Evolutionary approach to understand human low fertility phenomenon Affiliations: Authors: Jozef Černák* 1 1 Department of Nuclear and Sub-Nuclear Physics, Institute of Physics, Faculty of Sciences, Pavol Jozef Šafárik University in Košice, Jesenná 5, 04000 Košice, Slovak Republic. *Correspondence to: jozef.cernak@upjs.sk Abstract: Is it possible to turn the low fertility? We think that more radical change of the global economy is needed that will stimulate series of self-regulation processes and evolution toward the safe fertility. Proposed changes should stimulate more uniform spatial distribution of production and wealth usage, increase in a number of self-sufficient territories, decrease of labor mobility and social mobility and careful consideration of a biological nature of fertility in economical or social actions. Main Text: Long-term world population growth is a consequence of suitable life conditions while natural limits preventing the future growth as a lack of food or energy were not reached. In the past, serious concerns were raised about the abrupt population growth that led to global actions increasing food safety and limiting descendants. At that time, some scientists warned about ignoring biological nature of fertility and population growth, and accepting short-term solutions which would cause serious issues to the next generations (1). Population projections are notoriously uncertain (1), there are predictions that population will continue to grow (2) but real data show a slow down of its growth there are even claims that the world population will stabilize before the end of the century (3). The world fertility has fallen over a long period, from 5.061 in 1964 to 2.453 in 2014, and shown considerable geographical differences. It slowly
approaches to the critical fertility 2.1 births per woman that is needed for a safe population replacement. In developed areas Europe, USA (4), and East Asia (5), fertility has been under the critical value for a long time. In underdeveloped Africa, fertility also declines but is still above the critical value. What are the reasons for geographic differences of the fertility? Is it possible to turn the low fertility? To answer these questions we consider human population to be living system that interacts with environment while obeying evolutionary rules. Where: evolution is the necessary consequence of heredity (memory), variability (mutations), and the rule that each generation provides more individuals than can survive (surplus). This rule implies selection, and thus the principle of survival of the fittest (6). The historical event of Iron Curtain fall serves us to show a strong link between economy and fertility. In the Central Europe and the Baltic, political systems and economy were characterized by systematic planning of both production and usage, and by advanced social systems. In 1989 a free market and social system with significantly declined governmental guarantees were introduced. New long-term phenomena emerged like unemployment, corruption, crime, low quality education and health care, weak pension system, increasing of taxes and living expenses, and property differentiation of individuals. Opening of borders started a labor mobility to economically developed world territories (7). EU founding countries suffer from low fertility the whole time thus a permanent inflow of qualified labor from new territories assists them to fill in missing work positions even to increase population. Political efforts to extend and integrate EU guarantee a safe population replacement in the most developed part of EU in the long term perspective. However, the unit currency contributed to noticeable EU differentiation, stagnation and high unemployment of the young
(7). The EU differentiation is also strengthened by mobility together with many hidden regulations and restrictions of labor market. The visible effect of these processes is a formation of economically strong and large territory in West-North orientation so called EU core see Fig. 1 (A), and economically weak and large territory in South-East orientation so called EU periphery (7). Core-periphery structures are ubiquitous in the nature, a castle lower castle, city village, city center its periphery, USA Europe, North South hemispheres, that show common universal underlying phenomenon of their formation, i.e. a self-organization of complex systems (8) that reflects economical and power rules in societies. Fig.1 Spatial distribution of production and usage. (A) Core (dark blue)-periphery (light blue) economic structure. Arrows show labor mobility. (B) A proposed more uniform distribution of production and usage to slow down mobility (self-sufficient territories).
The consequences of economical and social changes in 1989 on demography were devastating see Fig. 2. Gradual decreasing of fertility dropped strongly after the changes and has remained under the EU average ever since. Immediately after the changes, low fertility and allowed mobility caused continuous decrease of population. Fig. 2 Decline of fertility and population. Trends in fertility (left y axis) of European Union (EU), the Central Europe, and the Baltic (CE&B) and population of CE&B (right y axis). The list of CE&B countries: Bulgaria, Croatia, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Slovak Republic, and Slovenia. Data: The World Bank, http://data.worldbank.org/indicator/. Low fertility phenomenon is a long-term problem of developed world where: the basic social forces that underlay the historical decline in fertility are the shift from an agrarian to an industrial (increasingly service) economy, the decline of a rural way of life, the shift in the economic status of children from producer to consumer, the spread of universal education, the substitution of an ethos of rationality for one of traditional values from more religious times, the declining functions of the traditional family, the changing status of women, the development of modem contraception, and so on none of these seems ready to reverse direction (4). Generally
accepted is a simplified view that a decision to limit descendants depends only on women and their education (2). However, each woman is free in her choice and there are no visible rational reasons to limit family size in developed world. Still, women there prefer to live alone without an offspring or, in a better case, with a small family and solid social connections. What is a mechanism behind a woman s choice to limit descendants? To understand an individual choice of a woman to reduce amount of offsprings we will consider a simplified model of human population as a complex system (8) with features of living species (6). The model consists of many individuals F and M that interact with one another and with environment through a lot of diverse interactions for example, economical, social, etc. (9, 10). Individuals F and M could multiply by sexual connection, and F could breed the next generation. Their instincts mimic basic human instincts and they can learn. Let us consider individuals for nodes of lots of mutually intertwined economic, social (11), cognitive (12) and other networks where each network has own topology, development rules and properties of links. Individuals can move freely in the space and create different space arrangements. A motion of nodes influences surrounding links in networks, some of links are weakened, strengthened, created or canceled. Each change of the system involves huge series of responses of individuals due to mutual interactions and positive or negative feedback. These changes are typical for complex interacting systems while some of responses are hidden before individuals. Adaptation to the new conditions is reached by self-organization, collective phenomena (8) and evolution (6). The individual choice of F could be simplified to an artificial neuron where its input signals (inputs) are assigned to each network link. The inputs are proportional to input excitations, they are weighted and used as arguments of a node function. If value of the node function is higher than a threshold, a binary output is changed, an answer is: yes/no. Weights and the node function
are unique for each node and reflect a state of F and M in time of the choice. All parameters in the model can evolve. An individual choice of F is influenced by many diverse inputs as well as the node function. Some of inputs are mutually bound and they act on F simultaneously. Let us consider only two limited cases of influences of surroundings on individuals. In the case of weak interactions with environment, low levels of input excitations and low weights, the choice depends only on individual behavior of F i.e. her node function. In the case of strong interaction with environment, some of inputs are strong and weights are high, a choice of F is influenced by by a few or many external factors. The fact that F individuals choose the same answer nodescendants needs serious attention. We will demonstrate an individual woman s choice in the case of low economic safety. In developed world, a lot of F individuals work and have high living standards. Detailed view shows that their prosperity is really very unstable and depends on many factors like a permanent income, personal savings, loans, wealth, etc. (13) If individuals lose job and remain unemployed in long term their living standard gradually decreases due to low savings and after a certain time they are socially isolated. Lots of F individuals evaluate this situation as a serious threat to their survival. A society promotes an idea of equality strongly and does not recognize biological differences between F and M when they ask for the same working position. This forces F to behave like M and live without descendants. It is evident that a choice of F to have descendants forces F out of her economic network and has an impact on her survival which in the end influences her final choice significantly. Another important reason could be a collective experience (illusion) obtained by learning (a node function) that in high living standards it is
easier to survive without descendants. However, there are many other reasons that influence her choice like psychological reasons (9) or a postponed motherhood and parenthood (10). It is possible to explain geographic differences of fertility between north and south hemispheres by different living standards and economies. The north economy at low fertility depends strongly on a mobility from South i.e. core-periphery economical system (Fig. 1 (A)). During economical contacts between North and South a fraction of wealth (14) from North (core) is transferred to South (periphery) where living standards slowly rise which has an impact on decreasing fertility on the periphery. Demographic trends of Latin America and North Africa confirm this hypothesis. We assume that increasing living standards (1) and introduction of global economy in Africa will reduce population there, similarly as it happened in much smaller core-periphery economy in Europe (Fig. 2). The world fertility trends are clear, a number of countries with low fertility grows year after year. Low fertility is not a big biological issue because living systems are able to regulate population by natural means (1) no mater that a few societies may extinct. However, it could be a serious economical problem because the current global economy needs to increase global production that presses on increase of global usage. The usage can be increased by increasing number of consumers (a population growth) or by increasing individual usage where both solutions have real limits. EU extension approached geographical boundaries (15) that prevent a population growth of EU core and EU stagnation persists. A moderately lower fertility and modest population decline will force individuals to consume much more and will favor higher living standards (16), but subsequently fertility will continue to decline (1). This solution (16) is not sustainable because fertility must be higher than 1.6. An introduction of particular legislative
actions without deeper economic changes in Germany and China (17) have neglectable effect to the fertility increase. Low fertility phenomenon has dangerously extended on large territories and affects a lot of earth inhabitants that leads us to believe that emerging global low fertility phenomenon is the result of biological nature of fertility, biological nature of population growth (1) and human evolution in the given global economy. An effective response to changing low fertility trends is not known. Nonetheless, economic prognoses predict a lower economic growth (9) that may press on solving the fertility issue. We think that more radical change of the global economy is needed that will stimulate series of self-regulation processes (1) and evolution toward the safe fertility. Proposed changes should stimulate more uniform spatial distribution of production and wealth usage see Fig 1(B), increase in a number of self-sufficient territories, decrease of labor mobility and social mobility (9) and careful consideration of a biological nature of fertility (1) in economical or social actions. These proposals could be options for the global economy that seems to be a significant reason of emerging global low fertility phenomenon. At least two pillars of modern society should respect more the natural rules of evolution and should be revised i.e. mobility and equality. Decrease of the mobility is important in order to create healthy social bonds and society (11). A safe economic conditions of women, accepting their biological nature of fertility, influence of their closest and legislative support for motherhood (14, 17) and parenthood in optimal time for a woman could change their decisions to accept offspring. Generally, it might be very useful to promote a standard life style in accordance with evolution rules (6) where descendants are an integral part of population. In history we found events where proposed actions worked well. For example, a shift from hunter to agrarian society (slowed-down motion and new economy) or the world economy
shortly after WW II (1945-1960) when the world population temporally produced really less than it needed and economic activities took place simultaneously on large territories i.e. production and usage were much more uniformly distributed across the globe (Fig. 1 (B)). Low fertility phenomena is long-term issue of EU. We think that EU does not make adequate actions for solving this issue. However, developed societies in global economy should investigate impacts of economic, political and regulation actions on fertility trends. Evolution rules are clear (6). We think that it is not too late to consider biological nature of fertility, population growth and its natural regulation means (1) to solve population growth issues. Demographic changes diminishes importance of childbearing in women s lives, however what will fill this space (10)? Acknowledgement I acknowledge my mother, Z. Eperješiová, S. Bartošová and M. Reľovská for thought-provoking discussions. References 1. C. B. Goodhart, World population growth and its regulation by natural means. Nature 178, 561-565 (1956). 2. P. Gerland et al, World population stabilization unlikely this century. Science 346, 234-237 (2014). 3. W. Lutz, W. Sanderson, S. Scherbov, The end of world population growth. Nature 412, 543-545 (2001).
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