Baltic hunter-gatherers began farming without influence of migration, ancient DNA suggests

Scientists extracted ancient DNA from a number of archaeological remains discovered in Latvia and the Ukraine, which were between 5,000 and 8,000 years old. These samples spanned the Neolithic period, which was the dawn of agriculture in Europe, when people moved from a mobile hunter-gatherer lifestyle to a settled way of life based on food production.

We know through previous research that large numbers of early farmers from the Levant (the Near East) — driven by the success of their technological innovations such as crops and pottery — had expanded to the peripheral parts of Europe by the end of the Neolithic and largely replaced hunter-gatherer populations.

However, the new study, published in the journal Current Biology, shows that the Levantine farmers did not contribute to hunter-gatherers in the Baltic as they did in Central and Western Europe.

The research team, which includes scientists from Trinity College Dublin, the University of Cambridge, and University College Dublin, says their findings instead suggest that the Baltic hunter-gatherers learned these skills through communication and cultural exchange with outsiders.

The findings feed into debates around the ‘Neolithic package,’ — the cluster of technologies such as domesticated livestock, cultivated cereals and ceramics, which revolutionised human existence across Europe during the late Stone Age.

Advances in ancient DNA work have revealed that this ‘package’ was spread through Central and Western Europe by migration and interbreeding: the Levant and later Anatolian farmers mixing with and essentially replacing the hunter-gatherers.

Holy chickens: Did Medieval religious rules drive domestic chicken evolution?

Now, an international team of scientists has combined DNA data from archaeological chicken bones with statistical modeling to pinpoint when these traits started to increase in frequency in Europe.

“Ancient DNA allows us to observe how genes have changed in the past, but the problem has always been to get high enough time resolution to link genetic evolution to potential causes. But with enough data and a novel statistical framework, we now have timings that are precise enough to correlate them with ecological and cultural shifts.” says Liisa Loog, the first author of the study.

To their surprise they found that this happened in High Middle Ages, around 1000 A.D. Intriguingly these strong selection pressures coincided with increasing urbanization and Christian edicts that enforced fasting and the exclusion of four legged animals from the menu. Could Medieval religious rules have increased the demand for poultry and thereby altered chicken evolution?

“With our new method we see that the time of selection coincides with an increase in the amount of chicken bones in the archaeological records across Northern Europe. Intriguingly, they also coincide with several socio-cultural changes, including a general increase in the popularity of Christian beliefs, new religious dietary rules and increase in urbanization (favoring traits that mean that animals could be kept in small spaces). We cannot say which one of these was most important but most likely a combination of all these factors affected selective pressures on European chickens and consequently their evolution.” Says author Anders Eriksson.

Mapping the migration of house shrews to illuminate historical trade networks

House shrews (Suncus murinus) are small mouse-like mammals that are widely distributed in southern parts of Asia, the islands of the western Indian Ocean, the Arabian Peninsula, and East Africa. They reached some regions by means of trade ships, thus expanding their habitats. Understanding their genetic origins could give an indication about the history of international maritime trade.

Past studies looked at the phylogeny (evolution and diversification) of the species in southern parts of Asia based on DNA polymorphisms. But these methods provided only a limited amount of information on how the species vary in different regions. The phylogeny of house shrews in other regions had not yet been investigated.

An international team from 8 countries, led by animal ecologist Satoshi Ohdachi at Hokkaido University, analyzed the phylogenetic information (including existing data) of 169 house shrews. These house shrews belonged to the species Suncus murinus and S. montanus from 44 locations. The team looked at the DNA sequence of mitochondrial cytochrome b gene to gain more precise genetic information and gain insight into the history of the animals’ migration routes.

They found that species from China, Japan, Vietnam and Indonesia descended from a common ancestor group, suggesting they originated from a single or a small number of locations. The results also showed that the shrew populations in Sri Lanka, Myanmar and Pakistan consisted of several genetic groups. The researchers say that some genetic groups in Sri Lanka and Myanmar may have come from other regions, while the origins of those in Pakistan were unclear.

What’s more, shrews in Zanzibar and Iran had very similar genetic traits despite the far distance between the two countries, indicating they had been physically moved from one country to the other. On the other hand, shrews in Madagascar and Grand Comore Island — located to the northwest of Madagascar — were genetically different from those in the French island Réunion — located to the east of Madagascar. Since the species in Réunion have similar traits to those in Sri Lanka, East Asia and Southeast Asia, the researchers suspect that the animal might have emigrated from these regions.

The findings suggest that people used to trade on a wider scale in the middle-modern ages around the 17th century AD than is currently thought, the team adds.

The researchers say that more samples of the house shrews are necessary, particularly from the Arabian Peninsula and India, in order to advance the understanding of the distribution and hybridization of the species. Further genetic information such as nuclear genes and morphological relationships should reveal genetic similarities and crossbreeding process in future investigations.