Sweating Apes.

I've been training to run a marathon recently, and, inevitably, that has led me to ponder the origins of humankind.

Humans have outrageously big brains - some admittedly bigger than others - and it has always been my understanding that the reason we survived the competition with all the horribly fast, ferocious and disgusting species out there was because of these bone-encased supercomputers. We out-thought our competition in tiny, incrementally larger ways. We made it because we're smart, we made tools to hunt, rafts to float on, and spread our way across the globe. The smartest kept surviving, and the race kept getting smarter. That simple. Or so I thought.

Evolutionary anthropologists - scientists that study human evolution - would point out that proto-humans have been eating meat for the last 2.6 million years, but the simple hunting tools that I imagined us using to get the better of our prey, like the bow and arrow, didn't get invented until around 50 thousand years ago.... That's a hefty 2.55 million years of tool-less meat eating. How did they do it? Scavenging would be one option, but the consensus is that this only played a partial role, hunting was the preferred method. I would be woefully pathetic at hunting even with tools, so I can't quite imagine how a similarly sized hairy humanoid, with no tools, no razor sharp claws, and no Google, could hunt a gazelle.

Have you heard the apocryphal tale of how the marathon, a 26.2 mile fun-run, got it's name? The tale goes that a guy called Pheidippides (let's call him Phil) ran 25ish miles from the Battle of Marathon to Athens to deliver the news that the Persians had been defeated. After delivering the glorious news (I assume the Persians were the bad guys), he collapsed and died. Before you start to feel sorry for Phil, this almost certainly never happened. Phil never existed. Cross country running as a means of delivering important news was common back then, and runners would often do many times this distance without issue. Horses had been domesticated by this point, so why were there runners? Because long distance running is just what we're good at. If the game of life is won by playing to your strengths, using human runners just makes sense.

The current best explanation for how we survived 2.55 million years of hunting without tools is that we became specialized in long distance running. We would literally just chase and chase and chase until the prey couldn't go on any longer, give up, and let us eat it. Cheetahs are incredible, reaching speeds of up to 75 mph (sorry, sometimes I'm imperial), but they can't maintain this speed for long without having to stop and cool down. In fact they will prioritize cooling over eating by sitting and panting for as long as half an hour before tucking in to their prize. After my 5 miler today, I dove straight into the fridge for my prize - a veggie samosa. No panting required.

We were the things of horror films, never relenting, always slowly creeping after you. You think you've escaped, but that small group of hairy bipeds will just never stop, not until you pass out and they eat you while you try and catch a breath. We were Earth's first zombies.

But why don't humans need to cool down like a Cheetah does? Speed plays a role, but eventually you're going to overheat either way, surely? Well, no. The reason I don't need to worry so much about cooling down is because I can do something most animals can't - full body sweat. Sure, all mammals sweat in some form, and in fact the name mammal comes from their tell-tale mammary glands, which are basically specialized sweat glands. Only rarely though is sweat used to cool down, and even more rarely does the sweating occur as the exercise is ongoing. Here comes some science. Our sweat glands release little droplets of slightly salty water (with small amounts of hormones and last night's alcohol added) that begin to evaporate in contact with the air. Evaporation takes a bit of energy to get going, a little bit of heat, and it extracts that heat from your skin. Simply put, evaporation makes things colder. Unlike dogs, for example, which only have sweat glands in their paws, we have them all over, and they release sweat as soon as our temperature starts to increase. This is why it's so uncomfortable in humid environments, because your sweat can no longer evaporate when the air is saturated, and so sweat does nothing to cool you down. It just makes you drip. 

Full body sweat is only one of our specially evolved traits that makes long distance running possible. Fossils show that around 2 million years ago we gained adaptations that can't easily be explained without us evolving as an army of Mo Farrahs.

This is likely what the fleeing gazelle saw every time it looked back. The gazelle died. Image courtesy of Tom Moore Photographics.

For example: elastic tendons in our legs and feet that store and release energy between strides, lowering the work requirement to keep going; large glute (ass) muscles for upper body support during a run; elastic ligaments in our necks to keep our heads steady during the continuous exercise; and an unusual tendency to swing our arms to maintain balance. Gorillas don't do this when they run... Though only a lucky few have seen a gorilla run and lived to tell the tale. If you're still unconvinced that we're marathon apes, a final piece of evidence is that there are still some tribes of aboriginal humans that use this relentlessness running tactic to chase their prey to exhaustion today.

This all adds up to us being natural born runners. Click here for a well referenced Nature article discussing this topic more eloquently, and here for a rant from an angry man that disagrees. 

In conclusion, there is absolutely no excuse for me to not complete this marathon. Though, I can't promise I won't collapse and die like ol' Phil didn't. 

Thumbnail image created by (and used with permission from) Jimbob Art. Thank you Jimbob.