Last Friday I went to a particularly interesting lecture about the science of laughter given by Professor Sophie Scott (from my alma mater UCL). It seems very little is understood about both why and how we laugh. But the lecturer gave us a canter through what we do know about the physiology of how we laugh (sadly rather less about why). Apparently, how we make sounds using our vocal chords, including laughter, is extremely complex. Basically speech and other sounds we make require extraordinary control of the diaphragm and other rib-cage musculature - which at the same time prevents us from taking a breath. Uncontrollable, ie involuntary laughter, is apparently trying to kill us. Helpless with laughter means just that - you're body is about to make you black out or worse.
The obvious question therefore is 'what is the evolutionary benefit of laughter if it hinders both fight and flight'? Well it would seem its all about socialising and confirming you're not only a nice friendly person, but also that you like the other person you're laughing with (but not laughing at). It's about putting people at ease in an infectious way. Passifying the people around you. Lots we still don't understand about this intriguing and apparently rarely researched topic. Do watch out for the lecture on the RIGB website if and when it eventually gets published.
The point to all of this is an interesting observation that Prof Scott made about the complexity of speech and the delicate control we need to have of our ribcage and diaphragm to achieve speech. Apparently we simply couldn't achieve this if we had continued to walk on all fours. It was only by taking the weight off our upper body that we gained the opportunity to develop extremely subtle control of all the upper body muscles, previously used to help us walk, run, climb etc, to enable us to manage delicate airflow between our vocal chords, while at the same time stopping us breathing. What we therefore sacrificed to some extent in agility and stamina, we gained in socialising which evolved into civilisation.
So arguably the single biggest step (sorry) change in our evolutionary history was when we learned how to stand and walk on two feet - itself a quite remarkable neurological skill we had to develop (subsconsciously too). And this suggests another intriguing evolutionary idea. Presuming therefore that only rudimentary vocal communication skills were possible while we were quadrupedal, the first primates who stood on two legs were taking a risk (slower, couldn't climb trees as easily etc). And since not everyone stopped standing on four feet at the same time, complex communication couldn't evolve for some time. So when the first primate did stand up, why did he (and she presumably) survive and pass on their behaviour to their offspring who ended up dominating the planet? What was it about standing up for these early humans that provided them with instant survival benefit/s?
There might have been at least two advantages to bipedal behaviour. The first is frequently cited by evolutionists - seeing predators and prey from greater distances, especially in long grass. This would have been particularly valuable since the front limbs had also been liberated to hold tools and weapons. But a benefit idea I have not heard suggested for those first bipedal experimenters might have been the ability they discovered of controlling their vocal chords more delicately in order to better imitate and therefore catch their prey = better fed ancestors. They could also better warn each other more precisely about dangers.
Who might have guessed that apes learning to stand on two feet would a million years later result in obesity, porn websites and religious fundamentalists? Maybe we haven't evolved all that much after all.