杏吧原创

One of history鈥檚 greatest journeys has been uncovered. People arrived on the islands of the Azores, in the central Atlantic, about 700 years earlier than thought.

鈥淲e can clearly identify evidence of early human impact on the islands before the official colonisation by the Portuguese,鈥� says at the Research Centre in Biodiversity and Genetic Resources in Ponta Delgada on S茫o Miguel Island in the Azores.

It isn鈥檛 certain who the first colonists were, but there is evidence that it was the Norse, ancestors of many modern Scandinavians 鈥� who also reached America.

The Azores is an archipelago about 1400 kilometres from the west coast of Europe with nine major islands. It is an autonomous region of Portugal, as Portuguese people colonised the area in the 1400s. The islands were known to Europeans a century before, but it was thought that nobody had previously lived there.

A team has spent a decade obtaining sediment cores from lakes on five of the islands. Such cores contain clues to past environments: pollen reveals which plants grew, and chemicals from faeces reveal which animals were present. The researchers claim they have clear evidence that people were present between 700 and 850 AD.

鈥淭he paper in fact summarises 10 years of really hard work,鈥� says at Geosciences Barcelona in Spain.

The evidence doesn鈥檛 come from archaeological remains like pottery because there are virtually none, says Raposeiro. Instead, the sediment cores held two kinds of traces of human presence.

The team found chemicals called stigmastanols and coprostanols, which are only found in the faeces of large herbivorous or omnivorous mammals. 鈥淭he islands were completely devoid of large mammals [prior to human settlement],鈥� says Giralt, so these chemicals can only have come from humans or animals they brought with them.

The team also found evidence of landscape changes. Tree pollen became rarer, suggesting people were cutting down trees 鈥� and soil run-off into the lakes increased at the same time.

The combination of all these lines of evidence adds up to 鈥渧ery strong evidence鈥� of human presence, says Raposeiro.

Without archaeological evidence there is no way to be sure who the first colonists were. But the team has performed climate simulations suggesting the prevailing winds came from the north-east. Domestic mice on the island also have genetic signatures from northern Europe.

鈥淭he best educated guess is it probably was the Norse,鈥� says Giralt. They possessed 鈥渢he skills and knowledge to sail the open seas鈥� and reached other Atlantic islands like Greenland and Iceland.