KK12 - migration of modern human populations

Evidence for examining our evolutionary past

• Fossil record - can use fossils as evidence for relatedness by pointing to comparative anatomy

  • Presence of homologous structures

• Molecular homology - use similarities between nucleotides in DNA sequences or amino acid sequence in proteins as evidence for realtedness

Spread of homo sapiens - human migration

• Fossil record - earliest known hominins first evolve in Africa

  • Early hominins (Australopithecines) remained in separate regions of Africa and continued to evolve

  • Resulted in the emergence of new species, inc. the earliest members of Homo species

2-2.35 myl

• Around 2-2.25 myl before hominin species began to migrate out of Africa and into the nearby regions of Europe and Asia

  • Accomplished by a small population of Homo erectus - fossils found outside of the African continent (in China and Indonesia)

2 mly

• homo sapiens are the last remaining linage of the homo genus

2 questions are left

1. How did this geographical expansion of Homo sapiens occur? 

2. How can we leverage the information contained in DNA and the fossil record to help us better understand these ancient migratory patterns?

Out of Africa hypothesis

• H. sapiens evolved in Africa around 200 000 to 300 00 years ago (long after the departure of H. erectus into Eurasia)

  • Remained there for an extended period (100,000 years)

• Emigrated in waves, replacing the existing hominin species (like H. erectus and H. neanderthalensis) in diff. Parts of Eurasia

• All modern humans are of African descent

Out of Africa hypothesis evidence (1)

• Repeated large-scale analysis of the mitochondrial DNA of modern humans

• Our mitochondrial lineages can be terraced back to a common ancestr that iced in Africa between 150,000 and 300,000 years ago

Out of Africa hypothesis evidence (2)

• Modern-day humans show very little genetic diversity compared to other species

  • Due to the relatively short existence and the idea that we originated from a small, centralised population

• Greatest genetic diversity is thought to exist in African popultion

  • Suggests that there has been more time for spontaneous mutations to accumulate in mtDNA

Out of Africa hypothesis evidence (3)

• Fossil evidence for H. sapiens is limited

• Still able to model what is thought to be our first migratory wave as a species

  • Found in early fossilised remains found along the east coastline of Africa

E.g. oldest Homo sapiens fossils found were uncovered in East Africa and dated to around 160 000 years ago. Fossils were later discovered in the Middle East and dated to 100,000 years. suggests migration into and out of Northern Africa

Out of Africa hypothesis evidence (4)

• artefacts along the far north-west into deeper parts of Europe

• stone tools, carvings, and cave paintings

  • Indicates increased complexity and cultural evolution

E.g. stone tools were found in the United Arab Emirates and dated to 80,000 years old, as well as 74,000 years old in India. Cave paintings and carvings have also been found in western European regions and dated to around 40 000 years

Multiregional hypothesis

• the evolution of modern humans, from Homo erectus to Homo sapiens, was an ongoing process across all regions of the world with gene flow between different continental populations

• H. sapiens evolved from several different geographically separate groups of H. erectus

  • Had migrated across Africa and Eurasia in the millions years before the emergence of modern human

• Modern humans are not of African descent but rather descendants of smaller, localised populations of early hominins

Multiregional hypothesis evidence

• Limited evidence

• Fossil record demonstrates what are known as morphological clases

  • combinations of various physical characteristics that are unique to particular geographical regions across a wide timespan

E.g. some researchers point to a morphological clade in the Chinese region characterised by a combination of ten features commonly seen in fossils uncovered in this locality, including facial flatness and a non-depressed nasal root. (Fossil record is too incomplete to rely on morphological clades)

Aboriginal and Torres Strait Islander people’s connection to Country and Place

• Arrival of Aboriginal Australians between 50,000 and 65,000 years ago

• Most of the genomes of modern-day Aboriginals can be traced back to the original ‘Out of Africa' event, where first ancient humans spread throughout the globe

History

• Wave of migrants reached a supercontinent called Sahul

  • Composed of Australia, Tasmania and New Guinea before separated due to rising sea levels

• First migrants to arrive were distinct groups that came from a single initial migration

  • Spread rapidly down the western and eastern coasts

• Extinction of Australian megafauna approx. 42,000 year ago = evidence for rapid migration of modern hominins across the continent

• evidence for prolonged connection between certain groups and their areas

•  other evidence from DNA and cultural artefacts suggests migration and gene flow between groups occurred

History (2)

• Separation of the Sahul made Aboriginal and Torres Strait Islanders geographically and genetically isolated

  • Thought to make them the world’s oldest surviving civilisation

• Indigenous Australians are the longest-surviving population of modern humans to have lived in a given location

• Have on of the strongest connections to country of any living population on earth

Connection to country

• Land they live on goes beyond a physical environment but is seen as a fundamental identity

• Country - a special kindred relationship that goes two ways

  • the land provides for the people

  • the people manage and sustain the land through their culture, ceremonies, and care

Dreaming beings -  children’s spirits are present in the landscape and enter women’s bodies when the child quickens, or first moves