Darwin’s big idea of natural selection essentially removed the necessity for skyhooks. According to natural selection, complex things could and did emerge from simpler things and hence we no longer need to invoke skyhooks to explain how they came about. Instead we now have ‘cranes’ that can do all the lifting we need.

Daniel Dennett in Darwin’s Dangerous Idea (1995) uses the metaphor of the cranes used in building construction to contrast with skyhooks. Cranes are devices that can lift things, just like skyhooks can, but they are not magical devices that suddenly appear out of the sky. They are real, we know how they are built and where they come from, and they are planted on solid ground. Furthermore, small cranes can be used to build bigger cranes that can in turn be used to build yet bigger cranes and so on, until we end up with some really powerful cranes that can do amazing and, to the untrained and unobservant eye, may appear to be skyhooks and do seemingly magical things. But the wonderful thing is that they come about naturally.

Dennett argues that in the evolution context, cranes are natural processes that speed up the process. Starting with the simple and basic process of natural selection, increasingly sophisticated organisms have appeared over time that act like cranes, enabling even more complex life forms to be created even more quickly. In other words, we have evolutionary cranes creating even bigger, more efficient evolutionary cranes.

For example, the evolution of DNA likely started with point mutations at single locations. But once that produced organisms that were capable of reproducing sexually, the process of gene swapping that occurs during the process of meiosis (by which the sex cells that contribute to reproduction are created in the testes and ovaries) has led to much faster genetic changes and more rapid evolution than could be obtained using point mutations alone. So sexual reproduction is a powerful evolutionary crane.

Natural selection favors those systems that can evolve faster because they are more adaptable to changes in the environment, so that the rate of change of systems increases with time. In other words, evolution speeds up. Massimo Pagliucci suggests that “natural selection may favor the evolution of particular molecules (called “capacitors” of evolution), or arrangements of gene networks, that make it easier for a population to evolve in response to new environmental changes.”

All these processes eventually resulted in the emergence of human beings who have language and science and technology and thus can be considered as yet more powerful cranes because we are now able, through our ability to significantly control our environment and with genetic engineering technology, to create new organisms that would have taken a long time to come about by themselves without our presence.

Thus we humans are not only the product of work done by other cranes, we ourselves serve as cranes for future development. As Dennett says:

Vast distances have been traversed since the dawn of life with the earliest, simplest self-replicating entities, spreading outward (diversity) and upward (excellence). Darwin has offered us an account of the crudest, most rudimentary, stupidest imaginable lifting process – the wedge of natural selection. By taking tiny – the tiniest possible – steps, this process can gradually, over eons, traverse these huge distances. Or so he claims. At no point would anything miraculous – from on high – be needed. Each step has been accomplished by brute, mechanical, algorithmic climbing, from the base already built by the efforts of earlier climbing. (p. 75)

To me this is an amazing and exciting thing to conceive, that we have the power to explain life without invoking skyhooks, if not in all its details now, at least in principle. But not everyone shares this sense of excitement at the ever-increasing explanatory power of science. In particular, many people (and not all of them are religious) are uneasy about the idea that we humans, with all our sophistication, are also simply the end products of this mechanical algorithmic process. They simply can’t wrap their minds around the idea that there is nothing at all, no vital essence or soul, that is unique and makes us human, not even our minds or our consciousness or our sense of morality. While we have some qualities (like language) that distinguish us (at least partially) from other species, there is not a single thing that we humans possess that could not have come about through the same algorithmic processes that also produced slugs or worms or a leaf.

This can be hard to take for those who have a sense of superiority about the human species. Darwin’s theory so completely undercuts the basis for believing that humans are possessed of some quality that is not the product of the Darwinian algorithm that it distresses people and many have tried to find ways to suggest that it is incomplete. As Steven Pinker says, “People desperately want Darwin to be wrong . . . because natural selection implies there is no plan to the universe, including human nature.” (Steven Pinker, How the Mind Works (1997), p. 165)

Next: The intelligent design skyhook

POST SCRIPT: From bacteria to humans in four minutes

In the space of four minutes, Richard Dawkins gives an overview of the sweep of evolution from bacteria to our common ancestors with apes.