CABINET OF CURIOSITIES Living Fossils
It is not uncommon to experience a deep confusion the first time you come across the term “living fossil.” Undoubtedly, the concept is quite disturbing; contradictory in the best of cases. We could even call it false.
If we were to be strict with the language, we could conclude that the expression lacks logic: something cannot be dead and living at the same time. Its meaning lacks clarity. Since a fossil is the petrified remnant of what was once alive, it may cause serious confusion. Are we talking about a rock blessed with the gift of free will? Are we perhaps suggesting the existence of a miraculous animated mineral? Can we openly state then that Michael Ende did not invent the stone man? Of course not. Although I must confess it would be quite interesting, at least in the real world, these proposals make no sense at all.
It is very likely that we owe the term – as so many other biological basics – to good old Darwin, who used it when he mentioned the platypus and the South American lungfish in his exquisite book, The Origin of the Species: “(…) and in fresh water we find some of the most anomalous forms now known in the world, as the Ornithorhynchus and the Lepidosiren, which, like fossils, connect to a certain extent orders now widely separated in the natural scale. These anomalous forms may almost be called living fossils.”
What the great English scientist indicated with this precept were the peculiar characteristics that define these organisms with the rest of their close relatives and that seem to connect them directly with taxonomic groups, completely different to their lineage. For example, in the case of the platypus, these characteristics are: reproduction by egg, the presence of a beak, and the use of venom as a means of defense (yes, as surprising as this may seem, platypus are venomous; the males have a spur in the hind limbs that they use to discharge the powerful toxin). As for the Lepidosiren, the term “living fossil” refers to those fish having a bone structure in the upper limbs similar to that of the terrestrial tetrapods, as well as the presence of lungs.
Since the term was coined in the mid-nineteenth century and beside its utter conceptual ambiguity, it has become strongly rooted in the naturalistic discipline. Needless to say, the most rigorous academics twitch just by hearing it; ultimately, that which is alive, by definition, cannot be a fossil. But let us not be so grouchy and give the wordplay a chance. The truth is we face a linguistic constriction, a communicational shortcut to designate various possible cases:
1) Living organisms that closely match the fossil record they represent. This means that for what seems like an extremely long period of geologic time, they haven’t suffered major morphologic and/or physiologic changes; these changes don’t necessarily happen to the same individual, as is the case of the Loch Ness Monster (that – if still doubt – does not exist), but within a whole species. The renowned limulus, for example.
2) Organisms that we only have evidence of through their fossil record. That is, species that were thought to have stopped inhabiting the earth in a remote past, and are still alive. This event is referred to in literature as “The Lazarus effect.” The most renowned case of this type of organisms is that of the Coelacanth, a huge deep ocean water fish.
3) The last remaining live organisms of taxonomic groups that bloomed millions of years ago. Species that still populate the earth, which are completely isolated in phylogenetic terms from the rest of the living creatures. In other words, they are the last representatives of genealogical trees that are primarily linked by their fossils, like the New Zealand Tuatara and the Ginkgo tree.
Perhaps one could say that under severe scrutiny, the definitions offered here are not able to solve the issue at hand. And I won’t deny it, we face an elusive biological term that holds various definitions; if one hopes to obtain a profound academic version, there are plenty of specialized publications available.
Cryptic elaborations aside, let us agree to a bit of uncertainty in the field of study and begin, once and for all, the catalogue of living fossils.