Addomesticamento del Cane

Addomesticamento del Cane: forse si sviluppò a partire dalla capacità del Lupo di apprendere da altri individui.

Domestication of dogs may have elaborated on pre-existing capacity of wolves to learn from humans

I lupi sono in grado di apprendere - osservando gli esseri umani e i componenti del branco - dove sia nascosto il cibo e sono in grado di distinguere dove si finge solamente di nasconderlo, secondo un resoconto apparso per la prima volta sulla rivista ad accesso libero  Frontiers in Psychology. Questi risultati implicano anche che quando i nostri antenati iniziarono l'addomesticamento del cane, forse interagirono con una preesistente capacità dei lupi di apprendere da altri individui, che non fossero necessariamente componenti del branco...

Wolves can learn from observing humans and pack members where food is hidden and recognize when humans only pretend to hide food, reports a study for the first time in the open-access journal Frontiers in Psychology. These findings imply that when our ancestors started to domesticate dogs, they could have built on a pre-existing ability of wolves to learn from others, not necessarily pack members.

The researchers conclude that the ability to learn from other species, including humans, is not unique to dogs but was already present in their wolf ancestors. Prehistoric humans and the ancestors of dogs could build on this ability to better coordinate their actions [Credit: Wolf Science Center]

Un articolo recentemente pubblicato sulla rivista Science suggerisce che l'uomo addomesticasse il cane circa 18000 anni fa, possibilmente a partire di una popolazione di lupi grigi che ormai è estinta. Ma resta ignoto quanta parte dell'abilità dei cani di comunicare con gli uomini derivi da precedenti caratteristiche degli antenati lupi, piuttosto che da tratti specifici e di nuova comparsa stimolati dall'addomesticamento. 

In uno studio recente,  ricercatori del Messerli Institute dell'Università di Medicina Veterinaria di Vienna ( Friederike Range e Zsófia Virányi) hanno condotto indagini per capire se  cani e lupi possano osservare un particolare soggetto "dimostratore", a loro familiare, (un essere umano oppure un cane addestrato) in modo da imparare da lui dove cercare il cibo in un particolare terreno.

Sia i lupi che i cani presentano da due a quattro volte più possibilità di rinvenire il cibo dopo avere osservato il 'dimostratore' che lo nascondeva, invece di basarsi solamente sull'olfatto. In più, essi mostravano di non cercare affatto il cibo laddove il dimostratore aveva solo finto di nasconderlo, dimostrando in tal modo di avere osservato molto attentamente.

I lupi si mostravano meno disposti a seguire il cane dimostratore verso il cibo nascosto. Questo non dimostrerebbe scarsa attenzione dei lupi verso i cani, bensì - almeno credono i ricercatori - la percezione della scarsa appetibiltà del cibo da parte dei cani dimostratori stessi, che rendeva pertanto meno ricercato il premio.

Tutto l'esperimento proverebbe che le preesistenti capacità d'apprendimento dei lupi antenati, anche da altre specie,si sarebbero dimostrate preziose anche durante l'addomesticamento da parte dell'uomo preistorico.

A paper published recently in the journal Science suggested that humans domesticated dogs about 18 thousand years ago, possibly from a European population of grey wolves that is now extinct. But it remains unknown how much the ability of dogs to communicate with people derives from pre-existing social skills of their wolf ancestors, rather than from novel traits that arose during domestication.

In a recent study, Friederike Range and Zsófia Virányi from the Messerli Research Institute at the University of Veterinary Medicine Vienna investigated if wolves and dogs can observe a familiar "demonstrator" -- a human or a specially trained dog -- to learn where to look for food within a meadow. The subjects were 11 North American grey wolves and 14 mutts, all between 5 and 7 months old, born in captivity, bottle-fed, and hand-raised in packs at the Wolf Science Center of Game Park Ernstbrunn, Austria.

The wolves and dogs were two to four times more likely to find the snack after watching a human or dog demonstrator hide it, and this implies that they had learnt from the demonstration instead of only relying on their sense of smell. Moreover, they rarely looked for the food when the human demonstrator had only pretended to hide it, and this proves that they had watched very carefully.

The wolves were less likely to follow dog demonstrators to hidden food. This does not necessarily mean that they were not paying attention to dog demonstrators: on the contrary, the wolves may have been perceptive enough to notice that the demonstrator dogs did not find the food reward particularly tasty themselves, and so simply did not bother to look for it.

The researchers conclude that the ability to learn from other species, including humans, is not unique to dogs but was already present in their wolf ancestors. Prehistoric humans and the ancestors of dogs could build on this ability to better coordinate their actions.
Source: Frontiers [December 03, 2013]

la Vita si ferma a -20°C.

Lowest temperature for life discovered

Scientists have pinpointed the lowest temperature at which simple life can live and grow  The study, published in PLoS One, reveals that below -20 °C, single-celled organisms dehydrate, sending them into a vitrified – glass-like – state during which they are unable to complete their life cycle.

Algae and bacteria in Scanning Electron Microscope [Credit: WikiCommons]

The researchers propose that, since the organisms cannot reproduce below this temperature, -20 °C is the lowest temperature limit for life on Earth.

Scientists placed single-celled organisms in a watery medium, and lowered the temperature. As the temperature fell, the medium started to turn into ice and as the ice crystals grew, the water inside the organisms seeped out to form more ice. This left the cells first dehydrated, and then vitrified. Once a cell has vitrified, scientists no longer consider it living as it cannot reproduce, but cells can be brought back to life when temperatures rise again. This vitrification phase is similar to the state plant seeds enter when they dry out.

'The interesting thing about vitrification is that in general a cell will survive, where it wouldn't survive freezing, if you freeze internally you die. But if you can do a controlled vitrification you can survive,' says Professor Andrew Clarke of NERC's British Antarctic Survey , lead author of the study. 'Once a cell is vitrified it can continue to survive right down to incredibly low temperatures. It just can't do much until it warms up.'

More complex organisms are able to survive at lower temperatures because they are able to control the medium the cells sit in to some extent.

Bacteria, unicellular algae and unicellular fungi – of which there are a huge amount in the world-are free-living because they don't rely on other organisms ,' Clarke explains.

'Everything else, like trees and animals and insects, has the ability to control the fluid that surrounds their internal cells. In our case it's blood and lymph. In a complicated organism the cells sit in an environment that the organism can control. Free-living organisms don't have this; if ice forms in the environment they are subject to all the stresses that implies.'

If a free-living cell cools too quickly it would be unable to dehydrate and vitrify; instead it would freeze and wouldn't survive.

This goes some way towards explaining why preserving food using deep freezing works. Most fridge freezers operate at a temperature of nearly -20 °C . This study shows that this temperature works because moulds and bacteria are unable to multiply and spoil food.

'We were really pleased that we had a result which had a wider relevance, as it provided a mechanism for why domestic freezers are as successful as they are,' Clarke says.

The scientists believe that the temperature limit they have discovered is universal, and below -20°C simple forms of unicellular life can grow on Earth. During the study they looked at a wide range of single-celled organisms that use a variety of different energy sources, from light to minerals, to metabolise. Every single type vitrified below this temperature.

'When you have a single-celled organism and cool it until ice forms in the external medium, in every case we looked at the cells dehydrated and then vitrified between -10°C and -25 °C. There were no exceptions,' explains Clarke. 

Author: Harriet Jarlett  | Source: PlanetEarth Online [August 21, 2013]