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Earliest Human Ancestors -- It looks like a chimp but walks upright!

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A Godless Philosophy - Contents

Preface  (What's this all about?)

The Story of Evolution

14,000,000,000 y.a. -- The Big Bang
Evolution begins

4,600,000,000 y.a. -- Our Sun and Earth
Stars evolve, producing the complex elements of organic life

2,500,000,000 y.a. -- First life forms on Earth
A bacteria reproduces itself, and the race is on

220,000,000 y.a. -- First mammals
A tiny shrew survives among the dinosaurs

30,000,000 y.a. -- The great apes of Africa
Chimps achieve sociability, planned combat, and use of natural objects as tools

5,000,000 y.a. -- Earliest human ancestors
It looks like a chimp but walks upright

3,000,000 y.a. -- Earliest toolmakers
Still chimp-like, this larger-brained ape makes the first stone tools

1,800,000 y.a. -- Later pre-humans
More human-looking without fur, this naked ape conquers fire and reaches Eurasia   

300,000 y.a. -- Neanderthals
Evolved in Europe's Ice Age, they hunt and kill 7-ton mammoths

50,000 y.a. -- Modern humans (Homo sapiens)
Fully human now, we narrowly escape extinction to follow our destiny

45,000 y.a. -- Spread of modern humans throughout Eurasia
Out of Africa, we encounter the pre-humans and fight our way north

30,000 y.a. -- Extinction of the last pre-humans
Neanderthals, the tough guys, hold out the longest

15,000 y.a. -- First settlements, city-states and empires
It takes us 35,000 years to create the first small city

600 y.a. -- Racial differences and European conquests
Guns, germs and steel

Now -- Human evolution in modern times
Where are we, and what lies ahead?

Theory or Science?  Sources and References

Evolution's Implications  (Summary)

Miscellaneous Musings

Five million years ago, the world was in the grip of a harsh ice age. With so much water locked in miles-high ice sheets, the Mediterranean Sea was largely drained, and even equatorial Africa was cool and dry.

It was a cruel time for tree-dwelling animals. As drought thinned the African rain forests, they were forced to forage and survive in more open woodlands, becoming easier prey for predators. Many forest apes went extinct.

The chimpanzee lineage of apes, who evolved to live in trees and only "knuckle-walked" when necessary, were under tremendous evolutionary pressure to move faster and further. Bipedalism -- walking erect -- offered that ability, but would require a major change in foot and pelvic structure.

Fossil evidence shows such changes occurring 4 to 5 million years ago. It's unclear whether these changes were from mutations or the culmination of gradual genetic changes, but when they spread through a lucky population of chimpanzees in East Africa, that population became "Australopithecines," our earliest human ancestors.

With just 400 cc. brain volume (little more than chimpanzees), Australopithecines was basically a "walking chimp." We know that it was about the same size as a chimp, and males were much larger than females, evidence of continuing male dominance by force. Apart from bone fragments, though, they left little that survived the eons, so we can only assume that Australopithecines was very chimp-like in its other behaviors.

While bipedalism was its only major evolutionary step (pun intended), that step greatly increased its range and freed its arms and hands, which were beginning to develop opposable thumbs. These changes helped set the long-term trajectory of human evolution in a direction increasingly divergent from chimpanzees.

Chimpanzees had been tree-dwellers for millions of years, and those who survived the drought were under no new pressure to evolve. In contrast, when our "walking chimps" left the trees, they faced one new challenge after another. For them, survival required ongoing innovation.

One dramatic piece of evidence was left behind. A 165-foot line of almost-human footprints, hauntingly preserved in hardened ash in Laetoli, Tanzania, has been reliably dated at over 3 million years ago. Like a prophecy, two erect apes left human footprints, in a portentous foreshadowing of the billions of human footprints which now traverse (trample?) the planet...

(Note: Anthropologists differ over whether Australopithecines ("Lucy") or Ardipithecus Ramidus ("Ardi") was our earliest ancestor. The difference is inconsequential at our level of discussion; both descended from Chimpanzees.)

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Copyright © 2011 Marshall C. Whitfield