Scientists explain why humans will not have longer lives

Humans may have reached their maximum limits for height, lifespan and physical performance, according to a first-of-its-kind research that looked at 120 years worth of historical information.

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

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.

Researchers 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," said Jean-Francois Toussaint from Paris Descartes University in France.

Rather than continually improving, we will see a shift in the proportion of the population reaching the previously recorded maximum limits.

Examples of the effects of these plateaus will be evidenced with increasingly less sport records being broken and more people reaching but not exceeding the present highest life expectancy.

However, 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," said Toussaint.

"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," he said.

"Observing decreasing tendencies may provide an early signal that something has changed but not for the better," he added.

"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," Toussaint said.