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Last Updated: Wednesday,December 1, 1999

Just Before Humans: Pre-hominoids

According to Richard Leakey, paleo-anthropologist from a family of paleontologists, there is about 1,000 fossilized skeletons of humanoid creatures which have been dated before 1,000,000 years ago. And all of them are incomplete.
For a discussion of the problems of interpreting what the whole creature looked like see "Lucy and Her Cousins".
Most paleontologists agree that the most likely scenario for humans evolving from apes in Africa was because of geological change about 15 million years ago. Understanding the process of plate tectonics and biological evolution would help greatly.

Here are the significant events, and their approximate times:

Years Ago Major Events
15,000,000-12,000,000 East Africa dries out because of the raising of the land mass due to continental plate collision. This leads to adaptation of apes in the dryer and cooler regions toward walking upright on two legs (bipedalism).
11,999,999-8,000,000 Several fossil remains are found that look like promising early hominoid species, but eventually all are classified as apes. "Rampithecus" was the last such controversy in the 1970's. To be classified as huminoid a fossil skeleton has to show the following criteria:
  • Small canine teeth,
  • An wide round-shaped lower jaw and rounded upper jaw(instead of rectanglar upper and lower jaws as in all true apes),
  • A box shaped pelvis, and wider than ape pelvises,
  • Clear signs of upright walking structures:
    • A skull which rests perpendicular to the spine (instead at an angle as in apes),
    • A pelvic and femur join that is consistent with upright standing and walking,
    • A knee joint where the angle between femur and tibia is consistent with upright walking,
    • Phalanges which a straight instead of curved, so 'flat-footed' walking is possible, and gripping around tree branches by the feet is impossible or difficult.

    As mentioned in the brief description of evolution, some of the fossils have some of these changes but not all until the A. Afransis ('Lucy') species skeletons are found.

7,999,999-4,000,000 Blood protein studies shows that somewhere in this time period some apes involved into hominids. There is a four million year gap in the fossil records here.


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