Dinosaurs Continued

[Xueirdna]

Of course, we have not dug up the entire earth yet, but if dinos had lived at the same time as men, then we should find their remains in the same layers pretty much everywhere, and not consistently many million years worth of strata below human remains.

That is a quote from the Dinosaurs thread. I pose my question out of curiosity and without any knowledge of my own.

Is there a possibility that the durability of dinosaur skeletons and human skeletons differ to the extent that we would not be able to find human fossils today? Also, are the layers of the earth reliable or have there been shifts that would create confusion as to what time period a fossil orginated? I believe I read in a magazine article that a particle human fossil was found that predated another prominent one, but showed "newer" features (for lack of better words)...looking more like humans do today as opposed to the neanderthal appearance of the other.

Curious to hear your thoughts!

[Jose]

It's interesting that this never got any discussion...but then, I just discovered it today, myself.

Is there a possibility that the durability of dinosaur skeletons and human skeletons differ to the extent that we would not be able to find human fossils today?

The nature of fossilization is that once the bone has been turned to rock, it's rock. Human fossils of the same age as dinosaur fossils, if they existed, would be just as stable.

Also, are the layers of the earth reliable or have there been shifts that would create confusion as to what time period a fossil orginated?

The layers are extremely reliable. In some places there have been shifts due to faulting and folding, but these have been figured out. Furthermore, the ages can be, and have been, determined by radiometric procedures. The only confusion comes from "reworking" in which a fossil from higher up erodes from its native stratum, and falls into a lower stratum to be re-buried. Paleontologists are aware of this, and make a distinct effort to recognize whether it has occurred for any fossil that they find. Even so, the age difference that would be achieved by such a "reworking" is usually not very great, since the strata involved are usually fairly close together. For dinosaurs vs humans, we're talking about a very large difference.

I believe I read in a magazine article that a particle human fossil was found that predated another prominent one, but showed "newer" features (for lack of better words)...looking more like humans do today as opposed to the neanderthal appearance of the other.

This kind of thing happens a lot. It's the nature of genetics and its role in evolution. Obviously, not all characteristics change at once during evolution, so in transitional fossils, one is guaranteed to find some "older" features and some "newer" features.

Furthermore, evolution doesn't work by a smooth and gradual change from an earlier type to a newer type. Rather, populations split up, and some evolve in one way while others evolve in different ways. This results in the presence of multiple related groups (even related species) co-existing. In the case of our species, only one of each such co-existing group can have been our direct ancestor. Nonetheless, fossils of all such groups may exist, and may be found. It isn't easy to determine whether a fossil represents the direct ancestor of an existing species, or a co-existing relative from the same time period as the direct ancestor.

Common belief is that species change gradually from one form to another, with every individual acquiring new characteristics in unison. This is a misconception that leads to confusion in interpreting the existing transitional fossils.