1. INTRODUCTION

We are immodest enough to think the belief in the idea that life exists in space and originated from, and continues to arrive from this source (i.e. panspermia), is a relatively modern idea, first elaborated during the late 1800s. Recent textbooks and popular accounts of astrobiology and panspermia (Kamminga, 1982; Temple, 2007; Tepfer, 2008) generally promote this view by providing only an incomplete history referring to contributions made by the fifth century BC, Greek philosopher, Anaxagoras and the much later contributions from the Victorians, Helmholtz and Lord Kelvin. Reference is then generally made to the work of the Swedish physical chemist, Svante Arrhenius in the early 1900s, to the more recent ideas of "cometary panspermia" (Hoyle and Wickramasinghe, 1999) and to so-called "directed panspermia" (Orgel and Crick, 1973). Although the above-mentioned contributions are obviously important to the development of the theory of panspermia (Wainwright 2010), the history of these ideas have been nearly forgotten; some components of which will be discussed here.

2. DE MAILLET: ARGUABLY THE FIRST "MODERN" PROPONENT OF PANSPERMIA

While it is clear that Greek philosophers, like Anaxagoras, suggested the possibility that life on Earth arrived from space or other planets, these ideas lay dormant for nearly 2,000 years, until the French philosopher, Benoit De Maillet provided a "modern" (that is as opposed to "ancient") argument in favour of panspermia. De Maillet, a French Government official, was widely travelled and was the author of an anonymous book entitled Telliamed (De Maillet spelt backwards). This book, which featured an imagined conversation between a fictitious oriental (Indian) and equally fictitious European, became a highly influential early text on geology and even detailed a theory of evolution. For many years, Telliamed circulated in manuscript form amongst French intellectuals, and was only published in 1748, ten years after De Maillet died. An English edition was published in 1750 (Anon, 1750), although the first unabridged version was only made available in the late 1960s (Carozzi, 1968).

The references made by De Maillet to panspermia can be found in a marginal note to his Third Conversation in which he states:

There is no doubt that De Malliet is here suggesting that "seeds" are found throughout the cosmos; but what does he mean by "seeds"? When De Maillet continues, we see he is not referring to plant seeds, but is arguing that all life forms have arisen from microscopic protoforms which contain the germ of life, i.e., "seeds". He continues:

The word "seed" then is used in its broad sense to mean a source, or beginning. It is also interesting that he speculates that such living forms might be sub-microscopic. De Maillet continues:

Clearly, De Maillet visualises that his "seeds" are concentrated around planets and held there by gravity. Further, he visualizes these seeds as traveling across the "void" of space. He also sees the oceans playing an important role in receiving these seeds and here he invokes Moses:

Now at this point we might imagine that De Maillet is merely talking about proto-life forms that merely resemble small seeds or sperm, but things become even more interesting with his next statement:

De Maillet is referring here to what Antonie van Leeuwenhoek and Robert Hooke observed and referred to as "animalcules." Whether De Maillet is quoting these sources, or actually saw such forms himself is not obvious. It is clear however, is that he is aware that animalculae (e.g., algae, bacteria and protozoa), are present in water in which grass is present. However, his over-developed imagination soon takes over, as he also states that:

It is however, more reasonable to assume that all species do not exist on all globes, and that there are still many more to hope for, on Earth, as well as on each of the other globes. The globe we live on has certainly shown us only a portion of the species of animals, trees and plants whose seeds are contained in the surrounding air and sea, and we cannot doubt that the future centuries will reveal new and unknown ones.

Finally he states:

Although the modern versions of panspermia theory generally sees microorganisms as the form that is transported throughout the cosmos, it is interesting to note that some other authors have speculated on the possibility that more advanced life forms may be involved in and may have directed panspermia. Lord Kelvin, for example talked of massy stones being transported, while Hoyle and Wickramasinghe (2000) have speculated on the possibility that insects may play a role in panspermia. More recently,Tepfer (2008) has suggested that plant seeds might also be transported across the cosmos. Echoing yet another theme of De Maillet, Joseph and Schild (2010) have argued that a vast array of diverse life may have evolved on other planets, that life on Earth represent only a small sample of life's possibilities, and that these "seeds" contain the genetic instructions for specific life forms. Thus, De Maillet’s views are completely in sync with modern views; further evidence that the only new ideas are those which have been forgotten.

De Maillet’s views were widely discussed in certain, esoteric circles but in the end had little influence on modern thought. The Tellaimed was initially left unpublished because of De Maillet’s fear of the violent reaction his ideas might evoke, especially in ecclesiastical circles. He was perhaps wise to do so, since, in addition to believing that life was not created by God, he claimed that it did not even originate here on Earth, but came from space. Such views were unlikely to make him popular amongst a philosophical and a scientific culture most of whose members firmly believed in God and his works. De Maillet in fact goes out of his way to avoid any mention of God, although he makes frequent reference to the Bible as a means of gaining insight into the mindset of ancient peoples. Perhaps he was wise to do so. Consider the fate of Giordano Bruno.

In 1584, Giordano Bruno a Dominican priest, published his book "Dell Infinito, universo e mondi" ("Of Infinity, the Universe, and the World"). Without benefit of a telescope, Bruno wrote that the stars were just like our sun, that planets must orbit these suns and that intelligent beings, just like the humans of Earth, lived on these planets. Bruno believed life was everywhere and that Earth was not the center of the biological universe. Bruno was arrested by the Catholic Inquisition, found guilty of heresy, and was then tortured and then burned at the stake on February 19, 1600 (Singer 1950; Yates, 1964).

In conclusion, De Maillet was one of the first "moderns" to see the Earth, not as the centre of creation, but merely one part of a vast cosmic sea of life. In this he is distinguished himself from subsequent philosophers and evolutionists, including Darwin, who believed life originated on Earth. In addition De Maillet differed from most philosopher-scientists of his age (including Buffon) when he stated that the Earth was two billion, rather than only a few thousand, years old. By being one of the first to express what might be called a post-Copernican view of biology De Maillet’s contribution to the history of astrobiology deserves to be better known.

3. SOME OTHER HISTORICAL REFERENCES TO THE IDEA THAT LIFE IS NOT RESTRICTED TO EARTH

When reading the historical literature it soon becomes apparent that what we often assume to be novel ideas in relation to the existence of life in the cosmos were often discussed in the ancient past, and even in the recent past in the 1500s and the 1700s. Certainly by the early 1800s many thinkers considered it an obvious possibility that life exists on other planets (or spheres and globes as they were often called). This belief was based largely on the simple dictum that the Creator (generally used in reference to the Christian God) would never have established so many worlds and then have left them empty, or as Isaac Taylor states, in his Physical Theory of Another Life of 1836 (Taylor,1836):

Darwin tended to avoid philosophical arguments. His book, On the Origin of the Species provides a straightforward synthesis of the then available arguments on the species question, extended by various references to Darwin’s own observations (Wainwright, 2008). Darwin in the main, avoided speculating on issues such as how life originated, although his grandfather Erasmus Darwin had earlier commented on this subject. In the same way, Darwin does not speculate on the possibility of life on other planets, or "globes" as they were frequently called.

Other Victorian thinkers did, however, consider the possibility of life on "other worlds", the most famous contribution being Of Plurality of Other Worlds by William Whewell (Whewell, 1855). Many authors commented on the possibility that the development of life on earth had been influenced by the catastrophic arrival of comets or asteroids from space, a possibility, which Darwin, the strict gradualist, did not entertain, or at least did not mention.

One of the most remarkable comments on the possibility that life might evolve in areas of the universe other than earth was made as early as 1770, by the French atheist and philosopher, Baron D’Holbach who, in his The System of Nature (first published in 1770) theorizes as follows (D’Holbach,1836):

James Lovelock is usually credited with the modern version of Gaia. However, the Victorian geographer, Sir Richard Strachey, stated the following in an address to Geographical Section of the British Association in Bristol on August 26th, 1875 (Strachey, 1875):

6. CONCLUSION

Astrobiology is a new science for which a history needs to be developed. This is important because the ideas of today’s thinkers need to be placed in context with those of the past. There is a tendency for modern commentators on the origin of life and its possible existence elsewhere, to come up with so-called new ideas which, as we have seen, turn out to have been discussed in some detail in the past. If this speaks to the "truth" of these ideas, is another matter.

A recent example of "new wine in old bottles" is the current, seemingly novel claim that life may have arisen on Earth on more than one occasion. Related to this are theories which proposed life continually arrives on Earth from space (Wainwright et al., 2010; Wickramasinghe et al., 2009). Since it has always been assumed that life originated on Earth (if it did so) only once, the possibility that life may have arisen multiple times appears novel and exciting. However, if we had a full history of astrobiology it would become obvious that this idea is far from new; Alfred Russel Wallace, for example, stated in 1890 that: