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The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period.
To provide an accessible overview, historians divide human history into different periods organized around key themes, events, or developments that have shaped human societies over time. The number of periods and their time frames depend on the chosen topics, and the transitions between periods are often more fluid than static periodization ...
Fertilization is the fusing of the gametes; a sperm cell and an ovum (egg cell) fuse to form a single-cell zygote.This is the beginning of the diploid phase of the human life cycle after two genetically unique haploid cells created via meiosis and chromosomal translocation combine their DNA and begin to develop into a multi-cellular organism.
The first debates about the nature of human evolution arose between Thomas Henry Huxley and Richard Owen. Huxley argued for human evolution from apes by illustrating many of the similarities and differences between humans and other apes, and did so particularly in his 1863 book Evidence as to Man's Place in Nature .
The first known footprints on land date to 530 Ma. [74] 520 Ma Earliest graptolites. [75] 511 Ma Earliest crustaceans. [76] 505 Ma Fossilization of the Burgess Shale: 500 Ma Jellyfish have existed since at least this time. 485 Ma First vertebrates with true bones (jawless fishes). 450 Ma First complete conodonts and echinoids appear. 440 Ma
The finding that "Mitochondrial Eve" was relatively recent and African seemed to give the upper hand to the proponents of the Out of Africa hypothesis.But in 2002, Alan Templeton published a genetic analysis involving other loci in the genome as well, and this showed that some variants that are present in modern populations existed already in Asia hundreds of thousands of years ago. [31]
The eponymous Silurians on Doctor Who are a race of reptilian humanoids from Earth's past, making their first appearance in the show in 1970. Frank and Schmidt cite Inherit the Stars, a 1977 novel by J. P. Hogan as containing a similar hypothesis, but also say they were surprised by how rarely the concept was explored in science fiction. [2]
Professor of biology Jerry Coyne sums up biological evolution succinctly: [3]. Life on Earth evolved gradually beginning with one primitive species – perhaps a self-replicating molecule – that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.