Evolutionary reasons why suffering prevails in nature

Evolutionary reasons why suffering prevails in nature

One of the main reasons the majority of nonhuman animals may experience more suffering than happiness in nature is that many more animals are born than can survive. The reasons behind these high mortality rates are rooted in the function of evolutionary processes and natural selection.

Evolution doesn’t optimize happiness, but fitness

Ecology and natural history are not shaped according to the interests of living individuals (i.e., what is good or bad for their wellbeing). Instead, they optimize the transmission of the animals’ genetic information. The relationships between different individual animals, and between them and their surroundings, are conditioned by those individuals’ traits, including the physical form they have, their physiology, the way they grow and develop, and their behaviors. All these features are elements of what is called an animal’s phenotype.1 An animal’s genes constitute their genotype, which evolved over many generations.

What determines the genetic makeup of animals in the first place? The simple answer is that the information has been transmitted to them by their ancestors. Different individuals carry certain information in their genes that leads them to be and behave in certain ways. Individuals who exist today had ancestors who managed to reproduce. If their ancestors had had different information, or if the genetic information of their ancestors had not been transmitted, then there would be no beings now with their genetic information.2

An animal’s inclusive fitness is the animal’s success in having their genes passed on to future animals (by them or by close relatives). But not all genetic information is equally likely to be transmitted. Generally, the more beneficial a gene is to an individual’s inclusive fitness, the more likely it is to be passed on.3 This is not always the case, since individual circumstances and chance are involved in whether or not an individual survives to be able to pass on their set of genes. But this is essentially what happens in natural selection and evolution. If a certain set of genetic information makes the animals who have it fitter to transmit it, then there will be a greater chance that future animals will have that genetic information. If, on the other hand, genetic information makes the animals who have it unable to transmit that information, then there will be no living beings who inherit it.

Because of this, different reproductive strategies have been selected for by evolution.4 Some strategies prioritize paternal care, longer lifespan, and features that often correspond with better welfare. These adaptations are important insofar as they improve each individual’s chances of survival to the point of reproduction. But since these adaptations require the investment of more energy, there are generally fewer offspring. Most other reproductive strategies produce large numbers of offspring, of which only a small percentage are statistically likely to survive into adulthood. The text Population dynamics and animal suffering explains how this causes immense amounts of suffering to occur in nature.

Reproductive strategies are among the traits that constitute what is called the life history of certain animals. The life history of animals is the sum of the patterns and events that happen in their lives at certain ages, in particular regarding their reproduction and survival. These include the age at which they reproduce, how many offsprings they have, how large their offsprings are when they come into existence, how much they invest in parental care, how many times they reproduce, and when they die. There are certain traits that provide a reproductive advantage to animals (that is, that make it more likely that the animals will have offsprings who will survive and reproduce themselves). Examples of these are reproducing at a younger age, having more offsprings rather than only one or a few, reproducing several times instead of just once, and investing significantly in their offsprings’ survival.

There are trade-offs that organisms and populations face between having some of these traits or others. If an animal has many descendants, it won’t be possible for that animal to invest significantly in their survival, and vice versa. Through evolution, animals end up having some of these traits instead of others, and the traits they end up with shape their life histories. The different traits are not all or nothing; animals have certain traits to different extents. For example, a species of animal might have only one or two offspring at a time and invest a lot in their care, but might give birth many times over a lifetime, so they will have more children than can survive in order for the population number to stay stable. Another species of animal might reproduce only once, but lay thousands of eggs, very few of which will survive infancy.5

The important thing to know about these traits is that the ones that are more common in nature aren’t traits that maximize the animals’ wellbeing; they are traits that maximize the chances that animals who have them will continue to have descendants through time.

Environmental resources are limited and competition is high to obtain the resources individuals need to survive (food, water, shelter, etc.). Many more animals are going to exist at any given point than their environment can feasibly support. Even if resources were to increase, the exponential rate of growth that occurs with each subsequent generation would make it impossible for their populations to remain stable, because it would require an extremely large amount of resources to continue this population growth. Many animals lay thousands or millions of eggs. Though not all of them hatch, the number of animals who come into being is vastly larger than the number that survive in order to keep population numbers stable (which on average is one offspring per parent each generation). Thus, for many types of animals, having a short lifespan and a high mortality rate is something that is biologically determined.

An evolutionary explanation of why animals have positive and negative experiences

As explained in the page on the problem of consciousness,6 positive and negative experiences (sometimes referred to as “states of welfare”) evolved as mechanisms motivating animal behavior that is more likely to lead to the animals’ survival, reproduction, or helping animals with similar genotypes to survive and reproduce (such as siblings). Ultimately, this leads to increasing the fitness of that animal, that is, promoting the transmission of the animal’s genetic information to new generations. Suppose some trait motivates animals to act in certain ways that benefit their fitness, i.e., they act in ways that support their survival, their reproductive potential, or the reproductive potential of other individuals who share their genes.7 Then we can expect that there will be a tendency for that trait to be selected for. Having positive experiences in certain situations motivates animals to be in such situations. This happens, for example, when they have enough resources to satisfy their physical needs. Likewise, when these resources are not sufficient and the fitness of these animals is accordingly reduced (for example, when they suffer physical harms or don’t have food), they tend to have negative experiences. In a changing environment, adaptability is key to the continuation of gene transmission. For the reasons we have just seen, one important adaptation that many animals share is the ability to consciously perceive the world through feeling and emotion – to be sentient.

We must also note that while happiness and suffering exist because they can increase fitness, they are not perfectly adjusted to maximize it. In natural history, features determined by genetic inheritance are selected simply when they work well enough to make a difference for genetic transmission. It is not necessary for them to work perfectly. So, conscious individuals have positive and negative experiences even if they themselves will never reproduce or contribute in other ways to the transmission of their genetic information (that is, helping other individuals with shared genes to reproduce).

How this leads to huge amounts of suffering in nature

This provides a background to understand why suffering can outweigh happiness in nature. Due to far more sentient animals coming into existence than can survive, and competition for resources,8 most animals have short lives and difficult deaths. They may starve, be eaten alive, or die from disease. If there were resources available for all at any particular moment in time, it wouldn’t last long because individuals would then multiply as much as they could until there were only resources available for a small percentage of them. It is therefore likely that more suffering exists than positive experiences in nature. Deaths due to the prevailing reproductive strategy of having large numbers of offspring appears to be a major cause.

Many of the harms animals in nature suffer result from other situations, such as extreme weather conditions or injuries. However, these harms can often be related to reproductive strategies. Population pressure can push animals into harsher environments than they are comfortable with, and many animals suffer injuries in their attempts to obtain the resources required for their own survival. In their weakened conditions, they are more susceptible to disease, parasites, and predators.

All this may sound strange to some people, because there is a tendency to expect that if something is the product of a natural process, it will be positive. However, this optimistic assessment is unwarranted. As explained in the section about the situation of animals in the wild, there are many ways nonhuman animals are harmed in nature. We have seen above an evolutionary explanation. The argument can be summarized as follows: In natural history, sentience is selected for because in many situations it increases an animal’s fitness, by encouraging behaviors that increase their fitness and discouraging ones that don’t, through the experience of pleasure and pain. But in natural history, certain life histories are also selected that favor certain reproductive strategies. These strategies imply that only a fraction of sentient beings can survive past infancy, and those who do survive usually suffer because of inhospitable environments that they cannot avoid. Of course, there can be many individuals whose lives contain much happiness. The argument we have seen doesn’t mean that suffering necessarily prevails for members of all populations or species. But it provides a basic explanation of why it is prevalent for so many of them.

Further readings

Barnard, C. J. & Hurst, J. L. (1996) “Welfare by design: The natural selection of welfare criteria”, Animal Welfare, 5, pp. 405-433.

Broom, D. M. (1991) “Assessing welfare and suffering”, Behavioural processes, 25, pp. 117-123.

Broom, D. M. (1998) “Welfare, stress, and the evolution of feelings”, Advances in the Study of Behavior, 27, pp. 371-403.

Catania, A. C. & Harnad, S. (eds.) (1988) The selection of behavior, Cambridge: Cambridge University Press.

Clarke, M. & Ng, Y.-K. (2006) “Population dynamics and animal welfare: Issues raised by the culling of kangaroos in Puckapunyal”, Social Choice and Welfare, 27, pp. 407-422.

Colgan, P. (1989) Animal motivation, London: Chapman and Hall.

Darwin, C. (1860) On the origin of species, New York: D. Appleton and Company [accessed on 17 January 2013].

Darwin, C. (2018 [1860]) “Letter no. 2814”, Darwin Correspondence Project Darwin [accessed on 29 August 2018].

Darwin, C. & Wallace, A. (1858) “On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection”, Proceedings of Linnean Society, 3, pp. 45-62.

Dawkins, M. S. (1998) “Evolution and animal welfare”, The Quarterly Review of Biology, 73, pp. 305-328.

Dawkins, M. S. (1990) “From an animal’s point of view: Motivation, fitness, and animal welfare”, Behavioral and Brain Sciences, 13, pp. 1-9.

Dawkins, M. I. S. (2001) “Who needs consciousness?”, Animal Welfare, 10, pp. S19-S29.

Denton, D. A.; McKinley, M. J.; Farrell, M. & Egan, G. F. (2009) “The role of primordial emotions in the evolutionary origin of consciousness”, Consciousness and Cognition, 18, pp. 500-514.

Fraser, D. & Duncan, I. J. (1998) “‘Pleasures’, ‘pains’ and animal welfare: Toward a natural history of affect”, Animal Welfare, 7, pp. 383-396 [accessed on 27 September 2019].

Lack, D. (1954) The natural regulation of animal numbers, Oxford: Clarendon.

Reznick, D.; Bryant, M. J. & Bashey, F. (2002) “r-and K-selection revisited: The role of population regulation in life-history evolution”, Ecology, 83, pp. 1509-1520.

Richards, R. R. (1989) Darwin and the emergence of evolutionary theories of mind and behavior, Chicago: University of Chicago Press.

Roff, D. (1992) The evolution of life histories: Theory and analysis. New York: Chapman & Hall.

Rolston, H., III (1992) “Disvalues in nature”, The Monist, 75, pp. 250-278.

Sagoff, M. (1984) “Animal liberation and environmental ethics: Bad marriage, quick divorce”, Osgoode Hall Law Journal, 22, pp. 297-307 [accessed on 15 April 2018].

Tomasik, B. (2014) “The predominance of wild-animal suffering over happiness: An open problem”, Essays on Reducing Suffering [accessed on 3 December 2014].


1 In a broader way, it has also been said to include the results of the individual’s behavior (for instance, a nest if it is an animal who builds nests for reproduction). See Dawkins, R. (2016 [1982]) The extended phenotype, Oxford: Oxford University Press; (2004) “Extended phenotype–but not too extended. A reply to Laland, Turner and Jablonka”, Biology and Philosophy, 19, pp. 377-396.

2 Dawkins, R. (2006 [1976]) The selfish gene, 30th Anniversary ed., New York: Oxford University Press. Smith, J. M. (1998 [1989]) Evolutionary genetics, 2nd ed., Oxford: Oxford University Press, p. 10. Mayr, E. (1997) “The objects of selection”, Proceedings of the National Academy of Sciences of the USA, 94, pp. 2091-2094 [accessed on 9 January 2013]; (2001) What evolution is, New York: Basic Books.

3 Fisher, R. A. (1930) The genetical theory of natural selection, Oxford: Oxford University Press. Hamilton, W. D. (1964) “The genetical evolution of social behaviour. I”, Journal of Theoretical Biology, 7, pp. 1-16. Dawkins, R. (1982) “Replicators and vehicles”, in King’s College Sociobiology Group (eds.) Current problems in sociobiology, Cambridge: Cambridge University Press, pp. 45-64. Mayr, E. (1997) “The objects of selection”, Proceedings of the National Academy of Sciences of the USA, op. cit.

4 See Pianka, E. R. (1970) “On r- and K- selection”, American Naturalist, 104, pp. 592-597 [accessed on 29 October 2019]; Parry, G. D. (1981) “The Meanings of r- and K-selection”, Oecologia, 48, pp. 260-264; Roff, D. A. (1992) Evolution of life histories: Theory and analysis, Dordrecht: Springer. See also the bibliography in Population dynamics and animal suffering.

5 MacArthur, R. H. & Wilson, E. O. (1967) The theory of island biogeography, Princeton: Princeton University Press. Stearns, S. C. (1992) The evolution of life histories, Oxford: Oxford University Press. Charnov, E. L. (1993) Life history invariants, Oxford: Oxford University Press.

6 This can be seen in Ng, Y.-K. (1995) “Towards welfare biology: Evolutionary economics of animal consciousness and suffering”, Biology and Philosophy, 10, pp. 255-285. Many more references are available in the section on animal sentience. See also Damásio, A. R. (1999) The feeling of what happens: Body and emotion in the making of consciousness, San Diego: Harcourt; Feinberg, T. E. & Mallatt, J. (2013) “The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago”, Frontiers in Psychology, 4 [accessed on 12 August 2019]; Barron, A. B. & Klein, C. (2016) “What insects can tell us about the origins of consciousness”, Proceedings of the National Academy of Sciences, 113, pp. 4900-4908 [accessed on 2 April 2019]; Godfrey-Smith, P. (2016) Other minds: The octopus, the sea, and the deep origins of consciousness, New York: Farrar, Straus and Giroux.

7 The latter is part of inclusive fitness, while personal fitness refers only to the extent to which an individual passes her or his genes to descendents after reproducing. See Hamilton, W. (1964) “The genetical evolution of social behaviour. I”, op. cit. See for a contemporary account Grafen, A. (2006) “Optimization of inclusive fitness”, Journal of Theoretical Biology, 238, pp. 541-563.

8 Suffering and death therefore occurs out of competition at both intraspecies and interspecies level. See for instance Cannon, G. B. (1966) “Intraspecies competition, viability, and longevity in experimental populations”, Evolution, 20, pp. 117-131; Connell, J. H. (1983) “On the prevalence and relative importance of interspecific competition: Evidence from field experiments”, The American Naturalist, 122, pp. 661-696 [accessed on 23 September 2019]; Chesson, P. L. (1985) “Coexistence of competitors in spatially and temporally varying environments: A look at the combined effects of different sorts of variability”, Theoretical Population Biology, 28, pp. 263-287.