Heya Gluadys, thanks so much for the reply.
My question here is, is there only 1 common ancestor?
For every pair of species or groups of species that are related, yes. There is one common ancestor of all cat families, one of all cattle families, one of humans and chimpanzees.
Then we can move to a wider relationship. Cats and bears are both mammalian carnivores. Can we find that the whole cat family and the whole bear family are related through a common ancestor? What about cattle and deer? Is the human-chimpanzee group related to other ape groups such as gorillas, orangutans and baboons? Is the whole bat group related to the whole rodent group?
Obviously we have not actually found fossils of all these common ancestors and we never will, but we do find that the evidence we have in the morphology and genomes of each family is consistent with a common ancestor and better explained by common ancestry than any other theory.
Now do we find this pattern extends to larger and larger groups? Does it make sense of the evidence to suppose all mammals have a common ancestor and that they are descended from a branch of early reptiles? Yes.
How do we know? Because, if this is the case, there ought to exist a series of ancient species showing characteristics intermediate between reptiles and mammals. And there is. Furthermore, the oldest of these intermediate species is mostly reptile in appearance with only a few indications of mammalian traits, while the most recent of these intermediate species are most mammalian in appearance with only a few remnants of reptilian traits.
Can we continue to work back through evidence (not just speculation) to a common ancestor of all animal life? Yes. We have both genetic and fossil evidence of key changes at key points in history, right where they ought to be in the time-line if all animals have a common origin. We have the fossils which show a transition from fish-type vertebrates to terrestrial vertebrates. We have possible intermediates showing transitions from invertebrates to vertebrates.
We can even show a plausible connection of all animal life to unicellular life.
Similarly if we began with an oak tree, we could trace relationships via common ancestry to other types of oak trees, to other flowering plants, to non-flowering seed-bearing plants, to plants that do not form seed (e.g. ferns and mosses) right back to unicellular green algae.
Similarly, with fungi. In fact, may fungi are still unicellular.
So all forms of complex life seem to have originated from one family or another of unicellular life.
That is a matter of evidence and not just speculation or wishful thinking.
Tracing lineages through unicellular species is much more complex because of the prevalence of lateral gene transfer. Unicellular organisms can gain DNA through other means than inheritance. So while it seems likely that unicellular life also had a common origin, and that complex life is therefore derivative from that common origin, the possibility of being able to actually track down a potential common ancestor of unicellular life is virtually nil.
What we can state with some confidence is that all main forms of complex life (plant, animal, fungi) came originally from unicellular ancestors. And all members of each group are related to each other i.e. all plants to all plants, all fungi to all fungi, all animals to all animals.
It also seems likely that the unicellular ancestors of plants and the unicellular ancestors of animals and fungi were related to each other as well.
Two excellent sources of information on phylogeny (the study of the pathways of evolution) are the Museum of Paleontology hosted by UC Berkeley
www.ucmp.berkeley.edu/exhibits/historyoflife.php
and the Tree of Life Project hosted by the University of Arizona.
http://tolweb.org/tree/phylogeny.html
For example, we trace pathways all the way back (I assume that the image of this resembles roots of a tree, starting at one place -the trunk- and then branching out... or... branches of a tree, basically a tree)
The trunk being the common ancestor, and then the branches leading to specific species, and then sub-branches to deviations in that species and so on. Essentially though, each branch has one common ancestor, ie all dogs came from the first dog and so on? Is that right?
Yes, and that branch is connected to other branches through a common main branch and all the main branches to each other via the trunk. So "cat branch" "dog branch" "bear branch" "seal branch" are all outgrowths of the original "mammalian carnivore branch" And the mammalian carnivore branch is one of several growing from the original mammalian branch, etc.
Ok but PE would significantly reduce the amount of time needed for all these changes to occur, as opposed to numerous slight changes over a much larger time-frame yes?
Not really. Gould explains that "gradual" has two connotations. One is "in small increments" i.e. there are many steps from point A to point B. No big jumps allowed. The other is "slowly". Traditionally evolution has been thought of as gradual in both senses, so that it was thought to occur at a steady but slow pace through the small increments. In punctuated equilibrium, you keep the meaning of "in small increments" but accept that these do not necessarily happen slowly. Instead you get alternations of many small increments happening rapidly and a few small increments happening very slowly indeed. So if we were to represent the two processes visually phyletic gradualism would look like a series of steady pulses:
A - - - - - - - - - - - - - - -B
while punctuated equilibrium would look like a sort of Morse Code alternating rapid dots with longer slower dashes:
A .... _ _ _ ..... _ _ _ ...B
But since the longer slower dashes are just as much part of punctuated equilibrium as the rapid dots, the overall time-frame is the same.
PE explains the jumps in the fossil record?
It explains why the fossil record sometimes looks jumpy although evolution is not.
Essentially, I mean do TEs think that man evolved (indirectly or otherwise) from microscopic organisms. That is what is meant by molecules-man evolution isn't it?
It shouldn't be. For one thing even microscopic organisms are made of thousands, if not millions of molecules. Also molecules are not alive while microscopic organisms are. And molecules on their own are not organized into cellular structures while microorganisms are structured cells into which molecules are arranged in certain patterns for certain functions. There is really a huge difference between molecules and micro-organisms. Like the difference between bits of paint on a palette and a finished work of art.
That we started as sludge, and ->billions of years<- are now man? Or have I got that wrong. Perhaps I should have specified.
I think you are confusing evolution with the origin of living cells. A common error. Check out theories of abiogenesis.
Evolution is not about the origin of living cells. It is about changes that occur in living species.
How have bacteria been evolving longer than vertebrates, yet are equally evolved? *confused*
Well, vertebrates, as vertebrates, have not been around as long as bacteria. But vertebrates have invertebrate ancestors. And invertebrates have unicellular ancestors.
And the unicellular ancestors of invertebrates go back as far as the ancestors of bacteria. In terms of their ultimate ancestry vertebrates and bacteria are equally evolved. But since vertebrates as a specific group originated more recently, they haven't had as much time to diversify as bacteria have had.
