Tracking Five Millennia of Horse Management with Extensive Ancient Genome Time Series.

Horse domestication revolutionized warfare and accelerated travel, trade, and the geographic expansion of languages. Here, we present the largest DNA time series for a non-human organism to date, including genome-scale data from 149 ancient animals and 129 ancient genomes (≥1-fold coverage), 87 of which are new. This extensive dataset allows us to assess the modern legacy of past equestrian civilizations. We find that two extinct horse lineages existed during early domestication, one at the far western (Iberia) and the other at the far eastern range (Siberia) of Eurasia. None of these contributed significantly to modern diversity. We show that the influence of Persian-related horse lineages increased following the Islamic conquests in Europe and Asia. Multiple alleles associated with elite-racing, including at the MSTN "speed gene," only rose in popularity within the last millennium. Finally, the development of modern breeding impacted genetic diversity more dramatically than the previous millennia of human management.

Bayesian Skyline Plots disagree with range size changes based on Species Distribution Models for Holarctic birds.

During the Quaternary, large climate oscillations impacted the distribution and demography of species globally. Two approaches have played a major role in reconstructing changes through time: Bayesian Skyline Plots (BSPs), which reconstruct population fluctuations based on genetic data, and Species Distribution Models (SDMs), which allow us to back-cast the range occupied by a species based on its climatic preferences. In this paper, we contrast these two approaches by applying them to a large data set of 102 Holarctic bird species, for which both mitochondrial DNA sequences and distribution maps are available, to reconstruct their dynamics since the Last Glacial Maximum (LGM). Most species experienced an increase in effective population size (Ne , as estimated by BSPs) as well as an increase in geographical range (as reconstructed by SDMs) since the LGM; however, we found no correlation between the magnitude of changes in Ne and range size. The only clear signal we could detect was a later and greater increase in Ne for wetland birds compared to species that live in other habitats, a probable consequence of a delayed and more extensive increase in the extent of this habitat type after the LGM. The lack of correlation between SDM and BSP reconstructions could not be reconciled even when range shifts were considered. We suggest that this pattern might be linked to changes in population densities, which can be independent of range changes, and caution that interpreting either SDMs or BSPs independently is problematic and potentially misleading.

Did Going North Give Us Migraine? An Evolutionary Approach on Understanding Latitudinal Differences in Migraine Epidemiology.

This commentary discusses a recent publication by evolutionary biologists with strong implications for migraine experts. The Authors showed that a gene polymorphism associated with migraine gave our ancestors an evolutionary advantage when colonizing northern, and thus colder, territories. They then highlight that the prevalence of migraine may differ among countries because of climatic adaptation. These results may prove useful in planning both epidemiological and physiological studies in the field of migraine.

Evolutionary Patterns and Processes: Lessons from Ancient DNA.

Ever since its emergence in 1984, the field of ancient DNA has struggled to overcome the challenges related to the decay of DNA molecules in the fossil record. With the recent development of high-throughput DNA sequencing technologies and molecular techniques tailored to ultra-damaged templates, it has now come of age, merging together approaches in phylogenomics, population genomics, epigenomics, and metagenomics. Leveraging on complete temporal sample series, ancient DNA provides direct access to the most important dimension in evolution­time, allowing a wealth of fundamental evolutionary processes to be addressed at unprecedented resolution. This review taps into the most recent findings in ancient DNA research to present analyses of ancient genomic and metagenomic data.

The female ancestor's tale: Long-term matrilineal continuity in a nonisolated region of Tuscany.

OBJECTIVES: With the advent of ancient DNA analyses, it has been possible to disentangle the contribution of ancient populations to the genetic pool of the modern inhabitants of many regions. Reconstructing the maternal ancestry has often highlighted genetic continuity over several millennia, but almost always in isolated areas. Here we analyze North-western Tuscany, a region that was a corridor of exchanges between Central Italy and the Western Mediterranean coast. MATERIALS AND METHODS: We newly obtained mitochondrial HVRI sequences from 28 individuals, and after gathering published data, we collected genetic information for 119 individuals from the region. Those span five periods during the last 5,000 years: Prehistory, Etruscan age, Roman age, Renaissance, and Present-day. We used serial coalescent simulations in an approximate Bayesian computation framework to test for continuity between the mentioned groups. RESULTS: Our analyses always favor continuity over discontinuity for all groups considered, with the Etruscans being part of the genealogy. Moreover, the posterior distributions of the parameters support very small female effective population sizes. CONCLUSIONS: The observed signals of long-term genetic continuity and isolation are in contrast with the history of the region, conquered several times (Etruscans, Romans, Lombards, and French). While the Etruscans appear as a local population, intermediate between the prehistoric and the other samples, we suggest that the other conquerors-arriving from far-had a consistent social or sex bias, hence only marginally affecting the maternal lineages. At the same time, our results show that long-term genealogical continuity is not necessarily linked to geographical isolation.

Patrilineal populations show more male transmission of reproductive success than cognatic populations in Central Asia, which reduces their genetic diversity.

OBJECTIVE: The extent to which social organization of human societies impacts the patterns of genetic diversity remains an open question. Here, we investigate the transmission of reproductive success in patrilineal and cognatic populations from Central Asia using a coalescent approach. METHODS: We performed a study on the mitochondrial DNA (mtDNA) and Y chromosome polymorphism of patrilineal and cognatic populations from Central Asia. We reconstructed the gene genealogies in each population for both kind of markers and inferred the imbalance level of these genealogies, a parameter directly related to the level of transmission of reproductive success. RESULTS: This imbalance level appeared much stronger for the Y chromosome in patrilineal populations than in cognatic populations, while no difference was found for mtDNA. Furthermore, we showed that this imbalance level correlates negatively with Y-chromosomal, mtDNA, and autosomal genetic diversity. CONCLUSIONS: This shows that patrilineality might be one of the factors explaining the male transmission of reproductive success, which, in turn, lead to a reduction of genetic diversity. Thus, notwithstanding the fact that our population genetic approach clearly shows that there is a strong male-biased transmission of reproductive success in patrilineal societies, it also highlights the fact that a social process such as cultural transmission of reproductive success could play an important role in shaping human genetic diversity, although we cannot formally exclude that this transmission has also a genetic component.

Following the niche: the differential impact of the last glacial maximum on four European ungulates.

Predicting the effects of future global changes on species requires a better understanding of the ecological niche dynamics in response to climate; the large climatic fluctuations of the last 50,000 years can be used as a natural experiment to that aim. Here we test whether the realized niche of horse, aurochs, red deer, and wild boar changed between 47,000 and 7500 years ago using paleoecological modelling over an extensive archaeological database. We show that they all changed their niche, with species-specific responses to climate fluctuations. We also suggest that they survived the climatic turnovers thanks to their flexibility and by expanding their niche in response to the extinction of competitors and predators. Irrespective of the mechanism behind such processes, the fact that species with long generation times can change their niche over thousands of years cautions against assuming it to stay constant both when reconstructing the past and predicting the future.

Climate shaped how Neolithic farmers and European hunter-gatherers interacted after a major slowdown from 6,100 BCE to 4,500 BCE.

The Neolithic transition in Europe was driven by the rapid dispersal of Near Eastern farmers who, over a period of 3,500 years, brought food production to the furthest corners of the continent. However, this wave of expansion was far from homogeneous, and climatic factors may have driven a marked slowdown observed at higher latitudes. Here, we test this hypothesis by assembling a large database of archaeological dates of first arrival of farming to quantify the expansion dynamics. We identify four axes of expansion and observe a slowdown along three axes when crossing the same climatic threshold. This threshold reflects the quality of the growing season, suggesting that Near Eastern crops might have struggled under more challenging climatic conditions. This same threshold also predicts the mixing of farmers and hunter-gatherers as estimated from ancient DNA, suggesting that unreliable yields in these regions might have favoured the contact between the two groups.

Author Correction: An earlier revolution: genetic and genomic analyses reveal pre-existing cultural differences leading to Neolithization.

A correction to this article has been published and is linked from the HTML version of this paper. The error has not been fixed in the paper.

Late Quaternary horses in Eurasia in the face of climate and vegetation change.

Wild horses thrived across Eurasia until the Last Glacial Maximum to collapse after the beginning of the Holocene. The interplay of climate change, species adaptability to different environments, and human domestication in horse history is still lacking coherent continental-scale analysis integrating different lines of evidence. We assembled temporal and geographical information on 3070 horse occurrences across Eurasia, frequency data for 1120 archeological layers in Europe, and matched them to paleoclimatic and paleoenvironmental simulations for the Late Quaternary. Climate controlled the distribution of horses, and they inhabited regions in Europe and Asia with different climates and ecosystem productivity, suggesting plasticity to populate different environments. Their decline in Europe during the Holocene appears associated with an increasing loss and fragmentation of open habitats. Europe was the most likely source for the spread of horses toward more temperate regions, and we propose both Iberia and central Asia as potential centers of domestication.

An earlier revolution: genetic and genomic analyses reveal pre-existing cultural differences leading to Neolithization.

Archaeological evidence shows that, in the long run, Neolitization (the transition from foraging to food production) was associated with demographic growth. We used two methods (patterns of linkage disequilibrium from whole-genome SNPs and MSMC estimates on genomes) to reconstruct the demographic profiles for respectively 64 and 24 modern-day populations with contrasting lifestyles across the Old World (sub-Saharan Africa, south-eastern Asia, Siberia). Surprisingly, in all regions, food producers had larger effective population sizes (N e) than foragers already 20 k years ago, well before the Neolithic revolution. As expected, this difference further increased ~12-10 k years ago, around or just before the onset of food production. Using paleoclimate reconstructions, we show that the early difference in N e cannot be explained by food producers inhabiting more favorable regions. A number of mechanisms, including ancestral differences in census size, sedentism, exploitation of the natural resources, social stratification or connectivity between groups, might have led to the early differences in Ne detected in our analyses. Irrespective of the specific mechanisms involved, our results provide further evidence that long term cultural differences among populations of Palaeolithic hunter-gatherers are likely to have played an important role in the later Neolithization process.

The Evolutionary Origin and Genetic Makeup of Domestic Horses.

The horse was domesticated only 5.5 KYA, thousands of years after dogs, cattle, pigs, sheep, and goats. The horse nonetheless represents the domestic animal that most impacted human history; providing us with rapid transportation, which has considerably changed the speed and magnitude of the circulation of goods and people, as well as their cultures and diseases. By revolutionizing warfare and agriculture, horses also deeply influenced the politico-economic trajectory of human societies. Reciprocally, human activities have circled back on the recent evolution of the horse, by creating hundreds of domestic breeds through selective programs, while leading all wild populations to near extinction. Despite being tightly associated with humans, several aspects in the evolution of the domestic horse remain controversial. Here, we review recent advances in comparative genomics and paleogenomics that helped advance our understanding of the genetic foundation of domestic horses.