Sponges in the Galaxy

Dr. Laurance R. Doyle

Feb 12, 2009



There are many questions of key interest to SETI (the Search for Extraterrestrial Intelligence). For example, Why didn’t the dinosaurs go to the Moon? They had 200 million years and many species had hands with an opposable digit, big brains, and were bipedal. Another entirely different SETI question could be: What do Medieval Arabic texts have to say about the origin of optics? Light was thought to come from the eye at the beginning of the Middle Ages but within a few centuries advanced optical studies emerged from Arab countries with refracting lenses, prisms, and light was understood clearly to go into, not out of, the eye. Such an emergent process would be essential to understand if one wants to generalize the development of telescopes by intelligent civilizations.

Another interesting SETI-related question: When considering the communication systems of more advanced technical civilizations, what can we expect their communication system to be like? Since something like 98% of the stars in the solar neighborhood are apparently older than the Sun (and other reasons) we can likely expect that an extraterrestrial technology will be significantly more advanced than ours. As an example, one can hardly ignore recent developments in quantum teleportation as a possible neat trick for instantaneously getting large amounts of information across the galaxy. (It may or may not be possible to then read that information faster than light, but that’s another story). These are all interesting SETI questions and might make good articles themselves. But for today’s essay let’s ask ourselves this SETI-related question: Would the development of our technical civilization have been possible without sponges? (We shall not so much answer this question in our essay as explain why we asked it.

Given that a tool-wielding species has to start somewhere, humans apparently started at least 4 million years ago chipping rocks to form cutting surfaces. We see wild chimpanzees also doing this today; they also train their offspring to do this as well so it is a learned, or cultural, behavior. But as it turns out, banging special kinds of rocks together can produce an additional feature of technology, one that would come to distinguish us as a species about 2 million years ago. It all started when we banged together iron pyrite with ocean sponges—actually, to state it more properly, we started to bang together iron pyrite with a metamorphosed mixture of chalk with the internal skeletons of ocean sponges. This metamorphic chalk and sponge skeletal material is commonly known as “flint.” And, as we know, when struck with iron, it makes a spark of fire. And we are the only species that uses fire. (I’m not counting an entertaining raven that actually does a nightclub trick in Las Vegas that includes striking a match to light a cigar.) 

So, although flint is an inorganic mineral, almost all the silicate in it is derived from the dissolved skeletons of sponges. This strike-sparking is considered the earliest form of fire making. Later steel would be substituted for the iron pyrite, but flint was used for millennia before the invention of matches in the 19th Century. And it would be difficult to argue for a more important invention to the survival of the human species than the making of fire—especially during the frequent ice ages that accompanied early northward migrations out of Africa. It could also be argued that fire making was the first big step of our species toward a technical civilization.

It turns out, then, that the process of sponge skeletons dissolving in pre-lithified chalk ooze—dehydrated and hardened into microscopic quartz crystals forming flint—was essential (along with trees, but that’s another story) to the survival and eventual technical success of our species on this planet. It could be argued that without sponges humans would not be listening to and transmitting messages over interstellar distances today. So, looking for extraterrestrial technology? Then it might be a good idea to know where in the galaxy the sponges are. The humble sponge, or something like it, may be essential for any species to first come up with the making of fire. And on our planet, if you don’t have a dishwasher, they still come in pretty handy too.