Does Chimp x Gorilla Hybrid Exist?

Darren Naish at Tetrapod Zoology posted an interesting post about chimp x gorilla hybrid or the koolo-kamba. Do you think such hybrid exists or these individuals just display a range of "genetic variation" previously unknown to science? Check out Darren's post now, The Yaounde Zoo mystery ape and the status of the Kooloo-Kamba.

Japanese Macaques Floss Teeth

Earlier this year, I blogged about long-tailed macaques (Macaca fascularis) in Thailand using human hair as dental floss to clean their teeth. This behavior gives us an insight to culture transfer as mothers were observed teaching their infants how to floss repeatedly.

In Kyoto, Japan, a Japanese macaque (Macaca fuscata) name Chonpe was observed flossing her teeth using her own hair. She perfected not one, but three flossing techniques.

Lead author Jean-Baptiste Leca told Discovery News that dental flossing could have been a fortuitous yet "accidental byproduct of grooming." Leca, a post-doctoral fellow at Kyoto University's Primate Research Institute, explained that "Japanese macaques sometimes bite into hair or pull it through their mouths to remove external parasites." The hair might have become stuck in Chonpe's teeth, and as she drew the hairs out, "she may have noticed the presence of food remains attached to them". "The immediate reward of licking the food remains off the hair may have encouraged her to repeat the behavior for the same effect in the future," he added.

Chonpe is a middle ranking female with no children. Her only close kin is her mother and her sibling, therefore diffusion of knowledge is somewhat limited to her only sibling. She was observed flossing her teeth about four years ago and had only recently seen this behavior spread among Chonpe's troop. Chonpe was also observed her rolling small stones in her hand while attempting to remove a spine stuck in her palm, so she might be particular an innovative individual, the researchers added.

Chonpe flossing her teeth. Photo by Jean-Baptiste Lena on Discovery News.

Read about the article from Discovery News, Tidy Monkey Flosses Teeth and The first case of dental flossing by a Japanese macaque (Macaca fuscata): implications for the determinants of behavioral innovation and the constraints on social transmission on the journal Primates.

First Molars And Life History In Living African And Asian Apes

Another interesting paper on teeth, specifically the eruption of the first molar (M1), by Jay Kelley and Gary Schwartz from The Institute of Human Origins, Arizona State University (ASU) Since the emergence of M1 correlates with many life history attributes in extant primates, data from this paper can be used to compare the life history among extant primates and also extinct apes and hominins.

"Knowing the age when the first molar appears in the mouths of most primates allows researchers to predict a host of life history attributes, such as gestation length, age at sexual maturity, birth spacing and overall lifespan," said Schwartz. "Humans are unique among primates because our life histories are so slow and thus our molars emerge relatively late. Given that apes are our closest living relatives, understanding the broader context of when the characteristic slower development of humans evolved is of great interest."

"Like annual growth rings inside trees, the cells that produce teeth (both the enamel and underlying dentine) leave behind a trace of their presence, not as annual markers, but as growth lines that appear every day," said Kelley. By slicing the teeth in half, he and Schwartz were able to examine these incremental growth lines in ape individuals that died as their first molars were just erupting into their mouths. "Because teeth preserve this phenomenal internal chronometer, we were able to count up how many days it took the first molars to form," said Schwartz. "In apes and monkeys, first molars start forming very close to the time of birth. As the first molars were still erupting in our specimens, development was incomplete and the final growth line was laid down on the day those animals died. Therefore, by counting backwards from the final growth line to the day of birth, we determined their age at death and thus the age at which that molar was erupting." Using this novel approach, the two scientists were able to mark the age of the gorilla's first molar emergence at 3.8 years, nearly identical to that of a wild chimpanzee's. The orangutan's age at first molar emergence was surprisingly much later, at 4.6 years, which falls closer to the age of approximately 6 years in modern humans.

Read the article, Molars provide insight into evolution of apes, humans by ASU and Dental development and life history in living African and Asian apes from PNAS.

Natural Selection In Great Apes Favor Those With Teeth That Can Handle Fallback Foods

Great apes (orangutan, gorilla and chimpanzee) depend on their teeth to get them through tough times when food is scarce. Natural selection favor individuals with teeth that can process fallback foods, foods that are harder than the great apes normal diet of fruits. The evolution of the thickness of enamel in great apes reflects the mechanical demand of their diet.

"It makes sense if you think about it," says GWU's Paul Constantino. "When resources are scarce, that's when natural selection is highly active in weeding out the less fit, so animals without the necessary equipment to get through those tough times won't pass on their genes to the next generation."

Read the Science Daily article, Among Apes, Teeth Are Made for the Toughest Times and The Influence of Fallback Foods on Great Ape Tooth Enamel by Constantino et al. (2009).

Chimps Observed Using Tools To Cut Food Into Smaller Pieces

From BBC News, chimps from the Nimba Mountains of Guinea, Africa were observed using tools to chop up and reduce food into smaller bite-sized pieces.

Kathelijne Koops and William McGrew of the Leverhulme Centre for Human Evolutionary Studies, University of Cambridge (UK) with Tetsuro Matsuzawa from Kyoto University, Inundate (Japan) observed this behavior and published it on Primates. They found that these chimps use tools to process Treculia fruits, a large volley ball-shaped fruit that is hard and fibrous.

Abstract:

Wild chimpanzees (Pan troglodytes) are renowned for their use of tools in activities ranging from foraging to social interactions. Different populations across Africa vary in their tool use repertoires, giving rise to cultural variation. We report a new type of percussive technology in food processing by chimpanzees in the Nimba Mountains, Guinea: Treculia fracturing. Chimpanzees appear to use stone and wooden “cleavers” as tools, as well as stone outcrop “anvils” as substrate to fracture the large and fibrous fruits of Treculia africana, a rare but prized food source. This newly described form of percussive technology is distinctive, as the apparent aim is not to extract an embedded food item, as is the case in nut cracking, baobab smashing, or pestle pounding, but rather to reduce a large food item to manageably sized pieces. Furthermore, these preliminary data provide the first evidence of chimpanzees using two types of percussive technology for the same purpose.

Do chimpanzees (Pan troglodytes) use cleavers and anvils to fracture Treculia africana fruits? Preliminary data on a new form of percussive technology (free abstract).