NYT/AP: Ancient Hominid Found in Ethiopia Is Yielding Teeth Like the Apes'

[DeepModem Mom]

Ancient Hominid Found in Ethiopia Is Yielding Teeth Like the Apes'
By THE ASSOCIATED PRESS
Published: January 20, 2005


Paleontologists working in Ethiopia have discovered bones and teeth up to 4.5 million years old from at least nine members of a little-known hominid species that was a primitive ancestor of humans.

The specimens are from Ardipithecus ramidus, a transitional creature with significant ape characteristics. The fossils are mostly teeth and jaw fragments, with some hand and foot bones, according to nine researchers from universities in the United States and Spain.

Their findings appear today in the journal Nature.

These are not the first such specimens but they are the latest in a growing collection of early human fragments that help explain the evolutionary history of humans.

The discoveries were made over a four-year span beginning in 1999 in digs at As Duma, a site in the Afar region that has yielded many important fossils. Among the tooth specimens, the canines are small and blunt, similar to those of other human ancestors. But most of the teeth, including molars, are like those of great apes. The size and wear of the teeth suggest that A. ramidus ate a plant-based diet, the researchers reported....


http://www.nytimes.com/2005/01/20/science/20bones.html

[Donkeyboy75]

1. Nice try.

We all know the good lord put those there to test our faith in creationism. ;)

[Used and Abused]

2. how can we confirm that it is actually an ancestor

and not just a "look alike?" I guess what I'm saying is, just because they had similar DNA and a lot of human like characteristics does not mean that humans evolved from that particular group.

[gottaB]

5. Seriously?

You basically take a list of features that distinguish humans from apes. If a specimen or group of specimens has a lot of human characteristics, call it a hominid. Then you spend twenty years arguing about it, all the while new data are coming in.

There are cases of hominids that aren't ancestral, for example among the Austrolopithecenes. To find the ancestors, you basically do the same thing in that group and weed out the ones with unusual features, like robustus. The reasoning is that once a successful adaptation takes place, it's not likely to revert to a more primordial state and start again. So you can't say with absolute certainty that A. robustus is not an ancestor, but it would be extremely unlikely. A. afarensis, on the other hand, is almost certainly an ancestor.

Here's a chart: http://www.archaeologyinfo.com/species.htm

In the case of ramidus, we see features associated with an adaptation for bipedalism. The position of the foramen magnum was mentioned in the Times article. There's also the phalanx that was unearthed. There is also a femur, which has a large balled head suggestive of bipedalism. Taken together it's pretty strong evidence of both a divergence from the line leading to modern Chimps, and the begining of the line leading to Homo sapiens.

[aquart]

6. But it was specialized to plants?

That bothers me. Feels like a branch, not a main trunk.

[gottaB]

12. Well, I'm not much on dentition, but here goes....

I think the teeth are basically ape teeth with a couple of features only present in later hominids.

One description:

A morphological description of the initial, mainly dental, fossil remains of Ardipithecus ramidus was published by White et al, 1994. The physical attributes of this hominid show a range of primitive traits, which are most likely character retentions from the last hominid/chimpanzee ancestor. At the same time, some hominid innovations are equally apparent. The currently known traits of Ardipithecus ramidus, in general, can be placed within two categories: ape-like traits and Australopithecine-like traits.

Much of the dentition is ape-like and this hominid most likely had a significantly different dietary niche than did later hominids. A small canine-incisor to postcanine dental ratio, typical of all other known hominids, is strikingly absent in Ardipithecus ramidus. In addition to the presence of a relatively large anterior dentition, tooth enamel is thin. Though slightly greater than in teeth of modern chimpanzees, enamel thickness of A. ramidus is extremely thin by hominid standards.

Premolar and molar morphology also point to niche affinities with the great ape ancestors. Strong crown asymmetries, in particular enlarged buccal cusps, characterize the upper and lower premolars. Additionally, an ape-like molar shape prevails. The length (in the mesiodistal plane) to breadth (in the buccolingual plane) ratio, which is roughly equal to 1 in later hominids, is much greater in A. ramidus.

Some important derived features, link Ardipithecus ramidus with the Australopithecines. Hominid-like canines are present. These are low, blunt, and less projecting than the canines of all other known apes. Upper and lower incisors are larger than those of the Australopithecines, but are smaller than those of chimpanzees. This character state can thus be considered transitional between apes and Australopithecines. Additionally, the lower molars are broader than those of a comparably-sized ape. This trait, too, approaches the common hominid condition.

http://www.archaeologyinfo.com/ardipithecusramidus.htm

In my view bipedalism represents a huge adaptation. By huge I mean it really alters the gross anatomy in a variety of ways. One could imagine such dramatic changes happening twice, but it would be unusual. The most parsimonious explanation is that it happened once in the human lineage, and that explanation does not appear to be inconsitent with the fossil record.

So in short I am not bothered much by ramidus' dentition, not to the point of putting it off to the side. I don't know. There is A. kadabba or A. ramidus kadabba, depending upon your preference. I suppose it will be argued for another decade at least.

Check this out:

http://www.cmnh.org/collections/physanth/documents/60B62Early_Hominid_Dental_Evolution60B62.html

[aquart]

20. He was standing up and eating plants?

But had our tiny canines? Still sounds like a branch.

[gottaB]

24. Ardipithecus --> Australopithecus --> Homo

Could you clarify your objection to recognizing Ardipithecus as ancestral to the Australopithecines?

I googled into the middle of a discussion about cladistics that might be of interest. In particular, this statement (but see the whole thread):

An ancestral taxon will always be the sister taxon to its descendants.

An ancestral taxon will share some synapomorphies of the descendant clade, but not necessarily all of them.

An ancestral taxon will probably not have any autapomorphies of its own (matter of debate).

An ancestral taxon will appear stratigraphically earlier than its descendants, and (perferably) within the geographic range of the descendants.

For example, Ardipithecus ramidus shares the basal synapmorphies of the hominids and of hominines (i.e., it shares derived features with Homo, Paranthropus, and Australopithecus, but not Pan and Gorilla). It occurs earlier than the other hominines. It is a very, very strong candidate for an ancestor to all later members of the human line.

http://dml.cmnh.org/1995Oct/msg00911.html

So in the lingo of cladistics, are you seeing an autapomorphy in the ramidus dentition? I don't quite see that.

I also googled up a critique of the overreliance upon craniodental evidence in hypothetisized primate (esp. human) phylogenies. My own sensibility is not so rigorous--I simply feel that dental features tend to be overweighted, perhaps due to the relative abundance of fossil teeth. Abstract:

Cladistic analysis of cranial and dental evidence has been widely used to generate phylogenetic hypotheses about humans and their fossil relatives. However, the reliability of these hypotheses has never been subjected to external validation. To rectify this, we applied identical methods to equivalent evidence from two groups of extant higher primates for whom reliable molecular phylogenies are available, the hominoids and papionins. We found that the phylogenetic hypotheses based on the craniodental data were incompatible with the molecular phylogenies for the groups. Given the robustness of the molecular phylogenies, these results indicate that little confidence can be placed in phylogenies generated solely from higher primate craniodental evidence. The corollary of this is that existing phylogenetic hypotheses about human evolution are unlikely to be reliable. Accordingly, new approaches are required to address the problem of hominin phylogeny.

http://www.pnas.org/cgi/content/full/97/9/5003

[aquart]

25. LOVE the jargon.

Is Little Two Feet specialized for plants or not? if he's specialized then I don't see it. Unless you believe his descendents would abandon specialization for a broader diet? Is that common?

All he is is a current theory. I'll wait and see what we dig up tomorrow.

[gottaB]

26. How specialized? And what is the primitive form?

Folivory, frugivory and the like are somewhat relative terms when applied to homonoids, are they not? After all, I eats me spinach. We're not talking about ruminant primates here, which isn't to say that there aren't speciations based upon adaptations to new dietary niches. But I think that sort of explanatory focus can be overdone, and when based solely upon dentition it can be misleading.

What are the specific features you would regard as autapomorphies? Because to this point we are talking about an interpretation based upon certain features. What are those features? Thin enamel? So thick enamel is the primitive condition of the hominoids? Fair enough, but the group exhibits remarkable variation in enamel thickness. And I think that's true of the Miocene Hominidae, though thick enamel seems to be the primitive condition. But the question isn't really what's ancestral for Hominidae, but for hominins, i.e. humans and African apes and their ancestors, and perhaps more specifically the hominini, which excludes Gorilla, because the supposition here is that of all the apes, the chimps share the most recent common ancestor with humans. I don't believe that Ardipithecus' enamel is any thinner than Pan's. So it could be that we have a sequence towards folivory, separating the hominins from Pongo and then, with the emergence of the australopithecines, away from it again and even towards "superthick" enamel. Given the apparent mutablity of this trait among the Hominidae, and our closeness to the Chimpanzee, I find that an acceptable hypothesis, and am much more interested in what seems to be a radical departure from the orthograde posture of the hominoidea.

And even so, the evidence concerning the tooth enamel of Ardipithecus is not settled:

The dentition of Ardipithecus is ambiguous and has revived the argument of whether enamel thickness is a defining feature of hominid lineages. The Aramis specimens have thin molar enamel (18), whereas the other hominids show thick tooth enamel. Chimpanzees and gorillas have thin enamel, whereas orangutans show an intermediate thickness (33). Moreover, the Ardipithecus fossils from Middle Awash, which are 0.8–1.4 Myr older than those found at Aramis, have challenged the enamel characteristics attributed to the genus. The enamel characteristics of Ardipithecus ramidus kadabba are incomplete, but it has been proposed that the available broken and little-worn teeth suggest a molar enamel thickness similar to or slightly greater than those of the younger Aramis samples of Ar. ramidus (32). In any case, the significance of tooth enamel is not definitive, but should be considered together with tooth shape and consideration of diet.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=164648

Well, I respect the wait and see attitude, but my inclination here is to accept the genus as ancestral and have move disputes to the level of species or even subspecies.


Papers of interest cluttering my desktop:

http://www.cast.uark.edu/local/icaes/conferences/wburg/posters/pungar/satalk.htm

http://www.pnas.org/cgi/content/full/97/25/13506

http://www.naturalhub.com/opinion_right_food_for_the_human_animal_evolution_of_the_human_diet.htm

[kcwayne]

7. Your theory is refuted by the facts

The reasoning is that once a successful adaptation takes place, it's not likely to revert to a more primordial state and start again

This is clearly not true. The portion of the American population that voted for Bush is absolute proof that a branch of the human species, which I have named Republicanus Moronus is reverting to a primordial state.

[DeepModem Mom]

9. Good one!

[aquart]

21. Refuted on the hominid facts, too.

The reasoning is that once a successful adaptation takes place, it's not likely to revert to a more primordial state and start again


We're omnivorous. We can eat anything but grass. We REALLY can't eat grass. These babies are all plant? That's an adapted niche. Dentition is what we're left with, but there are lots of digestive adaptations that go with it. You're saying they left the vegetarian specialty niche and became generalists again??? Why? Something dead looked delicious? Ever try to tempt a bunny with a burger?

[TheWraith]

19. LOL, thank you

"Then you spend twenty years arguing about it, all the while new data are coming in."

I think that's a wonderful description of the scientific community. ;)

[roguevalley]

I love this stuff. God bless the scientists who tell us the truth. They

sound like an amazing species. They also sound like robust hominids. A nice transition species toward us.

[gottaB]

3. they also found foot bones

http://www.iol.co.za/index.php?set_id=1&click_id=31&art_id=qw1106158685324B252

http://news.bbc.co.uk/1/hi/sci/tech/4187991.stm

[aquart]

22. Any bunions?

[aquart]

23. A common ancestor six million years ago.

Six million years ago, the Ross Ice Shelf formed, pulling up the oceans and widening the beaches. No big deal, unless your species was adapting to the ocean, with subcutaneous fat, hairlessness, diving adaptations, and upright posture, but lacked the final adaptation: permeable skin. This meant that life was in the ocean, but fresh water had to be nearby. And it had been. For at least a million years. Now, it was getting farther and farther away. Finally, a choice had to be made, and we walked back onto the land to get that damned drink of water.

However, we still really like the beach.

[Nothing Without Hope]

4. Extremely cool! Hope this gets into the Science forum n/t

Interesting that they ate a plant-based diet and that the canines, which some apes use for dominance fights, were small. So they sound less like the relatively warlike chimpanzees and more like the make-love-not-war bonobos. At least that is a pleasant speculation. Perhaps there was a sort of Garden of Eden after all.

[Disturbed]

8. Why...

do so many so called Christians try so hard to refute that modern humans evolved from the sea and then from other species?

[DeepModem Mom]

10. If one believes in a Creator, it's a beautiful plan, binding all of life -

together, and not at all at odds with the Book of Genesis.

[Boosterman]

11. Anyone ever read Julian May?

A series of books called the Plioscene Epic or something like that. Anywhoo this ramidus was featured in it. Interesting. I love stuff like this. Let me know if they find any Golden Torcs.

[muriel_volestrangler]

14. That's ramapithecus in the Julian May books

at least, it is in the opening chapters. That now seems to be regarded as an orang utan ancestor, not human.

[Boosterman]

17. Your right

Doh. See kids thats why you dont do drugs.

[xchrom]

13. thank you.

love this stuff.

[jdonaldball]

15. They found the first Freepers!

[rucky]

16. God obviously put them there...

to test our faith in the "theory" of intelligent design.

[daleo]

18. Intelligent design can mean nothing more than directed evolution

This doesn't necessarily test anyone's faith in that idea, as there are many people who think God directed evolution. To them, this would just reveal the specifics of that direction.

It would test anyone's faith in the literal interpretation of Genesis, or any other sacred book or tradition, though. Literalists might say this little non-human fellow shared the ark with Noah, perhaps tending to the Jesus horses (dinosaurs).