Linus Girdland Flink

Pig Domestication and Human-Mediated Dispersal in Western Eurasia Revealed through Ancient DNA and Geometric Morphometrics

Zooarcheological evidence suggests that pigs were domesticated in Southwest Asia ∼8,500 BC. They then spread across the Middle and Near East and westward into Europe alongside early agriculturalists. European pigs were either domesticated independently or more likely appeared so as a result of admixture between introduced pigs and European wild boar. As a result, European wild boar mtDNA lineages replaced Near Eastern/Anatolian mtDNA signatures in Europe and subsequently replaced indigenous domestic pig lineages in Anatolia. The specific details of these processes, however, remain unknown. To address questions related to early pig domestication, dispersal, and turnover in the Near East, we analyzed ancient mitochondrial DNA and dental geometric morphometric variation in 393 ancient pig specimens representing 48 archeological sites (from the Pre-Pottery Neolithic to the Medieval period) from Armenia, Cyprus, Georgia, Iran, Syria, and Turkey. Our results reveal the first genetic signatures of early domestic pigs in the Near Eastern Neolithic core zone. We also demonstrate that these early pigs differed genetically from those in western Anatolia that were introduced to Europe during the Neolithic expansion. In addition, we present a significantly more refined chronology for the introduction of European domestic pigs into Asia Minor that took place during the Bronze Age, at least 900 years earlier than previously detected. By the 5th century AD, European signatures completely replaced the endemic lineages possibly coinciding with the widespread demographic and societal changes that occurred during the Anatolian Bronze and Iron Ages.

Using ancient DNA to study the origins and dispersal of ancestral Polynesian chickens across the Pacific

Significance Ancient DNA sequences from chickens provide an opportunity to study their human-mediated dispersal across the Pacific due to the significant genetic diversity and range of archaeological material available. We analyze ancient and modern material and reveal that previous studies have been impacted by contamination with modern chicken DNA and, that as a result, there is no evidence for Polynesian dispersal of chickens to pre-Columbian South America. We identify genetic markers of authentic ancient Polynesian chickens and use them to model early chicken dispersals across the Pacific. We find connections between chickens in the Micronesian and Bismarck Islands, but no evidence these were involved in dispersals further east. We also find clues about the origins of Polynesian chickens in the Philippines. The human colonization of Remote Oceania remains one of the great feats of exploration in history, proceeding east from Asia across the vast expanse of the Pacific Ocean. Human commensal and domesticated species were widely transported as part of this diaspora, possibly as far as South America. We sequenced mitochondrial control region DNA from 122 modern and 22 ancient chicken specimens from Polynesia and Island Southeast Asia and used these together with Bayesian modeling methods to examine the human dispersal of chickens across this area. We show that specific techniques are essential to remove contaminating modern DNA from experiments, which appear to have impacted previous studies of Pacific chickens. In contrast to previous reports, we find that all ancient specimens and a high proportion of the modern chickens possess a group of unique, closely related haplotypes found only in the Pacific. This group of haplotypes appears to represent the authentic founding mitochondrial DNA chicken lineages transported across the Pacific, and allows the early dispersal of chickens across Micronesia and Polynesia to be modeled. Importantly, chickens carrying this genetic signature persist on several Pacific islands at high frequencies, suggesting that the original Polynesian chicken lineages may still survive. No early South American chicken samples have been detected with the diagnostic Polynesian mtDNA haplotypes, arguing against reports that chickens provide evidence of Polynesian contact with pre-European South America. Two modern specimens from the Philippines carry haplotypes similar to the ancient Pacific samples, providing clues about a potential homeland for the Polynesian chicken.

Establishing the validity of domestication genes using DNA from ancient chickens

Significance Recent studies have identified the genetic basis of numerous traits that differentiate modern domestic species from their wild counterparts. In both plants and animals, traits (and the genes underlying them) found ubiquitously in modern breeds are often presumed to have been selected early during the domestication process. Here, by determining genetic variability in ancient European chickens over the past 2,000 years, we show that a mutation thought to be crucial during chicken domestication was not subjected to strong human-mediated selection until much later in time. This result demonstrates that the ubiquity of mutations, which differentiate modern wild and domestic taxa, does not necessarily imply ancient origins. Modern domestic plants and animals are subject to human-driven selection for desired phenotypic traits and behavior. Large-scale genetic studies of modern domestic populations and their wild relatives have revealed not only the genetic mechanisms underlying specific phenotypic traits, but also allowed for the identification of candidate domestication genes. Our understanding of the importance of these genes during the initial stages of the domestication process traditionally rests on the assumption that robust inferences about the past can be made on the basis of modern genetic datasets. A growing body of evidence from ancient DNA studies, however, has revealed that ancient and even historic populations often bear little resemblance to their modern counterparts. Here, we test the temporal context of selection on specific genetic loci known to differentiate modern domestic chickens from their extant wild ancestors. We extracted DNA from 80 ancient chickens excavated from 12 European archaeological sites, dated from ∼280 B.C. to the 18th century A.D. We targeted three unlinked genetic loci: the mitochondrial control region, a gene associated with yellow skin color (β-carotene dioxygenase 2), and a putative domestication gene thought to be linked to photoperiod and reproduction (thyroid-stimulating hormone receptor, TSHR). Our results reveal significant variability in both nuclear genes, suggesting that the commonality of yellow skin in Western breeds and the near fixation of TSHR in all modern chickens took place only in the past 500 y. In addition, mitochondrial variation has increased as a result of recent admixture with exotic breeds. We conclude by emphasizing the perils of inferring the past from modern genetic data alone.

Use of domesticated pigs by Mesolithic hunter-gatherers in northwestern Europe.

Mesolithic populations throughout Europe used diverse resource exploitation strategies that focused heavily on collecting and hunting wild prey. Between 5500 and 4200 cal BC, agriculturalists migrated into northwestern Europe bringing a suite of Neolithic technologies including domesticated animals. Here we investigate to what extent Mesolithic Ertebølle communities in northern Germany had access to domestic pigs, possibly through contact with neighbouring Neolithic agricultural groups. We employ a multidisciplinary approach, applying sequencing of ancient mitochondrial and nuclear DNA (coat colour-coding gene MC1R) as well as traditional and geometric morphometric (molar size and shape) analyses in Sus specimens from 17 Neolithic and Ertebølle sites. Our data from 63 ancient pig specimens show that Ertebølle hunter-gatherers acquired domestic pigs of varying size and coat colour that had both Near Eastern and European mitochondrial DNA ancestry. Our results also reveal that domestic pigs were present in the region ~500 years earlier than previously demonstrated.

Unravelling the complexity of domestication: a case study using morphometrics and ancient DNA analyses of archaeological pigs from Romania

Current evidence suggests that pigs were first domesticated in Eastern Anatolia during the ninth millennium cal BC before dispersing into Europe with Early Neolithic farmers from the beginning of the seventh millennium. Recent ancient DNA (aDNA) research also indicates the incorporation of European wild boar into domestic stock during the Neolithization process. In order to establish the timing of the arrival of domestic pigs into Europe, and to test hypotheses regarding the role European wild boar played in the domestication process, we combined a geometric morphometric analysis (allowing us to combine tooth size and shape) of 449 Romanian ancient teeth with aDNA analysis. Our results firstly substantiate claims that the first domestic pigs in Romania possessed the same mtDNA signatures found in Neolithic pigs in west and central Anatolia. Second, we identified a significant proportion of individuals with large molars whose tooth shape matched that of archaeological (likely) domestic pigs. These large ‘domestic shape’ specimens were present from the outset of the Romanian Neolithic (6100–5500 cal BC) through to later prehistory, suggesting a long history of admixture between introduced domestic pigs and local wild boar. Finally, we confirmed a turnover in mitochondrial lineages found in domestic pigs, possibly coincident with human migration into Anatolia and the Levant that occurred in later prehistory.

An absolute chronology for early Egypt using radiocarbon dating and Bayesian statistical modelling

The Egyptian state was formed prior to the existence of verifiable historical records. Conventional dates for its formation are based on the relative ordering of artefacts. This approach is no longer considered sufficient for cogent historical analysis. Here, we produce an absolute chronology for Early Egypt by combining radiocarbon and archaeological evidence within a Bayesian paradigm. Our data cover the full trajectory of Egyptian state formation and indicate that the process occurred more rapidly than previously thought. We provide a timeline for the First Dynasty of Egypt of generational-scale resolution that concurs with prevailing archaeological analysis and produce a chronometric date for the foundation of Egypt that distinguishes between historical estimates.

Exploring the complexity of domestication: a response to Rowley-Conwy and Zeder

Abstract In their critique of our paper (Krause-Kyora et al. 2013), Rowley-Conwy and Zeder focus on two primary issues. Firstly, they discuss issues associated with the terminology and definitions of animal domestication. Secondly, they question the techniques we employed to explore it. While we completely agree with their points related to terminology, we feel they have misunderstood both the principals and application of shape analyses using geometric morphometrics, and that this misunderstanding undermines their criticism. Having said that, and though our differences are easily overstated, our respective interpretations of the data presented in Krause-Kyora et al. (2013) overlap significantly.

Reply to Beavan, Bryant, and Storey and Matisoo-Smith: Ancestral Polynesian “D” haplotypes reflect authentic Pacific chicken lineages

None of the letters in response to Thomson et al. (1) undermine our conclusions. However, several issues have been raised, which we address in this reply. Beavan (2) dismisses some of the concerns that have been raised about the accuracy of the radiocarbon dates of the El Arenal-1 chicken bones, which are immediately pre-Columbian. Although procedures, such as ultrafiltration of amino acids, are common practice for suboptimal bone samples, such as the oldest El Arenal-1 sample, further complex issues, including dietary sources and the potential for indirect marine carbon input (3), mean that a detailed assessment of the site through multiple further dates would be required to exclude the possibility that the specimens might actually be post-Columbian. This approach seems particularly advisable given that analogous issues were raised about a surprisingly early date for New Zealand colonization based on Pacific rat bone dates generated at the same laboratory using similar procedures (4), which were subsequently shown to be erroneously old (5).

New genetic and morphological evidence suggests a single hoaxer created ‘Piltdown man’

In 1912, palaeontologist Arthur Smith Woodward and amateur antiquarian and solicitor Charles Dawson announced the discovery of a fossil that supposedly provided a link between apes and humans: Eoanthropus dawsoni (Dawsons dawn man). The publication generated huge interest from scientists and the general public. However, ‘Piltdown mans’ initial celebrity has long been overshadowed by its subsequent infamy as one of the most famous scientific frauds in history. Our re-evaluation of the Piltdown fossils using the latest scientific methods (DNA analyses, high-precision measurements, spectroscopy and virtual anthropology) shows that it is highly likely that a single orang-utan specimen and at least two human specimens were used to create the fake fossils. The modus operandi was found consistent throughout the assemblage (specimens are stained brown, loaded with gravel fragments and restored using filling materials), linking all specimens from the Piltdown I and Piltdown II sites to a single forger—Charles Dawson. Whether Dawson acted alone is uncertain, but his hunger for acclaim may have driven him to risk his reputation and misdirect the course of anthropology for decades. The Piltdown hoax stands as a cautionary tale to scientists not to be led by preconceived ideas, but to use scientific integrity and rigour in the face of novel discoveries.

Correction to ‘New genetic and morphological evidence suggests a single hoaxer created ‘Piltdown Man’’

[This corrects the article DOI: 10.1098/rsos.160328.].