lpetrich

In the most recent issue of the Proceedings of the National Academy of Sciences (June 11, 2002; 99(12); <a href="http://www.pnas.org" target="_blank">http://www.pnas.org</a> -- one may need to be registered to get the full articles) are some very interesting articles on evolution.

One of them is simulation of mammalian tooth growth, which can produce some complicated tooth-shape patterns. This was done by simulating the expression of growth-control genes and diffusion and gene control of their products. The result was good agreement with not only the shapes of some mouse teeth, but also their gene-expression patterns.

Evidence of a curious correlation between carbon-dioxide content and species-origination rate in the Phanerozoic Era (after the base of the Cambrian). The article did have some speculations on how the causation might work, such as low CO2 meaning that the Earth becomes cold enough to allow lots of glaciers to form, which drains the oceans a bit, shrinking the continental shelves.

A proposed explanation of why molecular-evolution extrapolations may give ages that are too great. Estimated times are constrained from below, but not from above, meaning that their statistical distributions have overestimated centers -- thus the age overestimates.

I'll be discussing the very interesting result on coral growth-control genes in a post by itself, since it is worth more discussion than a simple blurb.

There's another stab at the overall eutherian family tree, this time using mitochondrial genomes. Some of the results were familiar, such as cetaceans being closest to the hippopotamus, and Afrotheria being a well-defined group, but there were some odd ones, like the hedgehogs being the first to split off, the rodents being next, and the Dermoptera (flying lemurs) branching off inside of the Primates (they're most closely related to the monkey-ape-human subgroup). Another curiosity is that rodents would sometimes be split into two groups mixed with non-rodents; this may be an artifact of rodents having had a very early divergence in their history.

And in the most recent issue of Science, 7 June 2002, (296) 5574, there is the report "EVOLUTION AND DEVELOPMENT: Comparative Biology Joins the Molecular Age". The genome of the tunicate (sea squirt) Ciona intestinalis is being sequenced; it weighs in at 160 million base pairs. But researchers have found gene-regulatory sequences to be very easy to find, often being around 500 bp away from targeted genes, because the Ciona genome has much less "junk DNA" in it.

And another tunicate is being sequenced, the larvacean Oikopleura dioica, which looks like a Ciona tadpole, but stays that way all its life. It is free-swimming, and it makes a shell that it uses to catch plankton. Its genome has only 72 million bp, and it has features comparable to the nematode genome, such as disorganized and reduced Hox genes.

Finally, there is someone working on the development of bat wings; he claims to have found some important genes for that, and he will be checking on what they do in mouse embryos. Will the result be mice with extra-long toes?

Ergaster

There's also an interesting one about the possession of an ethmoidally-derived frontal sinus in Aegyptopithecus, a primitive stem catarrhine. Since that means the ethmoidal frontal sinus is actually not a synapomorphy of hominoids (apes), then maybe Proconsul isn't really a basal hominoid as is generally thought.

Okay, okay--it's obscure, but still pretty interesting. Trust me on this.

Creation's Terrier

So, does this mean Proconsul joins the ranks of Nebraska Man, Piltdown Man and Ramapithecus, as another disproved missing link? Just curious.

CT

lpetrich

Creationists are fond of discussing cases like these as if they were the only putative hominid fossils that anyone has ever claimed to have found. But the truth is very different.

* Piltdown Man. A hoax that aroused a lot of skepticism before it was exposed. It was first thought to be a composite, and as lots of real hominids started to be found in Africa, it was relegated to an oddball side branch. When it was analyzed with improved dating techniques, it was discovered to be a composite created by a hoaxer.

* Nebraska Man. A short-lived false alarm extrapolated from a single molar that turned out to be an extinct pig -- and human and pig molars do resemble each other fairly closely.

* Ramapithecus. Known only from a few jaws and teeth at first; whether its jawbones look humanlike or apelike depended on how one oriented the pieces. More recent finds have been more detailed, and have established it as an orangutan ancestor or close early relative.

* As to Proconsul, I don't know whether it has an ethmoidally-derived frontal sinus, so I cannot comment on its relationship with Aegyptopithecus. The discussion suggests that it lacks one, meaning that it must be an extinct offshoot rather than an ancestor.

I think that, to be confident about what was an ancestor of what, one needs well-preserved fossils like the sort that have been found for equine ancestors and extinct offshoots.

Creation's Terrier

So that's a 'yes', then?! The alleged family tree is rootless...?

CT

Jack the Bodiless

Not "rootless", no: just that the braches are somewhat intertwined.

But I suspect you know that. You are trolling.

Ergaster

Yeah--right. As if any creationist actually knows what Proconsul is in the first place.

But I forget--creationists are not constrained by knowledge. Silly me.

Ergaster

Actually, Proconsul does have one; it's just that the genus is morphologically primitive in many other ways, so the ethmoidally-derived frontal sinus was one of the few characters that seemed to put it on the "hominoid" side of the line. But now, since this form of sinus has been found in a fossil catarrhine which is definitely *not* "ape", we can't use it to classify Proconsul as one.

Creation's Terrier

Sorry, but I resent that. Just because I'm a bit more familiar with the evolutionist literature than most 'cretinists' (as you 'Infidels' so pleasantly refer to us) doesn't mean I'm trolling. On what do you base that accusation?

How can lineages be 'intertwined'? I thought the point of 'species' was that kinds cannot interbreed Where's the intertwining?

And how can you tell that a scrap of bone belongs to one of these lineages or another, if there's intertwining?

Aren't evolutionists basing their theory on very very little fossil evidence for humans - what is it, a couple of table-tops full? Mostly single teeth or scraps of skull, and just two - incomplete - skeletons (one the rather chimp-like ape Lucy, the other the abnormal human Turkana boy), isn't it? Not a very solid foundation for such claims, no?

CT

Ergaster

Possibly because you made a comment that suggests a depth of misunderstanding so profound no reasonably knowledgeable person would have made it on purpose?

That'd be my guess....

I'll let JtB address what he means by "intertwining" (which I confess is unclear to me, too), but one can tell about fossils because one is intensively and carefully *trained* to tell. Unlike creationists.

I thought you said you were "familiar" with evolutionist literature? What--do you hide that familiarity when talking about evolution?

I only ask since you do not seem to actually be demonstrating very much knowledge about the fossil basis for human evolution; rather, you are spouting old and tired creationist propaganda. Pretty much everything you have claimed about the fossil evidence is wrong.

Besides--what do you think Proconsu has to do with human evolution, if anything? Any idea what Aegyptopithecus might actually be, or its significance?

Just wondering, since it seems rather curious to be objecting to *human* evolution via these particular fossils....

(flippin' codes. Why is there no preview screen here? Grumble...)

[ June 13, 2002: Message edited by: Ergaster ]</p>