human genome is identical to DNA found in Neanderthals.

• 100,000 year old DNA from Neanderthal fossils found in Siberia contained a significant amount of ancient human DNA not found in other Neanderthal populations

Explain how Human DNA can be used to help Map Neanderthal DNA

Although only 1-4% of the human genome is identical to Neanderthal DNA, the part of the Neanderthal genome found in different people varies. By taking samples from thousands of individuals, closer to 40% if the Neanderthal genome has been mapped.

Identify the 2 Hypotheses of Human Migration

• The ‘multiregional’ hypothesis

• The ‘out of Africa’ hypothesis

Give an Overview of the Multiregional Hypothesis

The multiregional hypothesis suggests that the evolution of modern humans was an ongoing process across all regions of the world with gene flow between different continental populations, rather than all modern human beings being of African descent.

Describe the Evidence for the Multiregional Hypothesis

There is limited evidence supporting the hypothesis. Combinations of various physical characteristics that are unique to particular geographical regions have been used as evidence, which has been argued against due to the incomplete nature of the fossil record.

Give an Overview of the Out of Africa Hypothesis

The out of Africa hypothesis suggests that humans first developed and evolved in Africa before migrating outwards ~100,000 years later, replacing existing hominin populations. This means that all modern humand are of African descent.

Give 3 Pieces of Evidence for the Out of Africa Hypothesis

There is compelling evidence for the out of Africa hypothesis.

• Repeated large scale mtDNA analysis traces mitochondrial lineages to common ancestors that lived in Africa between 150,000 and 300,000 years ago.

• Modern humans also have comparitively low genetic diversity, suggesting a small original population

• The greatest genetic diversity is thought to exist in African populations.

Explain why Indigenous Australians are Considered one of the Oldest Continous Populations

Research sequencing the genomes of modern-day Indigenous Australians can be traced back to the original ‘out of Africa’ event, indicating a continous population that migrated to Australia 50-60,000 years ago.