1 Introduction

The digital age is abandoning conceptions of “ethnicity” and “race” that are essentialist, static, or context-free. Embracing digital-era insights on data flows and connectivity, this research adopts an informatics perspective.Footnote 1 The proposed paradigm is buttressed by adding evolutionary and complexity theories to examine changes in information processing. With this digital-era focus, racial and ethnic signalsFootnote 2 can be seen as coevolving with society’s geospatial dynamics. It is theorized that the major impetus is evolving signal-processing complexity that realigns global geospatial barriers. Signal processing governs whether groups with distinct ancestral geographic origins—tagged with racial-ethnic signifiers—pass through geospatial checkpoints in workspaces, neighborhoods, countries, and other bounded social domains.

Focusing on evolving complexity in signal-boundary systems, two interrelated propositions are formulated. The first proposition applies if rivalrousFootnote 3 resources are inseparable from a specific geophysical location (hereafter referred to as “fixed-site rivalrous resources”). In zero-sum contests for control of this specific location and its resources, an ethnic group consistently denied full spatial access or control is subject to racialization. That is, the group can be tagged as inherently inferior. Second, in the post-industrial era, the coevolution of signal-processing complexity and non-territorialFootnote 4 adaptation will overall diminish racialized cleavages. Both these propositions suggest that ethnic–racial boundaries do not emerge from inherent qualities of signified entities—i.e., ethnic groups or so-called “races.” Unlike physical or material objects viewed as discrete entities, signals convey information about systemFootnote 5 dynamics and only derive meaning from the systems that process them (Holland 2012).

2 Boundary changes and the thermoeconomic aspects of an evolutionary informatics model

Increasing signal-processing complexity, as a key factor impacting racial–ethnic boundaries, may be rooted processes also found in biological evolution. For example, in one of evolution’s most significant transitions, the rigid outer cell wall in prokaryotes was replaced by a permeable membrane. The softer boundary paved the way for eukaryotes—more complex life forms with cellular nuclei.Footnote 6 Eukaryotes may have absorbed mitochondria through the permeable cell walls. This initiated thermoeconomic specialization, whereby increased energy from the ingested mitochondria permitted more information-carrying genes in the nucleus. Signal-processing complexity,Footnote 7 then, coevolved with energy-boosting specialization: a thermoeconomic division of labor between the mitochondria, nucleus, and the rest of the cell (cf. Adam Smith’s The Wealth of Nations; see Corning and Kline 1998). In turn, a further division of labor between protein-synthesizing RNA and nucleus-based DNA gave signal processing inside the cell’s nucleus greater independence from the surrounding physical environment (Jablonka and Lamb 2006; Szathmáry 2015). In part, more genetic complexity was enabled when chromosomes were no longer necessarily attached to the cell wall. Initiated by the eukaryote’s permeable cell walls, then, signal processing became less anchored to a specific physical location. Indeed, this may embody the basis for all major transitions in biological evolution—namely, more inclusive boundary realignments that coevolve with “novel ways of storing, transmitting and using information” (see Corning and Szathmáry 2015: 48; Maynard Smith and Szathmáry 1995, 1999; Szathmáry 2015). Using this evolutionary informatics model, new ways of processing signals will be shown to erode racial–ethnic barriers, much like eliminating the rigid wall in prokaryotes.

Successful ecological adaptation of systems, which includes adaptation of racial–ethnic barriers, is constrained by probabilistic processes and by path dependency (cf. Darwin’s (1859) principles of descent and divergence). Adaptive responses may fail to address pollution and irreparable environmental damage resulting from energy throughputs—fuel, fiber, and food (von Schilling and Straussfogel 2009). Ensuing environmental chaos or “entropy debt” can tax complex systems and cause them to collapse (see Arthur 1994; Dyke 1988; Foster 2011: 18; Tainter 1988). For example, such a threat is posed by global warming. In addition, racial–ethnic barriers can incur system-taxing entropic debt. As will be shown below, this may have been a factor in the collapse of colonial empires.

3 Racial barriers and “tools of empire”: policing spatial enclosures for resource extraction

The first proposition—formulated in the introduction—roots racial–ethnic signals within socio-ecological systems with geophysical boundaries. For most of human history, these systems were centered on extracting biotic and mineral resources (see Haberl et al. 2011; Stein 1999). Moreover, over the last five centuries, this extraction led to “unequal ecological exchange” undergirding the spatially expansive signal-boundary systems of Europe and eventually Japan (see Moore 2000). According to Ross (2017), the process was unequal, because expansive empires depleted resources in hinterlands generically referred to as “tropical landscapes.” Given the specific dynamics of hierarchically organized empires, these landscapes and the indigenous inhabitants were sacrificed to grant colonizers a vital resource subsidy. That is, tropical landscapes suffered wanton environmental destruction through deforestation, soil erosion, diminished local biodiversity, and disrupted food chains. Extensive damage was done to rivers, hills, valley floors, and aquatic ecosystems (see World Bank 2003). Such damage could be conceptualized as entropy debt.

Integral to unequal ecological exchange, empire-directing metropoles have basked ideologically in their perceived “victory” over nature and matter (see Adas 1989). This presumed victory included dominance over purportedly primitive, inefficient, and irrational peoples tagged by tropical geographic origins (Ross 2017). Although recent brain-scanning research confirms that power holders in general view others instrumentally (Fisk 2011), colonial dominance motifs would appear to resonate the insuperable power bestowed by “tools of empire” (Headrick 1981; Ross 2017). These resource-depleting tools—particularly fossil-fuel-driven and electricity-powered machines—provided colonizers with overpowering bursts of energy and superior armaments. Enduring power over tropical hinterlands signaled to the colonizers that they constituted the hub of a socio-spatial array. Racialization arose from the hub’s downward-radiating spokes universally ensnaring tropical and other hinterland peoples.

The physicalist hub-and-spokes view of dominance over tropical landscapes and peoples obscured “complex webs of interconnection” between crops, soil, disease, and climate (see Azzi 1956; Ross 2017). Whereas pre-colonial tropical peoples relied on regeneration through photosynthesis—drawing energy from human and animal muscles and from burning wood—colonial metropoles employed “tools of empire.” These tools extracted resources from hinterlands at a rate faster than these resources could be replenished (Tucker 2000). Consequently, although the hierarchical signal-boundary system provided the colonizers with concentrated firepower at strategic moments in history, the hierarchy could not be sustained indefinitely. There are limits to expending resources without renewing them. For example, the ecological mismatch of the metropole’s large-scale agricultural projects was epitomized by the failure of a British groundnut project in Kongwa, Tanzania in 1951 (Rizzo 2006) and the collapse a French oil palm project in Dahomey one decade later (Havinden and Meredith 1993; Dumont 1966; Ross 2017). Although the colonial metropolitan elite confidently expressed racializing contempt for tropical farmers, over time there was nonetheless a growing chorus of respect for ecologically adaptive indigenous practices: crop interleaving and rotation, shallow plowing, controlled natural ground cover, and regenerative forestry-management methods (see Azzi 1956; Faulkner and Mackie 1933; Jones 1936; Ross 2017).

3.1 Geo-ethnic checkpoints and global non-market channeling via spatial enclosure

Evolutionary informatics links racial–ethnic boundary constructionFootnote 8 with zero-sum contests over fixed-site rivalrous benefits. Such contestation was integral to colonialism’s unequal ecological exchange. Seeking maximal flow of resources into the colonial metropole’s treasury at the expense of hinterlands, mercantilist empires exported processed goods such as textiles and imported unprocessed inputs such as cotton (Findlay and O’Rourke 2007; Pincus 2012). Notably, this unequal exchange did not derive from a free market, but from policed channeling: enclosing and policing non-domestic space—often in ethnically distinct hinterlands—to guarantee a sufficient quantity of relatively unprocessed inputs. For example, eighteenth-century and nineteenth-century British textile manufacture—the springboard for the wider industrial revolution—relied on cotton cultivated by slave labor on land from which the indigenous people had been forcibly removed (Beckert 2015). Spatial checkpoints, based on police power, barred free movement or exchange for tropical and other hinterland peoples.

Interdisciplinary findings suggest that policed channeling of resources and people can prevail over voluntary exchange if the rivalrous benefits for a group are inseparable from a specific geophysical location. Such fixed-site benefits would include an ethnic group’s control over prime real estate, office space, farmland, or an area’s politics and culture. These fixed-site benefits may lose value if exchanged or shared with outside groups tagged with lineage from another territory. Unlike the dynamics for an expanding supply of manufactured goods, more consumers in more places do not increase benefits from economies of scale. For example, fixed-site rivalrous benefits motivate resident populations to exercise non-negotiable control over identity-bestowing homelands (Berg 2007; Toft 2002) and to exclude others from resource-poor areas lacking divisible assets (Carpenter and MacMillen 1976; Cashdan 1983; Toft 2002).Footnote 9 To reiterate, this is because a distributional zero-sum limit is eventually reached for non-expandable fixed-site resources, whether these are identity-bestowing, mineral, or biotic (see bottom panel in Fig. 1). These zero-sum group dynamics can also be triggered by fixed-site factor endowments. This can be seen for sugar, cotton, and indigo harvests limited to tropical landscapes, where free cultivators would be too costly (see Engerman and Sokoloff 1997; Fredrickson 1981).Footnote 10 In response, European empires used police power to spatially wall-in tropical resources and peoples. For example, slaves produced cotton on land from which indigenous inhabitants were forcibly cleared (see Beckert 2015).

Fig. 1
figure 1

Coevolution toward location-free signal topology and non-rivalrous resources

Full size image

Colonial empires spatially walled-in hinterland resources and peoples using geo-ethnic checkpoints. That is, based on a group’s lineage and geographic origins, these checkpoints restricted freedom of movement and market access (negotiation as free agents). Although such discriminatory practices can reduce market efficiency (Becker 1971), market exchange among free agents may depend on evolutionary complexity. For signal-boundary systems in the territory-expanding stage of evolution, fixed-site resources (biotic, mineral, identity-bestowing, etc.) that are rivalrous can engender a zero-sum dynamic. Consequently, competitors with greater “resource holding potential” (ability to win an all-out contest) use their superior power to wall-in these resources for either exclusive or priority use (see Johnson and Toft 2013: 22).

3.2 Duress from domestic geo-ethnic checkpoints channeling fixed-site rivalrous benefits

Even in the contemporary United States, spatial checkpoints continue to channel fixed-site benefits away from peoples with hinterland lineage. Although black spatial isolation from whites has been contracting by about 5% per decade since 1970, as recently as 2010 blacks were still hypersegregated in 21 metropolitan areas (Massey and Tannen 2015; Massey and Wagner 2018: 147).Footnote 11 Notably, this hypersegregation represents a form of spatial confinement having non-market origins. In 1917 the Chicago Real Estate Board—and somewhat later, the National Association of Real Estate Boards—officially adopted a policy that led to expelling any of their agents who brokered black purchases or leases in white neighborhoods (Jones-Correa 2000–2001; Philpott 1991; Roithmayr 2014). Because of the dual housing market created by restrictive covenants and sustained by racial steering by realtors, white neighborhoods have provided higher home appreciation rates than have black neighborhoods (Massey and Denton 1993; Oliver and Shapiro 2006). Although racial covenants are no longer legal, rivalrous benefits from racial steering and racially aligned school districts may be locked in by path-dependent switching costs. According to Roithmayr (2014), this would hold for politically costly legal remedies seeking to eliminate dual (“racially” partitioned) housing markets.Footnote 12

Racial–ethnic channeling of fixed-site resources engenders entropy debt. Exacerbating maintenance costs for geo-ethnic boundaries, there has been an escalation of police surveillance and street patrols in black neighborhoods that began in the mid-1960s (Hinton 2016). In the wake of violent civil disturbances erupting in U.S. inner cities from 1965 to 1968, municipal police patrolling black neighborhoods received “military-grade rifles, tanks, riot gear, walkie-talkies, helicopters, and bulletproof vests” (Hinton 2016: 89). Subsequently, the criminal justice system’s supervision of black residents has become especially prominent in hypersegregated cities such as Chicago (Alexander 2012). For example, more than half of black adult males in the Chicago’s Cook and collar counties had felony convictions in the year 2000 (Street 2002: 17). Between 1968 and 2004, the total proportion of US adult black males convicted of a felony rose dramatically from 15 to 33% (Uggen et al. 2006: Table 2). This trend has greatly increased policed spatial confinement of young black males in prisons and jails, a costly form of human warehousing adding to inner-city entropy debt (see Alexander 2012; Western 2006). “Racial” signal and physical topologies overlap, the signals being conveyed via direct police contact (see Fig. 1). Unlike most citizens, inner-city blacks are daily confronted with police surveillance and frequently submit to preemptive personal searches (Hinton 2016).

By allocating fixed-site rivalrous benefits, spatial (particularly residential) segregation is crucial for sustaining other racial–ethnic boundaries (see Massey and Denton 1993). Cordoning off space—and by default the resources within it—achieves both efficiency and the appearance of bias-free neutrality. That is, when the spatial partitioning of people governs resource allocations, it is not necessary to designate the specific groups or specific resources for which access is either explicitly permitted or denied (Sack 1983). Instead, spatial partitioning permits disparate-impact resource allocation to be politically neutralized through naturalization: differences between areas are simply rationalized as “that’s the way it is” (Bonilla-Silva 2018: 64–67). For example, black residential segregation concentrates poverty, inducing entropic biosocial costs such as shortened telomeres and heightened allostatic loads (Massey and Wagner 2018).Footnote 13 These costs are most visibly associated with characteristics of black inner-city areas—e.g., violent crime—rather than socio-spatial resource allocation. The view that these black health costs are entirely self-inflicted achieves credibility only through segregation that appears to be de facto or spatial rather than explicitly created in laws and in practices. This same logic can even be applied to property distribution under legal slavery, insofar as efficient resource allocation required passes and nonstop patrolling to block slave access to most white spaces (Camp 2004). Ultimately, then, ethnic and “racial” economies thrive when spatial (especially residential) segregation creates separate social networks (see Fig. 1). In turn, these separate networks restrict the inflow of social, cultural, and human capital that enables employment, exogamous marriage, and other social opportunities for people with hinterland lineage (Montgomery 1991; Roithmayr 2014; Tassier and Menczer 2008).

4 Innovation on the edge of chaos: requisite variety and recirculation’s multiplier effects

The first proposition has linked geo-ethnic checkpoints to agro-industrial society’s reliance on fixed-site resources. The second proposition predicts that system barriers rooted in geophysical location—including racial–ethnic barriers—can potentially be penetrated, eroded, or realigned by a society’s signal-processing complexity. Borrowing from biological evolution and computer science experiments, it appears that a more inclusive realignment of a system’s geospatial boundaries coevolves with the system’s signal-processing complexity. Specifically, computer science experiments suggest that nonlocal adaptation—the ability to handle new situations—is accelerated by spatially independent co-evolutionary competitors feeding on each other’s improvements (Mayfield 2013). Such competitor evolution illustrates that more inclusive geospatial boundary alignments in complex adaptive systems permit diverse and independent agents to learn from their mutual exchange of signals (see Holland 2006). Indeed, this signal-processing feature, labeled here as cybernetic parallelism, renders human brains remarkably creative (see Mayfield 2013).Footnote 14 Cybernetic parallelism—illustrated by the free exchange of ideas among diverse and independent thinkers—advances scientific discovery. More diversity enhances adaptive success according to Darwin (1859). Moreover, repeated computer experiments show that the special circumstances generating co-evolutionary pressure can cause competitive advantage to shift. The shift is from a system’s rigid protective structure to increasingly rapid and deep signal processing—that is, faster-acting algorithms that become more intricately layered and less compressible (see Lathrop 1997; Kim and Ashlock 2017).Footnote 15 Accordingly, a derivative corollary is that a society’s increasing signal-processing complexity makes adaptive capacity depend less on the system’s geophysical boundaries (measured by size and strength) and more on signal-processing depth or speed (see top of Fig. 1). Finally, major complexity-enhancing boundary realignments of this nature are most likely at the edge of chaos (see Kauffman 1993; Wolfram 2002).Footnote 16 The intersection of flux-free and high-flux environments appears to spawn complexity.

Cybernetic parallelism ostensibly bestows adaptive advantage. The advantage comes through ever more inclusive, boundary-expanding feedback loops recirculating energy (resources) and information through a division of labor (thermoeconomics). One example is the development of positive feedback loops that enhance resource usage among cooperative, cross-feeding microbes (Carlson et al. 2018; Pacheco et al. 2019). These non-rival benefits result when iterative cooperative exchanges enhance resource accumulation (Chadefaux and Helbing 2010).Footnote 17 The germane axiom for signal-boundary systems, then, is this: increasing system complexity can enhance system sustainability (adaptation) by recirculating or exchanging resources in innovation-testing feedback loops (Benbya and McKelvey 2006; Holland 2012; Kauffman 1993).Footnote 18 Feedback loops increase the system’s adaptive or competitive advantage by (1) conserving resources through constantly recirculating them in a more complex system incorporating realigned boundaries (an adaptation to increasing entropy or the second law of thermodynamics); (2) obtaining resource multiplier effects through a more synergetic division of labor with realigned boundaries; and (3) increasing the system’s requisite variety, so that it has sufficient internal diversification for managing varied external disturbances (see Holland 2012; see Ashby 1956 for the law of requisite variety). The geospatial realignments in an evolutionary informatics sequence suggest the following: insofar as racial–ethnic cleavages are endemic to less complex, space-enclosing agro-industrialism, the evolution of a more algorithmically complex knowledge economy erodes such space-tethered cleavages (but not without friction or reversals).

5 Progressive uncoupling from geophysical location: the leveling of racial–ethnic hierarchies by epistemic–geopolitical networks and the nativist backlash

Coevolving with less rigid national borders, cybernetic parallelism has reduced racial–ethnic barriers in the post-colonial era. Signals from diverse global activists have challenged the boundaries of empires. Key activists include anticolonial intellectuals and movements, as well newly independent governments in Asia, Africa, and Latin America. Their signals convey that use of police power to “racially” partition space, whether in ethnic ghettos or abroad, comes with a price. Such use of police power hinders the post-colonial world’s vigorous pursuit of military, economic, and diplomatic alliances. These strategic global partnerships have created more inclusive boundary alignments—indeed, a phase-transition edge preserving social order—in the chaos of WWII and the Cold War (see FitzGerald and Cook-Martin 2014). Significantly, WWII’s Allies defeated apartheid-promoting Axis empires (with ethnic ghettos) and then integrated them into more inclusive postwar alliances. These alliances eventually dismembered racial–ethnic spatial partitioning under formal apartheid. The Allied victory also discredited, but did not eliminate, eugenics ideology legitimating racial hierarchy (see Black 2012).

Similarly, racial–ethnic hierarchies have been partially leveled by security-enhancing Cold War alliances. Horizontal realignment of the US defense perimeter required cooperation from decolonized nations in Asia, Latin America, and Africa. Conscious of this, US presidents from Truman through Johnson lobbied for civil rights and for eliminating ethnically selective immigration quotas (Dudziak 2011; Tichenor 2002). Remarkably, by 2008, diplomatic alliances and trade expansion had contributed to eliminating ethnic-group exclusion or restriction—for Chinese, Japanese, Roma, Jews, blacks, or Middle Easterners—in the immigration laws for all 22 countries in the Americas (see FitzGerald and Cook-Martin 2014: 39-42). Again, this erosion of geo-ethnic checkpoints has arisen at the edge of chaos generated by unsustainable, violent boundary disputes: two world wars, unrelenting insurgencies, the 1960 Sharpeville massacre, the Civil Rights movement’s “Bloody Sunday” in 1965, etc. However, it is also true that checkpoint-eliminating alternatives emerged from horizontally exerted soft power.

Significantly, soft-power challenges to geo-ethnic checkpoints have been conceived by an emergent, knowledge-wielding expert class. A very diverse group of well-educated intellectuals led anticolonial and anti-segregation movements that have eroded geo-ethnic boundaries. Prominent leaders with university degrees are too numerous to list here: Mahatma Ghandi (University of London), José Martí (Central University of Madrid), Kwame Nkrumah (University of London), Jomo Kenyatta (London School of Economics), Amílcar Cabral (University of Lisbon), Nelson Mandela (University of the Witwatersrand), Martin Luther King (Ph.D. from Boston University), Mao Zedong (First Provincial Normal School in Changsha), etc. These leaders not only absorbed globally dispersed knowledge, but recombined it in innovative, region-specific ways. They constitute, from an evolutionary informatics perspective, diverse and independent agents learning from their mutual exchange of signals. This emergent community is a complex adaptive system increasingly reliant on global information flows (see top of Fig. 1).

As society’s boundaries have been shifting from geophysical sites to worldwide connectivity in clouds via 5G and IoT, the boundary-challenging expert class has increasingly networked in global epistemic communities.Footnote 19 These specialist networks—guided by evidentiary norms of validity and reliability and a common purpose—exchange information on complex problems requiring application of scientific or technical expertise (Haas 1992). For example, a UN scholar and activist from India, E. S. Reddy (M.A. from New York University), played a key role in promoting international sanctions against South African apartheid (Korey 1998; for college degree, see Yale University Library 2019).Footnote 20 The American Committee on Africa (ACOA), the brainchild of George Houser (educated at the Union Theological Seminary), was one of many NGOs developing alternative ideas for sanctions, divestment, and loan denials to defeat South African apartheid (Korey 1998). In still another instance of successful soft power, the global professional intelligentsia guided all 22 countries in the Americas into signing ICERD, the International Convention on the Elimination of All Forms of Racial Discrimination (Burke 2010; FitzGerald and Cook-Martin 2014). Ultimately, increasing leverage for the professional intelligentsia’s epistemic communities arises from a growing reliance on technical expertise, on information combined in novel ways, and on horizontal networking that overcomes the inertia of large, vertically integrated institutions (Haas 1992; Powell 1990). As global complexity grows, a premium derives from open innovation processes (Witt 2016). Such processes are greatly advanced when information—possessing perfectly partible value—is offered as a public good.

It is evident that borderless epistemic networks can challenge the space-enclosing logic of racial–ethnic barriers. Yet, brewing outside these networks is a turf-defending, nativist backlash (Kobrin 2017). In terms of evolutionary informatics, the backlash may represent the landlocked heartland walling off boundary-crossing signals from the globe’s most networked domains. Multinational values and lifestyles in worldly cities are resisted by interior regions more strictly adhering to traditional boundaries and local customs.

Significantly, resurgent nativism may be a response to entropic debt associated with globalization’s impact on less networked and less adaptive structures. For example, switching costs arise from automation and unequally distributed “gains from international openness” (Kobrin 2017: 162). In a study of 25 advanced economies between 2005 and 2014, the findings reveal real market incomes for two-thirds of households either stagnated or fell (McKinsey Global Institute 2016).Footnote 21 Boxed in by this economic horizon, less networked (non-cosmopolitan) stakeholders resent losing sovereignty over localities or conceding cultural and political space—e.g., the Brexit rebellion against London’s EU connection. When the stakeholder’s identity is invested in a familiar placeFootnote 22 rather than in exploring new venues, sharing one’s space with foreign people and cultures generates a zero-sum dynamic (see Kobrin 2017). Consistent with findings concerning fixed-site rivalrous benefits, a re-emergent nativist territoriality may reflect economic and spatial displacement—real and perceived—for the heartland population. The consequent zero-sum dynamic may be reinvigorating geo-ethnic cleavages. Complex systems can devolve toward greater simplicity, as evidenced by Nazi Germany (see Weidlich 2000). Complex systems may entirely collapse from mounting entropy debt as did the Roman Empire, which suffered diminishing returns from its overtaxed dominions (see Tainter 1988).

6 Conclusion

It is theorized that the erosion—and greater permeability—of geo-ethnic boundaries is ultimately enabled by the progressive uncoupling of more highly evolved complex adaptive systems from geophysical location. That is, the boundaries marking racial and ethnic cleavages are rooted in socio-geographic processes such as metropole-directed resource extraction from tropical landscapes. These processes required non-market spatial segregation of populations tagged with hinterland lineage. However, entropic debts arise from merely walling in fixed-site benefits and ignoring ecological webs of interconnection. A key benchmark has been the post-WWII collapse of colonial empires and some of their least ecologically sustainable landscape-altering projects.

From an evolutionary informatics perspective, society’s progressive uncoupling from geophysical location does not entail greater independence from the surrounding ecological system. Quite the contrary, this uncoupling requires more innovative, information-driven adaptations. Innovations entail crossing boundaries to connect resources grounded in separated networks (Granovetter 2005; Schumpeter 1983). By crossing boundaries, the digital age promotes cybernetic parallelism: increasingly interactive, independent power centers enabling multiethnic globalism. However, in light of the current nativist resurgence, unraveling geo-ethnic boundaries may be convulsing toward more “racially” divisive, authoritarian governance. The trajectory of the unfolding chaos is unclear, because, consistent with the most fundamental postulate of evolutionary informatics, not all signal-boundary systems successfully adapt.