Know Your Primate: Pongo abelii

Order: Primates
Suborder: Haplorrhini
Family: Hominidae
Genus: Pongo
Species: Pongo abelii
Common Name: Sumatran Orangutan

The sumatran orang lives, obviously, in Sumatra – they are an endemic species. According several genetic analysis the Sumatran and Bornean populations diverged from each other about 1.5-1.7 MYA. They are largely frugivorous and spend most of their time in trees. On the ground they are quadrupedal. Unlike the chimpanzee, bonobo, and gorilla, they are not knuckle walkers they use their fist. Males tend to be solitary.

Schwartz, Molecules, and Morphology: There Can Be Only One

Connor MacLeod: How do you fight such a savage?
Ramirez: With heart, faith and steel. In the end there can be only one.

Rudolf Raff, in The Shape of Life, has an interesting discussion on attempts to iron out the relationships between lungfish, trout, and humans. On the surface it is quite simple. Lungfish are more closely related to humans than trout are. The lungfish has some adaptations to air breathing and one of the questions raised by the above relationship is whether these adaptations are homologous to those of tetrapods, or are they independent solutions to the same problem.

Enter the coelacanth. Morphological analyses of where the coelacanth fit into the above scheme yielded conflicting results as did various and sundry molecular analyses. One of the keys to solving the problem came in a mitochondrial DNA analysis that indicated a lungfish-tetrapod clade with coelacanths as the next branch and finally ray-finned fish. Assuming this is true, what can the fossil record and morphology tell us? This is where the story gets interesting. According to Raff, the lungfish, the coelacanth, and tetrapods are the few surviving members of a, once, more diverse rhipidistian clade. Early lungfish were deep sea forms that had gills, while modern forms are air breathers. Getting back to the question above, this means that the adaptations to air breathing are convergent with tetrapods. Raff concludes:

An especially striking demonstration of this conclusion is that the earliest know tetrapod, Acanthostega from the upper Devonian of Greenland has been shown by Coates and Clack to have had functional internal gills. It probably also possessed lungs, which were a primitive feature shared by bony fishes. Tetrapods have lost their gills in becoming more terrestrial. The first tetrapods thus convergently resembled modern lungfishes more than they resembled the earliest lungfishes. [page 162 – afarensis]

The molecular data wasn’t wrong, just incomplete due to missing taxa. In this case the taxa were missing due to extinction and this problem also, one thinks, affected the morphological analyses. I suspect that one could achieve the same affect by simply omitting some species from a morphological analysis. The point to take away from this is that in order to untangle the problem, both molecules and morphology were required. Not to mention more data. All to often, morphology and molecular analysis have been presented as being in some kind of zero sum conflict where there can be only one.

More on Schwartz and Orangutans

I haven’t had a lot of time for reading lately, so I am still in the process of reading the paper. I am just now at the critique of the molecular evidence for a chimp/human clade. Here is a longish quote:

Just When You Thought It Was Safe To Say Chimps And Humans Share A Common Ancestor

The Red Ape rears it’s ugly head. Here is a lengthy quote from PhysOrg.Com:

Schwartz and Grehan scrutinized the hundreds of physical characteristics often cited as evidence of evolutionary relationships among humans and other great apes-chimps, gorillas, and orangutans-and selected 63 that could be verified as unique within this group (i.e., they do not appear in other primates). Of these features, the analysis found that humans shared 28 unique physical characteristics with orangutans, compared to only two features with chimpanzees, seven with gorillas, and seven with all three apes (chimpanzees, gorillas, and orangutans). Gorillas and chimpanzees shared 11 unique characteristics.

Schwartz and Grehan then examined 56 features uniquely shared among modern humans, fossil hominids-ancestral humans such as
Australopithecus-and fossil apes. They found that orangutans shared eight features with early humans and Australopithecus and seven with Australopithecus alone. The occurrence of orangutan features in Australopithecus contradicts the expectation generated by DNA analysis that ancestral humans should have chimpanzee similarities, Schwartz and Grehan write. Chimpanzees and gorillas were found to share only those features found in all great apes.

Schwartz and Grehan pooled humans, orangutans, and the fossil apes into a new group called “dental hominoids,” named for their similarly thick-enameled teeth. They labeled chimpanzees and gorillas as African apes and wrote in Biogeography that although they are a sister group of dental hominoids, “the African apes are not only less closely related to humans than are orangutans, but also less closely related to humans than are many” fossil apes.

The researchers acknowledge, however, that early human and ape fossils are largely found in Africa, whereas modern orangutans are found in Southeast Asia. To account for the separation, they propose that the last common human-orangutan ancestor migrated between Africa, Europe, and Asia at some point that ended at least 12 million to 13 million years ago. Plant fossils suggest that forests once extended from southern Europe, through Central Asia, and into China prior to the formation of the Himalayas, Schwartz and Grehan write, proposing that the ancestral dental hominoid lived and roamed throughout this vast area; as the Earth’s surface and local ecosystems changed, descendant dental hominoids became geographically isolated from one
another.

This research is being published in the Journal of Biogeography and can be found here (and is open access, so the link opens the pdf)

I haven’t had a chance to read it yet, but here is a cautionary story about dental apes and such (open access as well, so the link opens a pdf).

I haven’t had a chance to read it yet and will have more to say when I have.

The Centre for Orangutan Protection Does a Good Deed

They actually do many good deeds, but this one is on video. National Geographic has the story – and the video.

New Population of Orangutangs Discovered

According to National Geographic a new, and large, population of orangutangs has been discovered in the Indonesian sector of Borneo:

Von Economo Neurons and Hominoids

I mentioned a few weeks ago that I would have more to say about primates, brain evolution, and life history. I still plan on exploring that in future posts, but wanted to mention this interesting item that deserves a post of its own.

Save the Orangutan: A Comment From Michelle Desilets

I don’t often move a comment from the comment section to a post of its own, but I am doing so with the following comment for two reasons. First, it is a heartfelt and articulate plea on behalf of orangutans. So heartfelt and well written, in fact, that it brought shivers to my spine and I felt it deserved wider notice. Second, it got caught in my spam queue, where it went unnoticed for a day. The comment is from Michelle Desilets, Founding Director Borneo Orangutan Survival Foundation UK. You can find out more about Michelle’s organization at Borneo Orangutan Survival Foundation UK I hope it moves you to action.

Orangutan Populations Declining

Science News Daily has a report on declining Orangutan populations in Sumatra and Borneo:

A. afarensis vs. the Apes

All pictures: Top left A. afarensis Top right: P. troglodytes. Bottom left: P. pygmaeus Bottom right: G. gorilla

One of the most aggravating things one can hear, if one has any training in paleoanthropology, is that the australopithicines were nothing but glorified apes. So let’s study the issue (hey, I have to justify the name of this blog, okay! Which means more hominids.) The first set of pictures below is a frontal view of A. afarensis, a chimp, an orang and a gorilla. The first thing you witll notice is how robust the apes are. There are strong brow ridges, in the case of ornag and gorilla there are large crests. Notice also the size of the canines in the three apes. The roots of the canines form canine juga which are very pronounced in the apes, less so in A. afarensis. The canine juga fade into anterior pillars. Overall, there are a lot of features related to the size of the teeth and the need for for muscles to work the teeth. However, the anterior pillars, canine juga and large canines are less apparent in A. Afarensis. Note also that in A. afarensis the zygomatics (the cheekbones) start much higher up than in apes. One other thing deserves notice. You will note in A. afarensis that you can see part of the brain case (this is an artifact of photography in the chimp picture). A. Afarensis has an encephalization quotient (a measure of relative brain size) of around 3.1 compared to 2.6 in chimps. Basically this is the beggining of the cranial expansion characteristic of hominid evolution.


In lateral view quite a few differences become apparent. First, note the steeper line running from the (reduced) supraorbital torus to the top of the skull in A. afarensis. In chimps it is more rounded. In orangs and gorillas it is occupied by a massive saggital crest. Note, also, how robust the supraorbital torus is in chimps, orangs and gorillas. It is somewhat reduced in A. afarensis. Note againe that the zygomatics start higher up on the cheeks than in the apes. The apes have pronounced midfacial prognathism (snout sticking out) – A. afarensis is prognathic but not to the same degree. We are starting to see the reduction in prognathism characteristic of Homo sapiens. You can also see the large canines and canine juga in the apes. Towards the rear of the A. afarensis skull, where the zygomatic (cheekbone) joins the back of the skull you can see a small nuchal crest starting (actually a compound tempornuchal crest but lets not complicate things). The nuchal crest, as well as the sagital crest in orangs and gorillas, are areas of muscle attachment. Basically, the larger the crest the larger the muscle that attached to it. The nuchal area (basically the back area underneath the skull) is long and steep in A. afarensis. The ear (external auditory meatus) is similar in all four species. Finally, the ascending ramus of the mandible is wide and tall in all four species. This, along with the sagital and nuchal crests, as well as the anterior pillars are adaptations for large chewing forces.

lateral view 2

In basilar view, the first thing to notice is how long, straight and boxey looking the dental arcade is an chimps and gorillas (unfortunately I could not find a basilar view of an orang without the manible). In A. afarensis the dental arcade is somewhat rounded. Note there is a canine diastema (gap between the second incisor and canine) in A. afarensis and the apes. This is reduced in A. afarensis. Akthough you can’t see it to well A. afarensis has the begginings of a bicuspid premolar. Apes don’t. Also note that the incisors are more similar in size in A. afarensis (although not as much as in humans. The mandibular fossa (the area where the condyles of the mandible articulate with the skull – see the orang skull with attached manible) is flat in apes but has the begginings of human morphology. Finally, the foramen magnum (where the spinal cord enters the skull) is placed more underneath the skull in A. afarensis. Whereas it is not nearly so in apes. This is a trait characteristic of bipedal locomotion.



Basically, what we have in A. afarensis is a perfect transitional fossil. Although, really there where several transitional fossils between apes and humans (A better way of saying it is that there is a continua of species leading from a comon ancestor, between apes and humans, to humans). I think it is a common misunderstanding that there is only one transitional fossil between apes and humans. First, becuse apes didn’t evolve into humans, rather apes and humans had a common ancestor. The lineage then split with one, or more, lines evolving into apes and the other evolving into humans. That being the case, you can see a continua of species starting from, say, Ardipithicus ramidus and running through the various australopithicines (leaving the robust forms aside for the moment) to early homo and from there to anatomically modern humans. A. afarensis is one of these transitional species and is definatel not an ape.