Gorillas, the Missionary Position, and Oral Sex

To steal a line from my blog buddy Duane, I find this Science Daily article abnormally interesting. Fair warning, this post is probably not work or child safe.

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Ileret Fossils and Primate Sperm Competition

From the Ileret article by Spoor et al:

The intraspecific variation of vault size in H. erectus, including KNM-ER 42700, is larger than in extant humans and chimpanzees, but smaller than in gorillas … This degree of variation may well imply that H. erectus showed marked sexual dimorphism, rather than the reduced levels that characterize the derived condition in H. sapiens …

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Gorillas Discovered Using Tools

In a study to be published in the November issue of PLOS Biology scientist announce they have discovered gorillas using tools. It has been known for quite some time that chimps use tools but no one had ever witnessed gorillas using tools in the wild. What makes this study so important, though, isn’t the fact that gorillas were using tools. It’s how they used them that made the study so important.
From New Scientist:

They saw a female gorilla nicknamed Leah attempting to wade through a pool of water created by elephants. After quickly sinking waist deep, she got out of the water and picked up a metre-long stick, says Breuer. She then re-entered the water and repeatedly prodded the stick ahead of her as if to test for depth. She advanced about 10 metres before returning to her wailing infant on the edge of the pool.

“It was exactly how you or I might have tested the depth of the water,” Breuer told New Scientist, by satellite phone from a forest clearing in Nouabalé-Ndoki.

A second example was also captured on film, when Efi, a gorilla from another group, used a stick to lean on for support while she foraged for food with her free hand. She then used the same stick as a bridge to help her cross a patch of swampy ground, says Breuer.


“Both cases seem related to the problems of locomotion in this swampy forest clearing,” says Breuer. This suggests that the tool use stems from an ecological need.

“Most great ape tool use is based around the retrieval of food,” notes Gillian Sebestyen-Forrester who studies gorilla communication at the University of Sussex, UK. But the “incredibly intuitive” behaviour of using a stick to test water depth is something quite different, she says.

The gorillas have understood in some capacity that they can extend their sensory experience and find out more about their environment by physically extending their bodies with an inanimate object,” she says. “This suggests that the gorilla is capable of some mental calculation and abstract thought.

Footprints of gorillas were found on branches in nearby clearings suggesting their use as bridges could be widespread, says Breuer.

From National Geographic News:

“The most fascinating thing about this observation is the similarity [to humans] with which the gorillas solve the problems in this particular habitat,” he said. “If you or me want to cross a swamp, we use the same solutions as gorillas.”

Like humans, the gorillas in the swampy clearing jump from one dry patch to another, walk over branches, swing from trees, and—as the observations and photographs now show—use tools.

Totally cool research!

Added Later: Abnormal Interests has a post on the gorillas as well.

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.
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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 Posted by Hello

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.
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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.