Evidence Of Navigation Research Articles

Un état des connaissances sur la navigation préhistorique en Europe atlantique

Que ce soit en mer ou dans les eaux intérieures, l’usage des moyens de transport nautiques par les populations préhistoriques ne se laisse pas aisément approcher. On doit en effet composer avec la grande rareté des principaux témoins : les embarcations sur lesquelles se sont effectuées les navigations. Malgré cette limite posée par la documentation, il est possible de préciser certains aspects chronologiques et fonctionnels à partir des sources indirectes qui nous sont accessibles dans l’enregistrement archéologique et en analysant les témoins directs que constituent les rares épaves, équipements et représentations qui nous sont parvenus. Pour ce qui concerne l’Europe atlantique, sur laquelle est centrée cette étude, nous pouvons aussi préciser quelques données concernant le rythme et les contraintes qui s’y appliquaient sans doute en nous appuyant sur la connaissance des milieux dans lesquels évoluaient les embarcations, et auxquels elles étaient fortement soumises en termes d’adaptation de leur système technique. L’analogie diachronique avec l’histoire plus récente de ces moyens de transport peut aussi nous ouvrir quelques pistes quant aux modalités de déplacement plausibles. Si la revue de tous ces faisceaux d’indices ne permet pas de définir la nature exacte de toutes les embarcations alors utilisées, on peut cependant ouvrir et délimiter le champ des possibles. Il inclut une large variété typologique réalisée à partir de perches, de fûts, de planches et de fagots végétaux, parfois revêtus de peaux tendues, composant différents types d’architectures : radeaux, pirogues, bateaux de peaux, bateaux de planches assemblées. À l’exception du dernier type, qui n’apparaît vraisemblablement que vers la fin de la Préhistoire européenne, ces dispositifs ont pu, pour la plupart, naviguer au même moment et parfois sur les mêmes voies d’eaux, mais probablement pas pour les mêmes usages.

Billfish foraging along the northern coast of Chile during the Middle Holocene (7400–5900 cal BP)

Early maritime adaptation is well known from eastern South America; however, evidence for navigation and large marine fish exploitation, indicative of skilled foraging techniques, remains scarce. In the Atacama Desert, north central Chile, coastal archaeological sites show that during the Middle Holocene people relied mostly on marine resources. However, evidence from one of the shell middens (Zapatero – 7400–5900cal BP) indicates that not only were shallow waters and marine mammals exploited, but that a dedicated fishery for large pelagic fish (mainly billfish) existed; with indications suggesting that large swordfish, weighing up to 300kg, were being caught and brought back complete to the settlement. Although the peculiar topographic and oceanographic features of the area probably allowed pelagic fish to come well inshore, this is still the oldest evidence worldwide for such a fishery. These results provide new insights into maritime adaptation and seafaring along the Chilean coast from as early as the sixth millennium BCE.

Spatial Reorientation by Geometry in Bumblebees

Human and non-human animals are capable of using basic geometric information to reorient in an environment. Geometric information includes metric properties associated with spatial surfaces (e.g., short vs. long wall) and left-right directionality or ‘sense’ (e.g. a long wall to the left of a short wall). However, it remains unclear whether geometric information is encoded by explicitly computing the layout of surface geometry or by matching images of the environment. View-based spatial encoding is generally thought to hold for insect navigation and, very recently, evidence for navigation by geometry has been reported in ants but only in a condition which does not allow the animals to use features located far from the goal. In this study we tested the spatial reorientation abilities of bumblebees (Bombus terrestris). After spatial disorientation, by passive rotation both clockwise and anticlockwise, bumblebees had to find one of the four exit holes located in the corners of a rectangular enclosure. Bumblebees systematically confused geometrically equivalent exit corners (i.e. corners with the same geometric arrangement of metric properties and sense, for example a short wall to the left of a long wall). However, when one wall of the enclosure was a different colour, bumblebees appeared to combine this featural information (either near or far from the goal) with geometric information to find the correct exit corner. Our results show that bumblebees are able to use both geometric and featural information to reorient themselves, even when features are located far from the goal.

Models of Pacific salmon orientation and navigation on the open ocean

The assumptions and conclusions of a recent model of Pacific salmon ( Oncorhynchus spp.) migration at sea ( Jamon, 1990 , J. theor. Biol. 143 , 197–213.) are evaluated in light of empirical information on migratory behavior. The fundamental assumption underlying the model (random direction of movement) is incorrect; salmon movements at sea and in coastal waters are not random. A result of the simulation (salmon encountering the coast over a wide area) is contrary to fact. Finally, the data set used to evaluate the success of the model at simulating actual salmon homing (recovery in coastal waters of salmon tagged on the open ocean) was misinterpreted. While there is no experimental evidence for navigation by salmon at sea, any simulation must be consistent with the large body of information indicating rapid, directed movement and little spatial or temporal error in migration.