Human evolution and migration
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Human Evolution and Migration. It is important to remember that there were several species in the genus Homo that came before Homo sapiens. Homo habilis is the earliest fossil discovered so far. (2.3 million years old) It means “handy man”. Homo habilis used very simple tools.

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Human Evolution and Migration

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Human evolution and migration

Human Evolution and Migration


Human evolution and migration

It is important to remember that there were several species in the genus Homo that came before Homo sapiens.

  • Homo habilis is the earliest fossil discovered so far. (2.3 million years old)

  • It means “handy man”.

  • Homo habilis used very simple tools.


Human evolution and migration

Homo erectus was a serious toolmaker and a fine hunter. Evidence also indicates that they were the first to use fire.

  • Lived between 1 and 1.8 million years ago

  • Migrated from Africa and reached as far as eastern Asia

  • Used tools, although more sophisticated than those of their ancestors.


Fossils of several other species in the genus homo have also been found

Fossils of several other species in the genus Homo have also been found.

  • Homo ergaster.

  • Homo heidelbergensis.

  • The most famous is Homo neanderthalensis

    (Neanderthal Man).

  • Neanderthal Man lived in Europe.

  • They too went extinct.

  • Probably lived side-by-side with Homo sapiens.

  • Possibly interbred with them.


Human evolution

Human Evolution


Human migrations

Human Migrations

  • Fossils of modern humans, dating to 40,000-100,000 years ago, have been found throughout the "Old World" – Africa, Europe, and Asia – and in Australia.

  • Members of our own species, Homo sapiens, defined by

    • anatomical features (skull shape and size) and

    • behavioral attributes (use of blades, bone tools, pigments, burial goods, art, trade, hunting, and varied environmental resources).

  • These humans subsequently spread to Micronesia, Polynesia, and the "New World" (North and South America).


  • Theories of human emergence

    Theories of human emergence

    • There are two theories about the origin of modern humans

      • 1) they arose in one place – Africa

      • 2) pre-modern humans migrated from Africa to become modern humans in other parts of the world.

    • Most evidence points to the first theory because

      • fossils of modern-like humans are found in Africa

      • stone tools and other artifacts support African origin

      • DNA studies suggest a founding population in Africa


    Tracing the path of human migration

    Tracing the path of human migration

    • Fossils

    • Artifacts

    • DNA

      • Mitcondrial

      • Y chromosome

      • Entire Genomes


    Molecular clock

    Molecular Clock

    • When two groups split off from a common ancestor, each accumulates a unique set of random DNA mutations.

    • Provided that mutations accumulate at a constant rate, then the number of mutations is proportional to the length of time that two groups have been separated.

    • This relationship (number of mutations over time) is called the molecular clock


    Molecular clock1

    Molecular Clock

    • An event that has been independently established by anatomical, anthropological, or geochronological data is used to attach a time scale to the clock.

    • For example, fossil evidence shows that humans and chimps diverged about 5 to 6 million years ago.

    • Inserting this number, and the number of sequence differences between humans and chimps, into the equation above sets the clock. The clock is then used to gauge other events in human evolution.


    Mitochondrial eve

    Mitochondrial “eve”

    • Mitochondrial DNA

      • DNA that is passed from women

    • Mitochondrial “Eve”

      • Determined by analysis of modern mt DNA

      • Lived 200,000 years ago

        • Migration out of Africa was 95,000 to 45,000 years agoa

      • Most recent common female ancestor of all living humans

      • Lived in or around modern-day Tanzania in Africa

      • She was part of a group of early humans


    Mt dna does it mutate too easily to be used as a clock

    Mt DNA –Does it mutate too easily to be used as a clock?

    • The mt control region mutates at a much higher rate than nuclear DNA

    • Patterns of single nucleotide polymorphisms (SNPs) are stably inherited in a Mendelian fashion over thousands of generations.

    • However, the apparent mutation rate - based on the number of observed mt SNPs between population groups - does not reflect the true mutation rate.


    Mt dna

    Mt DNA

    • The high mutation rate of mt DNA predicts that

      • there is a statistical likelihood that many positions have "back-mutated" from a new mutation to the original state or

      • mutated several times during the course of primate evolution.

      • counting observed mutations underestimates the actual mutation rate.


    Y chromosomal adam

    Y-chromosomal “Adam”

    • Y-chromosome

      • DNA that is passed from men

    • Y-chromosomal “Adam”

      • Circa 60,000 years ago

      • Most recent common male ancestor of all living humans

      • Lived in Africa

      • He lived as part of a group of early humans


    Y chromosome shows paternal line

    Y chromosome shows paternal line

    • Within the last decade, Adam has been added to the evolutionary analysis through examination of Y chromosome polymorphisms.

    • Y chromosome SNPs are the male counterpart to Mt SNPs, and are inherited in a paternal lineage.

    • Population Genetics Tutorial


    Summary

    Summary

    Homo erectus, the precursor to modern humans, evolved in Africa and gradually expanded to Eurasia beginning about 1.7 million years ago.

    By around 100,000 years ago, several species of hominids populated the Earth, including H. sapiens in Africa, H. erectus in Southeast Asia and China, and Neandertals in Europe.

    By around 30,000 years ago, the only surviving hominid species was H. sapiens.

    But when did we leave Africa and where did we go? Here's where opinions diverge widely. Journey of Mankind


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