Are We Reaching the Limits of Homo sapiens?

Abstract

Echoing scientific and industrial progress, the Twentieth century was an unprecedented period of improvement for human capabilities and performances, with a significant increase in lifespan, adult height, and maximal physiological performance. Analyses of historical data show a major slow down occurring in the most recent years. This triggered large and passionate debates in the academic scene within multiple disciplines; as such an observation could be interpreted as our upper biological limits. Such a new phase of human history may be related to structural and functional limits determined by long term evolutionary constraints, and the interaction between complex systems and their environment. In this interdisciplinary approach, we call into question the validity of subsequent forecasts and projections through innovative and related biomarkers such as sport, lifespan, and height indicators. We set a theoretical framework based on biological and environmental relevance rather than using a typical single-variable forecasting approach. As demonstrated within the article, these new views will have major social, economical, and political implications.

Keywords: anthropocene; biometry; environment; human upper limits; life span; longevity; performance; public health.

Figure 1

Maximal physical performance has plateaued during the last three decades. Historical series of the best performances in Track and Field events have shown trends of plateauing since 1980 for both men and women, one of the early signs of established human physiological limits. (A) Annual World's 10 best performances from 1921 to 2016 in women for the 800 m event (blue), the high-jump event (green), and the shot-put (orange). (B) Annual World's 10 best performances from 1896 to 2016 in men for the 800 m event (blue), the high-jump event (green), and the shot-put (orange). Data are from International Association of Athletics Federations (IAAF: https://www.iaaf.org/home) and are normalized by the respective world records for the event at the end of 2016, that is, performances are divided by the current world record.

Figure 2

Maximal lifespan trends have shown a plateau for the oldest supercentenarian and the oldest Olympian. Since Jeanne Calment, who currently holds the lifespan record at 122.4 years in 1997, no one has lived more than 120 years and data suggest a plateau around 115–117 years that may indicate the potential biological upper limit of our species in terms of longevity. Oldest supercentenarian trends have shown a plateau for both women (purple) and men (blue). Similarly, maximal lifespan trends for oldest Olympians have shown a plateau for both women (red) and men (orange). Data for supercentenarians are available at the Gerontological Research Group (GRG; http://www.grg.org/). Data for Olympian athletes came from the most authoritative source of Olympian biographies (Clarke et al., ; Antero-Jacquemin et al., 2015).

Figure 3

Average adult height has followed a similar pattern toward a plateauing trend since 1980. The analysis of the growth patterns reveals that the gain in height during the last century is not a linear process. During the last 3 decades, data have shown a similar plateauing state in the tallest populations among women and men of high-income countries from North America to Europe. This recent asymptote suggests a potential upper limit to human height. (A) Average adult height of women (violet-purple) represented for each country from 1914 up to 2014. (B) Average adult height of men (blue) represented for each country from 1914 up to 2014. Data are compiled from NCD-RisC and available by country on their website (https://elifesciences.org/content/5/e13410).