There's a little confusion about the outcome of a separate phylogenetic tree arising form the prokaryotes of the preCambrian oceans. I believe the
point has been made by at least two members in more than one post, but it never hurts to make a point as clear as possible. Humans can trace their
ancestors through genetic and fossil records back for quite some way into distant history. So can rodents, cattle, horses, monkeys and elephants.
Here's an excellent diagram of
The Ancestors Tale
Mammals Phylogenetic Tree in mya.
Notice how humans haven't evolved from the preCambrian oceans all alone? They are just one branch of the tree. As we trace the branches back to
common ancestors it becomes clear that our phylogenetic tree has resulted in many other species.
This chart goes even further back...all the way to the preCambrian oceans of single celled organisms (prokaryotes etc). Notice the number and variety
of separate species as they diverge over the millions of years?
Source
Naturally,not all these species will survive and many are extinct. How do we know they are extinct? We have the fossil record and we also have the
cave paintings and rock art that feature some of them below...
Early Hominid
The sheer diversity of our phylogenetic tree is too immense to fully explain here (even if anyone could). It fills whole rooms in libraries and
thousands of drawers in museums and collections. Just focusing on our own lineage still makes the point of diversity...
Human Evolution (2 of 2)
The timeline in the above image shows that we had a common ancestor with all monkeys and primates alive today. We have a fossil record of those that
didn't make it. We have a fossil record of the steps in our evolution that led up to what we are today...
homo
sapiens. The fossil record isn't complete and how could it be? We've only been cataloging and piecing the evolutionary record together for a
couple of hundred years. What we do have is linked and cross-referenced to provide a reasonably accurate picture of life's development on Earth since
the preCambrian. Changes will be made, time lines will be extended or defined. Below is an image that reveals the development of our
human origins...
How did humans evolve? About six million years ago in Africa, the chimpanzee lineage and our own split. What happened to us after that split? The
hominid lineage did not march in a straight line to Homo sapiens. Instead, the early hominid lineage gave rise to many other (now extinct) hominids.
Examining the fossils, the artifacts, and even the DNA of these relatives has helped us understand how this complex hominid tree evolved, and how
modern humans came to exist.
Berkely: Evolution 101
Paleos: Eutheria
Now, allowing for the 'possibility' of a different/ separate/ divergent/ parallel preCambrian evolution, where could the evidence be? Where are all
the different species that would have arisen from that tree as it branched ever onwards to evolve a bipedal humanoid in the Americas? I'm sure some
people could imagine 'possibilities' that explain where the evidence has gone. Until the evidence is presented, the current model of evolution (one
phylogenetic tree) has to be accepted as being 'probably' accurate.
During the course of this magnificent ( and sometimes absurd!) thread the human aspect of the footprints has been overlooked or neglected. It's fair
to wonder what the person was doing? Where were they going? Did they have family? Happy? Healthy? Whatever the circumstances, when they laid those
footprints down around 40 000 years ago they couldn't possibly have imagined the interest they'd generate
Edit for the credits & sources
[edit on 17-6-2009 by Kandinsky]