I agree with some points in the first mega-post. I disagree with most of the second mega-post. I don't want to itemize exactly where, when and how. Maybe some other time when I have way more time and energy. Sorry. I don't find them offensive and inflammatory, I just disagree. There's a difference. I think the thread is fine, and I hope someone else has the time and energy to reply to them. Maybe you do, wolftrax, you're the one who wanted detailed and concise criticisms, I seem to recall.

Actually I asked for fact based criticisms, I told you that a few times, if you recall. Oh wait, that's right, you ignored that part and twisted my words around...

Saskeptic, a question from somebody who is not well versed in biology/anatomy regarding your comments above.

The example you provide seems to focus on the evolution of the skeleton, but I would think a more pronounced difference between reptiles and mammals is the fact that reptiles are cold blooded vs mammals being warm blooded.

It seems to me that that difference is more important because it involves (I'm not sure of the correct terminology here) the entire functioning system of the animal.

I don't see how an animal can be thought of being an intermediate species between a reptile and a mammal based solely on bone anatomy, given that there are other more important differences between the two species. Of course, it may just be my ignorance of the subject matter, which is why I'm asking.

-----
From wikiAmswers:

Reptiles:

* Air-breathing.
* Cold-blooded vertebrates.
* Skin covered in scales as opposed to hair or feathers.
* Young do not go through a larva stage like amphibians, but instead look like small versions of the adults when they hatch.
* Tetrapods (having or having descended from vertebrates with four limbs) and amniotes.
* Embryos are surrounded by an amniotic membrane.
* Majority of reptile species are oviparous (egg-laying).
* Ectotherms.

Mammals:

* Milk is produced by modified sweat glands called 'mammary' glands.
* Possession of hair.
* Lower jaw in mammals is a single bone on either side.
* Only the mammal middle ear, contains 3 bones. The Stapes or (Stirrup), Incus or (Anvil) and the Malleus or (Hammer).
* Main artery leaving the heart curves to the left becoming the aortic arch.
* Have a diaphragm. A sheet of muscle and tendon that separates the body cavity into two sections. Heart and lungs before/above, liver, kidneys, stomach, intestines, etc, behind/below. No other animal has a diaphragm.
----------

For the record, I'm tentatively a theistic evolutionist . I believe God created the universe and evolution occurred thereafter (the closest description of what I believe would be a "hands off watchmaker").

GREAT question, Gigantor. Let me preface this by stating up front that, while I am a biologist and an educator, I do not specifically conduct research in evolution, systematics, anatomy, physiology, genetics, paleontology, etc. So while I may be able to provide the undergraduate level answer, I'm sure there are graduate level answers that are more complex, and may offer more sophisticated insights.

How can we tell if something is a reptile or a mammal? Your question stresses the physiological, rather than anatomical differences. An animal can be a poikilotherm (meaning that its body temperature fluctuates with ambient temperature) or a homeotherm (meaning that its body temperature is maintained within some set range). We also pay attention to the source of body heat: an animal can be an ectotherm (derives it heat from the environment) or an endotherm (derives its body heat from internal metabolic processes).

In the olden days, we used to call animals cold-blooded if they were ectotherms, and warm-blooded if they were endotherms, but these labels don't really capture the spectrum of conditions. Some ectotherms will behaviorally occupy environments that allow them to maintain a relatively stable body temperature,. e.g., tropical fish associated with some coral reef. They may be ectotherms, but they may also maintain a consistent (and high!) body temperature. Some endotherms can be occasionally poikilothermic, e.g., rufous hummingbirds in the mountains of the PNW that enter into nightly torpor - allowing their body temperature to drop significantly - only to bring it back up again to a toasty 100 F or so as they go about their business during the day.

Modern-day intermediate mammals can provide some insights into the gray area between mammalian and reptilian physiology. The monotremes (echidnas and platypus) are mammals that lay eggs. (BTW, I've never heard a good explanation from creationists as to why a loving god would try to trick us into believing in evolution by intentionally making egg-laying mammals, but that's a question for another day.) These animals are mammalian in that they have fur and secrete milk from glands in the skin to feed their offspring (although they lack nipples so the babies must lick the milk from their mother's fur). (They also have dentary/squamosal jaw joints, but in all species, the jaws are highly modified for specific foraging modes, so they certainly have atypical jaws.) Their reptilian characters include bony structure of their limbs (sprawling stance, rather than limbs placed under the body) and the aforementioned egg-laying.

Metabolically, the monotremes are homeothermic endotherms, but they really kind of stink at it. We humans maintain 98.6 F (37 C) very consistently, and if we deviate from this even a little we feel quite rotten. Monotremes normally hold a much lower temp and fluctuate widely around it: typically 32 or 33 C (91F) but down to 28 C (82 F) with no apparent ill-effect. (This doesn't include hibernation temperature, this is active and awake temperature.)

While this stuff is really cool, it doesn't help us pin down assignment to a class when all we have to study are fossils (but see evidence for endothermy in dinosaurs inferred from analysis of bones). So systematists working with fossils are forced to rely on skeletal features. This is why Archaeopteryx would be considered a theropod dinosaur, rather than a bird, if we couldn't see those beautiful impressions of feathers in the rock.

While my post focused on the skull and jaw of Cynognathus, you can follow the link to see that this creature shared other skeletal features with mammals. For example, its forelimbs splayed out like a reptile, but its hindlimbs were suspended directly below the hips as in mammals. There is evidence that it had a muscular diaphragm and vibrissae ("whiskers") like mammals. So one could make a good case that Cynognathus was more mammal than reptile, even though it retained many important reptilian features as well. Some reproductions place fur on the skin, assuming at least some degree of endothermy in Cynognathus. The jaw articulation remains really important, however, because we could go to a museum today and look at the specific bones than form the jaw - no conjecture needed.

The NFL looks like a promising career.

Thanks Saskeptic, good explanation. I didn't know there were mammals that laid eggs!

I have to read and get more educated on the subject. My problem is, I'm mechanically inclined and studying biology/anatomy is like eating broccoli, cauliflower and brussel sprouts for me... now if you want to talk C++, Java or networking, I'm in my element.

Unfortunately for me, it looks like a good background in biology is essential for most of this BF stuff if one wants to get "serious" about it.

duck billed platypus is a really cool creature

http://en.wikipedia.org/wiki/Platypus

Just wanted to say two things:

1) I heart saskeptic and wolftrax.

2) This kills the idea BF being a pongid for me. Bye-bye Gigantopithecus theory. The transition away from opposable big toe now seems to have evidence of only taking place in the Homininae line, after Ardipithecus. Ponginae split from Homininae before then. Morphologically it now seems BF goes somewhere in Homininae (wow, this is amazingly speculative!).

(How's that for pulling this discussion towards BF? )

I caught the Discovery program(s) on the tv, last night. I must say it was quality production and I've a better grasp of the significance of this fossil discovery and its/their place in prehistory. The show will no doubt be repeated and I'd recommend it to anyone with an interest in Ardi.

I'm still slowly reading through the papers but set aside time to watch (nearly all 3 hours of) the programming last night. Thought it was a little overproduced (that much dramatic music- really?) and there were a couple really important things that got glossed over, but overall I found it really enjoyable and informative. I better understand the last 15 years- what an incredible amount of work.

I'm not sure this has been pointed out but to me there are a couple of very clear important things relating to the subject of this forum from the research (aside from Dr. Saskeptics insightful general observations):

1. Completely functioning biped with a flexible, flat foot (that many have criticized Meldrum for postulating).
2. A bipedal primate with an IMI of ~91 (by my own estimates).
3. Lack of canine tooth dimorphism.
4. High foot length: body height ratio (~19% by my own estimates)

There are also some characteristics that add to the con (e.g. not consistent with sasquatch theory) argument:
1. No major sagittal (or occipital) crest even for a large-jawed, long-faced animal.
2. Head position human-like- fully above shoulders (note these 2 could go hand in hand).
3. (Maybe) relatively short pelvis (e.g. human-like)?

Two other things:
Can anyone enlighten why they used "bipedality" throughout the show last night or the distinction (if any) between that term and "bipedalism?"(aside from what we can all look up online).

I've never really understood why anyone would think our last common ancestor was chimp-like. I've always figured chimps would have evolved nearly (because of our technology/language/tools) as much as we have since we separated, so there is little reason to assume they are currently "living fossils" (unchanged for 6-7 my)- even young ones. I figured this was somewhat of a popular misconception so was a little dumbfounded to hear White and Lovejoy and Co. articulating this notion last night. Can any of you folks that are better students of this subject explain if I am misunderstanding something here? I'm guessing I've taken "chimp-like" too literally but that didn't seem to be the case from what they were explaining last night.

Apeman

PS- I also Sakseptic, especially for displaying much more patience in this forum than I find myself capable of mustering!

Well, this is the part that gets a little sticky. Ardi's hallux is divergent and opposable, it was arboreal and the foot was used to grasp trees. Many of the same people who discovered and described Ardi also did considerable work on afarensis and the associated Laetoli tracks, and maintain that afarensis had a longitudinal arch and not a flexible foot. Afarensis also had an abducted hallux, it could not grasp branches with it's feet. These kinds of things kind of run with what Eisner was saying about form and function and the position of the hallux.

I know that in school they made it a point that we don't have the fossils of the last common ancestor of chimps and humans, and that there was reason to believe that it wasn't a knucklewalker.

Thanks Thigmo!!

(emphasis mine.)

I know, it's cool, right?!

Gigantor has just provided an excellent example of why evolutionary theory has such a hard time gaining traction these days. Unless you're "into animals" on your own, you can be a really sharp, well-educated person, yet unaware of many terrific illustrations of intermediate forms both in the fossil record and living and breathing on this planet with us as you're reading this. Darwin and Wallace were consummate natural historians. With their encyclopedic knowledge of anatomy and life history, evolution was to them self evident.

For decades, we've been dumping basic natural history training from biology curricula (if it was ever there in the first place), and there are repercussions. First, we lose a sense of connectedness to nature, and this is a problem both for human health and well being as well as for conservation. Second, the lack of natural history training is creating a shortage in people capable to detect, monitor, and solve those conservation issues. Could a third repercussion be something as critical as "having no frame of reference to grasp the significance of intermediate characters?" If so, this could not only affect one's likelihood to understand evolutionary theory, but, having rejected what the "experts" say about evolution, does the person become more skeptical of science in general? Are there people skipping their flu shots this season, ultimately because no one took the time to teach them about platypuses in middle school biology?

Maybe a stretch . . . maybe. My bias is organismal biology, i.e., whole animals. Though my lenses, we spend way too much time in biology curricula (elementary through graduate school) at the subcellular level, and not nearly enough at the whole organism level. It's a fair question: Is it better for our students to graduate high school knowing the function of endoplasmic reticuli or understanding a platypus' shared characters between mammals and reptiles?


Gigantor - I hope you don't think I'm being critical of you in this post. Far from it. People follow different educational tracks. For instance, I don't know why they gave you a C++ when you took that class in networking on the island of Java - I would've just given you a B. So I'm interested in where in the educational system everybody gets their last look at biology, and what it is we're showing them in that look.



Otherwise, thanks for the kind words everybody. Hopefully some of my musings in this thread have made sense.


Observation: I believe in my very first BFF post, I expressed my opinion that if there is a real bigfoot, it's probably a Gigantopithecus. I, too, have since abandoned that notion, and am more inclined to think that a Homo/Australo-/Ardi- explanation makes more sense.

All,

I also watched the special and found it a bit too overdone - particularly the last 1/2 hour or so.

On the subject of sasquatch, was it just me did anyone else notice how many of the common arguments for the existence of sasquatch were used by the presenters to explain events around Ardipithecus' discovery?

I was particularly struck by the sequence describing the reasons for the rareness of homonid fossil finds. It was verbatim the arguments used to explain why no sasquatch bones or fossil record exists. After the presenter spoke, I looked at my wife and said, "Just substitute sasquatch for ardi, and you've got why no bones have been found."

Regards,
unixguy

Not at all. I learned a long time ago that there is no shame in admitting your ignorance of a particular subject. Ignorance is not intellectual inability.

It's the people who are ignorant yet pretend to know better that should be ashamed. Anyway, biology classes ended for me in my softmore year in high school. For my science electives I chose physics, chemistry and trig/calculus. That continued in college and shifted to computer science (C++, systems architecture, etc).

I submit that a bachelor's degree today in most universities is equivalent to a 2 year AA degree 20 years ago. I've interviewed some college graduates with an "information technology" degree that are unable to solve a simple quadratic equation, it's kinda scary.

I saw part of the discovery program (in between fixing supper) and really enjoyed it too. It strikes me that Ardi was a very general creature. There doesn't seem to be any special adaptation in any direction, other than having developed "bipedality." The really interesting thing about this is that they have to throw away the whole idea that bipedalism developed as a response to climactic changes from forest to savanna or grass lands, or mixed areas, because the associated animals, particularly monkeys, were all arboreal. So Ardi was a creature of the forest, just as we postulate BF are. It was equally at home in trees as on the ground, perhaps more in trees than on the ground, in fact, but not to the extent that chimps are. Hmm, aren't some chimps supposed to be larger and more adapted to ground-living in the Cameroons, or was that all debunked? Can't remember. Anyway, the thing about Ardi is that it had a short pelvis like a human, but a divergent hallux a bit more like a gorilla (though they did point out that there is no creature discovered so far with exactly the same foot as Ardi). The arms are long, the cranium comparable in size to a chimp but with very gracile, undeveloped teeth--especially the canines. So the theory is that they had developed a system where instead of large canines being selected for in a harem-master situation, with males fighting over females, they figure that males that could carry more food back to the family were selected for. In fact, they suggested that it was pair bonding associated with a hidden estrus cycle that led to bipedalism. It did make sense, though of course it is all speculation.

Sorry if my basic questions irritate you. I'm not a bionerd like you, saskeptic and wolftrax.

What the is default block size of an NSS file system? You don't know because you are ignorant of the subject matter, it doesn't make you dumb or intellectually lazy, it's just not your thing. Just like biology/anatomy is not my thing.

No hard feelings, but your comment seems directed at me.

Gigantor, your questions and comments have made for a great conversation. I know I have a ton of questions about C++!

No, not at all. Sorry you felt that way.

-A

The thread has touched upon 'intermediate' fossils and, with rather fortuitous timing, 20 pterosaurs which could described as intermediate have just been found in north east China.

http://news.bbc.co.uk/1/hi/sci/tech/8306060.stm


Ludo

OK, now I heart ludo.

Good stuff. Oh, yeah, I am definitely a modular evolutionist. As an animal breeder I see this all the time. You don't need to have intermediate forms in an animal, say, between long and short tails, a single mutation in one generation, bred back to its mutated parent, can drastically modify a tail in an isolated, inbred population. Ditto with the number of digits and things like that, ear size and length, fur colour and length, and so on. Just look at cats.

Backatcha. How much are motel rooms where you are?

i spilled my coffee from that one, lol

Sasquatch nests are free.........

I want to apologize to Apeman for the previous comment, sorry, I had a bad day and hastily made the post. For what it's worth, I asked a mod to delete the comment but he rejected because people had already read it and responded to it by the time he got my request.

I guess "heart" means something a bit more in the UK than it does stateside . . . "Nudge-nudge, wink-wink, saynomore."

Don't try to weasel out of it, you already made a date.

Now that there's so much love in this thread...I am a bit perplexed, like Apeman, why we continue to say that humans evolved from chimps, yet we've (as well as the rest of the primates) undergone millions of years of evolution since that time. Thus, humans and chimps diverged a while back, so shouldn't the question be "what was the common ancestor to humans and chimps?" as opposed to "where's the chimp fossils from X million years ago?"

Knowing very little about bipedality or bipedalism, I also can't quite wrap my mind around exactly why Ardi is considered to be walking upright considering the foot formation. I understand it's all in the hips, but that seems like a bold statement from a simple observation.

Also, is it possible that Ardi is an ancestor to both humans and chimps, such that chimps and other primates evolved to be knuckle-walkers, while humans evolved to more upright locomotion? Granted, the issue of canines (teeth) and such shoots some holes in that theory, but essentially, are we going to continue to move back down the line of human evolution as far as we can and we'll never actually get a "common" ancestor because we're too busy looking for chimps in the fossil record?

According to Saskeptic, I'll never grasp this since as far as I'm concerned all of creation is simply a collection of DNA and proteins. Endoplasmic reticuli are WAY too big to be meaningful.

I was curious if any had considered that ardi was a link between fully upright bipedal animals that were evolving or adapting to a woodland environment. In other words, evolving back in to the woodland envirnment from the savana as dophins and the like from land to sea. If this were the case, ardi would not be a direct ancestor or close.

I thought the same thing. The other teams that found much older fossils are trying to say they haven't reached the common ancestor. We have gone back 7 million years with Sahelanthropus tchadensis. There are no known chimp fossil ancestors besides some teeth. I don't see how they can logically say any of those ancient hominids aren't ancestors of chimps just because it has some character in common with hominids and not chimps. There must have been some convergent evolution with chimps and gorillas just based on the opinion that the common ancestor with chimps and humans was a biped. They clearly want Ardi to be a human ancestor on the human branch and not the chimp branch. It probably is closer to the human line based on the age but it must be very close to the ancestor of chimps as well so it probably isn't a certainty.

It is perfectly logical that biting teeth are more important as a weapon when you are quadrupedal. The upright walker might use a fist or a club as a more effective weapon. It is harder for a chimp to carry around a club and its teeth are closer so make more obvious weapons due to its posture. Growing longer honing canines isn't much of an evolutionary feat. It seems to me what you would naturally expect.

I thought the part about the canines getting smaller because of a pair bond also had some problems. The Australopithecus afarensis were very sexually dimorphic. It makes me doubt the role of the males as less aggressive providers as an explanation for reduced canines. The likely fact that it was upright and the posture made biting more difficult seems a more likely reason.

I think the main point about bipedalism is the hands and wrist which demonstrate that they weren't knuckle walkers. That and the other evidence makes her bipedal without that intermediate step. They must have been bipedal or quadrupedal and if they were quadrupedal, they didn't have the structures for knuckle walking. Fossils would be much less valuable if it weren't in the human lineage so that makes them want to push back the common ancestor. If it were possibly before the divergence of chimps and humans then it could be interpreted as being an ancestor of chimps so they push it back. It could be they are still looking for chimps?

From the reconstruction of the skull, I was impressed with the shape of the jaw, displaying what looked to be the jaw on its way to becoming the distinctly human parabolic arch in contrast to the long parallel-sided "U" shape of our fellow primates, perhaps due to the reduction in the canines in our lineage.
A great refutation of the small canine/pair bonding presumption can be observed by looking up an image of gibbons skulls and dentition.
I think dentition, being as strongly conserved as it has been shown to be in evolution, reveals a lot about the origins of the jaws owners, but being slow to change, dentition doesn't tell us as much as we'd like as to exactly how the teeth were actually being used by the owners who actually actually grew them.

While I understand that, I guess the depiction of Ardi as a tree-dwelling creature in the feature makes her seem more like an orangutan that can walk upright (perhaps not always), but can also use her feet to grasp branches and the such in order to climb. In essence, she has features of both bipedal and quadrupedal primates. Thus, it makes some sense to me that this could be a tree-dweller that then came out of the trees and evolutionarily diverged in two ways, to become more quadrupedal (as a chimp) or more bipedal (as a human).

I suppose as a DNA-valuing person, I'd be curious to know whether Ardi is more closely related genetically to humans than to chimps. In theory, at a genetic level, chimps and humans could be equidistant from Ardi, suggesting that she may be an ancestor of both. I guess in some ways I'm having difficulty understanding why chimps and humans have been estimated to have diverged a certain number of years ago, and now with a new skeleton we're increasing that number. Wouldn't it suggest that either something was incorrect in the initial calculations or that Ardi is in fact along the human line prior to the divergence of chimps and humans?

I would tend to side more with your stated line of thinking myself!

I'm a bit out of my knowledge comfort zone here but I'm not sure the above statement is fully correct. From one of the new science papers:

CLCA= Chimpanzee/human last common ancestor

Perhaps that's unconventional (and part of the importance here?) but that has been my rudimentary understanding for years.

****

Also, isn't Toumai's placement still very much in contention?

Mon0705- I think I'm missing something on the DNA timelines, but am probably not up to date. Last I knew the DNA estimates for human-chimpanzee divergence were still something like 5-7 mya...which is still totally consistent with this fossil, right?

Here's the timeline from this issue of Science:

Click to view attachment

and another helpful, simple graphic;

Click to view attachment

There's a great table of the assembly of shared characteristics in one of the papers but it's a bit large to post here. Can you all access the full papers?

****

Here's a figure from the final Science paper that might help explain how the authors are thinking on some of the more theoretical issues under discussion here.


Click to view attachment

-Apeman

Toumai is controversial as an ancestor but you also have ardipithecus kadabba which goes back to 6 million years. My comment about them wanting to push back the common ancestor was more concerning the statement from another researcher on an older dig site that stated that they hadn't reached the common ancestor yet when they had much older fossils than Ardi. I don't see how they could conclude that. There really are no relevant known chimpanzee fossils so we don't know how they changed.

As far as the convergent evolution, I believe they went farther than saying that Ardi was a biped. They also said that the common ancestor wasn't a knuckle-walker. That is at least implied by us not having a knuckle-walker ancestor. Since the common ancestor with gorillas is somewhat earlier, it must have developed at least knuckle-walking independently. Chimps are closer to us than to gorillas so they didn't have an ancestral branch that didn't include us. If it is true that we don't have a knuckle-walker as an ancestor then gorillas and chimps must have coevolved that trait.

They are apparently using the logic that since Ardi is bipedal and very much arboreal, there was no need for the intermediate step.


That would seem to me to be saying that they are reinforcing the no knuckle-walker ancestor and that Ardi is apparently in transition to becoming more terrestrial. I will resist the urge to qualify my statements further. I am interpreting what someone else seems to be saying about the significance.

Wow - just read this entire thread, front to back, save the megaposts.

We have moved from science to the metaphysical, to amorous love (saskeptic and gigantor) and now back to science. Friends, lets keep science the focus here if at all possible.

And Saskeptic, just in case gigantor isn't simply a nickname, suggest you perform some pre-hookup stretching. Just a thought.

I meant convergently evolved that trait, not coevolved it by the way.

ZING!!!

Bob- Just to be clear, I am with you on the convergent evolution of chimps and gorillas in terms of locomotion and knucklewalking, I was just questioning the bipedal LCA part.

-A

lol, that was funny

Further support for Saskeptic's assertion that science is self-correcting.

On a related note, I'm starting to hear lots of grumblings within the primatology/anthropology communities that Ardi has been misplaced on the human lineage. I don't think this story is close to finished...even with 15 years of prep. Sure, these things are always dynamic but I'd think 15 years of work meriting 11 papers and special issue of Science would be pretty solid.

-A

I really wish they would go into more detail about why they think Ida is not a primate. I've looked at all the tarsier/prosimian skeletons I can find online and it is nothing like any of them. It does not have that "foxy" face, it has a domed head, oval muzzle and primate teeth! It is a lot like a plain old monkey! If there are clear differences, they must be in the details. To me Ida looks like evidence of primates being very ancient indeed. And you know, given their diversity and success, I would expect them to be. The great forests of the Eocene seem like a perfect place for a little generalized prosimian to become a little primate. Such a small shift to make. What's the big deal?

Darwinius Massilae
http://abrancoalmeida.files.wordpress.com/...phs_cropped.jpg
http://images.google.ca/images?source=ig&a...ved=0CCYQsAQwAw

Wiki on the Eocene
http://en.wikipedia.org/wiki/Eocene

The world in the Eocene
http://upload.wikimedia.org/wikipedia/comm...oceneGlobal.jpg

Interesting comment here: http://www.guardian.co.uk/science/2009/oct...zine-revelation



Great picture, too, showing the very primate-like maxilla and mandible.

If we found out it was a big deal between two factions of paleoanthroplogists, I wouldn't be surprised, after all, there are papers and professional careers at stake, but within the media there is something of an unstated law, based on the enonomics of journalism (it has to appeal to an audience) of framing any dissent within anthropology as some sort of an arousing conflict that will reflect on science's view of the human relationship to the objective world versus scripture versus traditions and previous accomodations or understandings. Monkeys get bored and in order to provoke them to get our of their state of inertia they (we) need to see a good fight no matter what it's all about. Seems to be a still very active part of our simian instinctual mentality, and I suspect it would be one of the most defining characteristics we have and it would be wise to evolve beyond it, if we want to get beyond our current fracturous state of developement. cheers.