Researchers reviewed 120 years worth of information on the evolution of human characteristics – including height, lifespan and physical performance – and concluded that there may be a maximum threshold which humanity cannot exceed.

The scientists claim humanity has plateaued as less sporting records are broken and more people reach but don't exceed the present highest life expectancy.

For example in athletics, Usain Bolt’s 100m and 200m records have not been broken since 2009, and no one has topped the US’ Kevin Young 400m hurdles record since 1992.

Similar peaks seem to have appeared in the world records for swimming, although Sweden’s Sarah Sjöström smashed two in freestyle earlier this year.

Professor Jean-François Toussaint from Paris Descartes University in France, said: “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.

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

And in a shock warning, the researchers have found that human abilities could start to decrease.

Professor Toussaint said: “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.

“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.

“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.”

According to the researchers, the next step is to discover ways to ensure “human capacities reach their highest possible values”.

Mr Toussaint 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.

“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.

“The utmost challenge is now to maintain these indices at high levels.”