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"However, if by "definitively transitional" you mean "we can demonstrate with
absolute certainty an direct ancestor-descendant relationship between fossil
A-fossil B-fossil C- etc.", then no. Direct ancestor-descendant
relationships are well nigh impossible to demonstrate: there is always the
possibility, for example, that fossil A was the sister species (or even the
sibling species: identical in morphology but different by some
non-morphological cue) of true ancestral fossil Q. We can propose that
fossil A is the ancestor, but we cannot demonstrate. It is a possibility
which is certainly falsifiable (for example, if all specimens of fossil A
occur stratigraphically after all specimens of fossil B, then the specimens
represented by fossil A cannot be the population which gave rise to fossil
B). In some cases (taxa confined to a particular geographic region, where
the stratigraphic and fossil sampling is exceedingly good) you might have a
very good potential set of ancestors and descendants; for the most part,
though, these are scattered much farther apart in time, space, and
phylogeny."

Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
College Park, MD 20742

http://dml.cmnh.org/2000Jul/msg00315.html

Interesting.

Thanks for responding. That's a pretty silly response, however. Of course direct linearility is difficult to establish, and you'd understand that if you ever examined mosaics of primitive and derived traits. Moreover, every new transitional species creates two new "holes."

I never claimed that human origins were set in stone -- that we had an exact uncontroversial picture. That said, everyone -- the entire scientific community -- accepts that the species I listed are transitional between non-human apes and humans. Their exact place on the tree is debatable, but their presence on it is not.

Fossils are important in determining evolutionary sequences, but the possibility of such studies to mistake "sister species" or some other sequence is irrelevant.

That fossil studies do not show "advanced" features in old strata (thus evolution is not falsified), and that they universally follow patterns of transitions *is* important.

But beyond fossils, thousands of recently discovered DNA ERV sequences common between primates and humans *do* prove we share a common ancestor with them. They demonstrate that a single individual got an ERV virus inserted in its DNA millions of years ago and passed that virus sequence to apes and humans.

That is the smoking gun demonstrating both common ancestry and evolution, and nit picking the shortcomings of fossil studies will not make it go away.

Evolution is a scientific theory, and evolution occurs and is thus a fact.

Deal with it.