Wednesday, June 17, 2009

Right handedness of Homo heidelbergensis from Sima de los Huesos (Atapuerca, Spain) 500.000 years ago

Handedness is a product of brain specialization, and so it has been subject of evolution. Handedness in living humans is well known and shows the highest degree of manual specialization. Studies on hand laterality in non human primates, particularly in chimpanzees are still controversial, since the results vary depending on features such as the tasks performed and the environment where the individuals live. Determining when handedness installed in human evolution has been traced back through several methods, including paleoneurological analyses, stone tool flaking, zooarchaeological studies and the dental wear analyses, being the latest the most reliable one.

Incisors of Homo heidelbergensis from Sima de los Huesos site (Spain) - Equipo Investigación Atapuerca (EIA)

Here we report an experimental and paleoanthropological study about the hand laterality of a sample of 28 hominids from Sima de los Huesos (Atapuerca, Spain), dated at about 500.000 years ago, and we compare the results with the dental microwear analyzed in other fossil samples such as Krapina (Croatia), as well as modern traditional societies.

Results point that European Middle Pleistocene Homo heidelbergensis was already as right-handed as modern populations.

Fore more information:

Article "Right handedness of Homo heidelbergensis froma Sima de los Huesos (Atapuerca, Sapin) 500.000 years ago", Lozano, M; Mosquera, M; Bermúdez de Castro, JM; Arsuaga, JL and Carbonell, E.

Evolution and Human Behaviour (in press, avalaible on line)


Marina Lozano
Catalan Institute of Human Paleoecology and Social Evolution (IPHES)
Marina Mosquera Area of Prehistory (Rovira i Virgili University)

Monday, June 08, 2009

Optimising the anaglyph technique to study ancient and forensic bloodstains

Anaglyphy is a stereoscopic technique based on the superimposition of two images of the same view, taken from slightly different angles as well as in two different colours. This superimposition produces a depth effect when viewed through glasses having one red and one green, blue or cyan lens acting as a colour filter. A study (reported in the journal Micron, vol. 40 (3), pp. 409–412), carried out by Policarp Hortolà, senior researcher & lecturer of the Rovira i Virgili University, and collaborator of Catalan Institute of Human Palaeoecology and Social Evolution (IPHES), has shown that digital anaglyphy provides a simple and feasible method to improve the relief effect of SEM micrographs of bloodstains.

Anaglyph obtained from two SEM micrographs of a human bloodstain. Suitable 3D glasses must be used for a correct viewing of the image

First, a chert fragment was smeared with human blood. Then, the specimen was coated with gold and examined via secondary electrons by a scanning electron microscope (SEM). After obtaining SEM micrographs, anaglyphs were digitally generated using a free software for making anaglyphs and other 3D images. The best results were obtained using pairs of SEM micrographs acquired at 10° differing angle and at SEM-stage tilts that were symmetric from the horizontal plane. The relief effect was more accentuated at low magnification. The most ergonomic colour combination for viewing bloodstain anaglyphs was red–cyan.

As a first consequence of this improvement, the results obtained in this study revealed that the outermost erythrocyte layer of a thin bloodstain – coinciding, in general, with the smear surface – can be much more uneven than that previously suggested by customary SEM micrographs.

For more information:

Article "Using digital anaglyphy to improve the relief effect of SEM micrographs of bloodstains"

Micron, 40: 409-412


Policarp Hortolà

Area of Prehistory (Rovira i Virgili University) & Catalan Institute of Human Palaeoecology and Social Evolution (IPHES)

Friday, February 27, 2009

Manual Laterality for Simple Reaching and Bimanual Coordinated Task in Naturalistic Housed Pan troglodytes

The study of manual lateralization in chimpanzees is today a subject of renewed interest. Currently there is no consensus whether manual dominance does or does not exist at a species level, mainly for wild and semicaptivity populations. The aim of this study was to evaluate the manual laterality in a group of chimpanzees living in an intermediate setting (semicaptivity) through two tasks: one simple and unimanual (simple reaching) and the other complex and bimanual (tube task).

Charly at a tube-task session - Miquel Llorente / IPHES

In simple reaching the hand is used to gather food with precision, and the type of grip and the posture are all evaluated. The tube task evaluates the hand used to extract food from the tube and the method of extraction (digital or instrumental). Through the handedness index we observed that the individuals show clear and strong individual lateralization for both tasks, particularly for the tube task (100%), but also for simple reaching (86%). Anyway, we did not detect population preferences for any of the tasks. However, considering both tasks jointly (multiple evaluation) it has been possible to detect for the first time a skilled manual dominance at the population level in semicaptive chimpanzees.

As a conclusion, our chimpanzee sample displays right handedness at population level when considering multitask values. This is the first time that data on handedness are recorded at population level in a chimpanzee sample living in an intermediate and naturalistic setting. Former researches on hand laterality with the same sample gave negative results (Mosquera et al. 2007), but that study was focused in unimanual and spontaneous tasks. Therefore, results of the current work point to three factors as decisive to force the displaying of hand laterality in chimpanzees: bimanual coordination, tool use, and grip precision.

References cited:
Mosquera, M., Llorente, M., Riba, D., Estebaranz, F., González, M., Lorenzo, C., Sanmartí, N., Toll, M., Carbonell, E., & Feliu, O. (2007). Ethological study of manual laterality in naturalistic housed chimpanzees (Pan troglodytes) from the Mona Foundation Sanctuary (Girona, Spain). Laterality, 12, 19–30.

For more information:

Article "Manual Laterality for Simple Reaching and Bimanual Coordinated Task in Naturalistic Housed Pan troglodytes"

International Journal of Primatology, 30: 183-197.


Marina Mosquera

Àrea Prehistoria Universitat Rovira i Virgili de Tarragona - IPHES (Institut Català de Paleoecologia Humana i Evolució Social)