Humans may have reached peak in physical performance; all downhill from here

Humanity may have reached its peak in terms of parameters like height, lifespan and physical performance and is now probably in its downfall, according to major new research.

The research suggests humans have biological limitations, and that anthropogenic impacts on the environment - including climate change - could have a deleterious effect on these limits.

People have long thought of human development as one long process of improvement, going on forever. But we are now running up against the limits of how good we can be, say scientists – and most likely we'll now just begin to fall again.

The major research review looked at 120 years of data and found that there appears to be limits on our characteristics, like when we die, how tall we can be and how strong we are. We are pushing up against those limits now, the research suggests.

This review is the first of its kind, considering the effects of both genetic and environmental parameters. Despite stories that with each generation we will live longer and longer, this review suggests there may be a maximum threshold to our biological limits that we cannot exceed.

A transdisciplinary research team from across France studied trends emerging from historical records, concluding that there appears to be a plateau in the maximum biological limits for humans' height, age and physical abilities.

"These traits no longer increase, despite further continuous nutritional, medical, and scientific progress. This suggests that modern societies have allowed our species to reach its limits. We are the first generation to become aware of this," explains Professor Jean-François Toussaint from Paris Descartes University, France.

When researchers considered how environmental and genetic limitations combined may affect the ability for us to reach these upper limits, our effect on the environment was found to play a key role.

"This will be one of the biggest challenges of this century as the added pressure from anthropogenic activities will be responsible for damaging effects on human health and the environment." Prof Toussaint predicts. "The current declines in human capacities we can see today are a sign that environmental changes, including climate, are already contributing to the increasing constraints we now have to consider."

To avoid us being the cause of our own decline, the researchers hope their findings will encourage policymakers to focus on strategies for increasing quality of life and maximise the proportion of the population that can reach these maximum biological limits.

"Now that we know the limits of the human species, this can act as a clear goal for nations to ensure that human capacities reach their highest possible values for most of the population. With escalating environmental constraints, this may cost increasingly more energy and investment in order to balance the rising ecosystem pressures. However, if successful, we then should observe an incremental rise in mean values of height, lifespan and most human biomarkers."

For a long time, humanity has looked to be improving. Sprinting speeds that once seemed impossible are now commonplace, for instance, and the record for oldest person in the world is often being broken.

But with time, we'll probably see fewer world records being broken, the new research suggests, and little development in how old the oldest people are. More people might reach those peaks of performance, but the peaks will get no higher, the research published in the journal Frontiers in Psychology found.

"Observing decreasing tendencies may provide an early signal that something has changed but not for the better. Human height has decreased in the last decade in some African countries; this suggests some societies are no longer able to provide sufficient nutrition for each of their children and maintain the health of their younger inhabitants."

The focus of politicians and other important decision makers should now be to focus on ensuring as many people as possible can reach the current limits, rather than stressing our need to keep pushing them higher, the researchers said.

"Now that we know the limits of the human species, this can act as a clear goal for nations to ensure that human capacities reach their highest possible values for most of the population," said Professor Toussaint.

"With escalating environmental constraints, this may cost increasingly more energy and investment in order to balance the rising ecosystem pressures. However, if successful, we then should observe an incremental rise in mean values of height, lifespan and most human biomarkers."