The Running Man

When time comes for the Olympics many scientific magazines likes to show how inferior humans are compared to other animals. High jumpers would not stand a chance against the Snow Leopard. Long jumpers would be an easy match for the kangaroo. Speed runners would be crushed by the cheetah and swimming fast certainly is not something humans do well compared to the Tuna. But there is one thing that humans do really well that would earn a medal at the animal Olympics.

Humans have great stamina and can outrun almost any animal over long distances. This is actually one of the benefits you get from being bipedal. Bipedalism is more energy conserving than walking on four legs. We have abundant sweat glands(eccrine) for cooling, those glands also have an endurance feature as they can keep on producing sweat without any recharging phase. This thermal eccrine system in humans is quite unique. Our Achilles tendons, our big knee joints and our muscular glutei maximi makes us very well designed for long distance running.

How would a man fair against a horse over a distance of say 22miles? Actually there is a yearly competition between man and horse in the Welsh village of Llanwrtyd Wells. In June 2004, for the first time ever, the human won.

Among the people who rejoiced at this outcome were University of Utah biologist Dennis Bramble and Harvard University paleoanthropologist Daniel Lieberman. Bramble had noticed that humans certainly are not adapted for speed, humans are comparably pitifully slow, a chimp can run at 60km/h while humans tops at 30km/h. So we certainly didn't go bipedal for speed. Also, bipedal speed runners all have tails. The tail is a major balancing organ for those animals.Bramble says.

In the whole history of vertebrates on Earth—the whole history—humans are the only striding biped that's a runner that's tailless.

So when did we become marathon runners? Most scientists agree that the chimp like Lucy, the 3.2-million-year-old hominid, couldn't have been a good endurance runner. Homo erectus(40.000-1.8million years ago) on the other hand had much longer legs, he had the disposition to run, but did he have the eccrine thermal regulation of modern humans?

Many animals use panting for heat regulation, this means increasing the breathing frequency to vent out heat. Experiments on chimpanzees show that they increase their breathing frequency when temperature increase, and sweat very little. This process has two major disadvantages. It needs muscular work, which itself increases heat, and it causes an excess loss of carbon dioxide from the lungs which in turn cause alkalosis. Heavily panting animals regularly become severely alkalotic. Cooling by sweating has the disadvantage that you loose precious water. This means that animals that sweat a lot need access to water to a greater extent than panting animals.

For long distance running the thermal regulation issue is very important, it is overheating that causes many animals to stop running. Suppose hominids started to travel long distances. Moving long distances gives you the advantage to adapt to changing environments i.e. move to areas that provide better opportunities for survival.But in this case, why give up panting? Wolves wander long distances and use panting for heat regulation which reduces their need for water.

Many animals can not control their breathing, studying panting animals you see that they follow a certain pattern, the respiratory system is elastic and has a natural frequency of oscillation. If it were not so the panting mechanism would generate more heat than it dissipates. Humans can control their breath, evolving from apes, this could mean that humans abandoned panting in favour of breath control if there were any benefits to gain. What benefits are there to be able to control your breath? It allows you to dive and it allows you to speak. Maybe it was the path through controlled breathing that led to a change in heat regulation in human evolution. This in turn led to humans, who already had the disposition to run, being able to exploit the niche of distance running and further develop in that direction.