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Last Updated: Wednesday,December 15, 1999
In the last 70 years the 1,000 skeletons of pre-hominids and one hominid all dated at more than 1,000,000 years, have been found, mainly in Africa. When a species changes somewhere that change 'radiates' from that location to other locations after several hundred years. That means that offspring of the individuals that had the genetic variation go elsewhere, and their have offspring have the same variation (as their parents have it). So the change is seen in skeletons from many locations. Since the fossils are not found in the order of the oldest first both radioactive dating, and other methods of relative dating the finds are used to decide in what order the changes were occuring. Sometimes this will also tell we the changes were radiating from.
Also as there are now individuals with the variations in different places each place might have more genetic variations which distinquish them from individuals in other areas. In Africa over the last 70 years 4 distinct variation sets have been found.
The four skeletons sets are ( and in brackets the number of years ago that they were alive rounded to the nearest million years):
There were likely other variations that have not yet been found.
- Australopithecus Afarensis (4,000,000),
- Austrolopithecus Africanus (3,000,000),
- Austrolopithecus Robustus (2,000,000),
- Austrolopithecus Boisei (1,000,000).
As you can tell from the names, these were all classified as apes. Not enough changes in any to be called human (Homo in Latin). But it is necessary to realize that the skeletons are often very incomplete.
The difficulty of finding such skeletons, and deciding how to classify them is well illustrated by the now famous story of Donald Johanson and discovery of "Lucy" who was dated as living about 3.7 million years ago. She was
and A. Afrarensis.
As can seen in the sketch of "Lucy's" bones , there is some of her skull and half of her pelvis, enough to get an idea how 'humanoid' she was. But from this skeleton there was no way to tell if she lived mainly in trees or walked about (although the hip suggests strongly upright two legged walking, and having feet that could easily curl around a branch is not able to walk upright easily at all.)
This is a sketch of a photograph of Austrolapithecus Afarensis.
Now the one phalange that was found, it is slightly curved. But what does that mean? Did she have some bone disease or malnutrition and her bones were soft?
Or more likely given the straight shape of her other bones, did this mean that Lucy had somewhat curved toes, able to grasp somewhat with each foot, and so useful in tree navigation, like an ape?
Owen Lovejoy, who was the first to analyze the bones concluded that Lucy walked like a human. However two anatomists Jack Stern and Russell Stern who studied the bones later concluded that the foot (one bone from it) was consistent with a creature which could use trees to sleep, eat or escape. This does not say that Lucy did use trees like that. But if she did, she was still equipped to use them effectively.
In 1976 Mary Leakey (mother of Richard) discovered well preserved footprints which were dated to about the same time (within a couple of hundred of thousands years that is) as Lucy, and in the same area where her skeleton had been found. The footprints are human like. Even more poignant is the smaller (child-like) foot prints that is inside one set of the larger prints. A child (like a human child would) literally stepping into each of the footprints of one of her parents she was following.
Given the little evidence when he examined the bones, Lovejoy was not wrong in stating that just because her foot bone was curved slightly that meant she could not walk upright, but rather her bone was just a vestigal shape left over the time when her species (millions of years before) had been apes living full time in trees. Modern humans have a vestigal organ called the veriform appendix when had a useful function once in our distant ancestors but not in us. However partly
there is a tendency in humans to want to find a structure to be wholly human, not a slow change over many generations.
The most striking evidence though is that all the skulls classified as Austrolapithecus had vertical ear canals that were identical in size to apes. In humans these canals are larger than those in apes to help stabilize the bipedal walking mode they use. However just because the canals are the same as apes, does not mean Lucy walked like an ape, her other structures (particularly the hip and knee joint ) clearly show she walked upright.
The pre-hominids were clearly vegetarians. The pre-hominids were not found with many animal bones, unlike some of the later hominids sites where many such bones (burnt too which indicates fire, and implies cooking).
The A. Bonsai even has the nickname of "The Nutcracker Man" since the molars are over half a centimeter wide, ideal for cracking tough nuts and roots.
Also linguists assume they could not speak. This assumption is very likely right but notice what has to be considered.
Every one of these points is an assumption and has never been proven.
- First, it is noticed that no buildings, or artistic products have been found with the skeletons. No burial arrangements for the dead likewise have been found for these pre-hominids. Also nothing we recognize as tools...even pebble tools. And if these species did not do anything so complicated then why would they need language.
- Second, their larnyxes are high up in throat like apes, and that severely limits sound making ability. Even human children have a high larnyx until about 3 months of age when it grows closer to the esophagus, and a wider range of sounds are possible (and choking on swallowing food becomes possible as well because of its new position in the throat).
- Finally, they were vegetarians. So there was no need to communicate in order to more effectively hunt.
- Oh, and their skulls were too small to hold a brain large enough to have speech neural centers.
This is how arguements begin, and they must be settled (if they can be) by gathering evidence.
- First, these creatures could have made many items out of grasses, vines, leaves and not a single one would have been preserved for five million years or even much much less time.
- Next, many creatures have multiple cries which have specific meanings. In the primate family, the Vervet monkeys have one call to warn of ground predators, like leopards, another for air predators like owls, and so on. Also humans who are born without speech and/or hearing learn to sign as complex as adults can teach them. And complex sounds can be made in the mouth cavity alone: the click speech of modern day !Kung is just one example.
- If these pre-hominids processed the vegetables in any way (there was no evidence of fire) then there is possibility of learnings to be passed on
- A small brain size does not determine specific skill abilities. Birds have small brains, even relative to their weight, yet their songs are not only complex, but they change the tune in complex ways. The changing is assumed to be random, but that just another unproven statement.
This example show how a lot of evidence and thinking are needed to decide whether one species was hominid or not. It illustrates how careful one must be in interpreting physical evidence.
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