Human Evolution

According to natural selection, the evolution of life, from its earliest single-cell beginnings, some 3.8 billion years ago, right through to the emergence of modern man, some 140,000 years ago, can be described in terms of small incremental steps. However, some 10,000 years ago, human civilisation started to develop at a rate that cannot be directly explained by natural selection. It would appear that humanity had stumbled across another path.


Past, Present Future

Today, it is generally accepted that human evolution is part of the story of life on Earth. We can encapsulate this perspective, without initially getting too lost in the details, by a timeline scaled to a 24-hour day. In terms of the Earth, past and future, our timeline starts 5 billion years ago, with the formation of the Earth, and ends some 5 billion years into the future, when science predicts that an expanding Sun will consume the Earth. So the start of our day begins with the creation of the Earth and ends with its destruction. As such, today, we are halfway through the lifetime of the Earth; it is midday. The following table tries to illustrate a number of key events in human evolution in terms of time, measured in years, our 24-hour/now clock and the number of human generations:

Evolutionary Event Years 24-Hours Now Generations
Earliest Hominids -5,000,000 11:59:17.0 -43seconds 1,000,000
Australopithecus -2,000,000 11:59:43.0 -17seconds 100,000
Neanderthals -500,000 11:59:55.0 -5seconds 25,000
Modern Man -140,000 11:59:59.0 -1second 7,000
Recorded History -10,000 11:59:59.9 -1/10thsecond 500

On our 24-hour clock, modern man would have only appeared about 1 second ago and the sum total of all recorded human history amounts to about 1/10th of a second. While the 24-hour clock analogy can be helpful in gaining some perspective relative to the lifespan of the Earth, it is also useful to consider the same events in terms of the number of human generations that have elapsed. This said, we might wish to ask ourselves the following question at this point:

What are we going to do for the rest of our 24-hour day?

However, before we can really start to consider such a question, we need to reflect a little further on the process of evolution, which has brought us to this point in time and, more importantly, reflect on the processes of evolution that may determine our future.

The Past

The very earliest fossils of single cell structures have been dated at some 3.8 billion years old. The evidence suggests that life existed in this primitive form for over 2 billion years until the earliest multi-cell organisms appeared. It would take another billion years or so for the diversity of life to explode during the Cambrian period, some 500 million years ago. So, half the 24-hour day has ticked by, all but for 1 second, with life centred on only one all-consuming purpose: survival. However, in the context of the 1-second of human evolution, which separates humanity from the rest of evolutionary history, a new aspect of life emerged, i.e. sentient intelligence. While natural selection does not suggest that intelligence, or even sentience, is unique to humanity, it does appear to have taken a path that has separated humanity from all other species on Earth. As indicated, the emergence of human intelligence is a very recent event on our 24-hour clock and possibly not an obvious one in terms of natural selection.

Note: The human brain has increased in size dramatically over the course of human evolution, possibly starting off more comparable to a chimp's brain, at some 500cc. However, by a million years ago it is estimated to have doubled in size to about 1000cc, while today, a typical brain is estimated to be around 1500cc. Exactly why our ancestors started to develop bigger brains is not obvious, as natural selection would suggest that there are several disadvantages from a survival perspective. First, there is a prolonged gestation period, followed by an even longer nurture period, before an infant can even remotely fend for itself. An enlarged brain also requires more protection, sophisticated temperature control and feeding, before it can offer any additional survival benefits. It has been estimated that ¼ of our metabolism is required to support our brain function, which only compounds the survival risks that an overheating brain would have caused in the hot climate of Africa. However, it is thought that the increase in brain size also caused changes in the human diet, which eventually led to new hunter-gather migrations in search of higher protein food and more temperate climates. So, on the upside, humanity started to become more adaptable to a wider range of changeable environments.

While there may have been an initial hominid exodus from Africa around 1.75 million years ago, there is growing genetic evidence suggesting that modern Homo Sapiens only started to migrate out of Africa around 140,000 years ago. While it is possible that Homo Sapiens initially co-existed with Homo Neanderthalus and Homo Erectus, these species were eventually eradicated or assimilated; a lesson we might have to reflect on again in the future. Evidence also suggests that Homo Sapiens continued to live as a nomadic hunter-gatherer, until about 10,000 years ago, at which point, the advent of farming would trigger a cultural evolution that would lead to some of the earliest civilisations in recorded human history.

Note: Under the heading `The Past`, we have only briefly covered a few of the most salient issues of the first 140,000 years of unrecorded human history, much of which is still open to speculation. For example, while it is often claimed that the human brain did not evolve over all this time, such a statement should come with a note of caution. The evidence underpinning this conclusion is predominately based on fossil records, i.e. skull sizes, which provides little to no insight as to the internal organisation of the brains they once contained. Of course, developments in genetic research might yet throw more light on this subject. However, while not doubting that natural selection was at work during this time, the majority of the evidence does appear to suggest the fact that significant evolution typically works on a much longer timeframe than human history. If so, we must look for other explanations for how human civilisation progressed from its first tentative steps into farming to its first tentative steps on the Moon in less than 500 generations, i.e. the 1/10th of a second on our 24-hour clock.

The Present

Let us simply define the `The Present` as the 10,000 years of recorded history. If we assume that the steps in human evolution over the last 140,000 years were, at best, small ones, then it is difficult to explain the rapid `evolution` of human civilisation by natural selection.

So what might account for this apparent quantum leap in evolution?

As a general description, natural selection works via DNA information encoded into `genes`, which is then physically transferred to future generations by way of direct descendents. However, in higher intelligent life forms, information can also be communicated through actions or gestures. In 1976, Richard Dawkins introduced the concept of a `meme` as a unit of transferable information that suggests a mechanism by which a collective group could evolve in much the same way as an organism, i.e. by passing its memes, and just not genes, from one generation to the next. Dawkins also suggested that some memes could increase or decrease the probability of survival of a group, thereby invoking a form of natural selection. However, while the transferring of memes has some parallels to genes, the transfer of information is much faster and not restricted to direct descendents. In fact, this process of information transfer might be better described in terms of a viral infection. However, while the spread of memes might be subject to a form of `survival of the fittest`, the rate at which memes spread is linked to attributes, which today might be better understood if described in terms of 'network communications':

  • Data Accuracy: If errors occur in transfer, then information may either become damaged or dangerous.

  • Speed of Transmission: The spread of information depends on speed and range of the distribution mechanisms available.

  • Longevity of Storage: Is dependent on the durability of the `media` on which the information is stored, plus the previous attributes.

If we accept some of these assumptions, then the advent of language, writing and the printing press all represented major evolutionary milestones by virtue of an associated increase in the amount of information that could be passed from one generation to the next. These milestones led to ever-faster rates of change and ultimately to two key `evolutions` in human civilisation:

  • The Industrial Evolution
  • The Computer Evolution

The industrial evolution changed the physiology of human civilisation, while the computer evolution is changing the neuro-physiology of human civilisation. Today, industrial processes dwarf the physical capability of earlier civilisations, while semi-automated computer systems exchange terabytes of information around the globe everyday. These successive evolutions have led to technology developments, which could now determine the future of humanity, at least, for the next 1/10th of a second!

The Future

We defined our 24-hour clock based on the lifetime of the Earth, even though there need be no explicit link between the fate of humanity and the Earth. However, the next 5 billion years is more than enough time for us to consider any further predictions regarding humanity. In this context, maybe we should consider our predictions concerning the far future as something closer to astrology, i.e. best kept vague. However, even nearer-term predictions tend to gloss over the social implications of the `brave new world` just around the corner. For example, two hundred years ago, the industrial revolution was going to free mankind from manual slavery and while partly true, it came at a price that was not initially predicted. Fifty years ago, computers were going to remove the drudgery of repetitive tasks leading to more leisure-time, but again few predicted the social implications that came along with this deal. However, with these cautionary tales noted, we might still wish to extrapolate a few possibilities based on some defined assumptions and then limit these predictions to a nearer future, say the next 1000 years or so. We will begin by outlining our assumptions:

  • Evolutionary Mechanisms:
    Based on earlier arguments, 'natural' selection will be discounted as an evolutionary mechanism operating on a future less than 1,000 years. If so, speculation will be orientated towards the idea of evolution-by-design and although this may not necessarily lead to a better future for humanity, it has the potential to diverge from what we now define as 'homo-sapiens'.
  • Social Cohesion:
    However, evolution-by-design is still assumed to be predicated on some degree of social cohesion in which technology can continue to develop. Therefore, we need to reflect on the possibility of a society trying to cope with evolutionary change, brought about by technology, while natural resources continue to fall due to the onslaught of an ever increasing population.

  • Environmental Stability:
    In this wider context, the stability of the earth's environment will become an increasingly important factor, at least, while humanity remains tied to planet Earth. Of course, within the next few centuries, we may see increasing numbers able to exist outside the Earth's biosphere and although they will be a minority of the population, they may become a key factor driving some aspects of evolution-by-design. For the remaining population, we might need to reflect on two other effects:
  1. Self-inflicted disasters
  2. Natural disasters

For today's generation, the most obvious examples  of self-inflicted disasters may be global warming and nuclear winters, while massive volcanic eruptions or meteor strikes may be more representative of natural disasters.

Note: Further discussion of future human evolution has been discussed in terms of 'Human Evolution' and 'Brave New Worlds'. These discussions may also be complemented by another discussion, e.g. 'Population & Resources' and 'Climate Change'.