Before discussing our common ancestry and the conventional wisdom regarding who were our closest relatives and, when did some monkeys start to lose their tails and become smart upright walking clever-clogs like ourselves, I need to update you on the wonderful revolution going on in evolution, if you are not already aware of it? This radical new, and not so new, thinking in biological evolution, is unfortunately not getting out to the mainstream as yet. This is for various reasons, which I go into in other writings, blogs and publications, but for the purposes of this series on how WE EVOLVED, let’s just say that, while it may seem perfectly natural for us to assume that life evolved via common descent from a simple ancestral form, and let’s face it: how else could have life unfolded on our big blue planet, the most-up-to date genomics, molecular biology and many other related disciplines are pointing to something very different indeed? This is a rather convoluted and somewhat unexpected evolutionary scenario and is turning out to be nowhere near as simple as any of us, including Darwin, could have ever imagined. I think the situation is best summarised in Prof. Shapiro’s statement in the Boston Review (1997):
“[several decades of] research in genetics and molecular biology have brought us revolutionary discoveries. Upsetting the oversimplified views of cellular organization and function held at mid-century, the molecular revolution has revealed an unanticipated realm of complexity and interaction more consistent with computer technology than with the mechanical viewpoint which dominated the field when the neo-Darwinian Modern Synthesis was formulated. The conceptual changes in biology are comparable in magnitude to the transition from classical physics to relativistic and quantum physics”. (1)
The problem as I see it, is trying to get all this complex science out into the public domain, so that we can really begin to appreciate what it means for us and our present and future lives; it really is that profound. Shapiro has been one of the few academics who is actively sharing all of this wonderful stuff, but it is still rather tied up in scientific jargon which is difficult to decipher. All I have tried to do here is to decipher the scientific language and present to you the main ideas of evolution and how we came to be HUMAN. I’ve done my best to break the concepts down so that firstly, I could understand them and secondly, so that I could present them to you, so that you can understand them.
For example, I have had to learn about genetics from scratch and being an archaeologist with a very keen interest in human evolution, didn’t help much as my PhD specialism is prehistoric stone tools. However, this background did give me a great starting position and the academic training gave me the tools to do some serious archival digging. So I am not presenting this information as a specialist, but, simply as a human who wants to know how we came to be human.
Seeing the wood for the Old Darwinian Tree
What I discovered is not easily summarised in a sentence, although I could put it in a neat catchy phrase such as: ‘Un-common descent by natural genetic modification according to universal scaling laws‘, it still wouldn’t do it justice. Ok, perhaps it isn’t that neat or that catchy, but, maybe you’ll get a sense of what it entails if you read the phrase again. I must confess though, that the greatest obstacle I encountered on this journey of having to rethink evolution, was not the concepts themselves, although, they were difficult enough, but it was the trying to get the thoroughly engrained traditional thinking about evolution out of my head to free up some space for the new and much more radical concepts. In other words, in order to see the wood for the trees, I had to first try and put the great edifice of the grand old Darwinian Tree to the one side.
The Tree has become a Web
The tree of life has become a mass thicket, and is more like a great web of life. Common Descent should be seen more in terms of evolving adaptive complex systems/mechanism (nature evolved strategies so that animals, plants, fungi, bacteria and all manner of life could evolve themselves, meaning that yeast or bacteria didn’t require a common and single line of descent that branched off forming more complex lines of descent. In other words: Bacteria do not require a common ancestor, just a common mechanism to evolve and this principle applies all the way through to increasingly complex (amalgamated and well-coordinated cellular) life such as ourselves. Indeed, the proposed common ancestor of simple cellular life may have been from many independent origins and unfolded according to more universal principles that are familiar to physicists for example, but equally applicable to biological complex systems.
Nature’s Natural Mechanisms become reinstated as science
In a sense Mother Nature re-writes the genetic programs, sometimes without even changing the code, just the way it is expressed. This is done according to the experience and interactions between organisms and its environment. Now, returning briefly to the modern synthesis version of Darwin’s Theory in which it is assumed evolution unfolded via common descent. The main driver of evolutionary change and ultimately the change in species, was believed to be via natural selection. Natural selection was seen as nature’s ‘selecting agency’ where, those inherited traits and characters would give an advantage for survival and would help to produce more prodegy of their own kind, if the creature was lucky enough to have accumulated certain selectable traits. On the other hand, less fortunate creatures became fossilised and superseded by their successors in the great struggle for life and were seen as being the failures in life’s great struggle and therefore did not adapt and survive and go on to pass on their genetics (as it came to be known in the updated Darwinian version of evolution).
Did you know, that Darwin didn’t even think that ‘selection’ was the only driver of changing (heritable) characteristics? Yes, he thought it was the main one, but not the exclusive driver of change within the species. Indeed, he always had difficulties with the idea of extrapolating what was effectively akin to animal breeding that humans did within the same species such as dogs and pigeons to breed-out unfavourable, or breed-in, certain favourable traits (micro-evolution in modern speak) being powerful enough to explain macro-evolution (speciation), how on species actually changed into another. Basically, no matter how much breeding one does with dogs: one still ends up with a dog.
These other mechanisms for change, that Darwin thought to be more and more important as he revealed in later editions of his writings, is becoming vindicated as a very real mechanism of evolutionary change as we gain a deeper understanding of the genome and molecular biological systems and processes. This alternative driver of evolutionary change relates to the importance of the environment and its impact upon an organism and its adaptability to changing environments. In fact, most people before, during and after the idea of selection was proposed, believed in such a mechanism for evolutionary change. Even Darwin’s own Grandfather, Erasmus Darwin, thought this to be the case way back before Darwin was born, and most of the great men of science thought that environment had a large role to play in shaping a creature and therefore shaping evolution.
All in all, adaptation via an organism’s interaction within its environment – passing on heritable traits was very popular thinking of the day and indeed, when Darwin suffered an eclipse as it is called to refer to the period from the late 19th and early 20th century when his theory was believed to be inadequate to explain speciation, this thinking about the environment driving evolution had something of a renaissance. Essentially, it was believed that there was a mechanism whereby inheritance and cell/fluids of the organism could be shaped in response to its environment, especially in the development stages in the womb for example (during embryological developement when things were more malueable). These traits and characters in turn could be inherited; adapting an organism ever more within its primary niche. This came to be known as Lamarckian type evolution of acquired characteristics.
The interesting thing is that Lamarck is returning as of late and in more recent years these principles of evolution along with many other different approaches to understanding evolution such as embryological and evolutionary development processes (as proposed by scientists of the EVO-DEVO school – short for evolutionary development) reflecting the early schools of thought which flourished in many parts of Europe after Darwin’s fall out of favour and have become recognised at a molecular/genetic and epi-genetic (meaning above the genome) as a real and experimentally testable mechanisms and processes as a complex interplay that ultimately has driven evolution and speciation. I’ll explain how the primate fossil record can be reinterpreted in the light of this newer thinking in evolutionary biology throughout this human evolution series.
The traditional view of how fins became feet and feet become fingers
The assumption that we share common descent did not originate with Darwin, but with a growing idea which itself evolved, of homology. I.e. a similar feature such as a fin or five-digits developed due to our common ancestral features evolving and becoming more complex. The main issue with this of course, is why did some fish go on to become walking fish-like creature, while others remained fish? Why are we still desperately hoping to find the missing links between fish and walking amphibian-like creatures (they haven’t found this creature yet, but that is a story for another day) between amphibians and reptiles and reptiles and mammals? Not, those primitive/proto-mammals that some refer to as mammal-like reptiles which have nothing what so ever to do with reptiles (again a fact of misleading terminology which I deal with in other published work and forthcoming works in more detail). Where is our ancestor, or the ancestor of chimps before our genetically estimated split? Gaps remain gaps and links continue to remain missing and seriously contentious.
DNA (genes) and relatedness
The real gaps and missing links are to be found within the genome – within the other 98% that has been called junk DNA as it was thought to be full of function-less and repeating wastelands of non-coding DNA. We used to think that the mere 2% of the human genome that codes for proteins (genes) was all that mattered. We used to think that because humans and chimps shared so much of this coding region (2%) that our common ancestry and close relatedness was an absolute. However, more recent evidence would suggest something far removed from that so-called scientific fact.This is the topic of my next article on our human origins: ‘How closely related are we to chimps REALLY?’ This article will be followed by one entitled: ‘How the monkey lost its tail?’
I hope you enjoy the rest of the series
Reference for this article
1. Shapiro, J. A (1997) A Third Way in the Boston Review, http://new.bostonreview.net/BR22.1/shapiro.html