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HUMAN EVOLUTION CHART

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(bbc.com)

Charles Darwin combined the ideas of geologists James Hutton and Charles Lyell, who proposed the ideas of gradualism and Uniformitarianism, respectively.  In 1859, Darwin published On The Origin of Species[pic], a revolutionary piece of literature that proposed the idea of evolution with natural selection as its main mechanism.  Thus, the Darwinian Revolution was set forward.  Our evolutionary history is far more extensive then simply dating our existence back to Mitochondrial Eve.

 

If you have not done so already, open the human evolution chart and take notice of extensive branching from ONLY 6 million years ago.  In terms of the geologic time scale (which will be discussed further later on), this accounts for only a small portion of our evolution.  In fact, homo sapiens can be traced to primates dating as far back as 50 million years ago!!

 

Here are some of the more common features mentioned when providing evidence for human evolution:

q      Brain Size: Our brain sizes have tripled in terms of size from 6 million years ago. [pic]

q      Bipedal Posture: Our hominoid ancestors  walked on all fours.

q      Jaw Shape: Our ancestors had longer jaws.

 

Others include: changes in family structure and reduced size difference between the sexes.

(Campbell, 2002)

Above is a picture of ape, who’s apart of a subgroup of Primates called anthropoids.   

(tolweb.org)

How do we know all this?  ....

 

THE FOSSIL RECORD

“The ordered array in which fossils appear within layers, or strata, of sedimentary rocks that mark the passing of geologic time” (Campbell, 2002). [pic]

 

Sedimentary Rock

Sedimentary rock is by far the best source for finding fossils.  It’s formed as pieces of our earth (such as sand) erode and settle to the bottom of bodies of water.   Thus, sediments pile up.  As organisms die settle into these sediments, fossilization may occur.  Note, however, that sedimentation occurs at different periods of time, thus rock forms in strata. [pic]

 

Some examples of sedimentary rock in which you may find a fossil include:

q      Sandstone [pic]

q      Limestone [pic]

q      Shale [pic]

q      Conglomerate [pic]

q      Gypsum [pic]

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Radiometric dating is the current standard in dating fossils by measuring radioactive isotopes.

(google.com)