Scientifically-minded people seem a little confused about whether they think that intelligent life is rather common in the universe, or exceedingly rare.
In 1961 Frank Drake postulated that there might be between 1,000 and 100,000,000 intelligent, communicative, civilisations in our own galaxy. The range of possibility is now thought to be between 2 and 280,000,000 following further review of the various values contained in Drake’s ‘equation’. In other words, we don’t know.
Christian theology has no great interest vested in the question of extra-terrestrial life. However it does have some interest in the ‘anthropic principle’, or the notion of cosmological fine-tuning. It notes in particular that the earth seems remarkably (uniquely?) suited to the development of intelligent life. We may be discovering more and more earth-like planets elsewhere in the Milky Way, but planet earth might just be one of a kind after all.
Brian Cox’s recent presentation on the BBC web site seems to support this ‘rare earth’ (or, at least ‘rare intelligence’) hypothesis. He identifies a number of key events that have led to humans being unique not only on our home planet, but possibly ‘in our galaxy, or even our Universe’.
What are these ‘accidental’ events?
1 million years ago changes in the elliptical nature of the earth’s orbit led to a time of extreme climate change. At this time, our ancestors developed larger and more complex brains, giving them huge evolutionary advantages in terms of adaptability and intelligence.
65 million years ago a huge asteroid crashed into the earth. Over half of Earth’s life was wiped out, including most of the dinosaurs. This left a ‘niche’ for mammals to develop, leading ultimately to human life.
2.4 billion years ago cyanobacteria developed, producing oxygen as a waste product. Without the subsequent build-up of oxygen in the atmosphere, animal life could never have evolved.
2.7 billion years ago, when life on earth consisted only of single-celled organisms, two such organisms combined in what is believed to have been a one-off event. The resulting hybrid organism thrived and proliferated, and is the distant ancestor of all multi-cellular life today.
3.8 billion years ago complex molecules combined to form life for the first time. Although this event is shrouded in mystery, it is believed by many to have occurred at hydrothermal vents on the ocean floor. If these rather unusual conditions had not existed, life might never have got going.
4 billion years ago water (necessary for life to begin and thrive) appeared on the surface of the earth. This water is believed to have originated partly from the interior of the earth, and released by erupting volcanoes, and partly from icy comets crashing into the earth.
4.5 million years ago the moon was formed as a result of a collision between the earth and another young planet. The impact released iron from the earth’s core, contributing to the chemical mix that would contribute to the development of complex life.
4.6 billion years ago our Sun, along with the planets of our Solar System, was born as a result of the explosion of another star.
13.8 billion years ago the Big Band occurred, along with the constants of nature such as the speed of light, the strength of gravity, and other parameters. These parameters seem remarkably fine-tuned for creating the kind of universe in which life could eventually develop.
Before, or ‘outside’ time, it is believed by many that a countless number of universes existed (and exist). Each of the universes in the so-called ‘multiverse’ has its own set of constants of nature. Only one universe – our universe – offers the conditions in which life as we know it can exist.
Not all of these events are absolutely unique. For example, there was a time when, within our own galaxy, planets and asteroids were crashing into one another on a regular basis (the craters of the Moon testify to this). But some of the events (such as the origin of multi-celled organisms) do appear to completely one-off. And it’s not just the occurrence of these events that we must consider, but also their order and timing. Plus, there’s more to be said about each of them: for example, the Moon contributes much more to the habitability of the Earth than simply the release of iron from the core.
For the scientifically-minded, it might be said that the universe ‘saw us coming’. For the theologically-minded, it can be argued that this remarkable series of events leading up to our own existence is not only consistent with an overseeing Intelligence, but actually points towards it (or Him).