Human Extinction: Not the Worst Case Scenario

Homo-velum The year is 3010 and an interesting new species has evolved: a muscular, knuckle-walking primate with sparse body hair and a strikingly human face. It appears to be deformed, with extra non-functional limbs in various anatomical positions–like something out of a sci-fi horror story or a genetic engineering experiment gone wrong. The creatures are vicious. Individuals routinely attack and eat members of their own species.

This generally isn’t how we envision our species a thousand years from now. More typical scenarios feature technological advancements, like flying cars and intergalactic travel. We might imagine that future humans will have eliminated disease and extended our lifespans substantially.

It’s debatable as to which of these scenarios is more likely. And of course, both could be far off the mark. But this much is clear: there’s trouble ahead for our species if we continue on our current path. The problems that future generations will face are largely predictable.

Our environment is becoming increasingly toxic, with carcinogens and teratogens, allergens, hormone distrupters, and pharmaceuticals accumulating steadily. Such pollutants also build up in the tissues of animals that we eat and depend upon.

Food shortages are anticipated. With the population increasing at alarming rates, there’ll be a lot more human mouths to feed. Heavier reliance on meat will worsen environmental problems, making clean drinking water harder to find. Non-animal food sources may also be much scarcer. If honey bees succumb to the threats they currently face, we’ll lose most of the foods that depend on bees for pollination.

Disease will be rife. Infectious disease will likely rise with the loss of biodiversity. Authors of a paper published last year in BioScience suggested that biodiversity loss “can increase the incidence and distribution of infectious diseases affecting humans.”1 Authors of a more recent paper appearing in Nature came to a similar conclusion, noting that, in many cases, biodiversity “seems to protect organisms, including humans, from transmission of infectious diseases.”2 Increased population size and proximity to one another will exacerbate the problem.

Cancer and environmental diseases will be widespread due in part to the greater toxicity of the physical environment and the foods we eat. Genetic disease is also expected to rise sharply. Michael Lynch, in a recent paper published in PNAS, suggested that the accumulation of deleterious mutuations will have a profound impact on members of industrialized societies within a few hundred years.3 He states: “Without a reduction in the germline transmission of deleterious mutations, the mean phenotypes of the residents of industrialized nations are likely to be rather different in just two or three centuries, with significant incapacitation at the morphological, physiological, and neurobiological levels.”

Unnatural selection2A society in which the majority of people have some degree of inherited or acquired disease won’t be able to function as our current society does. Presently, healthy able-bodied people in Western societies generally support those who are less fortunate. However, presently, healthy able-bodied people are the norm. What would happen if we all had some degree of impairment?

If we continue on our current path of unbridled consumerism and environmental destruction, the most likely future scenario is not one with flying cars and intergalactic exploration, but one with widespread disease and starvation, in which the quality of human lives is relatively low.

I think we can safely make two predictions: our species will have a markedly different array of traits in a few hundred years and we will be living in a vastly different environment. This has important implications for our evolution. With a different array of traits and a different fitness landscape, we can’t predict which traits will be most advantageous.

Of all of the species that have existed on the planet, only one has ever evolved the sort of intelligence and morality that distinguishes humans. It’s exceedingly rare that high intelligence arises through natural selection. It’s not safe to assume that either intelligence or morality will continue to be selected if our conditions change dramatically.

Circumstances are powerful determinants of human behavior. Plane crash survivors in the Andes ate less fortunate passengers in order to survive. Crime rates tend to surge when natural disasters strike and people will trample one another to escape a burning building. In a toxic environment where food is very scarce and dependent humans outnumber abler types, will morality confer fitness? Or might those who see members of their own species as an abundant, relatively uncontamined source of protein have an edge?

The average modern human may be more intelligent than the average human living a thousand years ago; but it is the gain in collective human intelligence that is most impressive and consequential. Our collective intelligence has given us technological and medical advances that greatly improve the quality of our lives. This intelligence is largely dependent on our technologies for storing and sharing information and on social infrastructure. Without industrialization, high quality education, and a healthy work force, we wouldn't enjoy these perks of modernity.

PollutionCivilization obscures our similarity to other animals. We tend to hold ourselves to different standards because we see ourselves as above nature. Many people find the slaughter of food animals objectionable. Yet no one is advocating intervention to save the gazelles from the lions or the rabbits from the foxes. Is the suffering of animals in the wild less important? Should we venture out in search of prey animals to rescue from their predators, and sick or injured animals in need of medical care? No, it would seem. It’s okay when nature imposes suffering on animals, but not when we do it. Similarly, it’s not okay when we are the subjects of nature's cruelty.

Civilization has bestowed our species with a distorted self-image. Many people seem to have the impression that we operate independently of nature. We are fortunate that we’ve been able to act as though we are independent for as long as we have. If we don’t adjust our way of living so that it becomes sustainable, however, nature will eventually do this for us.

The worst case scenario is not that humans will become extinct, but that we will come to experience the cruel will of nature as other animals do. We can’t rule out the possibility that we will become more similar to our primate cousins in intelligence, behavior, and quality of life. We may be enjoying the peak of human intelligence, morality, and technological advancement.

We currently enjoy an unprecedented standard of living, but we are headed for a grim future. Industrialized nations are riding a shortsighted, greed-driven juggernaut that may have more in common with the Titanic than with the Starship Enterprise. We ought to consider where we’d like to end up and plot a course.


1 Pongsiri, M. J. et al. Biodiversity loss affects global disease ecology. BioScience. 59, 945–954 (2009)

2 Keesing, F. et al. Impacts of biodiversity on the emergence and transmission of infectious diseases. Nature. 468, 647-652 (2010)

3 Lynch, M. Rate, molecular spectrum, and consequences of human mutation. PNAS. 107, 961-968 (2010)

Photo Credits:

top: The Daily Telegraph

middle: Luciano Morelli,

bottom: German History in Documents and Images (GHDI)