Issue Introduction: IDentities and Identity: Biometric Technologies, Borders and Migration

ABSTRACT

Biometric technologies using digital representations of bodily characteristics to identify individuals have become an institutionalised method of registering and recognising persons, thereby establishing their right to cross borders. Based on situated ethnographic fieldwork among tech-developers, border police, forensics, IT hacktivists and migrants, this special issue illuminates how biometric technologies are put to use and experienced by the diverse social actors who imagine and promote, develop, employ, are subjected to and attempt to circumvent such identification. In this introduction biometric identification (or IDentification) is presented as a relatively new area of investigation that has been subjected to little ethnographic scrutiny. It is argued that, while biometric technologies are promoted as enabling objective and incontestable IDentification of individuals, they are in practice embedded in specific social contexts, fraught with ambiguity and uncertainty, and dependent on substantial human interpretation and social identification. They are therefore of considerable interest and concern to anthropology.

KEYWORDS:

• Biometric technologies
• border control
• migration
• identity
• Europe

Introducing Biometric Technologies

Recent years have seen a proliferation in the use and development of biometric technologies involving a range of technologically mediated practices and images, such as fingerprint imaging, iris and bone scans, facial recognition and DNA analysis. Whether used singly or in combination, these technologies are applied in a wide variety of settings to measure bodily traits and to identify, verify and categorise individuals. They are increasingly employed in the context of border control and national security as a method of registering and verifying the identities of migrants and asylum-seekers in order to distinguish between legitimate and illegitimate movement. Such border control is based on the assumption that biometric technologies are neutral and objective and that ‘bodies do not lie’ (Aas 2006), but are reliable and ‘stable, unchanging repositor[ies] of personal information’ (Magnet 2011: 2). Biometric identification, then, links measurements of individual body parts to what is perceived to be a ‘stable, objective, unambiguous and thing-like identity’ (Aas 2006: 147). This is in strong contrast to the social identities that emerge in the course of human lives, identities that are malleable, changing, relative and partial. Some critics have therefore argued that border control now takes the form of ‘automated regimes of biometric classification’ far removed from human interaction and the more ‘nuanced judgements of justice, fairness and legitimacy’ that can emerge in actual encounters between human beings (Aas 2006; Wilson 2006: 102; Olwig et al. 2020).

Several studies have argued that biometric border control is far from infallible. Gates (2011) notes that biometric technologies do not take into account the fact that the bodies of registered individuals may undergo changes over time that can invalidate their usefulness as stable sources of information, whereas Magnet (2011) points out that the conversion of bodies into code by such technologies is open to error and dependent on practices of inscription, reading and interpretation. The encoded body, moreover, is not neutral. As van der Ploeg (2011) and Magnet (2011) observe, biometric identification is based on the assumed importance of certain ‘pre-given criteria’, such as nationality, ethnicity, gender, family relations and age, that are associated with different categories of traveller. This means that biometric technologies reinforce the state’s ability to determine a person’s identity according to particular criteria, even though this may not correspond to individuals’ understandings of themselves (cf. Amoore 2009). Finally, a recent study has demonstrated that gender and skin-colour biases are ingrained in a range of algorithms employed in facial recognition (Buolamwini & Gebru 2018). In sum, different forms of biometric identification and verification enact particular kinds of vision and conceptions of the body and the world that tend to reproduce pre-defined social biases along the lines especially of race, ethnicity and nationality. As a result, they enable or undermine specific social and spatial practices, understandings of personhood and notions of belonging within the context of crossing borders. This is particularly apparent in the case of undocumented migrants or refugees who have limited legal rights.

Anthropology and Biometric Technologies

Whereas biometric technologies have been the subject of critical discussion within the academic disciplines of criminology, political science, sociology, history, geography and philosophy, they have received little anthropological attention (but see, for example, Maguire 2009, 2012, 2014; Helén and Tapaninen 2013). Practically no analyses have been based on situated ethnographic fieldwork, with the notable exceptions of Rao and Nair’s studies of India’s national biometric identification programme (Nair 2018; Rao 2018; Rao & Nair 2019) and Tapaninen et al.’s Finnish research on DNA testing of ‘anchor children’s’ applications for family reunification (Tapaninen et al. 2019). This overall lack of empirical studies has shaped approaches to biometric technologies, often privileging a bird’s-eye perspective and focusing on the ubiquity of the technologies and the threats they pose. There has been very little ethnographic investigation of their everyday uses, their actual malfunctions and practical inadequacies, nor of the ways in which they can be circumvented or used for unplanned purposes.

This special issue of Ethnos will address this lack of ethnographic inquiry by approaching biometric technologies in their practical and social embeddedness, taking into account the diverse social actors who imagine and promote, develop, employ, are subjected to and circumvent them. All these actors interact with such technologies in their daily activities and thereby contribute to their practical application, their performance and their social and practical implications in the context of border control and migration. The ethnographic analyses presented in this issue show that, when examined within the specific social contexts of migration, a much more nuanced and contradictory picture of the technologies emerges. Thus, biometric identification methods rely on recognition, yet many migrants have not been previously registered, ruling out the basic principle of recognition. ID documents are frequently purchased and tampered with, also for migration purposes, and both migrants desperate to move and migration brokers become biometrically savvy technological specialists in their own right, developing techniques to circumvent or avoid such border technologies. Furthermore, biometrically determined identities may be challenged or, conversely, actively used as people employ them for other purposes than intended. Thus, whereas technology developers and stakeholders often portray biometric technologies as objective and incontestable, our studies show that they are embedded in specific social contexts, fraught with ambiguity and uncertainty, and dependent on substantial human interpretation.

Identity and IDentity

With the deployment of biometric technologies, according to Gates we are witnessing ‘a reconfiguration of identity, the attachment of new meaning and new practices to what identity is and to how it works’ (2011: 16–17; see also van der Ploeg 1999; Aas 2006). In anthropology the notion of identity generally refers to its social aspects, notably ‘the groups a person belongs to, who he or she identifies with, [and] how people establish and maintain invisible but socially efficient boundaries’ (Eriksen & Pijpers 2017: 153). Identity, notes MacClancy (2016: 21–22), concerns not only self-identity chosen by individuals and groups, but also categorical identity conferred on individuals and groups by others, and there is often a tension, even a contradiction, between internal and external definitions. Furthermore, the innate, stable identity implied in biometric technologies clashes with anthropological perspectives on identity as multiple, in motion and flexible, an amalgam of ‘multiple incoherent and unstable selves’ (Griffiths 2015: 1). Indeed, anthropological research has shown that identities may be invented, challenged and sustained for political and social purposes (Luhrmann 2001). In other words, the anthropological conceptualisation of identity differs in fundamental ways from biometric notions of identity. The ethnographic case studies in this special issue thus show that identity may be conceived of and practised in multiple ways in the various sites analysed.

When using biometric technologies to link body parts, biometric data and identities together, these different conceptions of identity are often collapsed. As a consequence, the distinction between the rich and complex identities embedded in, and resulting from, social life and the ascribed biometric identities based on biological traits becomes blurred. In order to avoid this convergence, we propose to use the term IDentity (see Møhl, this issue) to refer to identity determined on the basis of data sets established and registered through biometric technologies. These data sets have been called ‘virtual selves’ (Whitson & Haggerty 2008) and ‘data doubles’ (Haggerty & Ericson 2000: 611), which in some instances is how they are conceived in both the application of biometric technologies and criticism of them. We contend, however, that ID is not a simple copy of a person, as implied in the relationship between original and double (or Doppelgänger). Indeed, a piece of biometric data relates only to the body – of which it would then be an imprint or index – not to the identity of a person. We therefore differentiate between the types of rudimentary identity markers contained in biometric data – the IDentity – and the complex and variable senses of personal identities as situated, experienced, lived, temporal and far from static, always in the making through social processes of interaction. This demarcation also appears as an analytical distinction between those elements of a person’s life and identity that can be recorded and stored as biometric data and those that cannot. In the case studies presented in this issue, this blurring of identity continually emerges in technological processes that tend to erase or obscure the fundamental differences between data and persons in all their ambiguity.

IDentity, Borders and Border-making

These two disparate understandings of identity – as either an incontestable, permanent IDentity that biometric technology seeks to uncover, or a negotiable, changeable personal identity that emerges out of social life – can be related to different conceptions of borders. Biometric technologies enable the automated regulation and control of border crossings. In practice, however, borders are not clear physical lines of demarcation separating territories but instead, as Donnan and Wilson note (2010: 7), ‘countless points of interaction, or myriad places of divergence and convergence’. Borders are sites of both disjuncture and contact, opposition and attachment, and as such they form zones of encounter, engagement and friction, exactly because they are shared (de Certeau 1984: 127). Borders, then, are ubiquitous and constituted contextually by a multitude of interactions involving multiple places, actors and objects, including biometric technologies.

Borders are rarely restricted to junctions between regions or nation states or to points of passage that, once left behind, lose their grip on human mobility. In fact, with the emergence of biometric technologies and ID cards, we have come to a stage in the global regulation of mobility where, as Lyon notes, ‘the border is everywhere’ and ‘the experience of being counted as an insider or an outsider can be reproduced anywhere’ (Lyon 2004). Borders are detached from their territorial anchorage and become both internalised and externalised, projected far away from the original national borders (Olwig et al. 2020). They become externalised when the Schengen border emerges in the form of a DNA-test performed in a consular office in Kenya or when a Schengen visa is checked at an airport counter in Indonesia; they become internalised when the reason for immobility lies not in physical obstacles but in an individual’s genome or iris pattern. A person’s body in a sense becomes her or his primary obstacle to movement (Aas 2006; Amoore 2006). In this respect, if we follow Agamben’s notion of biological data as ‘identity without the person’ – biological features with which the person is intimately linked but with which the person can in no way identify (2011) – biometric technologies not only codify bodies, but also disconnect them from the person, creating, in our terms, an IDentity without the person or, in other words, an IDentity without identity.

This form of disconnect between person and body, between identity and IDentity, is a two-edged sword. As the articles show, reactions to the deployment of biometric technologies include desperate attempts to rid the body of its signifying, that is, ‘bio-measurable’ features; migrants’ and asylum seekers’ occasional use of biometric IDentities to cut connections they wish to leave behind; relatives’ desires to identify lost family members by reestablishing a connection between a formal IDentity and the missing person; and border guards needing to go beyond the use of mere IDentity and data in their assessment and filtering of travellers.

The Field

Our methodological approach to biometric technologies and migration in this special issue is based on a conceptualisation of the technologies as continuously unfolding and emerging objects of inquiry, as they circulate, produce different experiences and take on disparate meanings, shapes and forms. The articles include ethnographic analysis of the production of IDentities and the testing of new technologies (Grünenberg); the establishment and checking of IDentities at official border crossings (Møhl); migrants’ negotiation of IDentities en route and upon return (Simonsen); forensic age assessment practices of young asylum-seekers (Netz); verification of biological kinship based on DNA tests in family reunification cases (Olwig); practices and discourses surrounding the use or non-use of DNA in relation to disappeared and disappearing migrants and refugees (Huttunen and Sørensen); and hacktivist ideas about individual and collective privacy rights and their resistance to state surveillance (Horstmann).

Feldman has cautioned against privileging ethnographic sitedness, participant observation and the direct encounters they imply. Participant observation on its own, he argues, cannot capture the complex global infrastructures and apparatuses of biometric border systems, nor generate general theorising of these phenomena (Feldman 2011). While we take Feldman’s point, this special issue demonstrates that, when coupled with other methodological approaches, ethnographic fieldwork focusing on ongoing practices and face-to-face or virtual encounters can contribute important new insights into the production and use of biometric technologies with respect to migration and surveillance in general. Such insights, we argue, are essential if we want to move beyond a focus on the IDentities established through biometric registration and recognition towards an anthropological analysis of the socially contingent, convoluted and often conflicting practices and identities that emerge as variously positioned people engage with, transform and are transformed by the technologies.

This special issue, as noted, examines a range of sites in motion that we have defined as representing some key dimensions of biometric bordering. Most prominent here is the clearly demarcated physical site of biometric border control, experienced today by most travellers who cross national or supra-national borders where migration is controlled. This site, situated at officially and clearly designated public places on the physical boundary dividing neighbouring countries or in sites of arrival such as airports, presents a concrete manifestation of national and European attempts to protect their sovereignty and interests by drawing on the most modern, advanced and seemingly powerful technology. Less visible, but no less evocative as tools of control, are the mobile hot spots that pop up at different times and places to detect irregular migrants, preventing those who are caught from reaching their desired destinations. Another site involves the forensic departments at hospitals that perform age assessments of asylum-seekers as well as DNA analysis of biological kinship in family reunification cases with a view to delimiting or, perhaps more to the point, limiting the legal entitlements of border crossers. Closely connected to these sites are the research labs that rely upon state and private funding to develop new technologies intended to provide ever more sophisticated and secure tools of recognition and registration. Much more diffuse, confusing and, at times, crepuscular sites are constituted by the wide array of people who, from their different vantage points, engage with the biometric technologies. Through their daily activities and minute choice-making, they are involved in such disparate endeavours as managing and implementing biometric technologies to their best ability, attempting to circumvent them, subjecting themselves to them, trying to use them to their own advantage, pleading for their more extensive use, and attempting to disrupt and undermine them entirely. Studying such sites clearly poses a number of challenges, such as gaining access, adjusting methods to the particular possibilities and limits associated with the available sites, and coming to terms with the ethical issues raised by doing research in environments that are politically highly charged.

Cross-cutting Themes

A key contribution of these articles is the general point that, whereas in principle biometric technologies may appear to be objective, sophisticated, secure and efficient tools of identification and control, in practice this is often far from being the case. While there may be good reasons to maintain a critical stance towards the automated registration and transformation of individual bodies into IDentities by biometric technologies, with scant regard for their self-understanding and social identities, the articles’ ethnographic focus on social practice shows that the bird’s-eye approach to the technologies and their use represents only one side of a larger picture.

Technologies

Throughout this special issue, biometric technologies come across as artefacts produced between a whole range of contexts, people, agendas, policies and other artefacts. Indeed, in none of their manifestations in this special issue can biometric technologies stand alone. Instead they are dependent on a number of factors to work and perform as planned. Among such interrelated factors are researcher abilities to teach algorithms how to distinguish between real and fake faces; system errors and incompatibilities; legitimate and counterfeit ID papers and passports; suitable environmental conditions; border guards’ sensory apparatus, skills and practical daily work with the installations; hackers’ and migrants’ various ways of circumventing the technologies; particular ideas about what constitutes a family and signs of age; and sufficient funding and the political willingness to maintain and continually optimise and renew such systems. As such, the technologies are inextricably linked to their different uses, users and specific settings of their application, as well as to the relations, convergences and clashes between them. Rather than being overpowering mechanisms of control, biometric technologies then come across in the ethnographic studies as rather fragile, dependent and transitory artefacts that may nonetheless have longstanding consequences for those who make use of them or are subjected to them.

Borders

Throughout these articles, the border appears as ubiquitous, as well as taking many more or less abstract forms. Wherever it arises, it is never a non-place of anonymity, ahistorical and beyond relationality (Augé 1995) – quite the contrary. In some cases it constitutes a physical demarcation, a point of passage or retention. In other cases it takes the form of a means of social detachment, a legal or ideological barrier to one’s movement and reunification with others. Often the line between the abstract and the physical border becomes indistinct and dissolves. The border is also for some quite literally a place, that of their daily work, and as such not a point of passage – nor a non-place. Sometimes it is represented by a police officer, a forensic scientist or a consulate clerk, sometimes it is existential, between states of life and death, between the present and a hoped-for better future. In the case of the ‘disappeared’ or the unknown victims of a Mediterranean crossing, the essential borders are the lines of separation that exist between both bodies without an IDentity and IDentities without a body – in either case, bodies and IDentities in need of reunification. Sometimes there is a border between different social statuses, where social mobility can be sustained by obtaining new forms of IDentity. In the two latter cases, biometric technologies can be used to produce reunifications and enable social border-crossing. In other cases, the distinct line between identity and IDentity morphs into a synthetic figure, an ID-entity, by combining rudimentary data with the human work of imagination and foresight. Sometimes the border is symbolised by imaginary trespassers who provide the impetus to develop even ‘stronger borders’ and technologies. And sometimes the border is seen mainly as an alarming site of inspection and the violation of the right to privacy. In most cases, the border is a site of suspicion and of the legally installed right to inspect, search, inquire and control the legitimacy of the individual body and its supposed relation to an IDentity.

Migration

Early biometrics, such as fingerprints and DNA, were used primarily to identify criminals and others who were trying to evade the law (Olwig et al. 2020). It is therefore thought-provoking that biometric technologies are now increasingly employed to monitor and control cross-border migration, an activity that has become associated with potentially illicit practices, being subject to increasingly restrictive national and supra-national legislation such as that regulating entry into the Schengen area of the EU. The biometric technologies examined in these articles are thus used to identify a diversity of unlawful border-crossers as traffickers, smugglers, terrorists (checking biometrics against watch lists), undocumented migrants (fingerprints and facial recognition), individuals making claims for family reunification on false grounds (DNA analysis and age assessment) and people spoofing their way across borders by assuming fraudulent appearances.

Biometric technologies are becoming increasingly sophisticated and, as Grünenberg shows, new, ever more intricate technologies are emerging as governments and private industry continue to invest in the development of the most advanced and foolproof ways of detecting irregular travellers, while, at the same time, making travel as seamless as possible for those deemed legitimate. This ongoing preoccupation with having the most efficient biometric technology bears testimony not only to the high priority placed on tight border control, but also to the impossibility of ever establishing a secure system of technological control. Indeed, Horstmann’s study suggests that no biometric system or identity will be safe from hacking or spoofing. In fact, the innovation of new technologies only seems to pose novel challenges to hackers and, by extension, to biometric researchers. Furthermore, as Møhl shows, current technological systems of border control are limited by creating and drawing upon databases containing only body templates or crude IDentities. In concrete encounters at the border, she points out, they therefore rarely contain enough of the kinds of information needed to substantiate suspicions about, for example, shady activities such as trafficking or terrorism, suspicions that are instead based largely on the discretionary and imaginative work of border guards. Moreover, increasingly sophisticated systems of border control, as both Simonsen, and Huttunen and Sørensen make clear, will not stop people whose condition of life is so dire that they consider transnational mobility a necessity. They will seek new possible routes and sites of border crossing, even when they involve grave risks.

The ethnographic case studies in this special issue offer examples of both the devastating consequences of biometric IDentification for migrants and of situations where biometric IDentification may be actively appropriated by migrants for their own purposes. Netz’s careful ethnographic analysis shows that a biometric age assessment of young refugees may result in their being reclassified as adults with limited legal rights as minors, even when such assessments are uncertain and variable. Olwig demonstrates that DNA analyses and age assessments that define which individuals can be included in Somali refugee families can differ considerably from Somali understandings and practices of family relations. For the Somali migrants in Italy studied by Simonsen, however, biometric registration presents not only a hindrance to further movement, but also a document that makes it possible for them to prove their diasporic identity upon their return to Somalia. For many of the Somali refugees in Denmark involved in cases of family reunification, the mandatory DNA analysis of undocumented family members also offers an opportunity to renegotiate their transnational family obligations. Finally, as Huttunen and Sørensen show, DNA analysis has become important for families trying to identify relatives missing due to armed conflicts or travel on the perilous migratory routes because it enables them to connect the social identity and bodily remains of dead family members.

The Articles

The eight articles in this special issue all deal with several types of biometric technologies and the ways in which they are practised in our different field sites. They also address how biometric technologies intersect with migratory questions and experiences, and how different configurations of IDentity and identity are at play in the various empirical settings.

The first article, ‘Wearing someone else’s face: Biometric technologies, anti-spoofing and the fear of the unknown’, by Kristina Grünenberg, approaches the biometric field from the laboratory where researchers work on the stability of biometrically produced IDentities and the security of different biometric modalities. It focuses on ‘spoofing’, that is, on attempts to cheat biometric systems with the help of artefacts such as face masks, showing how the line of research called anti-spoofing presupposes and draws upon the creativity and imagination of researchers as they attempt to develop pre-emptive measures against any imaginable future attacks on biometric installations. In this context, a particular ‘spoofer figure’ has been configured as a potential central actor who can make threats both concrete and real and who affirms the continued need for biometric research.

The following article, ‘Biometric technologies, data and the sensory work of border control’, by Perle Møhl, takes us to the national and Schengen borders at airports where border guards performing IDentity checks become visually and sensorily enskilled as they interact with automated technologies, data, travellers and their belongings. Møhl shows how the registration of biometric IDentities only constitutes ‘the crude starting point’ for the daily routine work of border control that consists of human – technological encounters and affective interactions that, besides data, require the creativity and intuition of border guards. Through the evanescent synthetic figure of the ID-entity, established during the brief moments of interaction, cognition and recognition at the border, Møhl shows how biometric technologies and the senses and intuition of border guards become intricately entangled.

In her contribution, ‘The power to selectively reveal oneself: privacy protection among hacker-activists’, Nina Dewi Horstmann engages with biometric IDentity, identity and borders from the perspective of hackers-cum-digital rights activists. She shows how these ‘hacktivists’ highlight the need for the right to privacy through their multiple practices of cloaking and disturbing information flows. She argues that in hactivists’ understanding the protection of individuals’ privacy is a fundamentally social issue concerning the collective right to self-fashioned and changeable identities. Horstmann uses the distinction between ‘identity information’ and ‘identity in-formation’ to distinguish between IDentity, as defined by biometric and other surveillance technologies, and identity as perceived and shaped by her interlocutors.

In ‘The Right to a Family Life and the Biometric “Truth” of Family Reunification: Somali Refugees in Denmark’, Karen Fog Olwig examines the biometric control of family reunification and its implications for Somali refugees. She shows how the nuclear family, the only unit of family relations recognised for reunification, becomes validated through biometrically defined family IDentities, even though it is at odds with Somali family identities that are associated with extended family and kin groups. She argues that Somalis regard this biometrically defined family IDentity with considerable ambivalence due to their problematic position in Danish society. Thus it is seen to prevent many Somalis from reuniting with longed-for relatives, while at the same time offering others a way to make transnational kin relations more compatible with their present lives.

The article ‘Teeth and truth? Age IDentities of migrants in the making’ by Sabine Netz focuses on the topic of age assessment in a forensic laboratory and the wide-ranging consequences of these lab practices for the biometric IDentities as well as the social identities of young migrants and refugees. Through the story of Ferhad, an Afghan refugee, and detailed observation of laboratory practices and the ways in which forensic standards are applied and interpreted, Netz shows that age is an unstable category that is located more firmly in the instruments and practices of the forensic experts than in individuals’ bodies.

The ways in which biometric registration is encountered and experienced by Somali men on the move is explored in ‘Crossing (biometric) borders: turning “gravity” upside down’ by Anja Simonsen. Using the analytical concept of ‘gravity’, she shows how biometric registration and the EU Dublin regulation immobilise and ‘weigh down’ some of her interlocutors, keeping them in a precarious situation in Italy in spite of their possession of legally sanctioned IDentities and papers as recognised refugees. Simonsen goes on to demonstrate, however, that even though these European documents are no guarantee of safe livelihoods, the IDentities that they do produce may provide a way of negotiating social positions and attributed clan IDentities, thus paving the way for social mobility in one’s country of origin.

In the last article, ‘Missing migrants and the politics of disappearance in armed conflicts and migratory contexts’, Laura Huttunen and Ninna Nyberg Sørensen show how and when biometric technologies in the form of DNA analyses are applied in the context of missing migrants and people missing in connection with political and armed conflict. The authors show that biometric technologies are generally embraced by the relatives of those who have gone missing. However, whether or not DNA is used to connect the social identities of the missing to the biometric IDentities established through the DNA analysis of dead bodies is a matter intricately tied to politics, as well as to the representation of the disappeared in the dominant narratives of the state and supra-state organisations.

Finally, Zachary Whyte’s epilogue, ‘Automation, biocrats, and imaginaries in biometric border worlds: a commentary’, discusses how the ethnographic approach adopted in the articles illuminates the socio-cultural embeddedness of biometric systems. A key implication of this embeddedness, Whyte notes, is the authors’ demonstration of the capriciousness of biometric systems. Thus when examined in actual practice they can be seen to operate in quite variable and unexpected ways as they are challenged by the particular relational rationalities and agendas of people in concrete places. This includes a broad array of actors, ranging from the ‘biocrats’ who fund, promote, develop, implement and operate biometric technologies to the biometric subjects who resist, avoid and/or appropriate the technologies for their own purposes. In this way, the articles highlight that the border world is, fundamentally, a tensive field of contradictory relations involving people who are guided by varying agendas, ambitions, hopes and imaginaries shaped by their specific vantage point in a complex power structure.

Acknowledgements

We thank the participants at the international ‘Biometric Border Worlds’ workshop, Copenhagen 2017, among them, the contributors to this special issue. We also thank the editors of Ethnos and the anonymous reviewers for their pertinent reviews of the articles, and Zachary Whyte for his excellent commentary to the issues raised in the articles.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Velux Fonden [grant number 10351].