Evolving by eliminating - it's human nature!

A question one hears often about the whole creationism versus evolution debate is: if we have evolved from apes then how come they stopped evolving?! Are they actually more intelligent than we all thought, and once they managed to create humanoids and spread them throughout the planet, they sighed and went into retirement with no further interest in doing it again? A bit like man going to the moon. Been there, done that!

But it is an interesting question, and in the absence of the ultimate "missing link" being excavated tomorrow, it continues to come up. However, unless you never heard of that nasty acronym, DNA, and think of it as mere smoke and mirrors, then it is essentially impossible to deny our intimate relationship to the great beasts that came before. As Darwin always believed, the forceful scythe of evolution will exert its effect and carve out a better version of what preceded it - given time, favourable environment and sufficient resources.  

The mystery over why great apes stopped evolving into "us" doesn't seem that complicated to me.  First off, at some point, due to a collusion of advantageous circumstances, we split off from the apes at an evolutionary crossroads of sorts known as speciation, whereby a distinct new species evolved from its precursor. To this day we do not know precisely what it was that permitted this new branch to form on the tree of life, but we cannot rule out that some of it happened by geographical/environmental good luck. In other words, what might have transpired in one region of Africa might not have been repeated in other parts of the country. 

One fascinating aspect of how we appear to have evolved from more primitive relatives concerns social behaviour and fire. This has not changed that much in millions of years, which the millions of barbecues grilling slabs of raw meat in the summer bear witness to - we love to get together outside and cook on an open fire! From what is known about our evolution, it appears to have been when our ancestors discovered fire that everything changed. 

Why? Well, let's get to the more obvious point first. Whether it happened by accident or by a spark of early human-like genius, some bright spark threw their piece of a carcass onto the fire, and discovered that the meat was tastier and much more tender than the raw version. Bingo! The effect that this had on our development appears to have been a staggering one. Can you imagine why?

Well, all of a sudden, and keep Darwin's evolutionary scythe in mind, the need for such power in the jaws and teeth was obviated when the meat was juicy and tender. Unquestionably, over time, this led to changes in the maxillofacial skeleton: jaw size and maximum force were significantly reduced. This had an incredibly profound effect on the development of early hominids (as opposed to humanoids!) because with much less evolutionary pressure applied on the jaw, it meant that skull size (and therefore brain cavity) was increased. 

It seems perfectly obvious now that I write it, but it would never have occurred to me had I not read it myself. I guess it truly underlines the saying that "you are what you eat"! So, smaller facial muscles and jaws allowed the brain to take a major leap forward, and nothing would be the same again. Scientists have even determined that a mutation in the sequence of one gene, MHC-16 (a gene involved in muscle development), some 2-3 million years ago, seems to have been central to this development of increased skull cavity and brain size. 

Another take on this whole story is that it was as much the social behaviour that was part and parcel of cooking meat on an open fire (Friday night barbecue, gang?!) that played a major role in our evolution. It's impossible to imagine exactly what type of interactions occurred but maybe something about community building or joining forces and eating together seemed to be favourable for all? Social interaction is a major part of survival for many, many species, and to this day humans benefit from social contact among those close to them, even while fighting other members of the species farther afield. 

In any case, some combination of local environment, the appearance of fire, dietary improvements and changes in the jaw/skull size ratio led to a more truly evolved creature. I could be cynical and say that as far as we are aware, none of the great apes are sitting around cooking meat at campfires today, due to a key environmental factor being missing for such development, therefore there are no new early hominids. But that's a bit too easy, and is probably far from the real reason. 

You know, in many ways it is pretty accurate to say that the most deadly creature on the planet, is, well, wait for it - mankind. We have raped and pillaged, and colonised, and taken, and eliminated anything in our way on the journey. There's a line of thought (hardly a stretch) which suggests that early mankind was ruthless in eliminating its closest competitors - those bigger-jawed dumbass beasts that came to steal our food. It is entirely believable that our ancestors cleaned out their surroundings in order to survive and then spread out to spread the word. Go west, young man!  

We have eliminated so many species from the planet in the interests of our own survival, whether it was direct (food supply) or indirect via optimising the planet for our continued growth and evolution. If that ruined ecosystems or the ozone layer or polar ice caps, well, that's life, right? Had we discovered a violent species on the moon which threatened us, what would we have done? Back then, we would almost certainly have eliminated it, too. The negative effect of mankind's presence on the planet was recently underlined by reports that wildlife population in the world has declined by a massive 50% since 1970!

Modern man has devastated the natural ecosystem of species even close to extinction, so it's hardly surprising that apes no longer can evolve into hominids given that their natural environment of days gone by effectively no longer exists. The mere presence of man on the planet has made the jungles less safe places to be - for the animals! That expanding presence probably does represent a negative stress in the jungle, one which was absent earlier in evolution.  

In other words, not long after speciation occurred and we became slack-jawed but big-brained hominids, we eliminated our closest relatives, and the right combinations of favourable circumstances never occurred again. It's even believed that man eliminated Neanderthal man, some 40,000 years ago, and humans have since manipulated the planet in ways that are not strictly evolutionary, which has wreaked havoc on the Earth. But if one looks at it as a result of our increased cranial size and brain capacity, and it is all about survival of the fittest, then it will all go down in future history books as part of the ruthless evolutionary process.

But not everyone is as convinced as me, and to each their own. In fact, it's grey, cold and wet here again, making it a perfect day to go squatch hunting with the gang of "Finding Bigfoot" - however, the closest they have gotten so far is finding big feet - their own! I wonder why? ;)