Related Experiment Video
Updated: Aug 5, 2026
08:02
Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton
Published on: May 7, 2016
Variation in tooth morphology of Pongo pygmaeus
1Primate Research Institue, Kyoto University, Japan. uchida@bun.L.chiba-u.ac.jp
Journal of Human Evolution
|February 19, 1998
Summary
Sexual and population differences in Pongo pygmaeus postcanine morphology were studied. Cusp area proportions showed significant population-specific variations, even between Bornean groups separated by the Kapuas River.
Area of Science:
- Primatology
- Paleontology
- Anthropology
Background:
- Pongo pygmaeus (orangutan) postcanine morphology offers insights into evolutionary adaptations.
- Understanding variations is crucial for phylogenetic and biogeographic analyses.
Purpose of the Study:
- To investigate sexual, populational, and subspecific variations in Pongo pygmaeus postcanine morphology.
- To specifically analyze cusp area proportions in orangutan molars.
Main Methods:
- Morphological analysis of Pongo pygmaeus postcanine teeth.
- Comparative study focusing on cusp area proportions.
Main Results:
- Minimal sexual dimorphism observed in molar shapes.
- Cusp area proportions exhibit significant population-specific differences.
- Inter-population variations in Borneo are as pronounced as inter-subspecies differences (Borneo vs. Sumatra).
Conclusions:
- Cusp area proportions in Pongo pygmaeus are key indicators of population-specific adaptations.
- The Kapuas River acts as a significant biogeographic barrier influencing orangutan dental morphology.
Related Concept Videos
01:46Types of Selection
Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...
01:23Phylogeny
Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon (singular). Taxa (plural) can span different levels of the evolutionary hierarchy. For instance, the group containing all birds is a taxon (comprising the class Aves), and the group of all species of daisies (the genus Bellis) is a taxon. Phylogenies can likewise include just one genus (i.e., depict species relationships) or span an entire...
01:51Lampbrush Chromosomes
In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...
01:15Teeth
The formation of teeth, also known as odontogenesis, is a complex process that begins in utero, around the sixth week of embryonic development. There are three stages to this process: the bud stage, the cap stage, and the bell stage.
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...
01:21Tooth Anatomy
The human tooth enables us to eat a variety of foods, speak clearly, and even aid in shaping our faces. Teeth are composed of various elements that work together. Here's a detailed look at the anatomy of a human tooth.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.